Optimal Use of Plodia interpunctella as a Substitute Host for Cost-Effective Mass Rearing of Meteorus pulchricornis

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However, its large-scale application has been hindered by the challenges associated with rearing it on natural hosts. This study investigates the use of Plodia interpunctella , a stored-product pest, as a cost-effective and reliable substitute host for M. pulchricornis . Results While parasitoids reared on P. interpunctella showed slight reductions in body size and fecundity compared to those reared on its natural host Spodoptera frugiperda , key performance metrics—such as parasitism rate, cocoon formation rate, and adult emergence rate—did not differ significantly between the two host treatments. Conclusion P. interpunctella provides a feasible and cost-effective alternative host for rearing M. pulchricornis , offering substantial potential for its use in large-scale biological control programs targeting lepidopteran pests. Biological control Meteorus pulchricornis Plodia interpunctlla Spodoptera frugiperda Substitute host Figures Figure 1 Figure 2 Figure 3 Background Parasitoid wasps play an essential role in biological control programs by regulating pest populations in an ecologically sustainable manner (Wang et al., 2021; Cooperband et al., 2000). The efficiency of these natural enemies relies not only on their host specificity and parasitism capacity, but also on the feasibility of their large-scale production for augmentative releases (Man et al., 2025). Meteorus pulchricornis (Hymenoptera: Braconidae) is a solitary koinobiont endoparasitoid that parasitizes a wide range of lepidopteran larvae, including several economically important crop pests, such as Spodoptera frugiperda , Spodoptera exigua and Helicoverpa armigera (Li, 1984; Caballero et al., 1990). Its potential as a biological control agent has been recognized in multiple cropping systems, particularly for managing noctuid pests (Fuester et al., 1993; Liu et al., 2006; Walker et al., 2016). Despite its broad host range and adaptability, the practical use of M. pulchricornis is constrained by the difficulties associated with rearing on natural hosts. These hosts often present challenges such as high maintenance costs, and low reproductive efficiency under laboratory conditions. Consequently, the identification and evaluation of alternative or substitute hosts is a critical step toward establishing cost-effective and reliable mass-rearing protocols for this parasitoid (Settle et al., 1996). The Indianmeal moth, Plodia interpunctella (Lepidoptera: Pyralidae), is a globally distributed pest of stored products and has been widely used as a factitious host for various parasitoid species (Brower et al., 1982; Liu et al., 2022). Its high fecundity, short developmental cycle, tolerance to a broad range of environmental conditions, and ease of rearing under artificial diets make it a promising candidate for surrogate host systems (Arthur et al., 2013; Ndomo-Moualeu et al., 2014; Gvozdenac et al., 2018). However, its suitability for supporting the complete development and reproductive performance of M. pulchricornis remains untested. The present study aims to evaluate the feasibility of using P. interpunctella as a substitute host for M. pulchricornis . We assessed the influence of host density and prior oviposition experience on parasitism performance. In addition, we examined the parasitoid’s parasitism behavior, developmental success, and fitness-related traits when reared on P. interpunctella larvae, and compared these parameters to those observed on a conventional host— S. frugiperda . The findings are expected to provide insights into alternative rearing strategies for this parasitoid and support its broader application in biological control programs. Methods 1. Insect collection and rearing The laboratory colony of Meteorus pulchricornis was a parthenogenetic strain, originally collected from Ningbo, Zhejiang Province, China, and maintained in the laboratory for multiple generations using early third-instar Spodoptera frugiperda larvae and early fifth-instar Plodia interpunctella larvae as hosts. Adult wasps were reared in climate-controlled chambers ( 26 ± 1°C, 60 ± 5% RH, and 16L : 8D photoperiod ) and provided with 10% honey solution ad libitum. P. interpunctella was obtained from Zhejiang University and reared on an artificial diet under controlled conditions ( 26 ± 1°C, 60 ± 5% RH, and 16L : 8D photoperiod ) . The diet consisted of 750 g wheat flour, 150 g glycerol, 50 g honey, 50 g yeast powder, and 600 μl propionic acid per batch. Both insect colonies were maintained in separate growth chambers to prevent cross-contamination. 2. Effects of host density on Meteorus pulchricornis parasitism of Plodia interpunctella and Spodoptera frugiperda Preliminary evaluations were conducted to determine the most suitable developmental stages of both host species for parasitism. These assessments showed that early fifth-instar P. interpunctella and early third-instar S. frugiperda larvae were the most suitable stages and were therefore selected for subsequent assays. To assess host density effects, a single 7-day-old naïve M. pulchricornis adult was introduced into plastic containers containing early fifth-instar P. interpunctella larvae or S. frugiperda at six parasitoid-to-host ratios (1:5, 1:10, 1:15, 1:20, 1:25, 1:30), respectively. All assays were conducted under standardized conditions ( 26 ± 1°C, 60 ± 5% RH, and 16L : 8D photoperiod ) . Each exposure lasted 8 hours, based on preliminary trials showing no significant differences between 8- and 24-hour exposures. After exposure, parasitoids were removed and host larvae were individually reared in Petri dishes with fresh diet. Parasitized larvae were monitored daily for parasitoid egression. Dead larvae were dissected to confirm parasitism status by the presence of parasitoid eggs or larvae. Egressed larvae were allowed to spin cocoons, which were then transferred to vials for adult emergence. For each treatment (n = 10 replicates), the following indices were calculated: Parasitism rate (%) = (Number of parasitized larvae, / Total exposed larvae, ) × 100 Cocoon formation rate (%) = (Number of cocoons, / ) × 100 Adult emergence rate (%) = (Number of emerged adults, / ) × 100 3. Comparative development of M. pulchricornis progeny from different hosts To compare the developmental performance of M. pulchricornis on different hosts, individual early fifth-instar Plodia interpunctella larvae and early third-instar Spodoptera frugiperda larvae were each exposed to a single oviposition by M. pulchricornis in a plastic container (10 cm×10 cm). Upon confirmation of a successful oviposition event (via direct observation), the host larva was transferred to a Petri dish containing artificial diet and maintained under standard rearing conditions. Each parasitized host was monitored twice daily to record the following parameters: (1) Developmental duration: time from oviposition to adult emergence; (2) Adult longevity: measured under continuous access to 10% honey solution; (3) Morphometric traits: including body length, forewing length, and hind tibia length of ethanol-preserved adults, measured using a digital microscope. 4. Parasitism efficacy comparison of progeny from different hosts To assess host-origin effects on parasitism efficacy, newly emerged (< 24 h old) M. pulchricornis adults reared from either P. interpunctella or S. frugiperda hosts were evaluated in parallel. Each parasitoid was provided with five early third-instar S. frugiperda larvae under controlled environmental conditions (26 ± 1°C, 60 ± 5% RH, 16L:8D photoperiod). Hosts were replaced every 24 hours, and parasitoids were supplied with fresh 10% honey solution daily until death. All exposed host larvae were dissected 72 h post-parasitization to quantify egg load before the first-instar parasitoid larvae hatched (to avoid intra-host cannibalism). Adult longevity was recorded daily (n = 10 replicates per host origin). Additionally, to compare parasitism performance of F₁ progeny, 7-day-old adults from both rearing origins ( P. interpunctella -reared and S. frugiperda -reared) were exposed to S. frugiperda larvae (1:5 ratio) for 8 h under identical conditions. Parasitized hosts were then reared individually to calculate parasitism rate, cocoon formation rate, and adult emergence rate, using the same definitions and formulas described previously (n = 10 replicates per treatment). 