true bug

n.
A wingless or four-winged insect of the order Hemiptera, especially of the suborder Heteroptera, including the bedbug, louse, and chinch bug, having mouthparts adapted for piercing and sucking.

(True bugs, cicadas, leafhoppers, aphids, mealy bugs, and scale insects)

Class: Insecta

Order: Hemiptera

Number of families: More than 140

Evolution and systematics

Most of the diversification of the Hemiptera started in the late Paleozoic (Upper Permian), and the major lineages diverged early in the Mesozoic (Triassic). Regrettably, some key fossils come from beds of uncertain age. Well-preserved, complete fossils are scarce—for example Karabasia evansi (family Karabasiidae, Upper Jurassic?); Architettix compacta (family Cicadoprosbolidae, Cretacic); Incertametra santanensis (family Hydrometridae, Cretacic). For the most part only isolated structures have been reported, and many of them have not been assigned with certainty to groupings below the family. Certain very-well-preserved specimens are known from amber, such as Metrocephala anderseni (family Hydrometridae) and Succineogerris larssoni (family Gerridae) from Baltic amber (Eocene), and Brachymetroides atra (family Gerridae) and Halovelia electrodominica (family Veliidae) from Dominican amber (Oligocene-Miocene). Several schemes of phylogenetic relationships among Hemiptera have been proposed, based on varying criteria. In the last decades of the twentieth century, they succeeded at short intervals, with remarkable discrepancies among them, and the proposed schemes are in steady flux.

The partitioning into two suborders, Homoptera and Heteroptera, or into three, segregating the Coleorrhyncha, does not express the inferred (and most accepted) paths of evolution. The relationships between Heteroptera and Homoptera and between suborders and infraorders of both major groupings have been discussed in many papers by several hemipterists; interesting results were obtained by the end of the 1980s, based on important paleontological, chemical, morphological, cytogenetical, and behavioral facts of living Hemiptera. The Heteroptera plus the Coleorrhyncha represent the most advanced grouping, derived from an extinct homopterous stock of Scytinopteroidea. Updated and adjusted results were edited by Schaefer.

The Hemiptera are divided into four undergroupings: the aphids and scale insects (and perhaps the whiteflies), included in Sternorrhyncha; the cicadas, leafhoppers, treehoppers, plant-hoppers (and perhaps the whiteflies), included in Auchenorrhyncha; the conenoses, water bugs, stink bugs, and others, included in Heteroptera, or true bugs; and the moss bugs, included in Coleorrhyncha. The Sternorrhyncha and the Auchenorrhyncha together are called Homoptera; the systematic position of the whiteflies is still dubious. The Coleorrhyncha and Heteroptera make up the suborder Prosorrhyncha. The Sternorrhyncha are clearly monophyletic (derived from a single ancestor). The Auchenorrhyncha do not appear to be monophyletic; they comprise two infraorders, the more primitive Fulgoromorpha and the more advanced Cicadomorpha. The monophyletic Heteroptera, or true bugs, are grouped into eight infraorders: Enicocephalomorpha, Dipsocoromorpha, Gerromorpha, Nepomorpha, Leptopodomorpha, Cimicomorpha, Pentatomomorpha, and Aradomorpha. The Coleorrhyncha, with a single family, restricted to the Southern Hemisphere, evolved parallel to both Homoptera and Heteroptera. The exact number of families of Hemiptera is largely a matter of opinion; by 2003 approximately 140 extant families were accepted, some 60 in Homoptera, about 80 in Heteroptera, and one in Coleorrhyncha.

Physical characteristics

The body shapes are extremely diverse, ranging from plump, short, and cylindrical—such as the terrestrial scutellerid bugs and the aquatic pygmy backswimmers—to very slender—such as the semiaquatic water measurers, and some members of the assassin bug family—or even extremely flat—such as the aradid bugs. The sizes range from 0.03 in (0.8 mm: litter-dwelling bugs and some plant lice) to about 4.3 in (110 mm: giant water bug); of course, larvae in every case are much smaller. The head bears a beak, bent backward against the venter and varying from almost inconspicuous, as in the family Corixidae, to very long, reaching the rear end. It is a gutter-shaped, articulated labium holding the distal part of the very long and slender stylets. The antennae may be very short and concealed under the head border in aquatic bugs or longer and exposed in almost all other Hemiptera species. Although most adult hemipterans bear two pairs of wings, some are always wingless, like the females of scale insects. In Heteroptera the forewings are called hemelytra (derived from the classical Greek hemi, half, and elytron, case or etui), because the basal half is mostly stiff and the distal one is membranous. In some Auchenorrhyncha they are called tegmina (classical Greek for carapace, a somewhat flexible but fairly stiff structure), since they are entirely stiff. Hind wings are membranous and translucent or whitish; some Homoptera have all four wings of the same texture (aphids and cicadas, among others). The legs have a wide adaptative spectrum: for walking, running, jumping, swimming, or skating on water; for grasping prey; or for digging. Only seldom are legs missing. Larvae generally are similar to small adults but lack wings and genital appendages; the larvae of some Homoptera, however, are quite different from adults. In the whiteflies, adults are slender, with long legs and ample membranous wings, and the larvae are broad and flat, scale-like, and lack legs.

