Cricket Courtship

An early fall evening presents us with a symphony of songs emanating from fields far and wide. Most of the musicians are crickets, which are considered more musical than their close relatives, katydids, or their more distant cousins, grasshoppers. Instead of a raspy song, crickets produce melodic chirps. We don't see these musicians as frequently as we do grasshoppers, as they are nocturnal and, although most of the adults have wings and are capable of flying, they rarely do, making them much less conspicuous.

The surprising thing about the cricket's song is that crickets produce it by rubbing their wings against each other. At the base of the left forewing (most insects have two pairs of wings, one in front of the other) there is a very thick vein, or rib. The edge of this rib is serrated, with 50 to 300 minute ridges (the number depends on the species). There is a hard scraper on the right forewing. When the cricket raises its wings and rubs the rib against the scraper, a chirp is produced; this process is called stridulation. As the cricket stridulates, the membranes of its wings vibrate, amplifying the sound. Like birds and frogs, male crickets do the singing, with each species producing a slightly different song, recognizable to other crickets as well as entomologists.

The reason it is important for other crickets to recognize their own species' song is that stridulation is the means by which male crickets attract females in order to mate. Because most of their courtship takes place in the dark, their song is a crucial part of it. Crickets lack ears on their head, but are capable of hearing another cricket's song thanks to a membrane located on each front leg, visible just below the "knee" joint.

Crickets, like all other insects, are cold-blooded and thus, are the same temperature as their surroundings. Generally, the speed of a cricket's song reflects this temperature. The hotter it is, the more rapid the chirps. There is even one species of cricket, the snowy tree cricket, whose chirp-frequency allows you to calculate the temperature. Simply count the number of chirps in 15 seconds, add 40 to that number, and you have the temperature degrees Fahrenheit.