5. Data analysis Statistical analyses were conducted using R software (version 4.3.3) (Pritchard et al., 2017). A Two-way ANOVA, followed by Tukey's Honestly Significant Difference (HSD) post hoc test, was employed to examine significant differences in parasitism efficiency of M. pulchricornis under different host density levels. Independent-samples t-tests were used for statistical comparisons regarding development and parasitism. Before statistical analysis, percentage data were square root-transformed to meet normality and homogeneity of variances assumptions. A significance level P < 0.05 was applied to all statistical tests. All figures were prepared using GraphPad Prism 8.0 software. Results 1. Effects of host density on Meteorus pulchricornis parasitism of Plodia interpunctella and Spodoptera frugiperda The performance parameters of M. pulchricornis parasitizing P. interpunctella and S. frugiperda are presented in Table 1. Two-way ANOVA revealed that the number of parasitized larvae was significantly influenced by the interaction between host density and host species ( F 5, 108 = 22.80, P < 0.0001). Host density exhibited a highly significant main effect ( F 5, 108 = 1155, P < 0.0001), whereas the main effect of host species was not significant ( F 1, 108 = 0.5268, P = 0.4695). Similarly, the parasitism rate was also significantly affected by their interaction ( F 5, 108 = 5.337, P = 0.0002), with a highly significant main effect of host density ( F 5, 108 = 55.50, P < 0.0001) and a non-significant main effect of host species ( F 1, 108 = 0.002, P = 0.964). Table 1.Host density effects on parasitism parameters of Meteorus pulchricornis utilizing two lepidopteran hosts Parameters Host Host densities (larvae/jar) 5 10 15 20 25 30 Parasitized numbers P. interpunctella 2.90 ± 0.31 e A 4.70 ± 0.94 d A 5.60 ± 0.95 c B 6.90 ± 0.53 b A 8.20 ± 1.26 a A 8.50 ± 0.93 a B S. frugiperda 2.50 ± 0.31 e B 4.30 ± 0.91 d B 6.50 ± 1.61 c A 6.70 ± 1.49 c B 8.70 ± 1.64 b A 9.90 ± 1.86 a A Parasitism rates (%) P. interpunctella 58.00 ± 6.29 a A 47.00 ± 9.43 b A 37.33 ± 6.30 c B 34.50 ± 2.63 cd A 32.80 ± 5.05 cd A 28.33 ± 2.95 d B S. frugiperda 50.00 ± 12.38 a B 43.00 ± 9.07 ab A 43.33 ± 10.72 ab A 33.50 ± 7.46 bc A 34.80 ± 5.96 c A 33.00 ± 6.22 bc A Note: Data are presented as mean ± SD. Different lowercase letters within the same row indicate significant differences among density levels for the same host species, while different uppercase letters within the same column indicate significant differences between host species at the same density level (Tukey's HSD test, P < 0.05). The number of parasitized larvae increased significantly with increasing host density (Table 1). Post hoc comparisons indicated that the significant interaction stemmed from density-dependent shifts in host species preference. At low densities (5 and 10 larvae/jar), the parasitized numbers of P. interpunctella were significantly higher than those of S. frugiperda . However, this trend reversed at a density of 15 larvae/jar, where the parasitized numbers of S. frugiperda became significantly higher. No significant interspecific differences were detected at other higher densities. The parasitism rate, in contrast, exhibited a different pattern (Table 1). For P. interpunctella , the parasitism rate decreased significantly from 58.00% to 28.33% as host density increased, demonstrating a clear inverse density-dependent relationship. In contrast, the parasitism rate on S. frugiperda did not show a consistent density-dependent pattern. Interspecific comparisons revealed that the parasitism rate was significantly higher on P. interpunctella than on S. frugiperda at the low density (5 larvae/jar). However, at medium to high densities (15 and 30 larvae/jar), the parasitism rate was either significantly higher on S. frugiperda or not significantly different between the two host species. The subsequent developmental quality of the parasitoid was not significantly affected by host density or host species. Two-way ANOVA followed by Tukey's test showed that neither cocoon formation rate (Fig. 1A) nor adult emergence rate (Fig. 1B) exhibited any significant differences in any pairwise comparisons between host species at any density, or among different densities within the same host species (all P > 0.05). Furthermore, we identified that the removal of the silken structure produced by P. interpunctella larvae is a crucial step for the successful cocoon formation and adult emergence of the parasitoid in this host. As shown in Fig. 2, this procedure significantly enhanced the parasitoid's cocoon formation and adult emergence rates, from 71.52 ± 17.59% and 74.98 ± 15.24% (without removal) to 90.00 ± 10.57% and 92.80 ± 10.50% (with removal), respectively. 2. Comparative development of Meteorus pulchricornis progeny reared from Plodia interpunctella and Spodoptera frugiperda The developmental parameters of M. pulchricornis progeny were significantly affected by host origin. When reared at 26°C and provided with 10% honey solution, progeny from P. interpunctell a exhibited a longer developmental duration (15.27 ± 0.33 days) compared to those from S. frugiperda (14.73 ± 0.50 days) (P < 0.05). Conversely, adult longevity was significantly shorter in the P. interpunctella -reared group (16.63 ± 1.99 days) than in the S. frugiperda -reared group (17.73 ± 1.64 days) (P < 0.05; Table.2). Table 2.Developmental and morphological characteristics of Meteorus pulchricornis progeny derived from different host origins Parameters Host Result n t df p -value Pre-emergence time (days) P. interpunctella 15.27 ± 0.33 47 6.417 102 <0.0001 S. frugiperda 14.73 ± 0.50 57 Lifespan (days) P. interpunctella 16.63 ± 1.99 51 3.129 106 0.0023 S. frugiperda 17.73 ± 1.64 57 Body length (mm) P. interpunctella 3.87± 0.23 36 15.86 73 <0.0001 S. frugiperda 4.60 ± 0.18 39 Forewing length (mm) P. interpunctella 3.07 ± 0.21 35 13.83 73 <0.0001 S. frugiperda 3.63 ± 0.19 40 Hind tibial length (mm) P. interpunctella 1.35 ± 0.11 40 19.78 73 <0.0001 S. frugiperda 1.67 ± 0.06 35 Note: Data in the table are mean ± SD. Significant differences between host origins were determined by Independent samples t-test A correlation analysis revealed no significant linear relationship between developmental duration and adult longevity across individuals ( t = 0.687, df = 55, P = 0.495), suggesting that extended larval development does not predict increased adult lifespan in M. pulchricornis . Morphological measurements of M. pulchricornis progeny reared from P. interpunctella showed significantly smaller body dimensions compared to those reared from S. frugiperda , with mean body length measuring 3.87 ± 0.23 mm versus 4.60 ± 0.18 mm (P< 0.05), mean forewing length 3.07 ± 0.21 mm versus 3.63 ± 0.19 mm (P< 0.05), and mean hind tibia length 1.35 ± 0.11 mm versus 1.67 ± 0.06 mm (P< 0.05), respectively (Table.2). These results demonstrate consistent and significant size reductions across all three measured parameters (body length, forewing length, and hind tibia length) in M. pulchricornis progeny developed from P. interpunctella compared to those from S. frugiperda. 3. Parasitism performance of Meteorus pulchricornis progeny reared from Plodia interpunctella and Spodoptera frugiperda When continuously exposed to host larvae, M. pulchricornis progeny reared from P. interpunctella and S. frugiperda exhibited mean adult longevities of 9.40 ± 0.70 and 10.30 ± 0.95 days, respectively (Table 3). As shown in Figure 3, both groups displayed a unimodal pattern in daily oviposition on S. frugiperda , with egg-laying peaking midlife and then declining. Some parasitoids began ovipositing immediately upon emergence and continued parasitism throughout their lifespan. Table 3.Comparative parasitism performance of Meteorus pulchricornis progeny from different host origins on Spodoptera frugiperda Parameters P. interpunctella S. frugiperda t df p -value Parasitism rates (%) 48.00 ± 18.74 50.00 ± 12.38 0.3438 18 0.735 Cocoon forming rates (%) 90.00 ± 10.59 91.40 ± 10.58 0.2888 18 0.7761 Emergence rates (%) 93.60 ± 10.46 93.00 ± 11.15 0.1279 18 0.8996 Total oviposition 17.10 ± 4.82 26.70 ± 4.40 4.654 18 0.0002 Lifespan under persistent host exposure (days) 9.40 ± 0.70 10.30 ± 0.95 2.415 18 0.0266 Note: Data are expressed as mean ± SD of 10 replications.,Significant differences between host origins were determined by Independent samples t-test Peak daily fecundity occurred on day 5 for P. interpunctella -reared parasitoids (4.10 ± 0.94 eggs/day), with a total lifetime fecundity of 17.10 ± 4.82 eggs. In contrast, S. frugiperda -reared parasitoids reached peak fecundity on day 6 (6.20 ± 1.72 eggs/day) (Fig. 3) and produced significantly more eggs over their lifetime (26.70± 4.40 eggs) (P < 0.05; Table 3). Senescent parasitoids displayed signs of behavioral decline, including reduced mobility, unstable posture, and loss of flight ability, although some retained oviposition activity until death. As summarized in Table 3, both groups of progeny performed comparably when parasitizing S. frugiperda larvae. Mean parasitism rates were 48.00 ± 18.74% ( P. interpunctella -origin) and 50.00 ± 12.38% ( S. frugiperda -origin), cocoon formation rates were 90.00 ± 10.59% vs. 91.40 ± 10.58%, and adult emergence rates were 93.60 ± 10.46% vs. 93.00 ± 11.15%, respectively. None of these differences was statistically significant (P > 0.05 for all comparisons). These results collectively suggest that although P. interpunctella -reared progeny exhibited slightly reduced reproductive output, their parasitism performance remained functionally comparable. This supports the feasibility of using P. interpunctella as a cost-effective