Many hemipterans are dull-colored, for instance, most aquatic species; others display bright and contrasting colors, sometimes with a showy metallic shine. The color may be uniform, but stripes, dots, or extensive contrasting and brightly stained areas frequently appear. Larvae can be similar to adults in color or differ greatly; some evenly stained species may have spotted larvae, among them, many stinkbugs. Underground-dwelling cicada larvae are colorless or pale yellowish. The body surface sometimes is obscured by a whitish, compact, powdery, woolly, or filamentous wax cover, as in the mealy bugs and whiteflies.

Numerous hemipterans, such as the members of the stinkbug family, have scent glands, which are used against predators, as an alarm signal, or as a call to aggregation. These glands open ventrally or laterally in the hind thorax in adults, and dorsally on the abdomen in larvae. The strong smell justifies the name "stink bugs" for these offensive stinking species. Many families display alary polymorphism—individuals may have complete wings, reduced wings, or no wings. Fliers and nonfliers may coexist in a population, and proportions seem to be linked to the habitat. Among bugs living in the water, reduction affects only the hind wings; the forewings are complete, holding air for buoyancy. Several bugs living under water have adaptations for taking in oxygen at the water surface, such as siphons or dry, hairy areas. Some larvae take oxygen from the water itself.

Distribution

The Hemiptera are distributed broadly, both on land and in freshwater; moreover, the only insects dwelling on the open ocean are all bugs. On all continents families are more diverse in the tropics. In high boreal latitudes and high altitudes the ranges of some families extend close to permanent ice. Even remote oceanic islands such as Tristan da Cunha in the Atlantic and the Easter Islands in the Pacific are populated.

Habitat

Hemiptera may be either terrestrial or aquatic. They occur in almost all habitats, including deserts and at high altitudes. Those that have aquatic tendencies occur in every freshwater, brackish water, and saline habitat, including the open sea. Most hemipterans are terrestrial and dwell on plants (including roots), on the ground, in soil litter, or as external parasites on vertebrates. Many are linked to running or standing freshwater, living on the surface (semiaquatic bugs) or in the water (aquatic). Some live in water-filled tree holes or in epiphytic plants. Few are marine—only five species live on the surface of the open ocean. Certain species dwell in natural caves or those excavated by crabs. Others live in nests of social insects (ants and termites), or of birds. Still others live in spider webs.

Behavior

Most species are diurnal and dwell on the ground or on plants, searching for food or prey, for a mate, or for a suitable egg-laying site; every part of a plant, including the roots, may serve these purposes. Aquatic bugs thrive in or on water, frequently among aquatic plants, and almost all are predaceous. Stones, twigs, and other substrates may serve as perches or shelters, especially in swift-running brooks, or as egglaying sites. In the water they swim or crawl on the bottom or on supports (aquatic bugs); on the surface they walk or skate (semiaquatic bugs). Females and advanced larvae of most scale insects do not move from the site upon which they set down (only the first larval instar has active legs and moves around); the tiny males are winged and fly in search of ripe females. No hemipteran is truly social, as are ants and termites and some bees and wasps, but some live in dense aggregations, sometimes only transitorily.

Visual displays are achieved by expanded legs, wings, or antennae, which sometimes also are brightly or contrastingly stained or very hairy. Sounds are produced by scraping together two sclerotized parts of the body or by vibrating the tymbals, as in the cicadas; specialized hairs receive the sound waves. Some bugs drum with their legs on the substrate, and others (e.g., certain assassin bugs) scrape their beaks against their own chests, the vibration being transmitted via the legs to the substrate. Males of many water striders produce ripples on the surface with their legs, which are detected at a distance. Scent substances, the sex pheromones, usually are present too. All these signals are highly specific for attracting sexes to each other; some individuals can identify them and decide to flee, avoiding competition with individuals that had previously arrived and may have already established their territories.

