Hemiptera is an
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of
insectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s most often known as the
true bugs (
cf. bugA bug is an insect of the order Hemiptera, known as the "true bugs".Bug or BUG may also refer to:-Biology:* Informally, most arthropods, except marine crustaceans, including individuals or species of** centipede** insect** millipede** mite...
), comprising around 50,000–80,000
speciesIn biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of
cicadaA cicada is an insect of the order Hemiptera, suborder Auchenorrhyncha , in the superfamily Cicadoidea, with large eyes wide apart on the head and usually transparent, well-veined wings. There are about 2,500 species of cicada around the world, and many of them remain unclassified...
s,
aphidAphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s,
planthopperA planthopper is any insect in the infraorder Fulgoromorpha within the Hemiptera. The name comes from their remarkable resemblance to leaves and other plants of their environment and from the fact that they often "hop" for quick transportation in a similar way to that of grasshoppers. However,...
s,
leafhopperLeafhopper is a common name applied to any species from the family Cicadellidae. Leafhoppers, colloquially known as hoppers, are minute plant-feeding insects in the superfamily Membracoidea in the order Hemiptera...
s,
shield bugPentatomoidea is a superfamily of insects in the Heteroptera suborder of the Hemiptera order and, as such, share a common arrangement of sucking mouthparts...
s, and others. They range in size from 1 millimetre (0.0393700787401575 in) to around 15 centimetres (6 in), and share a common arrangement of sucking
mouthpartsInsects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts...
.
Sometimes the name
true bugs is applied more narrowly still to insects of the suborder
HeteropteraHeteroptera is a group of about 40,000 species of insects in the Hemiptera. Sometimes called "true bugs", that name more commonly refers to Hemiptera as a whole, and "typical bugs" might be used as a more unequivocal alternative since among the Hemiptera the heteropterans are most consistently and...
only.
Characteristics
The defining feature of hemipterans is their possession of mouthparts where the
mandiblesInsect mandibles are a pair of appendages near the insect’s mouth, and the most anterior of the three pairs of oral appendages . Their function is typically to grasp, crush, or cut the insect’s food, or to defend against predators or rivals...
and
maxillaeInsects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts...
have evolved into a
proboscisA proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...
, sheathed within a modified labium to form a "beak" or "
rostrumThe term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
" which is capable of piercing
tissuesTissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
(usually plant tissues) and sucking out the liquids — typically
sapSap is a fluid transported in xylem cells or phloem sieve tube elements of a plant. It transports water and nutrients throughout the plant....
.
The
forewingsInsects are the only group of invertebrates known to have evolved flight. Insects possess some remarkable flight characteristics and abilities, still far superior to attempts by humans to replicate their capabilities. Even our understanding of the aerodynamics of flexible, flapping wings and how...
of Hemiptera are either entirely membranous, as in the
SternorrhynchaSternorrhyncha is a suborder of the Hemiptera which contains the aphids, whiteflies, and scale insects, groups which were traditionally included in the order Homoptera. "Sternorrhyncha" refers to the rearward position of the mouthparts relative to the head...
and
AuchenorrhynchaThe Auchenorrhyncha is the suborder of the Hemiptera which contains most of the familiar members of what was called the Homoptera - groups such as cicadas, leafhoppers, treehoppers, planthoppers, and spittlebugs. The aphids and scale insects are the other well-known "Homoptera", and they are in...
, or partially hardened, as in most
HeteropteraHeteroptera is a group of about 40,000 species of insects in the Hemiptera. Sometimes called "true bugs", that name more commonly refers to Hemiptera as a whole, and "typical bugs" might be used as a more unequivocal alternative since among the Hemiptera the heteropterans are most consistently and...
. The name "Hemiptera" is from the
GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
(
; "half") and (
; "wing"), referring to the forewings of many heteropterans which are hardened near the base, but membranous at the ends. Wings modified in this manner are termed
hemelytra (singular:
hemelytron), by analogy with the completely hardened
elytraAn elytron is a modified, hardened forewing of certain insect orders, notably beetles and a few of the true bugs ; in most true bugs, the forewings are instead called hemelytra, as only the basal half is thickened while the apex is membranous...
of
beetleColeoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, and occur only in the suborder
HeteropteraHeteroptera is a group of about 40,000 species of insects in the Hemiptera. Sometimes called "true bugs", that name more commonly refers to Hemiptera as a whole, and "typical bugs" might be used as a more unequivocal alternative since among the Hemiptera the heteropterans are most consistently and...
