A new type of infrared organ in the Australian "fire-beetle" Merimna atrata (Coleoptera : Buprestidae)

The Australian buprestid beetle Merimna atrata (Coleoptera: Buprestidae) ap proaches forest fires because its larvae develop in freshly burnt wood. So far nothing is known about possible sensory systems enabling the beetles to detect fires and to cope with the thermal environment close to the flames. We found that M. atrata has two pairs of infrared (IR) organs on the ventr olateral sides of the abdomen. Each IR organ consists of a specialized IR-a bsorbing area which is innervated by one thermosensitive multipolar neuron. The primary dendritic branches ramify into more than 800 closely packed te rminal endings which contain a large number of mitochondria. We called the special morphology of the dendritic region a terminal dendritic mass. The t ype of IR receptor found in M. atrata is unique in insects and can best be compared with the IR organs of bold snakes.