substitute host for the mass rearing of M. pulchricornis under laboratory conditions. Discussion The search for efficacious substitute hosts represents a core objective in augmentative biological control. Although the Mediterranean flour moth Ephestia kuehniella Zeller has been identified as a potential host for M. pulchricornis (Nakano et al., 2018 ), its rearing efficiency remains limited around 80% adult emergence even under optimal conditions. As an alternative, Plodia interpunctella presents a promising option. Our study demonstrates that P. interpunctella can support the complete development of M. pulchricornis , with key performance metrics (parasitism rate: 90.00 ± 10.59%; cocoon formation: 90.00 ± 10.59%; adult emergence: 93.60 ± 10.46%) showing no statistically significant difference from those reared on its natural host, S. frugiperda . As a cosmopolitan stored-product pest, P. interpunctella offers several potential advantages for mass rearing, including relative ease of maintenance, short generation time, and rapid population growth. These characteristics suggest it could help alleviate some of the challenges associated with natural host high production costs. The reduced body size, fecundity and longevity of wasps from P. interpunctella align with the host-size principle in parasitoid biology (Bai et al., 1992 ; Liu et al., 2011 ). Progeny from the smaller P. interpunctella were significantly smaller and less fecund than those from S. frugiperda , likely due to limited nutritional resources. This resource constraint may also explain the extended developmental period in P. interpunctella , representing a necessary trade-off under limited resources (Qi et al., 2024 ; Suzuki et al., 2006). The absence of correlation between developmental duration and adult longevity confirms that parasitoid lifespan depends more on adult-stage resource acquisition than larval development pace (Jervis et al., 2008 ). Species-specific density-dependent responses in parasitism further reveal fundamental differences in host–parasitoid interactions. The inverse density dependence observed in P. interpunctella aligns with classical foraging models, where host defensive behaviors and parasitoid egg or time limitation drive reduced parasitism rates at higher host densities. Conversely, S. frugiperda exhibited density-independent parasitism, suggesting weaker host defenses and consistent parasitoid efficiency. This contrast suggests that P. interpunctella may be particularly well suited for controlled, low-density laboratory colonization, whereas S. frugiperda appears to maintain more stable parasitism rates across varying densities, a trait potentially beneficial in field conditions. A crucial step for successful rearing was the removal of the silken structure spun by P. interpunctella larvae. This removal improved cocoon formation and adult emergence rates by approximately 20%, increasing success rates to above 90%. This finding underscores that host suitability is not solely determined by biological compatibility but can be substantially influenced by physical or behavioral factors, such as the host's silk production. While this step adds to the handling procedure, the significant gain in parasitoid yield confirms its importance in the rearing protocol. While this study confirms P. interpunctella as an effective and economical substitute host under laboratory conditions, the performance and competitive fitness of M. pulchricornis reared on P. interpunctella in complex field environments—with variables such as fluctuating climate, host-plant interactions, and the presence of alternative hosts and predators—remain untested and constitute a critical next step for validation. Furthermore, while our assessment focused on the F1 generation, the long-term effects over multiple generations, including potential impacts on genetic diversity, fecundity, and behavior, warrant dedicated investigation. Declarations Acknowledgements The authors sincerely thank the Institute of insect Sciences, Zhejiang University, Hangzhou, China, for providing research facilities and support throughout this study. Author contributions PT, XC, XY, ZW and QW conceived the idea, designed the methodology. RS and JL wrote the first draft of manuscript. RS, JL, AS, LY, PW, YY and ZL performed experimentation. RS, JL and XS analyzed the data and prepared results. PT and XC technically edited and proofread the manuscript. All authors read and approved the final manuscript. Funding This work was supported by the National Key R&D Program of China (2022YFD1401400), the General Program of the National Natural Science Foundation of China (32070467), the Key International Joint Research Program of the National Natural Science Foundation of China (31920103005) and the Fundamental Research Funds for the Central Universities (226-2024-00070). Data availability All data are available in the manuscript. Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests. 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Cite Share Download PDF Status: Published Journal Publication published 26 Mar, 2026 Read the published version in Egyptian Journal of Biological Pest Control → Version 1 posted Editorial decision: Revision requested 05 Feb, 2026 Reviews received at journal 02 Feb, 2026 Reviewers agreed at journal 20 Jan, 2026 Reviews received at journal 12 Jan, 2026 Reviewers agreed at journal 07 Jan, 2026 Reviewers invited by journal 07 Jan, 2026 Submission checks completed at journal 18 Dec, 2025 First submitted to journal 17 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8249784","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":570850379,"identity":"3a567d04-c3b0-4972-b27b-152bc0f53739","order_by":0,"name":"Rui Shi","email":"","orcid":"","institution":"Zhejiang University","correspondingAuthor":false,"prefix":"","firstName":"Rui","middleName":"","lastName":"Shi","suffix":""},{"id":570850382,"identity":"53efb9ed-9ace-45e5-9d61-f2226028450d","order_by":1,"name":"Jiayan Lu","email":"","orcid":"","institution":"Zhejiang 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09:01:14","extension":"html","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":94107,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8249784/v1/e04667c72c510e5c60cad39e.html"},{"id":99870182,"identity":"cf9a6be0-66ad-4ff2-916a-6c3f20ed3fcb","added_by":"auto","created_at":"2026-01-09 09:01:14","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":133693,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of host species and density on developmental parameters of \u003cem\u003eMeteorus pulchricornis\u003c/em\u003e. Values represent mean + SD (A) Cocoon formation rates and (B) adult emergence rates of \u003cem\u003eM. pulchricornis\u003c/em\u003e reared from \u003cem\u003ePlodia interpunctella\u003c/em\u003eand \u003cem\u003eSpodoptera frugiperda\u003c/em\u003e across six host density levels (5, 10, 15, 20, 25, and 30 larvae/jar). Different lowercase letters indicate significant differences among density levels within the same host species, while different uppercase letters indicate significant differences between host species at the same density level (Tukey's HSD test, P \u0026lt; 0.05). Error bars are truncated at 100% because rates cannot exceed this theoretical maximum.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8249784/v1/7dbebfc1c1216c1d54e3834f.png"},{"id":100358221,"identity":"850312ff-e19e-48cd-a889-90e58c79d870","added_by":"auto","created_at":"2026-01-16 07:20:44","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":28866,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of silk removal procedure on developmental parameters in\u003cem\u003e Plodia interpunctella \u003c/em\u003ehost system. Values represent mean + SD Comparison of cocoon forming rates and adult emergence rates of \u003cem\u003eM. pulchricornis\u003c/em\u003e in \u003cem\u003eP. interpunctella \u003c/em\u003ewith and without removal of larval silken structures. Asterisks indicate statistically significant differences between treatments (Independent samples t-test, *P \u0026lt; 0.05,**P \u0026lt; 0.01). Error bars are truncated at 100% because rates cannot exceed this theoretical maximum.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8249784/v1/35c949d33bf88bbc22c99647.png"},{"id":99870183,"identity":"04f017a7-b07b-446e-97c7-fc4474360aee","added_by":"auto","created_at":"2026-01-09 09:01:14","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":50256,"visible":true,"origin":"","legend":"\u003cp\u003eDaily oviposition dynamics of \u003cem\u003eMeteorus pulchricornis\u003c/em\u003e progeny originating from different host species. Values represent mean ± SD Daily oviposition patterns of \u003cem\u003eM. pulchricornis\u003c/em\u003ereared from \u003cem\u003eP. interpunctella\u003c/em\u003e and \u003cem\u003eS. frugiperda\u003c/em\u003e when parasitizing \u003cem\u003eS. frugiperda\u003c/em\u003e larvae. Error bars are truncated at zero where necessary because oviposition counts cannot be negative.