Many hemipterans disperse by flight, especially water-dwelling species. Dispersal capacity may be retained for life or soon lost. Rain-pool species can fly almost their whole life span, and they successively colonize habitats avoided by stability-loving species, thus lessening the risk of competition because they are able to support environmental instability. No hemipterans have spectacular migratory swarms, and they do not fly great distances, as do certain butterflies, but some observations suggest that giant water bugs can fly many hundreds of kilometers at a time. In the dry and warm season, plant lice start shorter migrations by the thousands, producing a sort of fog. Territoriality was studied in only a very few Hemiptera species, and the results are not understood clearly. Signals, both mechanical and chemical, play an important role in marking territorial boundaries, as seems to be the case among certain water striders and large coreids.

Feeding ecology and diet

All the Homoptera are sap feeders. Heteroptera are primarily predaceous, and in the course of evolution several groups have evolved to exploit plants; some of these groups evolved and returned to the predatory condition or shifted to parasitism on higher animals. All take only liquids in the form of plant juices, chiefly sap, or animal juices, chiefly predigested tissues or blood; only a few water bugs are able to add small particles to their diet, such as algae. Plant juices are taken from leaves, stems, buds, flowers, fruits, or roots. Some species suck the contents of fungal threads under rotting bark; others suck from moss cells. Predators suck from almost every arthropod; some prefer snails; and others may attack small fish, frogs, and tadpoles. Certain bugs feed on dead or half-dead arthropods, mainly insects. Those that suck blood take only warm blood from birds or mammals, mostly bats. Cannibalism may occur, primarily in gregarious species. Some Hemiptera do not feed as adults, for example, the males of scale insects. Food is obtained in the places they live, but blood-sucking bugs rest in shelters and leave their shelters to bite warm-blooded hosts.

Water striders' main food consists of aerial insects blown onto the water surface; they localize these prey by the ripples they produce with their helpless movements. Oceanic bugs feed on dead, floating jellyfish, and on planktonic microcrustaceans and fish larvae trapped in the surface film. Larvae of most Hemiptera thrive and feed in the same manner as adults, but some stink bugs take sap at the first larval instar and later become predaceous like the adults. Adult cicadas take sap from twigs, but larvae dwell underground and take it from roots. The first-instar larvae of some species eat no food. Some Sternorrhyncha produce anomalous growths in leaves, stems, or roots, called "galls"; larvae and newly molted adults feed and develop therein, without seriously interfering with the plant's physiology. Some Homoptera that take dilute resources, such as plant sap, eliminate much of the water immediately, concentrating the nutritive substances. They excrete some sugar with the liquid feces, which, if abundant, can be used as food by mammals and humans, as the biblical "manna." Often a black mold that resembles soot develops on that substance and affects plant growth as it restricts the amount of light that reaches leaves.

The saliva may form a small cone on the plant surface, helping hold the slender mouthparts in position. Other saliva components break the cell walls down, to release the contents. Some bugs feed on dry seeds, piercing them to inject a digestive saliva and sucking the resulting fluid. Still others inject a plant hormone mimic, which mobilizes nitrogen-rich substances to the wound.

Reproductive biology

Courtship and mating take place mostly on perches among terrestrial species, generally on plants but sometimes on the ground or in shelters. Courtship, if any, is frequently brief and consists of chirps, scent emissions, or displays with the legs or antennae or a combination of these types of behavior. Courtship activities are undertaken by the males, but in some species females collaborate; in most boatmen the loud male chirps are answered weakly by females, allowing for mutual localization. Some bugs living in the water alternately take and expel air, thus rising and sinking at the surface and forming coarse waves, which orient the partner. Water bugs mate above or below the surface; submerged and floating plants and logs may serve as perches.

At mating the male mounts the female, but sometimes he shifts to an end-to-end position. The male also may lie at an angle across the female or beside her. Coupling may be brief or may last for hours. Insemination is internal, the male transferring sperm with specialized intromittent organs (a rather complex aedeagus). So-called traumatic insemination is known in a couple of families: males slash the abdominal wall of females with their swordlike claspers, discharging sperm in the general cavity. The number of scars shows how often a female has mated. Immobile, wingless female scale insects are mated by the winged males, which may have a very long copulating organ to reach beneath the shield or the wax cover.

Parthenogenesis (reproduction without mediation of males) is extremely rare in Heteroptera; it is mentioned in only a couple of unrelated species. It is frequent, however, in certain Sternorrhyncha. Most plant lice, for example, alternate yearly between one bisexual reproductive phase and few to many parthenogenetic phases, the females giving off living larvae, which in turn give off living larvae. At the end of the season, a bisexual, frequently winged phase reappears. Some pest plant lice are permanently parthenogenetic in warm areas. Some scale insects may be bisexual or parthenogenetic, depending on environmental or geographic factors.

