Defense Date


Document Type


Degree Name

Master of Science



First Advisor

Dr. Karen Kester

Second Advisor

Dr. Salvatore Agosta

Third Advisor

Dr. Shelley Adamo

Fourth Advisor

Dr. Derek Johnson

Fifth Advisor

Dr. D'Arcy Mays


Insect thermoregulatory research has demonstrated evidence of variation occurring within and among species with respect to infection, pathogens, and parasitism, but few studies have examined differences in thermoregulatory behavior in a host-parasite system with a coevolved symbiotic virus. I investigated the role of parasitism by Cotesia congregata (Say) (Hymenoptera: Braconidae) on the thermoregulatory behavior of Manduca sexta (L.) (Lepidoptera: Sphingidae) using an experimental design in a thermal gradient chamber and a complementary observational field study on wild M. sexta collected from tobacco farms. Parasitism and larval age were not found to have a significant effect on the preferred body temperature of M. sexta caterpillars. However, an interaction between parasitization status and larval age resulted in significant differences in the change in body temperature from the beginning to the end of the experiment. I believe this can be explained by both parasitized and unparasitized caterpillars at later instar stages having a greater temperature lag (surface temperature - body temperature). Results indicate the combined effect of parasitism by C. congregata and infection with a coevolved symbiotic virus does not induce behavioral fever in M. sexta. While thermoregulation did not differ between parasitized and unparasitized caterpillars in the thermal gradient chamber, caterpillars with post-emergent wasp larvae were found significantly higher on plants at collection sites than unparasitized caterpillars. In light of the field results, I recommend that a standardized thermal gradient chamber with an additional vertical axis be used in future studies of lepidopteran thermoregulation.


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Available for download on Wednesday, May 21, 2025