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8249784/v1/320cfbf28d0e49581bafb11f.png"},{"id":105756027,"identity":"ac62ccc7-0c17-482a-9dfd-d7017a41ec5d","added_by":"auto","created_at":"2026-03-30 16:34:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1007500,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8249784/v1/2e76e161-d572-41b7-b9a5-a31396b387da.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Optimal Use of Plodia interpunctella as a Substitute Host for Cost-Effective Mass Rearing of Meteorus pulchricornis","fulltext":[{"header":"Background","content":"\u003cp\u003eParasitoid wasps play an essential role in biological control programs by regulating pest populations in an ecologically sustainable manner (Wang et al., 2021; Cooperband et al., 2000). The efficiency of these natural enemies relies not only on their host specificity and parasitism capacity, but also on the feasibility of their large-scale production for augmentative releases (Man et al., 2025).\u0026nbsp;\u003cem\u003eMeteorus pulchricornis\u003c/em\u003e (Hymenoptera: Braconidae) is a solitary koinobiont endoparasitoid that parasitizes a wide range of lepidopteran larvae, including several economically important crop pests, such as \u003cem\u003eSpodoptera frugiperda\u003c/em\u003e, \u003cem\u003eSpodoptera exigua\u003c/em\u003e and \u003cem\u003eHelicoverpa armigera\u003c/em\u003e (Li, 1984; Caballero et al., 1990). Its potential as a biological control agent has been recognized in multiple cropping systems, particularly for managing noctuid pests (Fuester et al., 1993; Liu et al., 2006; Walker et al., 2016).\u003c/p\u003e\n\u003cp\u003eDespite its broad host range and adaptability, the practical use of \u003cem\u003eM. pulchricornis\u003c/em\u003e is constrained by the difficulties associated with rearing on natural hosts. These hosts often present challenges such as high maintenance costs, and low reproductive efficiency under laboratory conditions. Consequently, the identification and evaluation of alternative or substitute hosts is a critical step toward establishing cost-effective and reliable mass-rearing protocols for this parasitoid (Settle et al., 1996).\u003c/p\u003e\n\u003cp\u003eThe Indianmeal moth, \u003cem\u003ePlodia interpunctella\u003c/em\u003e (Lepidoptera: Pyralidae), is a globally distributed pest of stored products and has been widely used as a factitious host for various parasitoid species (Brower et al., 1982; Liu et al., 2022). Its high fecundity, short developmental cycle, tolerance to a broad range of environmental conditions, and ease of rearing under artificial diets make it a promising candidate for surrogate host systems (Arthur et al., 2013; Ndomo-Moualeu et al., 2014; Gvozdenac et al., 2018). However, its suitability for supporting the complete development and reproductive performance of \u003cem\u003eM. pulchricornis\u003c/em\u003e remains untested.\u003c/p\u003e\n\u003cp\u003eThe present study aims to evaluate the feasibility of using \u003cem\u003eP. interpunctella\u003c/em\u003e as a substitute host for \u003cem\u003eM. pulchricornis\u003c/em\u003e. We assessed the influence of host density and prior oviposition experience on parasitism performance. In addition, we examined the parasitoid’s parasitism behavior, developmental success, and fitness-related traits when reared on \u003cem\u003eP. interpunctella\u003c/em\u003e larvae, and compared these parameters to those observed on a conventional host—\u003cem\u003eS. frugiperda\u003c/em\u003e. The findings are expected to provide insights into alternative rearing strategies for this parasitoid and support its broader application in biological control programs.\u003c/p\u003e"},{"header":"Methods","content":"\u003ch3\u003e1. Insect collection and rearing\u003c/h3\u003e\n\u003cp\u003eThe laboratory colony of\u0026nbsp;\u003cem\u003eMeteorus\u0026nbsp;pulchricornis\u003c/em\u003e was a parthenogenetic strain, originally collected from Ningbo, Zhejiang Province, China, and maintained in the laboratory for multiple generations using early third-instar\u0026nbsp;\u003cem\u003eSpodoptera\u0026nbsp;frugiperda\u003c/em\u003e larvae and early fifth-instar\u0026nbsp;\u003cem\u003ePlodia\u0026nbsp;interpunctella\u003c/em\u003e larvae as hosts. Adult wasps were reared in climate-controlled chambers \u003cstrong\u003e(\u003c/strong\u003e26 ± 1°C, 60 ± 5% RH, and 16L : 8D photoperiod\u003cstrong\u003e)\u003c/strong\u003e and provided with 10% honey solution ad libitum.\u003cem\u003e\u0026nbsp;P. interpunctella\u003c/em\u003e was obtained from Zhejiang University and reared on an artificial diet under controlled conditions \u003cstrong\u003e(\u003c/strong\u003e26 ± 1°C, 60 ± 5% RH, and 16L : 8D photoperiod\u003cstrong\u003e)\u003c/strong\u003e. The diet consisted of 750 g wheat flour, 150 g glycerol, 50 g honey, 50 g yeast powder, and 600 μl propionic acid per batch. Both insect colonies were maintained in separate growth chambers to prevent cross-contamination.\u003c/p\u003e\n\u003cp\u003e2. Effects of host density on \u003cem\u003eMeteorus pulchricornis\u003c/em\u003e parasitism of \u003cem\u003ePlodia interpunctella\u0026nbsp;\u003c/em\u003eand\u003cem\u003e\u0026nbsp;Spodoptera frugiperda\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ePreliminary evaluations were conducted to determine the most suitable developmental stages of both host species for parasitism. These assessments showed that early fifth-instar \u003cem\u003eP. interpunctella\u003c/em\u003e and early third-instar \u003cem\u003eS. frugiperda\u003c/em\u003e larvae were the most suitable stages and were therefore selected for subsequent assays.\u003c/p\u003e\n\u003cp\u003eTo assess host density effects, a single 7-day-old naïve \u003cem\u003eM. pulchricornis\u003c/em\u003e adult was introduced into plastic containers containing early fifth-instar \u003cem\u003eP. interpunctella\u003c/em\u003e larvae or\u0026nbsp;\u003cem\u003eS. frugiperda\u003c/em\u003e at six parasitoid-to-host ratios (1:5, 1:10, 1:15, 1:20, 1:25, 1:30), respectively. All assays were conducted under standardized conditions\u003cstrong\u003e\u0026nbsp;(\u003c/strong\u003e26 ± 1°C, 60 ± 5% RH, and 16L : 8D photoperiod\u003cstrong\u003e)\u003c/strong\u003e. Each exposure lasted 8 hours, based on preliminary trials showing no significant differences between 8- and 24-hour exposures. After exposure, parasitoids were removed and host larvae were individually reared in Petri dishes with fresh diet. Parasitized larvae were monitored daily for parasitoid egression. Dead larvae were dissected to confirm parasitism status by the presence of parasitoid eggs or larvae. Egressed larvae were allowed to spin cocoons, which were then transferred to vials for adult emergence. For each treatment (n = 10 replicates), the following indices were calculated:\u003c/p\u003e\n\u003cp\u003eParasitism rate (%) = (Number of parasitized larvae,\u0026nbsp;\u003cimg width=\"17\" height=\"21\" src=\"data:image/png;base64,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\" alt=\"image\"\u003e\u0026nbsp;/ Total exposed larvae,\u0026nbsp;\u003cimg width=\"14\" height=\"19\" src=\"data:image/png;base64,R0lGODlhDgATAHcAMSH+GlNvZnR3YXJlOiBNaWNyb3NvZnQgT2ZmaWNlACH5BAEAAAAALAAABAAOAA8AhQAAAEBAQEFBZEFBhkFkZEFkpkGGxGRBQWRkQWSGpmSGxGSm4oZBQYZBhoaGpoaGxIam4obE/6ZkQaaGpqaGxKbi/8SGQcSGZMSGhsTi/8T//+KmZOKmhv/Ehv/Epv/ipv//xP/ixP//4uL//wECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwZmQACIETAAjsNAIHI8bgSVJqiRaR4viEXzA7ECRJRNYXTkMK2fyPCM0Xg5UYsR9PCKJuTOQNM5b7tfEgttXh1RTgQKdhNuRx8HfiEOSntNhAAeBwFenAAXh51IDY2hAB1GpUcWCRlBADs=\" alt=\"image\"\u003e) × 100\u003c/p\u003e\n\u003cp\u003eCocoon formation rate (%) = (Number of cocoons,\u0026nbsp;\u003cimg width=\"16\" height=\"19\" src=\"data:image/png;base64,R0lGODlhEAATAHcAMSH+GlNvZnR3YXJlOiBNaWNyb3NvZnQgT2ZmaWNlACH5BAEAAAAALAAABAAQAA8AhQAAAAAAAAAAOgAAZgA6OgA6kABmtjoAADoAOjo6ADpmtjqQ22YAAGYAZmY6AGZmtmaQ22a2/5A6AJBmkJBmtpCQtpC2/5Db/7ZmALZmOrZmZrbb/7b//9uQOtuQZtv///+2Zv/bkP//tv//2wECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwZsQICIETAAjsNAIHJsAjqCS1PU2DibmcSiGYJcjyNKp/A5epjfUGSI1nC+AI8UYxQ94KNJGTTggNBXXWASC25wIFJHHQQKeBNvRyEHgE5KfU2GkQ5RcE4hCBcgFp1NHVukThgRIxWoRyAHZABBADs=\" alt=\"image\"\u003e\u0026nbsp;/\u0026nbsp;\u003cimg width=\"17\" height=\"21\" src=\"data:image/png;base64,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\" alt=\"image\"\u003e) × 100\u003c/p\u003e\n\u003cp\u003eAdult emergence rate (%) = (Number of emerged adults,\u0026nbsp;\u003cimg width=\"16\" height=\"19\" src=\"data:image/png;base64,R0lGODlhEAATAHcAMSH+GlNvZnR3YXJlOiBNaWNyb3NvZnQgT2ZmaWNlACH5BAEAAAAALAAABAAQAA8AhQAAAEBAQEFBZEFBhkFkZEFkpkGGxGRBQWRkQWSGxGSmxGSm4oZBQYZBhoZkQYaGpoaGxIam4obE/4bE4qZkQaaGpqaGxKbE/6bi/8SGQcSGZMSGhsTi/8T//8Ti4uKmZOKmhv/Ehv/ipv//xP/ixP//4uL//wECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwZvQMCIETAAjsNAQHJsAj4CTHPU4DibGsSiKYpcjyXLp2A6gphfkWSI3nS+AJA0YxxB4KVKOTTohNBXXWAUC25wIVJHHwQJeBVvRyIHgE5KfU2GRyQOAQpwTiMPHiBbn4oBBBOmTRleIBerACEHAqpBADs=\" alt=\"image\"\u003e\u0026nbsp;/\u0026nbsp;\u003cimg width=\"17\" height=\"21\" src=\"data:image/png;base64,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\" alt=\"image\"\u003e) × 100\u003c/p\u003e\n\u003ch3\u003e3. Comparative development of \u003cem\u003eM. pulchricornis\u003c/em\u003e progeny from different hosts\u003c/h3\u003e\n\u003cp\u003eTo compare the developmental performance of \u003cem\u003eM. pulchricornis\u003c/em\u003e on different hosts, individual early fifth-instar \u003cem\u003ePlodia interpunctella\u003c/em\u003e larvae and early third-instar \u003cem\u003eSpodoptera frugiperda\u003c/em\u003e larvae were each exposed to a single oviposition by \u003cem\u003eM. pulchricornis\u003c/em\u003e in a plastic container (10 cm×10 cm). Upon confirmation of a successful oviposition event (via direct observation), the host larva was transferred to a Petri dish containing artificial diet and maintained under standard rearing conditions. Each parasitized host was monitored twice daily to record the following parameters: (1) Developmental duration: time from oviposition to adult emergence; (2) Adult longevity: measured under continuous access to 10% honey solution; (3) Morphometric traits: including body length, forewing length, and hind tibia length of ethanol-preserved adults, measured using a digital microscope.