Eggs are often barrel-shaped, more or less elongated, and sometimes weakly curved; they may bear a long stalk. The shell is translucent or whitish, but frequently the stained vitellum makes them brightly colored. The surface is smooth or rugose or is ornamented with spines, tubercles, crests, and so on, giving them a bizarre appearance. Eggs laid under the water's surface have a thick and complex shell, formed by extremely fine spun work, which traps the tiniest air bubbles, providing oxygen for the embryo. Most eggshells have a weak strip, which breaks at hatching; it may form a distal ring, defining a cap, which drops away. In some species the strips form a distal rosette: the shell "bursts," and the larva emerges through the opening. Some banana-shaped eggs are embedded in aquatic plants, and the strip is longitudinal, allowing for easy emersion (emergence from the egg). Many first-instar larvae bear a sharp "egg burster" on the head, which tears the eggshell.

Eggs may be laid singly or in groups in suitable sites for the emerging young to find food soon. Most plant-feeding bugs glue eggs with a special secretion; aquatic and aerial bugs embed them into tissues. Predators and blood-feeders glue them to a firm substrate or let them drop to the floor of the host's resting site. Many scale insects hide the egg batch below themselves or below the rigid dorsal shield or below a wax cover. Among certain giant water bugs the female lays the eggs on the back of the male. Bat parasites do not lay eggs; instead, they retain and nourish the young in the genital tract.

No hemipteran species spins nests or egg cases. Only a few species care for eggs or young or both. Males of some giant waterbugs protect the eggs glued to their backs and clean them using their legs, which also ensures an oxygen supply for the embryos. Males of other giant water bugs stay near the egg clusters laid on twigs emerging out of the water, guard them, and readily threaten potential egg predators. Egg guarding has been observed in isolated cases among several terrestrial families; the female or male covers the egg batches until they hatch. This behavior perhaps is more frequent than usually is assumed. The best protective action probably is to select a proper site for laying the eggs, lowering the risks at hatching.

Many hemipterans living in temperate zones have a single yearly reproductive cycle, but some have two or more generations per year. Exceptions are the cicadas, which have an extended larval development lasting several years. Embryos or adults, but rarely larvae, overwinter; some species aggregate en masse to pass this period. In the tropics generations frequently overlap, and insects at all stages of development are found there year-round. If marked climatic seasonality occurs (humid vs. dry and warm vs. cold), estivation or hibernation may take place. The unfavorable season sometimes is passed in a dormant, hormonally driven diapause; the embryo, the larva of every instar, or the adult may engage in this diapause, which may last up to half a year or even more (nine months in one Alaskan shore bug).

Conservation status

Among insects, hemipterans are not a frequently mentioned group of conservation concern. By 2002 the IUCN Red List had cited only five species of Homoptera (two Extinct and three Near Threatened) and no species of Heteroptera. There are some regional listings for Europe, North America, New Zealand, and other countries, which also include very few Hemiptera. More extensive samplings might indicate that more species are of conservation concern.

Among wild species, decline follows environmental damage. For aquatic species, water pollution is a widely occurring alteration. For water striders and the like, any surfactant present in the water, even in low amounts, is lethal. Extensive control of pests with insecticides, which are never specific, put at risk every insect, whether a pest or not. Extensive forest clearing eliminates many scarce trees and shrubs, perhaps the only food resource of some bugs, and also water-filled epiphytic plants where some bugs live. Forest clearing also increases the light intensity at the ground level, affecting shade-adapted plants and insects. Only in protecting ecosystems and ensuring their sustainable use will the Hemiptera be protected.

Significance to humans

Humankind profits from bugs by eating them, by using them against pests, and as models in art. Bugs are also used as a source of amusement and entertainment; for example, cicadas are often tied together with thread to make decorations or jewelry, and children have races with insects. On the other hand, humankind suffers from bug bites, from illnesses transmitted by certain species, and from agricultural pests. Some Mexicans eat the egg masses of the boatmen species, called "ahuautle." Shrub twigs are drowned in ponds after large amounts of eggs have been glued to them; eggs are later gathered and either fried or dried in the sun. In India the adults of one species of giant waterbug are cooked in syrup, which is considered an expensive delicacy. Roasted, egg-filled female cicadas are eaten in some Asian countries. In several places, stink bugs are dried and powdered for use as a condiment. People have engaged in other forms of recreational and ceremonial insect eating.

