First record of a mermithid nematode (Nematoda: Mermithidae) parasitizing winged females of gall-forming aphids (Hemiptera: Aphididae: Eriosomatinae)

Juvenile mermithid nematodes were found to parasitize winged females (sexuparae) of Erisoma auratum and Tetraneura radicicola . The morphological characteristics of mermithid nematodes are briefly described. The 18S rDNA and 28S rDNA extracted from one nematode were sequenced and used to construct a Bayesian phylogenetic tree, on which the host ranges of mermithid nematodes were represented. Our study indicated that mermithid parasitism of sexuparae led to fewer and smaller sexual female embryos. This is the first record of a mermithid in relation to eriosomatine aphids and the fourth record with respect to Aphididae.