Caterpillar setae: insulation for an ectotherm.

Gypsy moth caterpillars have long, soft setae distributed along the lateral portions of the body, but only short, stiff setae on the dorsal surface. Setae act as selective insulation for caterpillars by reducing the rates of convective heat exchange without affecting the rates of radiative heat exchange. Changes in posture abolish the effects of the setae by maximizing convection and minimizing radiant heat uptake.