. The forewings may be held "roofwise" over the body (typical of
SternorrhynchaSternorrhyncha is a suborder of the Hemiptera which contains the aphids, whiteflies, and scale insects, groups which were traditionally included in the order Homoptera. "Sternorrhyncha" refers to the rearward position of the mouthparts relative to the head...
and
AuchenorrhynchaThe Auchenorrhyncha is the suborder of the Hemiptera which contains most of the familiar members of what was called the Homoptera - groups such as cicadas, leafhoppers, treehoppers, planthoppers, and spittlebugs. The aphids and scale insects are the other well-known "Homoptera", and they are in...
), or held flat on the back, with the ends overlapping (typical of
HeteropteraHeteroptera is a group of about 40,000 species of insects in the Hemiptera. Sometimes called "true bugs", that name more commonly refers to Hemiptera as a whole, and "typical bugs" might be used as a more unequivocal alternative since among the Hemiptera the heteropterans are most consistently and...
). In all suborders, the hindwings - if present at all - are entirely membranous and usually shorter than the forewings.
The
antennaeAntennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
in Hemiptera are typically five-segmented, although they can still be quite long, and the tarsi of the
legsThe arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
are three-segmented or shorter.
Although hemipterans vary widely in their overall form, their mouthparts (formed into a "rostrum") are quite distinctive; the only orders with mouthparts modified in a similar manner are the Thysanoptera and some Phthiraptera, and these are generally easy to recognize as non-hemipteran for other reasons. Aside from the mouthparts, various insects can be confused with hemipterans, including
cockroachCockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...
es and
psocidsPsocoptera are an order of insects that are commonly known as booklice, barklice or barkflies. They first appeared in the Permian period, 295–248 million years ago. They are often regarded as the most primitive of the hemipteroids. Their name originates from the Greek word psokos meaning...
, both of which have longer many-segmented antennae, and some
beetleColeoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, but these have fully hardened forewings which do not overlap.
Classification
The present members of the order Hemiptera were historically placed into two orders,
Homoptera and Heteroptera/Hemiptera, based on the differences in wing structure and the position of the rostrum. These two orders were then combined into the single order Hemiptera by many authorities, with Homoptera and Heteroptera classified as suborders. The order is presently more usually divided into four or more suborders, after it was established that the families grouped together as "Homoptera" are not as closely related as had previously been thought (see
paraphylyA group of taxa is said to be paraphyletic if the group consists of all the descendants of a hypothetical closest common ancestor minus one or more monophyletic groups of descendants...
).
AuchenorrhynchaThe Auchenorrhyncha is the suborder of the Hemiptera which contains most of the familiar members of what was called the Homoptera - groups such as cicadas, leafhoppers, treehoppers, planthoppers, and spittlebugs. The aphids and scale insects are the other well-known "Homoptera", and they are in...
contains the
cicadaA cicada is an insect of the order Hemiptera, suborder Auchenorrhyncha , in the superfamily Cicadoidea, with large eyes wide apart on the head and usually transparent, well-veined wings. There are about 2,500 species of cicada around the world, and many of them remain unclassified...
s,
leafhopperLeafhopper is a common name applied to any species from the family Cicadellidae. Leafhoppers, colloquially known as hoppers, are minute plant-feeding insects in the superfamily Membracoidea in the order Hemiptera...
s,
treehopperTreehoppers and thorn bugs are members of the family Membracidae, a group of insects related to the cicadas and the leafhoppers. There are about 3,200 known species of treehoppers in over 600 genera...
s,
planthopperA planthopper is any insect in the infraorder Fulgoromorpha within the Hemiptera. The name comes from their remarkable resemblance to leaves and other plants of their environment and from the fact that they often "hop" for quick transportation in a similar way to that of grasshoppers. However,...
s, and
froghopperThe froghoppers, or the superfamily Cercopoidea, are a group of Hemipteran insects, in the suborder Auchenorrhyncha. Traditionally, most of this superfamily was considered a single family, Cercopidae, but this family has been split into three separate families for many years now: the Aphrophoridae,...
s. The 12,500 species in the suborder
SternorrhynchaSternorrhyncha is a suborder of the Hemiptera which contains the aphids, whiteflies, and scale insects, groups which were traditionally included in the order Homoptera. "Sternorrhyncha" refers to the rearward position of the mouthparts relative to the head...
are the
aphidAphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s,
whitefliesThe whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...
and
scale insectThe scale insects are small insects of the order Hemiptera, generally classified as the superfamily Coccoidea. There are about 8,000 species of scale insects.-Ecology:...
s. The suborder
ColeorrhynchaPeloridiidae is a family of true bugs, comprising 17 genera and 36 species. They are small, ranging in length from 2 to 4 mm, rarely seen, peculiarly lumpy, flattened bugs found in Patagonia , New Zealand, eastern Australia, Lord Howe Island and New Caledonia. All the Peloridiidae species are...
