Orthoptera (Grasshoppers, Locusts, Crickets, Etc.)
Usually medium- or large-sized insects; winged, brachypterous or apterous. Mouthparts mandibulate. Prothorax large. Hind legs usually enlarged and modified for jumping; coxae small and somewhat widely separated; tarsi 3- or 4-segmented, rarely with 5 or f
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ORTHOPTERA (GRASSHOPPERS, LOCUSTS, CRICKETS, ETC.) Usually medium- or large-sized insects; winged, brachypterous or apterous. Mouthparts mandibulate. Prothorax large. Hind legs usually enlarged and modified for jumping; coxae small and somewhat widely separated; tarsi 3- or 4segmented, rarely with 5 or fewer than 3 segments. Fore wings forming more or less thickened tegmina with submarginal costal vein. Wing-pads of nymph undergo reversal during development. Female generally with well-developed ovipositor, not concealed by 7th or 8th abdominal sterna. Male external genitalia symmetrical, concealed at rest by enlarged 9th abdominal sternum which may or may not bear a pair of styles. Cerci usually short and almost invariably unsegmented. Specialized auditory and stridulatory organs frequently developed. Metamorphosis slight.
This large order, with over 17 ooo described species, was formerly held to include the groups here treated as the separate orders Grylloblattodea, Dictyoptera and Phasmida. As restricted by the above definition, the Orthoptera includes not only such familiar forms as the grasshoppers, locusts and crickets but also the mole-crickets and grouse-locusts together with the wetas and king-crickets of Australasia and many others. The order is best represented in the tropics though members occur in all but the coldest zones. They are almost all terrestrial and, though usually capable of jumping actively, relatively few strong fliers are known, all belonging to the Acrididae. The large literature on the order is best approached through the general accounts of Beier (1972) and Chopard (1938; 1949). External Anatomy - Among other anatomical works may be mentioned those of Albrecht (1953; 1956), Ander (1939), Blackith and Blackith (1966), Carbonell (1959), Davis (1927), Jannone (1939a, b), Kramer (1944), Maskell (1927), Snodgrass (1929; 1935; 1937) and Zolessi (1968). The head-capsule (Yuasa, 1920; Strenger, 1942) is hypognathous or occasionally prognathous and exhibits most of the sulci and sclerites in a relatively primitive condition though the ecdysial cleavage line is not always O. W. Richards et al., Imms’ General Textbook of Entomology © O. W. Richards and R. G. Davies 1977
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GENERAL TEXTBOOK OF ENTOMOLOGY
fully developed. The frontoclypeal sulcus is distinct and a trans-clypeal sulcus is usually present. The tentorium is well-developed, X-shaped and without a central aperture (Hudson, 1945). The compound eyes are usually large, but are reduced in some Stenopelmatids and the Cylindrachetidae. Ocelli are absent in apterous species but in winged forms there are usually three, though some Tettigoniidae have only two. The frons bears wind receptors in Acridoids (Camhi, 1969). The antennae of the suborder Ensifera are elongate, filiform structures, often greatly exceeding the length of the body and composed of a large number of small segments. In the Caelifera they are shorter, with fewer than 30 segments (Mason, 1954) and though generally filiform are sometimes
FIG. 248 Labium of Melanoplus differ
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