Some like it hot: the Firebrat Thermobia domestica

One of the pleasures of being a professional biologist is that people often bring things for me to identify that I might otherwise never see. This strange insect – a firebrat Thermobia domestica – arrived today in a jam jar. It was a little tattered – with a couple of broken tail spines and a damaged antenna, but still very much alive.

 

Firebrats are relatives of the much more familiar silverfish – primitive wingless insects belonging to an order known as the thysanura and commonly known as bristle-tails. One of their most curious features is that they’re totally covered with overlapping, iridescent scales rather like the scales on a butterfly’s wing.

Unlike silverfish, which tend to live in damp places like the space under baths and cupboards under stairs, firebrats can only survive in warm places and are very drought tolerant. They thrive at temperatures of around 37C and were once common inhabitants of crevices around bread ovens in bakeries. The name firebrat refers to the fact that crevices around hearths of open fires also suited then very well.

Thysanura, the name of the order to which bristletails belong, is derived from two Greek words meaning ‘fringed tail’ and you can see here the fringes on the central tail filament and its two flanking cerci. A large specimen is about a centimetre long, including the tail filament.

As soon as the insect was placed under the warm light of a microscope it perked up and demonstrated its ability to move like greased lightning. I’d rather like to get hold of a few more specimens, because I came across this fascinating description of their courtship in a book called The Living House by George Ordish, published back in 1960. “Firebrats have a curious courtship procedure”, he writes, ”not unlike that of the display of birds. The male dances in circles around the female and repeatedly touches her with his antennae. The actual mating is somewhat akin to that of spiders in that the male deposits a sperm bag in front of the female and then retires, while the female herself undertakes the necessary movements to absorb it, if she so desires”.