Where to get a meal? An perspective from mixed source of records of the crab spiders hunting ground traits

Where to get a meal? An perspective from mixed source of records of the crab spiders hunting ground traits | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 7 February 2026 V1 Latest version Share on Where to get a meal? An perspective from mixed source of records of the crab spiders hunting ground traits Authors : Bianca Snowarski and Rubem Avila Jr 0000-0003-4004-3980 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.177046040.04207070/v1 147 views 79 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Crab spiders (Thomisidae) are sit-and-wait predators that commonly hunt on flowers and inflorescences, where they may influence plant–pollinator interactions. We investigated whether specific floral reproductive traits are associated with crab spider occurrence and hunting success. Using observational records from Brazil and South Africa, complemented with global data from iNaturalist, we compiled 70 different plant–crab spider interactions and categorized floral morphology, reproductive structure, color similarity, relative size, and hunting success. Crab spiders were more frequently associated with inflorescences, rotate flower types, flowers larger than spiders, and chromatic contrast between spiders and flowers. Inflorescences and rotate flowers showed higher frequencies of successful hunting events, likely due to increased floral visitor abundance. Contrary to expectations, color dissimilarity did not reduce hunting success. Our results validated the use of citizen science to increase our knowledge through the high quality records highlighting the importance of plant reproductive structures and floral accessibility in shaping tri-trophic interactions among plants, pollinators, and their predators, suggesting that patch quality and visitor availability are key drivers of crab spider foraging strategies. Nature notes Where to get a meal? An perspective from mixed source of records of the crab spiders hunting ground traits Bianca Pereira Snowarski and Rubem S. de Avila Jr* Laboratório de Pesquisa em Interações Ecológicas, Universidade Federal do Pampa, campus São Gabriel, Rua Aluízio Barros Macedo, s/n, BR 290 km 423 CP 02 CEP 97300-970, São Gabriel, Rio Grande do Sul, Brazil * Corresponding author: [email protected] RS Avila Jr ORCID: https://orcid.org/0000-0003-4004-3980 Abstract Crab spiders (Thomisidae) are sit-and-wait predators that commonly hunt on flowers and inflorescences, where they may influence plant–pollinator interactions. We investigated whether specific floral reproductive traits are associated with crab spider occurrence and hunting success. Using observational records from Brazil and South Africa, complemented with global data from iNaturalist, we compiled 70 different plant–crab spider interactions and categorized floral morphology, reproductive structure, color similarity, relative size, and hunting success. Crab spiders were more frequently associated with inflorescences, rotate flower types, flowers larger than spiders, and chromatic contrast between spiders and flowers. Inflorescences and rotate flowers showed higher frequencies of successful hunting events, likely due to increased floral visitor abundance. Contrary to expectations, color dissimilarity did not reduce hunting success. Our results validated the use of citizen science to increase our knowledge through the high quality records highlighting the importance of plant reproductive structures and floral accessibility in shaping tri-trophic interactions among plants, pollinators, and their predators, suggesting that patch quality and visitor availability are key drivers of crab spider foraging strategies. Introduction Crab spiders (Araneae, Thomisidae) are masters of the art of patiently waiting for their snacks (Fig.1). These cursorial predators (non-web-building) employ a sit-and-wait strategy to get their preys (Morse, 2007). The foraging strategy for food is a species trait associated with different weapons and behaviours that involves a trade-off between costs and energetic benefits from captured prey (Anderson, 1970; Bell, 1991; Cloudsley-Thompson, 1996). By remaining still instead of actively searching, crab spiders reduce the costs of the constant foraging, especially when prey are fast-moving (Ross & Winterhalder, 2015), and this seems to be the case with their meals. Flowers and inflorescences of flowering plants serve as their hunting grounds, where they ambush a variety of insect species. Many crab spiders enhance their success through camouflage, either by mimicking the colors of the flowers or by minimising chromatic contrast (Chittka, 2011; Marrero et al., 2014; Vieira, et al., 2017). However, the prey are often insects, which are potential pollinators of the plants used, and hence these crab spiders can influence the dynamics of plant-pollinator interactions, altering the behaviour of floral visitors with potential effects on plant reproduction (Dukas, 2005; Kelley et al., 2017). Despite this potential adverse effect, the presence of crab spiders on flowers could result positively as flower-eating herbivores (Romero & Vasconcellos-Neto, 2004), and the overall effect of crab spider presence on flowers will be context-dependent (Knauer et al., 2018). Plant-pollinator interactions result from specific