Talk:Orthoptera

Distribution

• New Zealand

etc.

Taxon description

The Orthoptera is one of the oldest lineages of insects; the oldest fossils attributed to this order are from the Carboniferous period. The two currently recognized suborders of Orthoptera, Ensifera and Caelifera, separated probably by the late Carboniferous. The suborder Ensifera (long-horned grasshoppers) is divided into 6 superfamilies and 21 families, with approximately 1,900 genera and 11,000 described species. The Caelifera (short-horned grasshoppers) includes 8 superfamilies, 22 families, nearly 2,400 genera, and over 10,400 described species.

Most species of the Orthoptera are large or medium sized insects. Body lengths of less than 10 mm are uncommon, while many exceed 50 mm in length, with some having bodies over 100 mm long and a wingspan of 200 mm or more. The smallest Orthoptera are ant-associated crickets (Mymecophilus and other genera), whose body length rarely exceeds 2 mm, while the largest are katydids of the genera Siliquofera and Macrolyristes. The heaviest of all Orthoptera (and also the heaviest living insect) is New Zealand weta Deinacrida heteracantha, with the recorded body weight of 71 g.

Orthopterans are hemimetabolous insects, with nymphs resembling adult forms in their general appearance but lacking fully developed wings and reproductive organs. Mouthparts of orthopterans are of the chewing/biting type. The head is hypognathous (mouthparts pointing down), rarely prognathous (mouthparts pointing forward); the antennae are usually long, thread-like, consisting of fewer than ten to several hundreds articles. The part of the body immediately behind the head, or the pronotum, is usually large, often shield-like, and in extreme cases covers a large part (many katydids) or the entire body of the insect (pygmy grasshoppers). The front and middle legs are cursorial, i. e. adapted for walking, yet in some cases the front pair of legs may be modified for digging (mole crickets, pygmy mole crickets, sandgropers) or both the front and middle pairs may be modified for grasping (predatory katydids). In some orthopterans (most katydids and crickets) the front legs have tibial auditory organs (the ear). The hind legs of most orthopterans are saltatorial, i.e. modified for leaping, with large, muscular femora and long, slender tibiae. Certain groups of orthopterans, especially those leading subterranean life, lost their ability to jump and their hind legs resemble typical cursorial legs.

The wings of orthopterans are either fully developed or reduced to various degrees. Wing polymorphism, or the occurrence of individuals with well-developed and reduced wings within the same species, is not uncommon. The forewings are somewhat thickened, forming leathery tegmina. In most katydids and crickets parts of the tegmina are modified for stridulation. The hindwings, when present, are fan-like, folded under the first pair in the resting position. The base of the abdomen in grasshoppers has lateral auditory organs known as abdominal tympana. Females of most orthopterans have a prominent ovipositor at the end of the abdomen, derived from the eight and ninth abdominal segments. Katydids and crickets usually have the ovipositor well developed, sword-, sickle-, or needle-shaped, whereas females of grasshoppers and their relatives usually lack a long, external ovipositor.

Biology

Orthopteran species occur in nearly all parts of the world and almost all habitats where insects are found. They inhabit virtually all terrestrial habitats of the world, from rock crevices of the littoral zone of the oceans, subterranean burrows, and caves, to rainforest treetops and peaks of the alpine zones of mountain ranges. There are few strictly aquatic forms among the Orthoptera, but many are associated with marshes and other semi-aquatic environments. Reed-beds are home to numerous conehead katydids (Conocephalinae), while on muddy banks of rivers one will find both pygmy grasshoppers (Tetrigidae) and pygmy mole crickets (Tridactylidae). The true mole crickets (Gryllotalpidae) and sandgropers (Cylindrachetidae) are perfectly designed for life underground, where they dig tunnels with their enlarged, shovel-like front legs, feeding on insect larvae and earthworms.

The food preferences and foraging behavior of the Orthoptera are quite diverse. Virtually all Caelifera (short-horned grasshoppers) are herbivorous. Most grasshoppers are polyphagous i.e., they can feed on a variety of species of plants, but a number of taxa (especially within the neotropical subfamilies Ommatolampinae and Rhytidochrotinae) are restricted to feeding on single or only few species of plants, frequently those with high levels of toxic secondary compounds (e.g., many Solanaceae). Pygmy grasshoppers (Tetrigidae) are some of the few insects that feed on mosses and lichens. Ensifera (katydids, crickets, and their relatives) range from herbivorous to omnivorous, to strictly predaceous. Members of the Australian genus Zaprochilus feed exclusively on pollen and nectar of flowers. Others, such as many species of the genera Neoconocephalus and Ruspolia feed mostly on seeds of grasses, whereas many members of the subfamily Phaneropterinae specialize in eating broad leaves. One of a few katydids feeding on pine trees and other conifers is Barbitistes constrictus from Europe. Strictly predaceous katydids employ both the “sit-and-wait” strategy (Saginae) or actively forage and hunt living insects (Listroscelidinae).

Most orthopteran species are solitary animals, although gregarious tendencies are common among many crickets (especially members of the family Phalangopsidae), and cave and camel crickets (Rhaphidophoridae). Some crickets (Brachytrupinae) even form small family groups. The most spectacular example of gregarious behavior in the Orthoptera is that of locusts. Locusts are not members of any particular genus or subfamily of grasshoppers, but rather a term applied those species of grasshoppers that exhibit a clearly defined shift in their behavior, morphology, and physiology, from a solitary to a migratory phase. An example of such a species is the desert locust (Schistocerca gregaria) from arid regions of Africa and SW Asia.

The single characteristic most frequently associated with grasshoppers and their relatives is their ability to produce sounds. Although less widespread than generally believed, it is nonetheless quite common in some groups of the Orthoptera. The role of sound production is three-fold and similar in some respects to that of bird calls: (1) attraction of mates, (2) territoriality, and (3) release calls (= alarm calls produces when seized by a predator). The calls of orthopterans are usually species-specific and play a very important role in species recognition. The dominant mechanism of sound production in Orthoptera is stridulation. It involves rubbing one modified area of the body against another. Contrary to popular belief, no orthopterans produce sound by rubbing their hind legs against each other. Katydids (Tettigoniidae) and crickets (Grylloidea) produce sound by rubbing a modified vein (the stridulatory vein) of one tegmen (=front wing) against a hardened edge of the second tegmen (the scraper). Grasshoppers use the same principle of stridulation, but instead of rubbing their tegmina against each other, these insects produce sound by rubbing the inner surface of the hind femur against one of the veins of the tegmen. The sound frequencies produced by orthopterans during stridulation vary from a few kHz (most crickets and grasshoppers) to well above 100 kHz (some katydids).