(comprising the single family Peloridiidae), contains fewer than 30 species of
GondwanaIn paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
-distributed bugs, and is sometimes grouped with the Heteroptera (to form the suborder
ProsorrhynchaThe name Prosorrhyncha is a name for a suborder of Hemiptera, comprising a grouping of the traditional taxon "Heteroptera" plus its sister taxon, the family Peloridiidae...
).
HeteropteraHeteroptera is a group of about 40,000 species of insects in the Hemiptera. Sometimes called "true bugs", that name more commonly refers to Hemiptera as a whole, and "typical bugs" might be used as a more unequivocal alternative since among the Hemiptera the heteropterans are most consistently and...
itself is a group of 25,000 species of relatively large bugs, including the
shield bugPentatomoidea is a superfamily of insects in the Heteroptera suborder of the Hemiptera order and, as such, share a common arrangement of sucking mouthparts...
s,
seed bugThe Lygaeidae are a family in the Hemiptera , with some 60 genera in six subfamilies. The family includes the insects commonly known as milkweed bugs, and also some of those known as seed bugs...
s, assassin bugs,
flower bugsThe Anthocoridae are a family of bugs, commonly called minute pirate bugs or flower bugs.-Name:The vernacular name probably stems from the notion that these very small animals can do much pain to humans, just like small pirate vessels can do so to big ships.The scientific name is a combination of...
,
sweetpotato bugThe sweetpotato bug is a species of insect in the family Coreidae. Native to Southeast Asia, the species has immigrated to the Pacific Islands...
s and the water bugs (see below).
The closest relatives of hemipterans are the
thripsThrips are tiny, slender insects with fringed wings . Other common names for thrips include thunderflies, thunderbugs, storm flies, thunderblights, and corn lice...
and
liceLice is the common name for over 3,000 species of wingless insects of the order Phthiraptera; three of which are classified as human disease agents...
, which collectively form the "hemipteroid assemblage" within the
ExopterygotaThe Exopterygota, also known as Hemipterodea, are a superorder of insects of the subclass Pterygota in the infraclass Neoptera, in which the young resemble adults but have externally-developing wings. They undergo a modest change between immature and adult, without going through a pupal stage...
subclass of the Class
InsectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
a.
The fossil record of hemipterans goes back to the Early Permian. Homopterans appeared first, with Heteroptera first appearing in the
TriassicThe Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
.
Life cycle and ecology
Hemipterans are
hemimetabolousHemimetabolism or hemimetaboly, also called incomplete metamorphosis, is a term used to describe the mode of development of certain insects that includes three distinct stages: the egg, nymph, and the adult stage, or imago. These groups go through gradual changes; there is no pupal stage...
, meaning that they do not undergo
metamorphosisMetamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
between a
larvaA larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
l phase and an
adult phaseIn biology, the imago is the last stage of development of an insect, after the last ecdysis of an incomplete metamorphosis, or after emergence from the pupa where the metamorphosis is complete...
. Instead, their young are called
nymphsIn biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
, and resemble the adults to a large degree, the final transformation involving little more than the development of functional wings (if they are present at all) and functioning sexual organs, with no intervening
pupaA pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
l stage as in
holometabolousHolometabolism, also called complete metamorphism, is a term applied to insect groups to describe the specific kind of insect development which includes four life stages - as an embryo or egg, a larva, a pupa and an imago or adult. Holometabolism is a monophyletic trait that all insects in the...
insects. Hemiptera is the largest insect order that is hemimetabolous; the orders with more species all have a
pupaA pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
l stage (
LepidopteraLepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
,
ColeopteraColeoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
,
DipteraTrue flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
and
Hymenoptera Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
).
Many aphids are
parthenogeneticParthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...
during part of the life cycle, such that females can produce unfertilized eggs, which are
clonesCloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...
of themselves.
