Thursday, 23 February 2012

CRICKETS, GRASSHOPPERS, AND KATYDIDS

DEFINITIONS:

CRICKET - 1 any of various families (esp. Gryllidae) of generally dark-coloured, leaping, orthopteran insects usually having long antennae: the males produce a characteristic chirping noise by rubbing parts of the fore wings together 2 a small metal toy or signalling device that makes a clicking sound when pressed.

GRASSHOPPER - 1 any of various families (esp. Acrididae) of leaping, plant-eating orthopteran insects with powerful hind legs adapted for jumping 2 a cocktail made of green creme de menthe, cream, and, usually colourless creme de cacao 3 [Mil. Slang] a small, light aeroplane for scouting, liaison, and observation.

KATYDID - any of several large, green orthopteran insects (esp. family Tettigoniidae) having long, slender antennae and long hind legs: the male has highly developed stridulating organs on the fore wings, that produce a shrill sound.

Crickets, grasshoppers, and katydids are among the most musical of insects. More than
10,000 species live throughout the world.

Orthopterans, as they are sometimes called, characteristically have two pairs of wings. The outer, forward pair is thick and tough and used only as a protective covering for the filmy rear wings. The thin rear wings move when the insect is flying. The forward wings are held stiff and motionless. When the rear wings are not in use, they fold up like fans and lie along the back beneath the forward pair. Many orthopterans are wingless or have small wings that are useless for flying.

Most species have legs that are highly efficient for jumping. The front and middle pairs are short. The rear pair is longer than the entire body and very powerful. The upper section of the hind legs, called the femur, has very strong muscles. The lower part, called the tibia, has sharp spines that are located at the end near the foot. When a grasshopper, for example, prepares to jump, it digs the spines into the ground, bringing the tibia and femur together.
Then it straightens its legs and shoots forward like a released spring. Some kinds of grasshopper can jump more than 100 times their length.

Crickets, grasshoppers, and katydids are among the noisiest and most musical of the insects. The chirp of crickets has even been considered a blessing in Europe and America.
In his story 'The Cricket on the Hearth', Charles Dickens wrote about a cricket that sings when things are going smoothly and is silent in times of trouble. The Chinese, who consider the cricket a creature of good omen, predict good luck for the house with many crickets.

These insects produce sound by rubbing particular parts of the body against one another. In most species, only the males make sound, primarily as a means of attracting mates or as identification to other males. The cricket's song is produced when males scrape the rough surfaces of the wing covers together. Katydids and grasshoppers also use their wings to make a chirruping noise. Like crickets, katydids rub their wings against one another.
Grasshoppers, however, usually rub a leg in a sawing motion across a wing to create the sound.

Orthopterans are well equipped for hearing and seeing. They have large, compound eyes, which are groups of seeing units, that allow them to see in all directions at once. Simple eyes, which detect light but do not form a visual image, may also be present in the head region around the compound eyes. Hearing is also well developed as might be expected in such a noisy group. Two structures known as tympani are located on the legs or on the body. A tympanum acts as an ear.

Another sensory device of these insects is the antenna, two of which are located on the head in front of the compound eyes. The antennae, or "feelers," are segmented and are used as organs of smell, touch, and sometimes hearing. The majority of crickets, grasshoppers, and katydids have chewing mouth parts Most are vegetarians but some specialize on a diet of other insects.

Crickets 

About 1,000 kinds of crickets have been discovered by scientists. Most do not fly, though hard, shiny wing covers lie across the back. Under the outer wings are two tiny wings that are useless for flight. Nonetheless, crickets can be extremely quick and lively and can jump long distances. Crickets have a pair of long, slender antennae.

The common field cricket of the United States and southern Canada is black and about 1 inch (2.5 centimetres) long with antennae longer than its body. It feeds chiefly on plant foliage but will eat other small insects. During the summer it lives in fields. Beneath rocks, wood, or other debris it digs a burrow that has a small chamber at the end. The burrow is used for shelter when the cricket is not feeding.

During the fall the female deposits in the ground eggs that hatch the following summer. But, unlike most other insects, crickets do not go through larval and pupal developmental stages after hatching from the egg. In these stages the youngster looks nothing like the adult. Instead crickets undergo what is known as incomplete metamorphosis, a characteristic of other members of the order Orthoptera.

The newly hatched cricket, called a nymph, is similar in appearance to the adult but has no wings. Nymphs grow in a series of moults, during which they literally burst out of their skin, emerging slightly larger after each shedding.

Most adult crickets die in the late autumn, but some that find a warm corner in a house may spend the winter there. One form, the house cricket, is particularly common around people's living quarters. The house crickets of Europe and northern Africa are straw-coloured and have been introduced to many regions of the world, including North America. They are about 1/2 inch (1.3 centimetres) long.