\u003c/p\u003e\n\u003ch3\u003e4. Parasitism efficacy comparison of progeny from different hosts\u003c/h3\u003e\n\u003cp\u003eTo assess host-origin effects on parasitism efficacy, newly emerged (\u0026lt; 24 h old) \u003cem\u003eM. pulchricornis\u003c/em\u003e adults reared from either \u003cem\u003eP. interpunctella\u003c/em\u003e or \u003cem\u003eS. frugiperda\u003c/em\u003e hosts were evaluated in parallel. Each parasitoid was provided with five early third-instar \u003cem\u003eS. frugiperda\u003c/em\u003e larvae under controlled environmental conditions (26 ± 1°C, 60 ± 5% RH, 16L:8D photoperiod). Hosts were replaced every 24 hours, and parasitoids were supplied with fresh 10% honey solution daily until death.\u003c/p\u003e\n\u003cp\u003eAll exposed host larvae were dissected 72 h post-parasitization to quantify egg load before the first-instar parasitoid larvae hatched (to avoid intra-host cannibalism). Adult longevity was recorded daily (n = 10 replicates per host origin).\u003c/p\u003e\n\u003cp\u003eAdditionally, to compare parasitism performance of F₁ progeny, 7-day-old adults from both rearing origins (\u003cem\u003eP. interpunctella\u003c/em\u003e-reared and \u003cem\u003eS. frugiperda\u003c/em\u003e-reared) were exposed to \u003cem\u003eS. frugiperda\u003c/em\u003e larvae (1:5 ratio) for 8 h under identical conditions. Parasitized hosts were then reared individually to calculate parasitism rate, cocoon formation rate, and adult emergence rate, using the same definitions and formulas described previously (n = 10 replicates per treatment).\u003c/p\u003e\n\u003ch3\u003e5. Data analysis\u003c/h3\u003e\n\u003cp\u003eStatistical analyses were conducted using R software (version 4.3.3) (Pritchard et al., 2017). A\u0026nbsp;Two-way ANOVA, followed by Tukey's Honestly Significant Difference (HSD) post hoc test, was employed to examine significant differences in parasitism efficiency of \u003cem\u003eM. pulchricornis\u003c/em\u003e under different host density levels. Independent-samples t-tests were used for statistical comparisons regarding development and parasitism. Before statistical analysis, percentage data were square root-transformed to meet normality and homogeneity of variances assumptions. A significance level P \u0026lt; 0.05 was applied to all statistical tests. All figures were prepared using GraphPad Prism 8.0 software.\u003c/p\u003e"},{"header":"Results","content":"\u003ch3\u003e1. Effects of host density on\u0026nbsp;\u003cem\u003eMeteorus\u003c/em\u003e\u003cem\u003e\u0026nbsp;pulchricornis\u003c/em\u003e parasitism of \u003cem\u003ePlodia interpunctella\u0026nbsp;\u003c/em\u003eand\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003eSpodoptera frugiperda\u003c/em\u003e\u003c/h3\u003e\n\u003cp\u003eThe performance parameters of\u003cem\u003e\u0026nbsp;M. pulchricornis\u003c/em\u003e parasitizing \u003cem\u003eP. interpunctella\u003c/em\u003e and \u003cem\u003eS. frugiperda\u0026nbsp;\u003c/em\u003eare presented in Table 1. Two-way ANOVA revealed that the number of parasitized larvae was significantly influenced by the interaction between host density and host species (\u003cem\u003eF\u003c/em\u003e\u003csub\u003e5, 108\u0026nbsp;\u003c/sub\u003e= 22.80, \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.0001). Host density exhibited a highly significant main effect (\u003cem\u003eF\u003c/em\u003e\u003csub\u003e5, 108\u003c/sub\u003e = 1155, \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.0001), whereas the main effect of host species was not significant (\u003cem\u003eF\u003c/em\u003e\u003csub\u003e1, 108\u003c/sub\u003e = 0.5268, \u003cem\u003eP\u003c/em\u003e = 0.4695). Similarly, the parasitism rate was also significantly affected by their interaction (\u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u0026nbsp;5, 108\u003c/sub\u003e = 5.337, \u003cem\u003eP\u003c/em\u003e = 0.0002), with a highly significant main effect of host density (\u003cem\u003eF\u003c/em\u003e\u003csub\u003e5, 108\u003c/sub\u003e = 55.50, \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.0001) and a non-significant main effect of host species (\u003cem\u003eF\u003c/em\u003e\u003csub\u003e1, 108\u003c/sub\u003e = 0.002, \u003cem\u003eP\u003c/em\u003e = 0.964).\u003c/p\u003e\n\u003cp\u003eTable 1.Host density effects on parasitism parameters of \u003cem\u003eMeteorus pulchricornis\u003c/em\u003e utilizing two lepidopteran hosts\u003c/p\u003e\n\u003cdiv align=\"Left\"\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"703\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 110px;\"\u003e\n \u003cp\u003eParameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 145px;\"\u003e\n \u003cp\u003eHost\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"6\" style=\"width: 448px;\"\u003e\n \u003cp\u003eHost densities (larvae/jar)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 78px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 110px;\"\u003e\n \u003cp\u003eParasitized numbers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 145px;\"\u003e\n \u003cp\u003e\u003cem\u003eP. interpunctella\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e2.90 \u0026plusmn; 0.31 e A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e4.70 \u0026plusmn; 0.94 d A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 78px;\"\u003e\n \u003cp\u003e5.60 \u0026plusmn; 0.95 c B\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e6.90 \u0026plusmn; 0.53 b A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e8.20 \u0026plusmn; 1.26 a A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e8.50 \u0026plusmn; 0.93 a B\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 145px;\"\u003e\n \u003cp\u003e\u003cem\u003eS. frugiperda\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e2.50 \u0026plusmn; 0.31 e B\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e4.30 \u0026plusmn; 0.91 d B\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 78px;\"\u003e\n \u003cp\u003e6.50 \u0026plusmn; 1.61 c A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e6.70 \u0026plusmn; 1.49 c B\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e8.70 \u0026plusmn; 1.64 b A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e9.90 \u0026plusmn; 1.86 a A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 110px;\"\u003e\n \u003cp\u003eParasitism rates (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 145px;\"\u003e\n \u003cp\u003e\u003cem\u003eP. interpunctella\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e58.00 \u0026plusmn; 6.29 a A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e47.00 \u0026plusmn; 9.43 b A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 78px;\"\u003e\n \u003cp\u003e37.33 \u0026plusmn; 6.30 c B\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e34.50 \u0026plusmn; 2.63 cd A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e32.80 \u0026plusmn; 5.05 cd A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e28.33 \u0026plusmn; 2.95 d B\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 145px;\"\u003e\n \u003cp\u003e\u003cem\u003eS. frugiperda\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e50.00 \u0026plusmn; 12.38 a B\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e43.00 \u0026plusmn; 9.07 ab A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 78px;\"\u003e\n \u003cp\u003e43.33 \u0026plusmn; 10.72 ab A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e33.50 \u0026plusmn; 7.46 bc A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e34.80 \u0026plusmn; 5.96 c A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e33.00 \u0026plusmn; 6.22 bc A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eNote: Data are presented as mean \u0026plusmn; SD. Different lowercase letters within the same row indicate significant differences among density levels for the same host species, while different uppercase letters within the same column indicate significant differences between host species at the same density level (Tukey\u0026apos;s HSD test, P \u0026lt; 0.05).