Cicadas have received considerable attention, as it is said that their chirps predict warm or stormy weather. They have been highly regarded as symbols of resurrection. In the Far East jade carvings in the shape of cicadas once were put in the mouth of dead princes and other important people. The Chinese keep cicadas in cages, like singing birds, and also fly kites made in their shape. Kissing bugs, especially the domestic species that transmit Chagas' disease, are reputed to bring luck and happiness, which has made them popular and has contributed to the dissemination of the illness and constraining sanitary controls. A few predaceous bugs are used as biological control agents against crop pests and are reared to be released in the field. Some species of stink bugs, chiefly a plant feeder family, are efficient at attacking pest caterpillars on soybean plants; certain species ingest and transmit caterpillar disease viruses (e.g., polyhedrosis virus).

Carmine is a very valuable dyestuff produced by an American cactus-dwelling scale insect; the plant and the insect were introduced to other continents by the eighteenth century, producing a noxious spread of the weed that rendered vast tracts of land unusable. Shellac is produced by another tropical scale insect that dwells on fig trees. Several Hemiptera occurring on different wild plants shifted to crop plants once they were introduced into new areas and then turned into pests. Some are genus specific or family specific; others are generalists. The ensemble is extensive and includes many of the plant-feeding bug families. The pest condition is achieved through the generous food supply offered by cultivation, encouraging insect numbers to rise quickly. Families with many serious pest species are Aphididae, Coccidae, Diaspididae, Delphacidae, Pentatomidae, Miridae, and Alydidae, among others. Underground-dwelling larvae of some cicadas may cause locally severe losses in sugarcane fields. Often the damage caused to crops is not so much due to the removed sap but to the transmission of microbial diseases, mainly plant viruses and fungi. Species of the family Delphacidae cause losses in corn and other cereals by transmission of viruses; some Pentatomidae transmit disease-producing fungi. One American species of Phylloxera may produce severe damage in the production of grapes by attacking the roots and leaves of the vines; they have caused extensive losses in European countries where the species was accidentally introduced.

Some water bugs, and members of the assassin bug family sting very quickly with their mouthparts when they are taken by hand, injecting a poisonous saliva and causing intense pain and sometimes swelling. Some exclusively blood-sucking bugs attack humans and may transfer parasitic microbes, causing diseases; indeed, Chagas' disease, widespread in tropical and temperate South America, is due to a flagellate, Trypanosoma cruzi, which also is a common parasite of many wild and domestic mammals.

Species accounts

Greenhouse whitefly
Pea aphid
Giant water bug
Spittle bug
Seventeen-year cicada
Bed bug
Tomato bug
Water boatman
Delphacid treehopper
Unique-headed bug
Sea skater
Water measurer
Creeping water bug
Backswimmer
Moss bug
Southern green stink bug
Spiny soldier bug
Rhodesgrass mealybug
Staining bug
Kissing bug
Shore bug

Resources

Books:

Andersen, Nils M. The Semiaquatic Bugs (Hemiptera, Gerromorpha): Phylogeny, Adaptations, Biogeography, and Classification. Entomonograph 13. Klampenborg, Denmark: Scandinavian Science Press, 1982.

Schaefer, Carl W. "Prosorrhyncha (Heteroptera and Coleorrhyncha)." In Encyclopedia of Insects, edited by V. H. Resh and R. T. Cardé. Amsterdam: Academic Press, 2003. ——, ed. Studies on Hemipteran Phylogeny. Thomas Say Publications in Entomology. Lanham, MD: Entomological Society of America, 1996. ——. "True Bugs and Their Relatives." In Encyclopedia of Biodiversity, vol. 5. San Diego: Academic Press, 2000.

Schaefer, Carl W., and A. R. Panizzi, eds. Heteroptera of Economic Importance. Boca Raton, FL: CRC Press, 2000.

Schuh, R. T., and J. A. Slater. True Bugs of the World (Hemiptera: Heteroptera): Classification and Natural History. Ithaca, NY: Cornell University Press, 1995.

Periodicals:

Evans, J. W. "A Review of Present Knowledge of the Family Peloridiidae and New Genera and Species from New Zealand and New Caledonia (Hemiptera: Insecta)." Records of the Australian Museum 34, no. 5 (1981): 381–406.

Wheeler, W. C., R. T. Schuh, and R. Bang. "Cladistic Relationships among Higher Groups of Heteroptera: Congruence between Morphological and Molecular Data Sets." Entomologia Scandinavica 24 (1993): 121–137.

