Katydids are insects in the family Tettigoniidae and are part of the suborder Ensifera. They are sometimes referred to as bush crickets or long-horned grasshoppers. More than 6,400 species are known. Tettigoniidae is the only family in the superfamily Tettigonioidea. Tettigoniids are found on every continent except Antarctica. The vast majority of katydid species live in the tropics. Some katydids proliferate in cooler and dry temperate regions, with about 255 species in North America.
Primarily nocturnal in habit, with strident mating calls, many katydids exhibit mimicry and camouflage, commonly with shapes and colors similar to leaves.
Tettigoniids range in size from as small as 5 millimeters to as large as five inches. The smaller species typically live in drier or more stressful habitats which may lead to their small size. The small size is associated with greater agility, faster development, and lower nutritional needs. Tettigoniids are tree-living insects that are most commonly heard at night during summer and early fall. Tettigoniids have longer antennae than grasshoppers.
Katydids live for roughly one year, with full adulthood usually developing very late. Females most typically lay their eggs at the end of summer beneath the soil or in plant stem holes. The eggs are usually oval-shaped and laid in rows on the host plant. Tettigoniids lay eggs in dead or living plant matter, or variously in grass stems. When tettigoniids hatch, the nymphs often look like smaller versions of adults, but in some species, the nymphs look nothing at all like the adult and rather mimic other species to prevent predation. Once nymphs complete their last molt, they are then prepared to mate.
The diet of tettigoniids includes leaves, flowers, bark, and seeds, but many species are exclusively predatory, feeding on other insects, snails, or even small vertebrates such as snakes and lizards. Some are also considered pests by commercial crop growers.
Male tettigoniids have sound-producing organs located on the hind angles of their front wings. In some species, females are also capable of stridulation. Females chirp in response to the shrill of the males. The males use this sound for courtship, which occurs late in the summer. The sound is produced by rubbing two parts – one a file or comb and the other a plectrum – of their bodies together, called stridulation. Tettigoniids produce continuous songs known as trills. Many katydids stridulate at a tempo which is governed by ambient temperature, so that the number of chirps in a defined period of time can produce a fairly accurate temperature reading. For American katydids, the formula is generally given as the number of chirps in 15 seconds plus 37 to give the temperature in degrees Fahrenheit.
When tettigoniids rest during the day, they assume a roosting posture which fools predators into thinking the katydid is either dead or just a leaf. Their coloration mimicking leaves allows them to blend in with their surroundings.
The males provide a nuptial gift for the females in the form of a spermatophylax, a gelatinous protrusion attached to the males’ spermatophore and consumed by the female. Females prize a large and nutritious spermatophylax. Tettigoniidae have polygamous relationships with one another. The polygamous relationships of the Tettigoniidae lead to high levels of male-male competition. Male competition in the Tettigoniidae species is caused by the decreased availability of males able to supply nutritious spermatophores to the females. Females will produce more eggs on a high-quality diet; thus, the female looks for healthier males with a more nutritious spermatophore. Females will use the sound created by the male to judge the fitness of the male. The females adduce a louder and more fluent trill to represent a fitter male. Studies found that the tuberous bushcricket (Platycleis affinis) has the largest testes in proportion to body mass of any animal recorded. They account for 14 percent of the insect’s body mass and are thought to enable a fast re-mating rate.
The scientific name “Tettigoniidae” is derived from the genus Tettigonia, first described by Carl Linnaeus in 1748. Latin tettigonia means leafhopper; it is from Greek tettigonion, the diminutive of the imitative (onomatopoeic) τέττιξ, tettix, cicada. The common name “katydid” is also onomatopoeic.
From Wikipedia