First Report of a Mermithid Nematode Parasite on Coccinella transversalis (Fabr.) (Coleoptera: Coccinellidae) from Rajnandgaon, Chhattisgarh, India

Mermithids are parasitic nematodes belonging to phylum Nematoda which are generally translucent white, thin, and cylindrical in shape. Mermithids vary in length ranging from 10-100 mm and are easily detectable in host insects simply by dissection or when they leave their hosts. Mermithid infective juveniles cause significant disruption in the morphology, physiology, and behavioral responses of the various host insects. The present infection on Cocconella transversalis was observed during survey of crop cultivating areas during August-September 2024, in which adult beetles of C. transversalis were collected on the leaves of Parthenium weed from a Horticulture farm situated in Surgi- village of Rajnandgaon, Chhattisgarh, India. Notably, nematodes were found only in stink bugs collected from plants, not those attracted to store lights, suggesting potential host behavioral changes. DNA sequencing and morphological analysis identified the nematodes as belonging to Hexamermis. Mermithids belong to a family of nematodes specialized in parasitizing insects and play a significant role in regulating insect population dynamics. This finding opens new possibilities for considering mermithids as potential biological control agents for triatomine insects.