Some (perhaps most) insects respond to changes in light intensity even when all known photoreceptive structures are rendered inoperative. This dermal light sense has been attributed to the response of individual neurons in the brain and/or ventral nerve cord. There is also convincing evidence that some insects can perceive infrared radiation (heat), although specific receptors for this ability have not been described.
Blind cavernicolous beetles of the genus Anophthalmus respond to the light of a candle. Blinded Blattella and Perplaneta still settle for preference in the dark after complete blinding. Caterpillars will go towards a source in the dark after complete blinding. A dermal light sense is present in all the tergites of the larvae of Acilius and Dytiscus but is particularly well developed in the region of the spiracles at the end of the abdomen. The antennae of apis fabae appear to be the site of a dermal light sense which is source of kinetic stimulation. In all these cases it is important to be sure that it is the light itself which is the effective stimulus, and not the heat into which it degenerates after absorption.