Most hemipterans are phytophagous, feeding on plant sap, such as
aphidAphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s,
scale insectThe scale insects are small insects of the order Hemiptera, generally classified as the superfamily Coccoidea. There are about 8,000 species of scale insects.-Ecology:...
s and
cicadaA cicada is an insect of the order Hemiptera, suborder Auchenorrhyncha , in the superfamily Cicadoidea, with large eyes wide apart on the head and usually transparent, well-veined wings. There are about 2,500 species of cicada around the world, and many of them remain unclassified...
s. Most of the remainder are
predatoryIn ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
, feeding on other insects, or even small vertebrates. A few, however, are parasites,
feeding on the bloodHematophagy is the practice of certain animals of feeding on blood...
of larger animals. These include
bedbugCimicidae are small parasitic insects. The most common type is Cimex lectularius. The term usually refers to species that prefer to feed on human blood...
s and the kissing bugs of the family
ReduviidaeReduviidae is a large, cosmopolitan family of predatory insects in the suborder Heteroptera...
, which can transmit potentially deadly
TrypanosomaTrypanosoma is a genus of kinetoplastids , a monophyletic group of unicellular parasitic flagellate protozoa. The name is derived from the Greek trypano and soma because of their corkscrew-like motion. All trypanosomes are heteroxenous and are transmitted via a vector...
infections.
Several families of Hemiptera are
water bugs, adapted to an
aquatic lifestyleAn aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
, such as the
water boatmenCorixidae is a family of aquatic insects in the order Hemiptera that inhabit ponds and slow moving streams, where they swim near the bottom. There are about 500 known species worldwide, in 33 genera, including the genus Sigara....
and
water scorpionsNepidae is a family of insects in the order Hemiptera, suborder Heteroptera. They are commonly called waterscorpions for their superficial resemblance to a scorpion, which is due to the raptorial forelegs and the presence of a long slender process at the posterior end of the abdomen, simulating a...
. They are mostly predatory, and have legs adapted as
paddleA paddle is a tool used for pushing against liquids, either as a form of propulsion in a boat or as an implement for mixing.-Materials and designs:...
s to help the animal move through the water. The "pondskaters" or "water striders" of the family Gerridae are also associated with water, but use the
surface tensionSurface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
of standing water to keep them above the surface; they include the genus
HalobatesHalobates or sea skaters are a genus with over 40 species of water striders. While many are coastal, about five of these are able to survive and stand on the surface of the open ocean, a habitat containing very few insect species. They are predators, coastal species feeding mainly on fallen...
which is the only group of insects to be truly
marineMarine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
.
Economic significance
Many species of Hemiptera are significant pests of crops and gardens, including many species of
aphidAphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
and various
scale insectThe scale insects are small insects of the order Hemiptera, generally classified as the superfamily Coccoidea. There are about 8,000 species of scale insects.-Ecology:...
s, including the
cottony cushion scaleIcerya purchasi is a scale insect that feeds on several species of woody plants, most notably on Citrus and Pittosporum. Originally identified in 1878 as a New Zealand located pest of kangaroo acacia, it is now found worldwide where citrus crops are grown.-Life cycle:This scale infests twigs and...
, a pest whose infestation of American
citrusCitrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
crops sparked one of the earliest
biological pest controlBiological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
programmes, when the Australian beetle
Rodolia cardinalisRodolia cardinalis is a species of ladybird beetle that is sometimes described as endemic to Australia.-New Zealand:...
was introduced as a natural enemy of the scale insect.
Conversely, some predatory hemipterans are themselves biological pest control agents, such as various
nabidsThe insect family Nabidae contains the damsel bugs. The terms damsel bug and nabid are synonymous. There are over 400 species. They are soft-bodied, elongate, winged terrestrial predators. Many damsel bugs catch and hold prey with their forelegs, similar to mantids...
, and even some members of families that are primarily phytophagous, such as the genus
GeocorisGeocoris is a genus of insects in the family Lygaeidae . Commonly known as the big-eyed bug, Geocoris is a beneficial predator often confused with the true chinch bug, which is a pest.Big-eyed bugs are true bugs in the order Hemiptera...
in the family Lygaeidae. Other hemipterans have positive uses, such as in the production of the dyestuffs
cochinealThe cochineal is a scale insect in the suborder Sternorrhyncha, from which the crimson-colour dye carmine is derived. A primarily sessile parasite native to tropical and subtropical South America and Mexico, this insect lives on cacti from the genus Opuntia, feeding on plant moisture and...
and
crimsonCrimson is a strong, bright, deep red color. It is originally the color of the dye produced from a scale insect, Kermes vermilio, but the name is now also used as a generic term for those slightly bluish-red colors that are between red and rose; besides crimson itself, these colors include...
, or
shellacShellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and sold as dry flakes , which are dissolved in ethyl alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish...
.