Melanophila acuminata (De Geer), along with other members of the submenus Melanophila, has the habit of flying to forest fires and other sources of heat. Infrared receptors and wax glands are situated in pits next to the middle coxal cavities. Sense organs averaging 70.8 were found in the pits of 23 beetles examined. Each sense organ consists of a spherical, cuticular structure, approximately 15μ in diameter, with a central cavity that is connected to the distal process of a nerve cell. Adjacent to each sense organ there is a wax gland continuously secreting strands of wax which serves to protect the organs from dust particles. The sense organs probably function by selectively absorbing the wavelengths of greatest energy emitted by the forest fires. However, the mechanism of this selectivity is unknown.