The ontogeny of the social structure in a captive Bombus terrestris colony

Abstract

In this paper the results are presented of an analysis of the interaction—structure and dominance hierarchy in a captive Bombus terrestris colony. The results show that: 1. The workers start their lives at a position on the hierarchical ladder far removed from that of the queen and subsequently approach the queen. Once a worker has reached a position on the queen-side of the axis, established in a principal co-ordinate analysis (PCA), she remains on that side until the queen leaves the nest. At all stages of the observation period the number of workers at the queen-side of the axis is about one quarter of the entire population. The workers who approach the queen generally become laying workers. 2. The dissimilarity between the queen and the workers on her side of the axis (the ‘elite group’) is remarkably constant. The elite workers show more interaction with other workers than do the common workers and they have a high dominance index towards workers in transition towards the elite group. Workers tend to interact more frequently than estimated with their own age class than with others. During the period of their admission to the elite the older workers show an increased frequency of interaction with the queen. 3. After the departure of the queen many of the older workers drop to a lower position; a false queen emerges who has a position similar to that of the queen. Force of numbers, rather than senescense of the queen, seems to cause the queen's loss of dominance.