\u003c/p\u003e\n\u003cp\u003eThe number of parasitized larvae increased significantly with increasing host density (Table 1). Post hoc comparisons indicated that the significant interaction stemmed from density-dependent shifts in host species preference. At low densities (5 and 10 larvae/jar), the parasitized numbers of \u003cem\u003eP. interpunctella\u003c/em\u003e were significantly higher than those of \u003cem\u003eS. frugiperda\u003c/em\u003e. However, this trend reversed at a density of 15 larvae/jar, where the parasitized numbers of \u003cem\u003eS. frugiperda\u003c/em\u003e became significantly higher. No significant interspecific differences were detected at other higher densities.\u003c/p\u003e\n\u003cp\u003eThe parasitism rate, in contrast, exhibited a different pattern (Table 1). For \u003cem\u003eP. interpunctella\u003c/em\u003e, the parasitism rate decreased significantly from 58.00% to 28.33% as host density increased, demonstrating a clear inverse density-dependent relationship. In contrast, the parasitism rate on \u003cem\u003eS. frugiperda\u003c/em\u003e did not show a consistent density-dependent pattern. Interspecific comparisons revealed that the parasitism rate was significantly higher on \u003cem\u003eP. interpunctella\u003c/em\u003e than on \u003cem\u003eS. frugiperda\u003c/em\u003e at the low density (5 larvae/jar). However, at medium to high densities (15 and 30 larvae/jar), the parasitism rate was either significantly higher on \u003cem\u003eS. frugiperda\u003c/em\u003e or not significantly different between the two host species.\u003c/p\u003e\n\u003cp\u003eThe subsequent developmental quality of the parasitoid was not significantly affected by host density or host species. Two-way ANOVA followed by Tukey\u0026apos;s test showed that neither cocoon formation rate (Fig. 1A) nor adult emergence rate (Fig. 1B) exhibited any significant differences in any pairwise comparisons between host species at any density, or among different densities within the same host species (all P \u0026gt; 0.05).\u003c/p\u003e\n\u003cp\u003eFurthermore, we identified that the removal of the silken structure produced by \u003cem\u003eP. interpunctella\u003c/em\u003e larvae is a crucial step for the successful cocoon formation and adult emergence of the parasitoid in this host. As shown in Fig. 2, this procedure significantly enhanced the parasitoid\u0026apos;s cocoon formation and adult emergence rates, from 71.52 \u0026plusmn; 17.59% and 74.98 \u0026plusmn; 15.24% (without removal) to 90.00 \u0026plusmn; 10.57% and 92.80 \u0026plusmn; 10.50% (with removal), respectively.\u003c/p\u003e\n\u003ch3\u003e2. Comparative development of\u0026nbsp;\u003cem\u003eMeteorus\u003c/em\u003e\u003cem\u003e\u0026nbsp;pulchricornis\u003c/em\u003e progeny reared from \u003cem\u003ePlodia interpunctella\u003c/em\u003e and \u003cem\u003eSpodoptera frugiperda\u003c/em\u003e\u003c/h3\u003e\n\u003cp\u003eThe developmental parameters of \u003cem\u003eM. pulchricornis\u003c/em\u003e progeny were significantly affected by host origin. When reared at 26\u0026deg;C and provided with 10% honey solution, progeny from \u003cem\u003eP. interpunctell\u003c/em\u003ea exhibited a longer developmental duration (15.27 \u0026plusmn; 0.33 days) compared to those from \u003cem\u003eS. frugiperda\u003c/em\u003e (14.73 \u0026plusmn; 0.50 days) (P \u0026lt; 0.05). Conversely, adult longevity was significantly shorter in the \u003cem\u003eP. interpunctella\u003c/em\u003e-reared group (16.63 \u0026plusmn; 1.99 days) than in the \u003cem\u003eS. frugiperda\u003c/em\u003e-reared group (17.73 \u0026plusmn; 1.64 days) (P \u0026lt; 0.05; Table.2).\u003c/p\u003e\n\u003cp\u003eTable 2.Developmental and morphological characteristics of \u003cem\u003eMeteorus pulchricornis\u003c/em\u003e progeny derived from different host origins\u003c/p\u003e\n\u003cdiv align=\"Left\"\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"626\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 160px;\"\u003e\n \u003cp\u003eParameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003eHost\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003eResult\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003en\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 47px;\"\u003e\n \u003cp\u003e\u003cem\u003et\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 45px;\"\u003e\n \u003cp\u003e\u003cem\u003edf\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 84px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 160px;\"\u003e\n \u003cp\u003ePre-emergence time (days)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eP. interpunctella\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e15.27 \u0026plusmn; 0.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 47px;\"\u003e\n \u003cp\u003e6.417\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 45px;\"\u003e\n \u003cp\u003e102\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 84px;\"\u003e\n \u003cp\u003e\u0026lt;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eS. frugiperda\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e14.73 \u0026plusmn; 0.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e57\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 160px;\"\u003e\n \u003cp\u003eLifespan (days)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eP. interpunctella\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e16.63 \u0026plusmn; 1.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 47px;\"\u003e\n \u003cp\u003e3.129\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 45px;\"\u003e\n \u003cp\u003e106\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 84px;\"\u003e\n \u003cp\u003e0.0023\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eS. frugiperda\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e17.73 \u0026plusmn; 1.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e57\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 160px;\"\u003e\n \u003cp\u003eBody length (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eP. interpunctella\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3.87\u0026plusmn; 0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 47px;\"\u003e\n \u003cp\u003e15.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 45px;\"\u003e\n \u003cp\u003e73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 84px;\"\u003e\n \u003cp\u003e\u0026lt;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eS. frugiperda\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e4.60 \u0026plusmn; 0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 160px;\"\u003e\n \u003cp\u003eForewing length (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eP. interpunctella\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3.07 \u0026plusmn; 0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 47px;\"\u003e\n \u003cp\u003e13.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 45px;\"\u003e\n \u003cp\u003e73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 84px;\"\u003e\n \u003cp\u003e\u0026lt;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eS. frugiperda\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3.63 \u0026plusmn; 0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 160px;\"\u003e\n \u003cp\u003eHind tibial length (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eP. interpunctella\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.35 \u0026plusmn; 0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 47px;\"\u003e\n \u003cp\u003e19.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 45px;\"\u003e\n \u003cp\u003e73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 84px;\"\u003e\n \u003cp\u003e\u0026lt;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e\u003cem\u003eS. frugiperda\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1.67 \u0026plusmn; 0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 52px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eNote: Data in the table are mean \u0026plusmn; SD. Significant differences between host origins were determined by Independent samples t-test\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA correlation analysis revealed no significant linear relationship between developmental duration and adult longevity across individuals (\u003cem\u003et\u003c/em\u003e = 0.687, \u003cem\u003edf\u003c/em\u003e = 55, \u003cem\u003eP\u003c/em\u003e = 0.495), suggesting that extended larval development does not predict increased adult lifespan in \u003cem\u003eM. pulchricornis\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003eMorphological measurements of \u003cem\u003eM. pulchricornis\u003c/em\u003e progeny reared from \u003cem\u003eP. interpunctella\u003c/em\u003e showed significantly smaller body dimensions compared to those reared from \u003cem\u003eS. frugiperda\u003c/em\u003e, with mean body length measuring 3.87 \u0026plusmn; 0.23 mm versus 4.60 \u0026plusmn; 0.18 mm (P\u0026lt; 0.05), mean forewing length 3.07 \u0026plusmn; 0.21 mm versus 3.63 \u0026plusmn; 0.19 mm (P\u0026lt; 0.05), and mean hind tibia length 1.35 \u0026plusmn; 0.11 mm versus 1.67 \u0026plusmn; 0.06 mm (P\u0026lt; 0.05), respectively (Table.2). These results demonstrate consistent and significant size reductions across all three measured parameters (body length, forewing length, and hind tibia length) in \u003cem\u003eM. pulchricornis\u003c/em\u003e progeny developed from \u003cem\u003eP. interpunctella\u003c/em\u003e compared to those from \u003cem\u003eS. frugiperda.