2025/07/14 by Joseph C Iacovazzi, Jin Joo Yun, Dylan Miller +3
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · #Entomological Studies and Ecology #Lepidoptera: Biology and Taxonomy #Insect-Plant Interactions and Control
paper · doi:10.1093/aesa/saaf031
Abstract Caterpillars of the tobacco hawkmoth, Manduca sexta (Sphingidae) (Linnaeus, 1763), can strike by whirling their mandible-bearing head capsule toward an aversive stimulus and biting. The strike response may defend the caterpillars against parasitism by the wasp Cotesia congregata (Say, 1836). We hypothesize that in parasitized caterpillars, this behavior may be manipulated so the caterpillars exhibit elevated defensive behavior for the developing wasp larvae, preventing additional parasitic events, which we show can be deadly to host and parasitoid. We compared the thresholds for strike behavior in response to a mechanical stimulus between parasitized and unparasitized M. sexta. We also explored the differences in sensitivity to touch between parasitized and unparasitized M. sexta. We then asked whether already parasitized caterpillars might defend themselves (and their parasitoids) more effectively than caterpillars that have not previously encountered a wasp. If such were the case, the caterpillar could serve as bodyguard for the parasitoid by exhibiting elevated defensive behavior. Finally, we asked whether the strike response is an effective way to ward off parasitism initially. To do this, we examined whether unparasitized caterpillars with innately lower strike thresholds were more difficult for a wasp to parasitize than less sensitive caterpillars. We measured the time to parasitism and the number of defensive strikes by the caterpillar and correlated these to the initial strike sensitivity of each caterpillar. Taken together, our results indicate that the parasitized caterpillars are more likely to ward off additional parasitic events, protecting not only themselves but also the growing wasp larvae they are hosting.