Other:

"Fulgoromorpha Lists on the Web." November 30, 1999 [May 12, 2003]. "Halobates—Oceanic Insects." June 26, 2002 [May 12, 2003]. . "The International Heteropterist's Society." January 3, 2002 [May 12, 2003]. . "Periodical Cicada Page." December 16, 2002 [May 12, 2003]. . "Scale Net." March 19, 2003 [May 12, 2003]. . "Whitefly Taxonomic and Ecological Website." November 5, 2002 [May 12, 2003]. .

[Article by: Axel O. Bachmann, Doctor en Ciencias Biológicas; Silvia A. Mazzucconi, Doctor en Ciencias Biológicas]

An order of the class Insecta sometimes referred to as the Heteroptera. Both these names refer to the fore-wings, which are differentiated into a thickened basal area and a membranous apical region. These are the true bugs. Included in Hemiptera are such common insects as the bedbugs, stink bugs, plant bugs, lace bugs, and backswimmers.

The true bugs number about 25,000 species. They are known from all continents except Antarctica and occur on most islands. Hemiptera range in size from small aquatic and ground-inhabiting forms approximately 0.04–0.08 in. (1–2 mm) in length to giant water bugs 4 in. (100 mm) or more.

In habits, the true bugs range from strictly phytophagous types attached to a single host plant, to general predators on other insects, and even to specialized ectoparasites of bats. Many species are of economic importance as plant pests or vectors of disease. They occur in vegetation, on the ground, in and on the water, and in the nests of termites. Most water bugs depend on surface air held to the body by air spaces and hairs on the abdomen. As oxygen is depleted in the air bubble, it is replaced from the surrounding medium by diffusion.

Most Hemiptera are bisexual and oviparous, but parthenogenesis is known. Mating usually takes place on vegetation or on the ground, the pairing being end-to-end in stink bugs, squash bugs, chinch bugs, and similar species, and with the male above the female in most others.

Morphology

In Hemiptera the mouthparts are elongate and slender, forming a sucking mechanism. The beak arises from the anterior part of the head and the head is commonly directed forward or downward.

Hemiptera are further characterized (see illustration) by antennae, usually of four or five segments, a pair of compound eyes, and often two ocelli. The thorax consists of a prominent pronotum, a triangular mesothoracic scutellum, and a broad metathorax which is partly fused with the first abdominal segment. The mesothoracic wings, or hemelytra, overlap at their membranous apices when at rest. The hindwings are hitched to the forewings in flight by grooves and pegs. Wings are sometimes reduced to short pads and may be lacking in certain groups or even in members of a single species. The front legs are frequently enlarged and sometimes chelate in predacious forms, and the middle and hindlegs are adapted for swimming in some groups. The abdomen is of 10–11 segments, but only seven are commonly seen.

External anatomy of a bug.

Subdivisions

Families of the Hemiptera and their distinguishing characteristics are listed in the table under the respective subdivisions.

Families of Hemiptera

Family	Common name	Distribution	Number of species
Subdivision Hydrocorisae
Corixidae	Water boatmen	General	300
Nepidae	Water scorpions	General	170
Belostomatidae	Giant water bugs	General	140
Notonectidae	Backswimmers	General	170
Pleidae	None	General	20
Helotrephidae	None	Tropical	20
Naucoridae	Creeping water bugs	General	200
Gelastocoridae	Toad bugs	Tropical and subtropical	80
Ochteridae	Velvety shore bugs	Tropical and subtropical	20
Subdivision Amphibicorisae
Gerridae	Water striders	General	300
Veliidae	Smaller water striders	General	200
Hydrometridae	Marsh treaders	General	50
Mesoveliidae	Water treaders	General	20
Hebridae	Velvety water bugs	General	40
Subdivision Geocorisae
Superfamily Leptopodoidea
Saldidae	Shore bugs	General	200
Leptopodidae	None	Tropical and subtropical	20
Leotichidae	None	Asian	2
Superfamily Dipsocoroidea
Dipsocoridae	None	General
Schizopteridae	Jumping ground bugs	Tropical and subtropical
Superfamily Cimicimorpha
Cimicidae	Bat, bed, bird bugs	General	80
Anthocoridae	Flower bugs	General	300
Polyctenidae	Bat bugs	Tropical and subtropical	20
Miridae	Plant bugs	General	5000
Microphysidae	None	Palearctic	30
Plokiophilidae	None	Tropical	20
Nabidae	Damsel bugs	General	250
Tingidae	Lace bugs	General	700
Vianaidae	None	Neotropical	2
Thaumastocoridae	Palm bugs	Tropical	11
Superfamily Enicocephaloidea
Enicocephalidae	Gnat bugs	General	300
Superfamily Reduvioidea
Reduviidae	Assassin bugs	General	3500
Superfamily Aradoidea
Aradidae	Flat bugs	General	800
Termitaphididae	Termite bugs	Tropical	10
Superfamily Pentatomorpha
Idiostolidae	None	Chilean	2
Lygaeidae	Lygaeid bugs	General	2000
Thaumastellidae	None	Ethiopian	1
Colobathristidae	None	Tropical	70
Berytidae	Stilt bugs	General	100
Malcidae	None	Ethiopian, Asian	30
Piesmatidae	Ash-gray leaf bugs	General but discontinuous	20
Pyrrhocoridae	Pyrrhocorid bugs	General	300
Largidae	None	General	100
Coreidae	Coreid bugs	General	2000
Rhopalidae	None	General	300
Stenocephalidae	None	Old World, Neotropical	20
Hyocephalidae	None	Australia	1
Pentatomidae	Stink bugs	General	2500
Phloeidae	Bark bugs	Neotropical	5
Plataspidae	None	Old World	400
Lestoniidae	None	Australia	1
Cydnidae	Ground or burrower bugs	General	600
Urostylidae	None	Asian and Australian	50
Aphylidae (not placed)	None	Australian	2
Joppeicidae	None	Mediterranean	1

