Reproductive Adaptations
Many Hymenopterans display adaptations for endothermic regulation that
are specifically related to the area of reproduction. Many bumblebee species
(Bombus) are a good example of these adaptations, especially when comparing
temperate zone bees with those that survive in arctic conditions.
Early Emergence
Emerging bumblebee queens in arctic conditions employ several
adaptations to deal with the short season in which it is necessary to
establish a colony. Winter may not break until mid-May and the summer
season can be as short as two months. During this time queens must forage
for their food, rear a brood, and establish a nest, fending for themselves
until workers can be born to allow the colony to grow. Queens employ many
of the already discussed adaptations, such as flight muscle control and
shivering to help them maintain body temperatures high enough to function
in extremely low body temperatures. They also appear much more quickly
than their temperate zone relations. Arctic bumblebee queens were found
flying and foraging on the very first day of snowmelt when willow blossoms,
the earliest available food source, first appeared. The queens also displayed
accelerated rates of foraging (aided by almost continual sunlight), and
had begun to hunt for nests by the second day (Vogt 1994). A full chronology is displayed
in Figure 1 below.
| May 19 | 100% Snow cover; No Willow blossoms; No queens seen |
| May 20 | Snow begins to melt; Willows start blossoming; First queens appear |
| May 21 | First queen seen nest searching |
| May 22 | |
| May 23 | First queen seen carrying pollen |
| May 24 | |
| May 25 | Snow covers less than 10% of ground |
| May 26 | |
| May 27 | 90% of queens are foraging; 10% are nest searching |
| May 28 | |
| May 29 | |
| May 30 | |
| May 31 | |
| June 1 | Queens are still foraging excluseively on Willow |
| June 2 | Only widely scattered snowdrifts remain on the ground |
| June 3 | |
| June 4 | First queen seen foraging on alternate food source (alpine azalia) |
| June 5 | First workers are seen in the field |
Figure 1 Adapted from Vogt 1994
Comparison with Temperate-zone Species
Arctic bumblebees also displayed rapidly increasing ovary masses (50% greater than temperate bees of similar phase) and synchronous emergence. Temperate zone bees lacked synchronous emergence, and took longer to achieve similar ovary masses and colony founding rates when compared to arctic bees as seen in Figure 2 below (Vogt 1994).
Figure 2 Adapted from Vogt 1994