Crickets

Nighttime brings out animals that are nocturnally active or that may simply be more noticeable during night hours.  Rarely seen, but heard widely throughout the night, members of the cricket family, Gryllidae, may call at all hours of the day, or sing only during the night.  Crickets are in the order Orthoptera, distinguished by having two pairs of wings, long, segmented antennae, chewing mouthparts, and the ability to sing by rubbing one body part against another.

There are six groups of crickets found in Illinois encompassing many species.  Field crickets are small, up to an inch long, black or dark red, and live in undergrowth that provides protection from wind and cold.  Found across all of North America, adults and young cannot survive freezing temperatures and whole populations die off in the northern part of their range each year, while southern populations may produce multiple generations.  Eggs are laid singly, in the soil in autumn, and a new generation hatches the following spring.  A second group, house crickets, are not native to North America, and also cannot survive winter.  Imported for many years as fishing bait and pet food, many escape to live and reproduce indoors.  Females emit a chemical repellant to other females that encourage them to start new families elsewhere.

Two additional groups, bush crickets and tree crickets, are common throughout the United States.  Residing in trees, shrubs, and other vegetation, they are excellent singers.  Females, locating a male to mate with by his song, nudge the male to interrupt his singing and they mate.  The female punches a series of pin-like holes in thin bark, filling each with mucus and one egg, then plugs holes with chewed bark.  The pattern of holes can be used to determine the species.  Eggs overwinter under the bark, hatching in spring.  Nymphs grow into adulthood by mid-summer.  The last two groups include mole crickets that are strong flyers, but spend most of their lives underground, and camel crickets with short, wingless, hump-backed bodies.

Crickets, like grasshoppers, have a sharp edge called a scraper on one forewing that rubs against a bumpy ridge, called a file, on the underside of the other forewing.  The song produced can be a chirp or a rapid trilling which is more musical than the grasshopper’s rasp and buzz.  A cricket’s wings are long and tough.  They are generally used for protection and flight, and are always used for singing.  In addition to flight, crickets are jumping insects.  They have three pairs of legs attached to the thorax.  The first two are small, but the hind legs have enlarged, muscular thighs and rigid lower legs, with a knee joint designed to provide the ability to jump long distances.

Cricket songs are directly affected by temperature.  As temperatures decrease, individuals will sing more slowly.  For crickets, the pitch also decreases.  Field crickets sing a series of chirps, and the outside temperature can be calculated from their song by applying Dolbear’s Law, named after A.E. Dolbear, who quantified the formula in 1897.  Take the number of chirps per minute, subtract 40 and divide the result by four.  Add fifty to get the temperature in degrees Fahrenheit, accurate to within one  degree.  Collecting crickets for their songs is a pastime in China and Japan where artisans have created beautifully decorated, hand-crafted cages for the past one thousand years.  Tonight, after dark, take a stroll outside to hear the wonderful chorus in your neighborhood.