Ovary development in bumble bee queens: the influence of abdominal temperature and food availability
The influence of abdominal temperature (Tab) on ovary development was determined for queen bumble bees (Bombus impatiens) recently aroused from hibernation. Ovary growth was accelerated in queens with high Tab: after 6 days, laboratory-reared queens with mean Tab = 24°C showed negligible ovary growth (compared with the ovaries of queens sacrificed before arousal from hibernation), whereas queens with mean Tab = 27 and 32°C exhibited near 35 and 135% increases, respectively. The presence of pollen and honey in the diet also had a pronounced effect on ovary development. Queens provided with pollen and honey ad libitum nearly tripled the mass of their ovaries in 8 days, whereas bees fed pollen alone or honey alone showed about a 50% increase. Queens provided with neither pollen nor honey exhibited about a 25% increase in ovary mass during the same period (all queens presumably can gain sustenance for ovary development from the reserve of food left in their honey crop when they emerge from hibernation). These results show that ovary growth can be rapid when queens maintain a high Tab with access to ample pollen and nectar, thereby enabling them to potentially accelerate colony founding. High Tab and nearly continuous access to food are factors that enable bumble bees to successfully rear colonies in a short growing season.