Circulation Combines and Integrates Functions

Bees are efficient. One moving fluid serves multiple functions. Not only does circulating hemolymph transport foodstuffs, hormones, immune cells and wastes, it shuttles heat around the body and dissipates it to the environment cooling thoracic engines that power the wings and legs. For example, heating and cooling are reasons why we might try to emulate insects in building our smallest devices: A flying mosquito maintains less than a one degree centigrade difference between the temperature of its body and the temperature ofthe air swirling around it. The mosquito maintains this temperature differential despite enormous heat production. Taking size into account, larger honeybees heat up their thoraxes to about fifteen degrees centigrade. Having larger thoraxes and, therefore, smaller surface to volume ratios than mosquitoes, honeybees must generate and then maintain higher temperature gradients before achieving the requisite rate of dissipation of heat. One converse of this principle is that arctic bumblebees are quite hairy. Hair helps retain body heat, but in comparison, tropical bees at low elevations may be quite naked facilitating heat dissipation.

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