Crickets chirp their songs for a specific purpose. Like many animals they are viciously territorial, engaging in often fatal fights in defense of their space and reproductive rights. But those not willing to fight have their own devious way of finding mates. And they DO bite, just not often.
It is not unusual for some species of insects to all die off during the winter months while the whole gene pool of the species survives in the egg form. Black flies have the same characteristic.
Anatomically the Cricket is very insect-like with the usual three body parts, head, thorax and abdomen. The head contains a brain, such as it is, two compound eyes and two simple eyes that are capable only of sensing light from dark. The jaws, with which the webbing between my fingers is so familiar, are accompanied by a pair of palps, long segmented mouth parts used to manipulate food. The very long antennae serve to sense smell and objects by touch. These are important since when Crickets or Grasshoppers launch themselves into the air they have only a vague idea what obstacles they might encounter in flight. They are a somewhat misguided missile.
The thorax is equipped with four walking legs and two very strong jumping legs. Two fore wings contain the rasp and scrapper with which the male Cricket makes his chirps, and two hind wings. Crickets cannot really fly so much as the wings give it some control over and add length to the powerful jump using the hind legs. The abdomen contains the spiracles, a series of holes on either side used for breathing. Female also have an ovipositor for egg laying.
True Crickets are in the family Gryllidae. They more resemble katydids than grasshoppers. Some very Cricket-like insects are not of the family Gryllidae.
There are over 900 subspecies of Crickets but the ones you are most likely to encounter are these four: House Crickets, Camel Crickets, Field Crickets and Mole Crickets.
Of course the house Crickets are the ones most likely to invade your house, but others can wander by accident into human habitats, especially the Camel Crickets which is often found in dark places in your basement, especially if there are any cracks in your foundation.
What use do humans have for Crickets? In China they are used as pets, for fighting and as food. So you young entrepreneurs, how about cricket ranching.