Influence of exogenic and endogenic factors on worker reproducktion in Bombus terrestris

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Social insects feature highly complex interactions that add to their enormous ecological impact and success. Chemical communication plays an important role in task sharing and regulation of reproduction. In the bumblebee Bombus terrestris (Hymenoptera: Apidae) the development of worker ovaries and worker reproduction is inhibited by a primer pheromone of the queen as well as so-called signals of fertility. The queen uses both chemical signals to uphold reproductive dominance and thus maintain the social structure of the annual colonies. A characteristic of B. terrestris colonies are two distinct stages of reproductive regulation. In the initial stage the queen is the only reproductive female within the colony. After the so called “competition point” dominant workers with developed ovaries compete with their queen and other workers for the production of male offspring. Despite extensive research, it is still unknown how certain workers overcome the pheromonal inhibition of ovarian development. The aim of this project is to investigate the role of different endogenic and exogenic factors that are suggested to influence the reproductive behaviour of workers in B. terrestris. An integrative approach including chemoecological, neurophysiological, endocrinological and morphological methods will be applied to determine the physiological mechanisms and/or ecological factors that influence the individual decision of a bumblebee worker to lay eggs or not and thus its performance of social tasks.