D3422: Neonicotinoids and pyrethroids can cause arrested ecdysis in Coleoptera

Recently, we reported a novel mode of action in several Lepidoptera larvae exposed to neonicotinoid insecticides: arrest in pupal ecdysis following successful larval ecdysis. In this poster, we explored this phenomenon in several species of Coleoptera. Topical application of neonicotinoids and pyrethroids to pupae caused arrested ecdysis when adults tried to emerge. After application of the insecticide the adults continued to develop as seen below the pupal cuticle. When the adults tried to emerge, they initiated ecdysis with typical pre-ecdysis movements followed by the abdominal pupal cuticle starting to be shed along with the major tracheal branches. However, at this stage the ecdysis process was arrested and the adults could not shed the remainder of the pupal cuticle and partially shed trachea. The wings remained unexpanded, the head and thoracic ecdysial line did not break, and the legs did not straighten as would happen during normal adult ecdysis. The adults are still alive as observed by antennae and leg movements. We will report on dose response profiles for 5 neonicotinoids and 3 pyrethroids. The mode of action of these insecticides with regards to how they are causing arrested ecdysis will be discussed. This research has implications in risk assessment and pest management. Additionally, it will broaden our understanding of the insect ecdysis process and help elucidate the interplay between neuroendocrine hormones and neurotransmitters.