Extra molting, cannibalism and pupal diapause under unfavorable growth conditions in Atrophaneura alcinous (Lepidoptera: Papilionidae)

Abstract

Atrophaneura alcinous adopt multiple strategies such as extra molting, cannibalism and pupal diapause under unfavorable growth conditions. The conditions under which these strategies are adopted have been separately verified, but their relationship has often been overlooked. We examined which strategy A. alcinous adopted and the relative advantages of strategies using four experimental groups under different food quantity and individual density conditions. Our results indicated that A. alcinous often extra‐molted, prolonged the larval period, and larval and pupal weights were lighter under food shortage. Cannibalism and disease often occurred under the high density and food shortage condition. We also showed that individuals cannibalized during the prepupal or pupal period were less likely to extra molt before they were killed. Extra molting tended to occur more frequently in females than in males under a shortage of food. In addition, we showed that, when food was insufficient, A. alcinous might initiate pupal diapause under low densities, but not under high densities. These results suggest that A. alcinous prolongs the larval period by engaging in extra molting during times of unfavorable food conditions. This strategy might decrease the risk of cannibalization because surrounding larvae who could potentially cannibalize others pupate before larvae who prolong the larval period pupate. Our results also suggest that diapausing pupae under a shortage of food can only survive when there are few surrounding conspecifics, due to a lower cannibalization risk. In conclusion, there is a complex interaction between extra molting, cannibalism and pupal diapause strategies.

Sex and stress modulate pupal defense response in tobacco hornworm

“…For example, Bowers (1980 , 1981 ) found that Euphydryas genus adults are usually not palatable to their predators due to sequestration of iridoid glycosides from host plants ( Bowers 1980 , 1981 ). However, in between the larval and adult stages, holometabolous insects have a semi-dormant pupal stage that is comparatively immobile and resting ( Torres-Muros et al 2016 ; Nakahara et al 2020 ), making it possibly the most vulnerable stage against potential predators.…”