The relation between worker numbers and the production of males and queens in the bumble bee Bombus perplexus

The first-brood worker populations of 18 artificially fed colonies of Bombus perplexus were adjusted to two, four, or eight and allowed to treble with the emergence of the second brood. The timing of male production was independent of the number of workers present and independent of the time of colony initiation. Consequently the duration of the premale period was correlated with the earliness of colony initiation. The first queens emerged after a mean delay of 3.2 days after the first males, this delay being shorter if more workers were present. The rate of pollen consumption per unit larval area was lower with only two workers present than when there were four or eight, but no association was found between the time of initiation of queen production and high ratios of worker numbers to larval area.