\u003c/em\u003e\u003c/p\u003e\n\u003ch3\u003e3. Parasitism performance of \u003cem\u003eMeteorus\u003c/em\u003e\u003cem\u003e\u0026nbsp;pulchricornis\u003c/em\u003e progeny reared from \u003cem\u003ePlodia interpunctella\u003c/em\u003e and \u003cem\u003eSpodoptera frugiperda\u003c/em\u003e\u003c/h3\u003e\n\u003cp\u003eWhen continuously exposed to host larvae, \u003cem\u003eM. pulchricornis\u003c/em\u003e progeny reared from \u003cem\u003eP. interpunctella\u003c/em\u003e and \u003cem\u003eS. frugiperda\u003c/em\u003e exhibited mean adult longevities of 9.40 \u0026plusmn; 0.70 and 10.30 \u0026plusmn; 0.95 days, respectively (Table 3). As shown in Figure 3, both groups displayed a unimodal pattern in daily oviposition on \u003cem\u003eS. frugiperda\u003c/em\u003e, with egg-laying peaking midlife and then declining. Some parasitoids began ovipositing immediately upon emergence and continued parasitism throughout their lifespan.\u003c/p\u003e\n\u003cp\u003eTable 3.Comparative parasitism performance of \u003cem\u003eMeteorus pulchricornis\u003c/em\u003e progeny from different host origins on \u003cem\u003eSpodoptera frugiperda\u003c/em\u003e\u003c/p\u003e\n\u003cdiv align=\"Left\"\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"709\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 292px;\"\u003e\n \u003cp\u003eParameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 122px;\"\u003e\n \u003cp\u003e\u003cem\u003eP. interpunctella\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cem\u003eS. frugiperda\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e\u003cem\u003et\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e\u003cem\u003edf\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 292px;\"\u003e\n \u003cp\u003eParasitism rates (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 122px;\"\u003e\n \u003cp\u003e48.00 \u0026plusmn; 18.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e50.00 \u0026plusmn; 12.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e0.3438\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 76px;\"\u003e\n \u003cp\u003e0.735\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 292px;\"\u003e\n \u003cp\u003eCocoon forming rates (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 122px;\"\u003e\n \u003cp\u003e90.00 \u0026plusmn; 10.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e91.40 \u0026plusmn; 10.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e0.2888\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 76px;\"\u003e\n \u003cp\u003e0.7761\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 292px;\"\u003e\n \u003cp\u003eEmergence rates (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 122px;\"\u003e\n \u003cp\u003e93.60 \u0026plusmn; 10.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e93.00 \u0026plusmn; 11.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e0.1279\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 76px;\"\u003e\n \u003cp\u003e0.8996\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 292px;\"\u003e\n \u003cp\u003eTotal oviposition\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 122px;\"\u003e\n \u003cp\u003e17.10 \u0026plusmn; 4.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e26.70 \u0026plusmn; 4.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e4.654\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 76px;\"\u003e\n \u003cp\u003e0.0002\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 292px;\"\u003e\n \u003cp\u003eLifespan under persistent host exposure (days)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 122px;\"\u003e\n \u003cp\u003e9.40 \u0026plusmn; 0.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e10.30 \u0026plusmn; 0.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e2.415\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 76px;\"\u003e\n \u003cp\u003e0.0266\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eNote: Data are expressed as mean \u0026plusmn; SD\u0026nbsp;of\u0026nbsp;10 replications.,Significant differences between host origins were determined by Independent samples t-test\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePeak daily fecundity occurred on day 5 for \u003cem\u003eP. interpunctella\u003c/em\u003e-reared parasitoids (4.10 \u0026plusmn; 0.94 eggs/day), with a total lifetime fecundity of 17.10 \u0026plusmn; 4.82 eggs. In contrast, \u003cem\u003eS. frugiperda\u003c/em\u003e-reared\u0026nbsp;parasitoids reached peak fecundity on day 6 (6.20 \u0026plusmn; 1.72 eggs/day) (Fig. 3) and produced significantly more eggs over their lifetime (26.70\u0026plusmn; 4.40 eggs) (P \u0026lt; 0.05;\u0026nbsp;Table 3). Senescent\u0026nbsp;parasitoids displayed signs of behavioral decline, including reduced mobility, unstable posture, and loss of flight ability, although some retained oviposition activity until death.\u003c/p\u003e\n\u003cp\u003eAs summarized in Table 3, both groups of progeny performed comparably when parasitizing \u003cem\u003eS. frugiperda\u003c/em\u003e larvae. Mean parasitism rates were 48.00 \u0026plusmn; 18.74% (\u003cem\u003eP. interpunctella\u003c/em\u003e-origin) and 50.00 \u0026plusmn; 12.38% (\u003cem\u003eS. frugiperda\u003c/em\u003e-origin), cocoon formation rates were 90.00 \u0026plusmn; 10.59% vs. 91.40 \u0026plusmn; 10.58%, and adult emergence rates were 93.60 \u0026plusmn; 10.46% vs. 93.00 \u0026plusmn; 11.15%, respectively. None of these differences was statistically significant (P \u0026gt; 0.05 for all comparisons).\u003c/p\u003e\n\u003cp\u003eThese results collectively suggest that although \u003cem\u003eP. interpunctella\u003c/em\u003e-reared progeny exhibited slightly reduced reproductive output, their parasitism performance remained functionally comparable. This supports the feasibility of using \u003cem\u003eP. interpunctella\u003c/em\u003e as a cost-effective substitute host for the mass rearing of \u003cem\u003eM. pulchricornis\u003c/em\u003e under laboratory conditions.\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe search for efficacious substitute hosts represents a core objective in augmentative biological control. Although the Mediterranean flour moth \u003cem\u003eEphestia kuehniella\u003c/em\u003e Zeller has been identified as a potential host for \u003cem\u003eM. pulchricornis\u003c/em\u003e (Nakano et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), its rearing efficiency remains limited around 80% adult emergence even under optimal conditions. As an alternative, \u003cem\u003ePlodia interpunctella\u003c/em\u003e presents a promising option. Our study demonstrates that \u003cem\u003eP. interpunctella\u003c/em\u003e can support the complete development of \u003cem\u003eM. pulchricornis\u003c/em\u003e, with key performance metrics (parasitism rate: 90.00\u0026thinsp;\u0026plusmn;\u0026thinsp;10.59%; cocoon formation: 90.00\u0026thinsp;\u0026plusmn;\u0026thinsp;10.59%; adult emergence: 93.60\u0026thinsp;\u0026plusmn;\u0026thinsp;10.46%) showing no statistically significant difference from those reared on its natural host, \u003cem\u003eS. frugiperda\u003c/em\u003e. As a cosmopolitan stored-product pest, \u003cem\u003eP. interpunctella\u003c/em\u003e offers several potential advantages for mass rearing, including relative ease of maintenance, short generation time, and rapid population growth. These characteristics suggest it could help alleviate some of the challenges associated with natural host high production costs.\u003c/p\u003e \u003cp\u003eThe reduced body size, fecundity and longevity of wasps from \u003cem\u003eP. interpunctella\u003c/em\u003e align with the host-size principle in parasitoid biology (Bai et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Liu et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Progeny from the smaller \u003cem\u003eP. interpunctella\u003c/em\u003e were significantly smaller and less fecund than those from \u003cem\u003eS. frugiperda\u003c/em\u003e, likely due to limited nutritional resources. This resource constraint may also explain the extended developmental period in \u003cem\u003eP. interpunctella\u003c/em\u003e, representing a necessary trade-off under limited resources (Qi et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Suzuki et al., 2006). The absence of correlation between developmental duration and adult longevity confirms that parasitoid lifespan depends more on adult-stage resource acquisition than larval development pace (Jervis et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSpecies-specific density-dependent responses in parasitism further reveal fundamental differences in host\u0026ndash;parasitoid interactions. The inverse density dependence observed in \u003cem\u003eP. interpunctella\u003c/em\u003e aligns with classical foraging models, where host defensive behaviors and parasitoid egg or time limitation drive reduced parasitism rates at higher host densities. Conversely, \u003cem\u003eS. frugiperda\u003c/em\u003e exhibited density-independent parasitism, suggesting weaker host defenses and consistent parasitoid efficiency. This contrast suggests that \u003cem\u003eP. interpunctella\u003c/em\u003e may be particularly well suited for controlled, low-density laboratory colonization, whereas \u003cem\u003eS. frugiperda\u003c/em\u003e appears to maintain more stable parasitism rates across varying densities, a trait potentially beneficial in field conditions.