Mole crickets are burrowing forms that have huge forelegs and claws adapted for digging. Their bodies are covered with fine hairs. During the day they remain underground. Some species fly around at night. Mole crickets are well known in Europe and North America, and many species live in tropical areas.

Tree crickets are a major group. Some, such as the common snowy tree cricket, are light green in colour Tree crickets are among the most persistent music makers. Some species sing at night, others during the day. Because the song of crickets slows down as the temperature drops, a rough estimate of the temperature can be made by counting the number of tree cricket chirps. The temperature in degrees Fahrenheit is determined by dividing the number of chirps per minute by 4 and adding 40.

Numerous other crickets exist around the world, including such specialized forms as the ant-loving crickets that live in ant mounds. Cave, or camel, crickets are recognizable by their extreme hump-backed appearance and long antennae. They inhabit caves or other dark, damp places.

Grasshoppers 

Grasshoppers are closely related to crickets. The most common varieties belong to the group known as the short-horned grasshoppers. Although some of the more than 5,000 species of grasshopper are wingless, most have well-developed wings.

Grasshoppers usually fly only short distances. But when forced to migrate in search of food, they can fly for a series of "short hops" that total hundreds of miles. The grasshoppers that are also called locusts are among the world's worst insect pests and have been recognized as such throughout history.

About 10 different species of grasshoppers have been known to form the enormous migratory swarms that can cause such agricultural havoc. Red locusts and desert locusts are major problems in Africa. Australia, South America, and Eurasia also have problem species. Great locust swarms have devastated crops and natural vegetation in a matter of days.

According to some reports, the grasshoppers appear on the horizon like a black storm. The roar of their wings can be deafening. When they land, they eat every living plant in sight and then move on. Modern pesticides have controlled this in most agriculturally developed areas of the world, but locust swarms still are a problem in many areas. Surprisingly, the same species that causes such problems in great numbers will often go for years living a peaceful, inconspicuous existence. Most grasshoppers, however, lead solitary lives, joining others of their species only for mating.

Grasshoppers lay their eggs in the late summer and fall. At the end of the female's body are four short, thick prongs, together called an ovipositor. With her ovipositor she bores a hole 1 to 2 inches (2.5 to 5 centimetres) deep in the soil of fields or grassy areas. She then spreads the ovipositor apart and deposits the eggs in the hole in a mass that may total only a few eggs or may number more than a hundred. She covers the eggs with a frothy substance that hardens and forms a protective pod. The pod also provides air space for the young grasshoppers when they hatch underground. The female lays several egg masses with protective pods, each in a different hole. She may lay as many as 20 pods in a season.
As winter approaches, the adult grasshoppers die, and the young pass the winter in the egg stage. When the grasshoppers hatch in the spring, they quickly work their way to the surface and shed the membrane that covers them. The newly hatched grasshoppers look like miniatures of their parents with big heads and long legs, but their wings have not yet developed. They begin to eat green plants and grow rapidly. They moult five times in about six weeks, finally emerging as fully developed adults.

A familiar grasshopper in the south eastern United States is the lubber grasshopper, a black grasshopper measuring over 4 inches (10 centimetres) in length. These creatures sometimes accumulate in great numbers. They walk more than they fly because their colourful wings are small. They eat vegetation and have the unique behaviour of squeaking and forming a droplet of brown liquid at the mouth when picked up. They are harmless and are often used in biology courses to demonstrate insect characteristics.

Katydids  

Katydids are members of a family of more than 4,000 species. They are sometimes called long-horned grasshoppers or bush crickets. Katydids usually have green or brown wings and bodies with long, thin antennae. They live in trees or low-lying vegetation. Sounds of "katydid-katydid" in the eastern United States dominate late summer nights. Katydids make the sound by rubbing a "scraper" at the base of a front wing across a "file" on the base of the other.

Although crickets and grasshoppers are generally harmless creatures to handle, katydids can inflict a painful bite. Some katydids are plant eaters, but many of them eat other insects. The tree-dwelling forms lay their eggs on leaves or branches in the autumn. The adults die during the winter, and the following spring the young hatch out of the eggs. They are pale in colour at first but turn leaf-green like the adults as they get older.

Scientific Classification

Crickets, grasshoppers, and katydids are members of the order Orthoptera and the class Insecta, which also includes cockroaches, mantids, and walking sticks. Field, house, tree, and mole crickets belong to the family Gryllidae; camel crickets to the family Gryllacridae; short-horned grasshoppers to the family Acridae; katydids and Mormon crickets and other long-horned grasshoppers to the family Tettigoniidae. The American mole crickets are in the subfamily Gryllotalpinae. The common field crickets belong to the genus Gryllus; the common katydids to the family Tettigoniidae. The scientific name of the house cricket is Acheta domestica; of the snowy tree cricket, Oecanthus fultoni; of the Mormon cricket, Anabrus simplex; of the south eastern lubber grasshopper, Romalea microptera.

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