communication between the plant and pollinator through many kinds of floral cues. In this way, flower colors, chemical scent volatiles, or tactile signals on some perianth structures have a fundamental role in the floral reward location and availability on flowers (Dötterl & Vereecken, 2010). Some studies have pointed out that the same floral cues cited above, used by pollinators, can be involved in the crab spider’s attraction to those reproductive structures (Heiling et al., 2003, 2004; Defrize et al., 2010; Knauer et al., 2018). Thus, a tri-trophic interaction system emerges from this particular scenario, with plants, their pollinators and the pollinator’s predators configuring a very intriguing complex interaction system driving the plant community structure, the ecosystem dynamics and the evolutionary history of flower traits (Marrero et al., 2014; Vieira et al., 2017; Abdala-Roberts et al., 2019; Benvenutti, 2022). During the last years, we have accumulated some observations of crab spiders inhabiting flowers and inflorescences in several plant species. Some of them were made in KwaZulu-Natal and Cape Town states, South Africa, during a researcher visitor period (2018-2019, R.S Avila Jr) (Fig.1A, B), and others from our locality at subtropical grasslands from Rio Grande do Sul, Brazil (2020-2025). After a careful look at the personal pictures from both places, a question came to light: is there some pattern in the floral structures behind the crab spider choices promoting a higher probability of hunting success? We hypothesised that plant species with less restrictive reproductive structures to pollinators and inflorescences, instead of isolated flowers, will have more interactions observed with crab spiders. Besides that, high similarity between flower and spider colors and smaller flowers than spiders would be prevalent despite some indication of chromatic contrasting between crab spiders and flowers having been observed (Welti et al., 2016). All these hypotheses are associated with the prediction that these parameters will favour the crab spider hunting process through an increasing rate of floral visitors on flowers and inflorescences of the plants. Material and Methods To answer our question, we utilized interactions observed from our database (data from Brazil and South Africa) and added several other interactions from around the world to increase our predictive potential of the plant traits associated with crab spiders. For this, we utilized the records of plant-crab spiders from the INaturalist database (inaturalist.org) utilizing “Thomisidae” as a key-word on website. All the image records used in our study must have good quality to enhance the Thomisidae identification and the plant reproductive structures traits evaluation (Fig. 1C, D). In this way, we recorded 70 different plant-crab spider interactions (60 from iNaturalist website and 10 other from our database). The two images utilized here had the respective author’s license. With the selected image records we categorized the plant reproductive structures and the crab spiders associated with them. For each image record, we determined the colors of the flowers and crab spiders inhabiting and wheter they were similar or different, the size of the crab spiders in relation to the flowers occupied, the kind of reproductive structure of the plant (isolated flowers or inflorescences), and the morphological type of flowers (campanulated, rotated, tubular, papilionated, and labiated). Additionally, all image records were verified in relation to hunting success based on the prey presence. To verify differences in the proportions of the various categories attributed to interaction records compiled from the two databases, we utilized a chi-square test. To verify the differences in crab spider hunting success between the categories, we compare the frequencies of hunting observations in the different categories with the distribution of frequencies of the different categories observed through a goodness-of-fit test. So, significant results of this test mean that the distribution of frequency of hunting events was not associated with the distribution of frequency of other categories evaluated. All results were considered statistically significant at a p-critical value of 0.05 and were performed in R (R Core Team 2024). Results Three-quarters of the interaction records showed a chromatic contrast between flower and crab spider (Chi-square Test, χ2 = 17.128, d.f = 1, p < 0.001) with non-significant difference in the frequency of captured preys observed for this dissimilarity (Chi-square Test, χ2 = 2.12, d.f = 1, p = 0.14) denoting a more effective hunting success when spider and flower differing in colors (Fig. 2 A). Crab spiders were in most of the 50% of the records smaller than inhabited flowers (Chi-square Test, χ2 = 23.44, d.f = 2, p < 0.001) with higher incidence of hunting success in this case (Chi-square Test, χ2 = 0.82, d.f = 2, p = 0.66) (Fig. 2 B). In relation to the reproductive structure traits of the plant species, we recorded a prevalence of observations of crab spiders inhabiting inflorescences (more than 75% of the records) compared to isolated flowers (Chi-square Test, χ2 = 17.13, d.f = 1, p < 0.001). Once more this kind of reproductive structure promoted a higher number of successfull hunting events (Chi-square Test, χ2 = 1.16, d.f = 