Wings, when present, usually number four that may vary in size; basal portion of forewings thick and leathery, .... leg species;

Head overlaps front of prothorax; scutellum small, usually concealed by pronotum; front legs short, 1-segmented tarsus with fringe of long hairs beneath for gathering food; middle legs long, slender, for submerged anchoring; males with stridular pegs on front femurs and tibiae of legs, a polished black strigil above on asymmetrical abdomen; females nonstridulatory, abdomen symmetrical; colour pattern commonly alternating light and dark transverse stripes; inhabit fresh, brackish, or salt (Great Salt Lake) waters; use diving air stores; phytophagous on algae and diatoms, but may eat insect larvae; more than 300 species; in all major faunal regions. Head not overlapping prothorax; scutellum large, exposed; all legs long and slender, hind pair longest; male stridulating mechanism involving front legs and labium; inhabits fresh and mineral waters; diving air stores trapped under hairs on underside of abdomen, hence inverted position in swimming; bite painful to man; predatory on! insects, small crustaceans, fish, and tadpoles; almost 200 species; in all zoogeographical regions. Body stout to very slender; legs long, generally slender, front pair adapted for grasping; abdomen of most nymphs and adults with snorkel-like breathing tube at tip; nymphs and adults stridulate by opposable files on anterior coxae and coxal cavity plates; inhabit fresh water; swim poorly or not at all; predatory; principal food, other insects; nearly 200 species; in all zoogeographical regions. Slender bodied; legs long, slender, front pair short, used for support or grasping prey; middle pair longest, used for propulsion over water surface; hind femurs extends beyond tip of abdomen; tips of tarsi project beyond insertion of claws; body covered below with hydrofuge hairs; on quiet or flowing fresh or marine water; Halobates occurs on open oceans hundreds of miles from land; predatory generally on insects; oceanic forms feed on plankton and floating jellyfishes; about 350 sp! ecies; in all zoogeographic regions and intervening oceans bet! ween 40 north and 40 south latitudes. Body, head, and legs long and slender; claws arise at tip of tarsus; wings present or absent; crawl weakly and clumsily among emergent plants in fresh water; predatory; more than 100 species; mostly tropical, a few species in North America and Eurasia. Small; body and legs slender; live on fresh water, especially among emergent plants or on saturated mud; one New Guinea species lives on the forest floor away from water; about 30 species; in all zoogeographical regions. Head large; eyes prominent; labium apparently 3-segmented, long, first segment very short and stout, second very long; legs long and slender for running or leaping; generally inhabit land surfaces near fresh or salt water; some species live on rocks in the intertidal zone, hide in air trapped in crevices when rocks are covered at high tide; predatory on small or crippled insects; over 200 species, in all zoogeographic regions. Small, fragile; ocelli absent; labium 4-segme! nted; front wing with cuneus, membranous area with 1 or 2 closed cells; legs slender to stout, for walking, running, or jumping; predatory, phytophagous, or both; often host-specific; includes major crop pests ( e.g., lygus bugs of the Northern Hemisphere, the tea blight [ Helopeltis ] in southeastern Asia), also several important predators of small insects; about 8,000 species; in all zoogeographic regions; found north of the Arctic Circle. Head small, without ocelli; antennae slender to stout, generally with first 2 segments very short, 3rd long; pronotum and forewings often finely to coarsely reticulate (lacy); tarsi 2-segmented; phytophagous, on anything from mosses to flowering plants, often host-specific; several species are common pests on maize, cotton, cacao, and other cultivated plants; almost 2,000 species; in all zoogeographic regions. Ocelli present; beak 4-segmented, long, generally curved away from underside of head; no striated groove between front coxae of ! legs; front legs more or less thickened for grasping; forewings without! a cuneus; predatory on soft-bodied insects; frequently investigated as a possible biological control agent for insect pests of field crops; about 300 species; in all regions of the world. Head with side margins generally expanded over bases of antennae; ocelli usually present; antennae usually 5-segmented; scutellum large to very large, triangular or U-shaped; without claval commissure; tibiae without rows of spines; phytophagous or predatory, sometimes within same species; several important pests, including the southern green stinkbug ( Nezara viridula ), a serious pest of fruit and vegetable crops throughout the world; the harlequin cabbage bug ( Murgantia histrionica ), on North American cruciferous crops; the senn bugs ( Eurygaster species), on small grains in the Old Worldseveral genera ( Podisus, Zicrona ) feed on caterpillars and other larvae; about 5,000 species; in all zoogeographic regions; taxonomy unsettled, especially assignment of taxonomic levels; definition! and relationships of subgroups not in dispute. Family Antennae 4-segmented, inserted on side of head below an imaginary line connecting middle of eye to front end of buccula; ocelli present except in brachypterous forms; forewings with a claval commissure; wing membrane with 4 or 5 simple, longitudinal veins; phytophagous (on sap or seeds) or predatory (on mites and small insects); pests include the chinch bug ( Blissus leucopterus ) of North America, the Old World cotton stainer ( Oxycarenus hyalinipennis ), and several species of false chinch bugs in the widely distributed genus Nysius ; in North America Geocoris , considered beneficial, feed upon mites and small insects attacking crop plants; almost 3,000 species found in all parts of the world, including many small islands. leg species;