Crickets, family Gryllidae (also known as "true crickets"), are insects somewhat related to grasshoppers and more closely related to katydids or bush crickets (family Tettigoniidae). They have somewhat flattened bodies and long antennae. There are about 900 species of crickets. They tend to be nocturnal and are often confused with grasshoppers because they have a similar body structure including jumping hind legs.
The left forewing of the male has a thick rib (a modified vein) which bears 50 to 300 ridges. The chirp (which only male crickets can do) is generated by raising the left hind leg to a 45 degree angle and rubbing it against the right hind leg edge of the right hind leg, which has a thick scraper (Berenbaum 1995). This sound producing action is called stridulation and the song is species-specific.
There are four types of cricket song: The calling song attracts females and repels other males, and is fairly loud. The courting song is used when a female cricket is near, and is a very quiet song. An aggressive song is triggered by chemoreceptors on the antennae that detect the near presence of another male cricket and a copulatory song is produced for a brief period after successful deposition of sperm on the female's eggs.
Crickets chirp at different rates depending on their species and the temperature of their environment. Most species chirp at higher rates the higher the temperature is (approx. 62 chirps a minute at 13°C in one common species; each species has its own rate). The relationship between temperature and the rate of chirping is known as Dolbear's Law. In fact, according to this law, it is possible to calculate the temperature in Fahrenheit by adding 40 to the number of chirps produced in 15 seconds by the snowy tree cricket common in the United States.
Crickets, like all other insects, are cold-blooded. They take on the temperature of their surroundings. Many characteristics of cold-blooded animals, like the rate at which crickets chirp, or the speed at which ants walk, follow a special equation called the Arrhenius equation. This equation describes the activation energy or threshold energy required to induce a chemical reaction. For instance, crickets, like all other organisms, have many chemical reactions occurring within their bodies. As the temperature rises, it becomes easier to reach a certain activation or threshold energy, and chemical reactions, like those that occur during the muscle contractions used to produce chirping, happen more rapidly. As the temperature falls, the rate of chemical reactions inside the crickets' bodies slow down, causing characteristics, such as chirping, to also slow down.
Crickets have tympanic membranes located just below the middle joint of each front leg (or knee). This enables them to hear another cricket's song.
In 1975, Dr. William H. Cade discovered that the parasitic tachinid fly Ormia ochracea is attracted to the song of the male cricket, and uses it to locate the male in order to deposit her larvae on him. It was the first example of a natural enemy that locates its host or prey using the mating signal. Since then, many species of crickets have been found to be carrying the same parasitic fly, or related species. In response, a mutation leaving males unable to chirp was observed amongst a population of field crickets on the Hawaiian island of Kauai.
Content Resource : http://en.wikipedia.org/wiki/Cricket_(insect)
