Thermal buffering in a sessile insect herbivore

For ectotherms such as insects, which have high surface area-to-volume ratios and are dependent upon environmental temperatures, physiological traits and/or a combination of behavioral mechanisms allow them to temporarily avoid sub-optimal or extreme temperatures typically found in hot, arid regions. However, sessile insects, such as cochineal (Dactylopius spp.) in the Sonoran Desert of the USA, are faced with the challenge of being minimally able to move to avoid extreme heat. Using artificial warming experiments and in situ thermography, we investigated the thermal function of the cottony wax produced over their bodies. We found that the wax buffers the cochineal from high temperatures relative to their host, and that the surface area of the wax reduces the temperature that the insects experience. These results reveal a mechanism for mitigating environmental exposure, a possible trade-off in defensive functions, and the importance of research on insect strategies for a warming climate.