Author (Your Name)

Tara Bergin, Colby College

Date of Award


Document Type

Honors Thesis (Open Access)


Colby College. Biology Dept.


Catherine R. Bevier


Competition is important in environments with limited resources. Males of many insect species are territorial and will defend resources, such as a food source or egg-laying site, against intruders, or even compete to attract a mate. In insects, evidence suggests that juvenile hormone acts as an aggression mediator, much like testosterone in other animal species. In this study I tested this idea using a group of male Painted Lady butterflies, Vanessa cardui, and Eastern Black Swallowtail butterflies, Papilio polyxenes, that were treated prior to metamorphosis with either a high or low dose of methoprene acid (a juvenile hormone mimic). Male-male encounters were staged with treated and untreated adults or males treated with a high dose or low dose to observe effects of hormone augmentation on aggression and territoriality. Hemolymph was sampled from larvae and analyzed for JH content using gas chromatography. In each encounter a female was positioned to witness the encounter; after a winner was determined, she was released and allowed to choose a male. Male V. cardui treated with either a high or low dose of methoprene were significantly more likely to win an encounter over a control male, and males given a high dose of methoprene were more likely to win an encounter over a male given a low dose. This result suggests that juvenile hormone influences the aggressive potential of male V. cardui butterflies. High mortality among adult P. polyxenes limited the experimental data collection for that species. Finally, females were not interested in males of any dosage and showed no preference. This suggests that females of V. cardui are not choosing males based on JH level or perhaps not in captivity.


Juvenile hormones, Painted lady (Insect), Vanessa (Insects), Black swallowtail butterfly, Butterflies -- Evolution, Butterflies--Behavior

Included in

Biology Commons