RESOURCE AVAILABILITY AND TIMING OF REPRODUCTION IN BUMBLE BEE COLONIES (HYMENOPTERA, APIDAE)

North temperate bumble bee colonies produce workers for the first part of the summer, then, at some point, switch to rearing only reproductives. The firs occurrence of males and gynes (new queens) of one bumble bee (Bombus flavifrons) was used to estimate when the reproductive switch point occurred in colonies distributed among 20 discrete subalpine meadows. Occurrence of reproductives in meadows was correlated with forager and flower abundance: males and gynes appear earlier in meadows with high forager and flower densities. While males were observed in each of the 20 meadows, gynes occurred in only 15. The five meadows where gynes were not observed had lower flower densities and supported significantly fewer foragers relative to meadows producing gynes. Differences among meadows in phenological patterns of flower availability were not related to the temporal occurrence of reproductive switch points.