Feeding frequency and caste differentiation in Bombus terrestris larvae

The frequency with which bumble bee larvae are fed during their development was studied using video-recordings. The behaviour of the workers while feeding worker, male and queen larvae of Bombus terrestris was recorded. At the beginning of development, female larvae of both castes were fed at a similar frequency. However, during their last phase queen larvae were fed much more often than worker larvae. Despite the differences in frequency, both queen and worker larval feeding followed a similar pattern. Male larvae were fed more often than worker larvae, but less often than queen larvae. They also differed from the female larvae in the way their feeding frequency increased during development. This suggests that the process of feeding male larvae occurs in a different way. The time intervals between feedings were very variable for all larvae: from a few seconds up to 3 h. Although there was a general tendency for the intervals to decrease in duration with larval development, the irregularity was always present. The differences in feeding frequency found at the individual level for larvae of the same age and the irregularity of the feeding process can be explained by the variation in the amount of food per feeding. Finally, our data suggest that larvae play an active role in the regulation of the feeding process. This subject is discussed and compared to the situation in honey bees.