\u003c/p\u003e \u003cp\u003eA crucial step for successful rearing was the removal of the silken structure spun by \u003cem\u003eP. interpunctella\u003c/em\u003e larvae. This removal improved cocoon formation and adult emergence rates by approximately 20%, increasing success rates to above 90%. This finding underscores that host suitability is not solely determined by biological compatibility but can be substantially influenced by physical or behavioral factors, such as the host's silk production. While this step adds to the handling procedure, the significant gain in parasitoid yield confirms its importance in the rearing protocol.\u003c/p\u003e \u003cp\u003eWhile this study confirms \u003cem\u003eP. interpunctella\u003c/em\u003e as an effective and economical substitute host under laboratory conditions, the performance and competitive fitness of \u003cem\u003eM. pulchricornis\u003c/em\u003e reared on \u003cem\u003eP. interpunctella\u003c/em\u003e in complex field environments\u0026mdash;with variables such as fluctuating climate, host-plant interactions, and the presence of alternative hosts and predators\u0026mdash;remain untested and constitute a critical next step for validation. Furthermore, while our assessment focused on the F1 generation, the long-term effects over multiple generations, including potential impacts on genetic diversity, fecundity, and behavior, warrant dedicated investigation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors sincerely thank the Institute of insect Sciences, Zhejiang University, Hangzhou, China, for providing research facilities and support throughout this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePT, XC, XY, ZW and QW conceived the idea, designed the methodology. RS and JL wrote the first draft of manuscript. RS, JL, AS, LY, PW, YY and ZL performed experimentation. RS, JL and XS analyzed the data and prepared results. PT and XC technically edited and proofread the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Key R\u0026amp;D Program of China (2022YFD1401400), the General Program of the National Natural Science Foundation of China (32070467), the Key International Joint Research Program of the National Natural Science Foundation of China (31920103005) and the Fundamental Research Funds for the Central Universities (226-2024-00070).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data are available in the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eArthur FH, Campbell JF, Toews MD (2013) Distribution, abundance, and seasonal patterns of \u003cem\u003ePlodia interpunctella\u003c/em\u003e (H\u0026uuml;bner) in a commercial food storage facility. 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Methods in Ecol Evol, 8(11):1528\u0026ndash;1534. https://doi.org/10.1111/2041-210X.12784\u003c/li\u003e\n\u003cli\u003eQi M, Yin YF, Luo TY, et al (2024) Variation in parasitoid adult size is related to host egg size, maternal state and developmental time. J Appl Entomol 148(9):1060-1067. https://doi.org/10.1111/jen.13323\u003c/li\u003e\n\u003cli\u003eSettle WH, Ariawan H, Astuti ET, et al (1996) Managing tropical rice pests through conservation of generalist natural enemies and alternative prey. Ecology 77(7):1975-1988. https://doi.org/10.2307/2265694\u003c/li\u003e\n\u003cli\u003eSuzuki M, Tanaka T (2006) Virus-like particles in venom of \u003cem\u003eMeteorus pulchricornis \u003c/em\u003einduce host hemocyte apoptosis. J Insect Physiol 52(6):602-613. https://doi.org/10.1016/j.jinsphys.2006.02.009\u003c/li\u003e\n\u003cli\u003eWalker GP, MacDonald FH, Wallace AR, et al (2016) Interspecific competition among Cotesia kazak, Microplitis croceipes, and \u003cem\u003eMeteorus pulchricornis \u003c/em\u003e(Hymenoptera: Braconidae), larval parasitoids of \u003cem\u003eHelicoverpa armigera \u003c/em\u003e(Lepidoptera: Noctuidae) in New Zealand. Biol Control 93:65-71. https://doi.org/10.1016/j.biocontrol.2015.11.005\u003c/li\u003e\n\u003cli\u003eWang Y, Wu X, Wang Z, et al (2021) Symbiotic bracovirus of a parasite manipulates host lipid metabolism via tachykinin signaling. PLoS Pathog 17(3):e1009365. https://doi.org/10.1371/journal.ppat.1009365\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"egyptian-journal-of-biological-pest-control","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ebpc","sideBox":"Learn more about [Egyptian Journal of Biological Pest Control](http://ejbpc.springeropen.com)","snPcode":"41938","submissionUrl":"https://submission.springernature.com/new-submission/41938/3","title":"Egyptian Journal of Biological Pest Control","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Biological control, Meteorus pulchricornis, Plodia interpunctlla, Spodoptera frugiperda, Substitute host","lastPublishedDoi":"10.21203/rs.3.rs-8249784/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8249784/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e \u003cem\u003eMeteorus pulchricornis\u003c/em\u003e is an important parasitoid of various lepidopteran pests with promising applications in biological control. However, its large-scale application has been hindered by the challenges associated with rearing it on natural hosts. This study investigates the use of \u003cem\u003ePlodia interpunctella\u003c/em\u003e, a stored-product pest, as a cost-effective and reliable substitute host for \u003cem\u003eM. pulchricornis\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e While parasitoids reared on \u003cem\u003eP. interpunctella\u003c/em\u003e showed slight reductions in body size and fecundity compared to those reared on its natural host \u003cem\u003eSpodoptera frugiperda\u003c/em\u003e, key performance metrics—such as parasitism rate, cocoon formation rate, and adult emergence rate—did not differ significantly between the two host treatments.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e \u003cem\u003eP. interpunctella \u003c/em\u003eprovides a feasible and cost-effective alternative host for rearing \u003cem\u003eM. pulchricornis\u003c/em\u003e, offering substantial potential for its use in large-scale biological control programs targeting lepidopteran pests.\u003c/p\u003e","manuscriptTitle":"Optimal Use of Plodia interpunctella as a Substitute Host for Cost-Effective Mass Rearing of Meteorus pulchricornis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-09 09:01:03","doi":"10.21203/rs.3.rs-8249784/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-02-05T12:52:08+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-02T11:37:40+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"155995927118788791115611700022077647067","date":"2026-01-20T06:58:42+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-12T08:15:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"162857626401147267768239383663103262896","date":"2026-01-07T12:24:53+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-07T08:20:40+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-18T13:48:09+00:00","index":"","fulltext":""},{"type":"submitted","content":"Egyptian Journal of Biological Pest Control","date":"2025-12-17T12:02:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"egyptian-journal-of-biological-pest-control","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ebpc","sideBox":"Learn more about [Egyptian Journal of Biological Pest Control](http://ejbpc.springeropen.com)","snPcode":"41938","submissionUrl":"https://submission.springernature.com/new-submission/41938/3","title":"Egyptian Journal of Biological Pest Control","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"87d1903b-ccc8-4fec-9867-82c621b98812","owner":[],"postedDate":"January 9th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-03-30T16:29:26+00:00","versionOfRecord":{"articleIdentity":"rs-8249784","link":"https://doi.org/10.1186/s41938-026-00898-z","journal":{"identity":"egyptian-journal-of-biological-pest-control","isVorOnly":false,"title":"Egyptian Journal of Biological Pest Control"},"publishedOn":"2026-03-26 16:10:17","publishedOnDateReadable":"March 26th, 2026"},"versionCreatedAt":"2026-01-09 09:01:03","video":"","vorDoi":"10.1186/s41938-026-00898-z","vorDoiUrl":"https://doi.org/10.1186/s41938-026-00898-z","workflowStages":[]},"version":"v1","identity":"rs-8249784","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8249784","identity":"rs-8249784","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}