Hydrocorisae

This subdivision contains nine families of water bugs with concealed antennae and without a bulbus ejaculatorius in the male. Many species are predaceous.

Corixoidea is a superfamily which contains the single family Corixidae, or water boatmen. Corixidae lack ocelli and have a unique type of mouthpart. Corixids swim with the dorsal side uppermost, using the oarlike middle and hind legs. Eggs are stalked and there are five nymphal instars. Adults sometimes fly to lights in great numbers.

In the superfamily Nepoidea, the Nepidae, or water scorpions, have a long breathing tube at the tip of the abdomen, through which they obtain air directly from the surface. The beak is short and stout to suck the juices of other insects on which they prey. Belostomatidae, or electric-light bugs, have short, straplike respiratory appendages at the tip of the abdomen. Giant water bugs of the genus Lethocerus are pests in fish ponds where they attack fry. They can inflict a painful bite when handled carelessly.

The superfamily Notonectoidea includes the Notonectidae or backswimmers: they swim ventral side uppermost, the hindlegs serving as oars. Breathing is facilitated by an air bubble, obtained by touching the tip of the abdomen to the surface.

The minute bugs of the families Pleidae and Helotrephidae (superfamily Pleoidea) are suboval, with legs not fitted for rowing.

The creeping water bugs (superfamily Naucoroidea) are sometimes separated into the Naucoridae and Aphelocheiridae. They are suboval in body form. Respiration is either by an air bubble or by means of a plastron; in the Old World genus, Aphelocheirus, the plastron consists of an ultramicroscopic hair pile which acts as a physical gill; the bug is thus able to remain submerged permanently.

In the superfamilies Gelastocoroidea and Ochteroidea, the Gelastocoridae, or toad bugs, and the Ochteridae (or Pelogonidae) are shore-line or mud inhabitants. Both have ocelli. The former are cryptically colored, resembling the sand or mud background. Ochterids are black with a silky sheen.

Amphibicorisae

This subdivision contains surface water bugs with antennae exposed and without a bulbus ejactulatorius in the male. Only the single, diverse superfamily Gerroidea has been proposed for the surface water bugs. All have conspicuous antennae, and the body is clothed with hydrofuge hairs. All Gerroidea are predacious.

Gerridae are the large water striders with long middle and hind legs and a median scent gland opening on the metasternum. The claws are inserted before the tips of the tarsi. The marine forms are always wingless but all others are polymorphic, with fully winged forms occurring together with short-winged or apterous types.

Veliidae are small water striders which have shorter legs and a longitudinal groove between the eyes. The claws are preapi-cal. Like the Gerridae, these are pond inhabitants, stream-riffle bugs, and marine types, but the last are found only near shore in tropical reefs.

Hydrometridae are long, slender marsh treaders in which the head is longer than the thorax. The claws are apical.

Mesoveliidae and Hebridae are two small families which differ from others in having the well-developed ocelli and the single dorsal abdominal scent gland openings of the nymphs.

Geocorisae

This subdivision contains the land bugs with conspicuous antennae and an ejaculatory bulb in the male reproductive system. This subdivision can be divided into seven groups, each of which may be equivalent in rank to the Hydrocorisae and Amphibicorisae. Superfamilies that do not fit the above groupings are the Reduvioidea, the Saldoidea, the Aradoidea, and the Enicocephaloidea and Dipsocoroidea, of isolated position in the system.

