Sex and age related changes in the locomotor activity and phototactic behaviors of two closely related species of Camponotus ants

Abstract

A virgin ant queen has only one opportunity in her lifetime to realize her reproductive fitness when she leaves her nest for a mating flight. After successful mating she sheds her wings, excavates a nest and starts laying eggs to initiate her own colony. Here we report the results of our study on two related species of Camponotus ants - day active Camponotus paria and night active Camponotus compressus - aimed at investigating (i) if there exist inter-species differences in the activity and phototactic behaviors of males and queens, (ii) whether these behaviors in the queen change after mating, and (iii) whether the activity rhythm of queens changes with age. We find that while activity profiles differ between C. paria and C. compressus virgin males and queens, such differences in queens disappear after mating. Once mated, the activity rhythm of queens shows little change with age; the rhythm in virgin queens, on the other hand, changes considerably. As virgins, C. paria queens are positively phototactic, while C. compressus queens are negatively phototactic. After mating, C. paria queens become less phototactic, particularly during the subjective night, while C. compressus queens remain negatively phototactic. These results indicate that there are considerable differences in the activity and phototactic behaviors of virgin queens of the two related species of Camponotus ants. Most of these differences disappear after mating, which suggests that these behaviors may have evolved primarily for the proper execution of pre-mating events.