1, p = 0.98) (Fig. 2 C). Regarding to flower type, almost 75 % of the crab spiders records were made in plant species presenting rotate flowers (Chi-square Test, χ2 = 43.89, d.f = 4, p < 0.001) with higher prevalence of hunting success in this flower morphology than other flower morphologies (Chi-square Test, χ2 = 1.95, d.f = 4, p = 0.74) (Fig. 2 D). Discussion Hunting for too long on low-quality patches must be critical to crab spiders’ fitness (Morse & Fritz, 1982), and the choices that optimize the energetic gain will be favoured in the hunting patch selection. Studies indicate that the spider’s choice is influenced by a combination of visual characteristics of the flowers, prey abundance, and the compatibility between the spider’s and flower’s colors (Heiling et al., 2003; Defrize et al., 2010). Despite some bias could occur on the use of citizen science database (iNaturalist), our results confirm some preferences associated with plant reproductive structures and the hunting success of crab spiders. The high prevalence of crab spiders found in inflorescences and in rotate flower types could be related to benefits associated with a higher probability of floral insect visitors as postulated by Fornoff et al. (2016). Robakiewicz and Daigle (2004) experimentally highlighted the significant effect of the number of flowers as a proxy of patch quality. Added to this, morphologically complex flowers (e.g. bilateral symmetry and tube-like corolas) are recognized as restrictive to floral visitors, constrasting with the more pollinator visits to open and accessible floral morphologies, such as rotate flowers (Bosh et al., 1997; Krishna &Teaser, 2018), increasing the hunting probability by crab spiders as we found in this study. Contrasting results were found in a Cerrado plant community from Brazil, where Rocha-Filho & Rinaldi (2011) found prevalence of crab spiders in campalulated and tube-like flowers. However, their analysis considered the small flower tubes from Asteraceae flowers as a tubular category, and we recognized them as a functional rotate inflorescence (with non-restriction to insect pollinators). Regarding flower color, we found a significant dissimilarity between flower and spider colors accordingly with experimental studies that pointed out the crucial role of contrast between flower and spider colors (Heiling et al., 2005; Peixoto et al., 2012; Welti et al., 2016). The mechanisms that guide the crab spider’s choice remain poorly explored and could be related to the effective reflection of UV light, as highlighted by Vieira et al. (2017). However, despite our evaluation being made from a human vision perspective, our study shed some light on the chromatic contrast effects between flowers and spiders and the fundamental role of reproductive plant structures that promotes a higher probability of insect visits like the open wide floral morphology. Data Availability Statement The data used in this work is availiable on Figshare repository https://doi.org/10.6084/m9.figshare.31266460. 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Q. (2017). Crab spider lures prey in flowerless neighborhoods. Scientific Reports, 7, 9188. https://doi.org/10.1038/s41598-017-09456-y Figure captions Figure 1 : Some interactions between crab spiders (Thomisidae). Personal observations from South Africa with spiders inabhiting Scabiosa sp. and preying a monkey beetle (Coleoptera, Scarabaeidae) (A) and in Tritoniopsis parviflora inflorescences (B). Two others examples of records from Inaturalist database (autorizhed by their authors) (C and D). Figure 2: Histograms of records from personal and Inaturalist database of the interactions between crab spiders (Araneae, Thomisidae) and plants (blue columns) and the effective hunted preys recorded (green columns) associated to each category. A) Frequency of interactions recorded associated with the colours of the spider and the reproductive structure of plant similar colours (left columns) and different colours (right columns); B) Frequency of interactions in different spider-floral structure size categories (spiders bigger, smaller and similar than flowers sizes, respectively in the abscisse axis); C) Frequency of interactions when reprodcutive structures were isolate flowers (left columns) or inflorescences (right columns) and D) the frequency of interactions associated to flower morphology (campanulated, rotated, tubular, papilionated and bi-labiated respectively in the abscisse axis). Information & Authors Information Version history V1 Version 1 07 February 2026 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords behavioral ecology comparative invertebrate natural history terrestrial Authors Affiliations Bianca Snowarski Universidade Federal do Pampa - Campus Sao Gabriel View all articles by this author Rubem Avila Jr 0000-0003-4004-3980 [email protected] Universidade Federal do Pampa - Campus Sao Gabriel View all articles by this author Metrics & Citations Metrics Article Usage 147 views 79 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Bianca Snowarski, Rubem Avila Jr. Where to get a meal? An perspective from mixed source of records of the crab spiders hunting ground traits. Authorea . 07 February 2026. DOI: https://doi.org/10.22541/au.177046040.04207070/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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