The superfamily Saldoidea comprise the shore bugs which have three pairs of trichobothria on the vertex and a single nymphal scent gland opening. Dipsocoroidea is a group of minute ground inhabitants, of which the Schizopteridae live in leaf mold and the Dipsocoridae are predators on small insects under bark or in rotten wood or amid stones at the edge of streams.

Enicocephaloidea is a unique group in which the head is bilobed, the pronotum trilobed, and the wings completely membranous. They live under stones, beneath bark, and in leaf mold and are predators. Some species are wingless; others can cast off their wings.

Reduvioidea includes only the assassin bugs or conenose bugs of the family Reduviidae. Nearly all have a stridulatory furrow on the prosternum, which is scraped by the rostrum to produce a squeaking sound. Ocelli are generally present and the beak is three-segmented.

Among the Aradoidea are flat bugs of the family Aradidae and their specialized relatives, Termitaphididae. They lack ocelli and have four-segmented antennae. Most, if not all, are fungus feeders. The Termitaphididae have no wings. They are known from termite nests in the Old and New World tropics. Aradidae are nearly cosmopolitan and fully winged, brachypterous, stenopterous, or apterous.

Cimicimorpha is the largest group of the Geocorisae and is divided into three superfamilies, the Cimicoidea, Tingoidea, and Thaumastocoroidea.

1. Cimicoidea. Anthocoridae, or the flower bugs, are small predators on thrips, mites, and similar species in vegetation, in stored products, and in the nests of birds. The ocelli are distinct, and the front wings have a marginal fracture. Cimicidae contains the bedbugs, which lack ocelli, and have the short wings reduced to pads. The food consists of blood of birds and mammals. The Polyctenidae are bat ectoparasites which lack eyes and have ctenidia and strong claws. The Miridae family contains a majority of the species of Hemiptera. Included are plant bugs of both herbivorous and predacious type. Ocelli are lacking, the antennae are four-segmented, and there is only one dorsal abdominal scent gland opening in nymphs. Two small families, the Plokiophilidae and Microphysidae, are predacious. The Plokiophilids live in the webs of spiders and embiids.

   Nabidae are the long “damsel” bugs which are slender predators on other insects. The ocelli are well developed, and the rostrum is four-segmented. The tropical Velocipedidae are related but differ in the broader form and darker coloration.

2. Tingoidea. This superfamily contains the lace bugs of the family Tingidae which have wings with many lacelike areolae. They lack ocelli, have four segments in the antennae and beak, and commonly have one or more bulbous or hoodlike elevations on the thorax. Pests are known on ornamental plants.

3. Thaumastocoroidea. The only family, the Thaumastocoridae, occurs in Australia and the New World tropics; it includes the royal palm bug of Florida.

Pentatomorpha includes the superfamilies Lygaeoidea, Pyrrhocoroidea, Coreoidea, and Pentatomoidea.

1. Lygaeoidea. This is the first of the superfamilies with ventral trichobothria (bristles) on the abdomen. The antennae are four-segmented. Ocelli are present. The Lygaeidae include the chinch bug, the false chinch bugs, and the milkweed bugs. Small families related to the lygaeids are the thread-legged Neididae (Berytidae), the small Piesmidae, and the tropical Colobathristidae. Some of the last have a unique method of stridulation with a filelike arch on the sides of the head.

2. Pyrrhocoroidea. This group includes the cotton stainers, which attack cotton bolls in the southwestern United States and over most of the tropics, and stout, dark bugs with a reddish border.

3. Coreoidea. The squash bugs and their relatives include the Coreidae, Rhopalidae, Alydidae, and Hyocephalidae. They have four-segmented antennae, a beak, distinct ocelli, and many veins in the membrane.

4. Pentatomoidea. This large group has marginal trichobothria. The antennae are usually five-segmented and the beak is four-segmented. Scutelleridae, or shield bugs, are not injurious in the United States. Cydnidae include the ground-burrowing bugs, which attack strawberries in sandy soil, and the negro bugs. Smaller families of little or no economic importance in the United States are the large tropical Tessaratomidae, the Acanthosomatidae, the Dinidoridae, the Aphylidae, the Urostylidae, the barklike Phloeidae, the shining, oval Plataspidae, and the Lestoniidae. The true stink bugs, Pentatomidae, include the black-and-red harlequin cabbage bug, and several green stink bugs on cotton and other crops.

Insecta

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An order of arthropods (class Insecta); includes some 30,000 species, known as the true bugs; characterized by having mouthparts adapted to piercing or sucking, and usually having two pairs of wings.

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