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Hemiptera /hɛˈmɪptərə/ (Ancient Greek hemiptera ("half-wings")) or true bugs are an order of insects comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, bed bugs and shield bugs. They range in size from 1 mm (0.04 in) to around 15 cm (6 in), and share a common arrangement of sucking mouthparts. The name "true bugs" is often limited to the suborder Heteroptera. Many insects commonly known as "bugs", especially in American English, belong to other orders; for example, the lovebug is a fly and the May bug and ladybug are beetles.

Behavior[]

Most hemipterans feed on plants, using their sucking and piercing mouthparts to extract plant sap. Some are hematophagous, while others are predators that feed on other insects or small invertebrates. They live in a wide variety of habitats, generally terrestrial, though some species are adapted to life in or on the surface of fresh water. Hemipterans are hemimetabolous, with young nymphs that somewhat resemble adults. Many aphids are capable of parthenogenesis, producing young from unfertilised eggs; this helps them to reproduce extremely rapidly in favourable conditions.

Biology[]

Mouthparts[]

Calidea dregii

Hemipteran mouthparts are distinctive, with mandibles and maxillae modified to form a piercing "stylet" sheathed within a modified labium. The defining feature of hemipterans is their "beak" in which the modified mandibles and maxillae form a "stylet" which is sheathed within a modified labium. The stylet is capable of piercing tissues and sucking liquids, while the labium supports it. The stylet contains a channel for the outward movement of saliva and another for the inward movement of liquid food. A salivary pump drives saliva into the prey; a cibarial pump extracts liquid from the prey. Both pumps are powered by substantial dilator muscles in the head. The beak is usually folded under the body when not in use. The diet is typically plant sap, but some hemipterans such as assassin bugs are blood-suckers, and a few are predators.

Both herbivorous and predatory hemipterans inject enzymes to begin digestion extra-orally (before the food is taken into the body). These enzymes include amylase to hydrolyse starch, polygalacturonase to weaken the tough cell walls of plants, and proteinases to break down proteins.

Although the Hemiptera vary widely in their overall form, their mouthparts form a distinctive "rostrum". Other insect orders with mouthparts modified into anything like the rostrum and stylets of the Hemiptera include some Phthiraptera, but for other reasons they generally are easy to recognize as non-hemipteran. Similarly, the mouthparts of Siphonaptera, some Diptera and Thysanoptera superficially resemble the rostrum of the Hemiptera, but on closer inspection the differences are considerable. Aside from the mouthparts, various other insects can be confused with Hemiptera, but they all have biting mandibles and maxillae instead of the rostrum. Examples include cockroaches and psocids, both of which have longer, many-segmented antennae, and some beetles, but these have fully hardened forewings which do not overlap.

Wing structure[]

Cybister lateralimarginalis

The forewings of Hemiptera are either entirely membranous, as in the Sternorrhyncha and Auchenorrhyncha, or partially hardened, as in most Heteroptera. The name "Hemiptera" is from the Greek ἡμι- ('hemi'; "half") and πτερόν ('pteron'; "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 elytra of beetles, and occur only in the suborder Heteroptera. In all suborders, the hindwings – if present at all – are entirely membranous and usually shorter than the forewings. The forewings may be held "roofwise" over the body (typical of Sternorrhyncha and Auchenorrhyncha), or held flat on the back, with the ends overlapping (typical of Heteroptera). The antennae in Hemiptera typically consist of four or five segments, although they can still be quite long, and the tarsi of the legs have two or three segments.

Sound production[]

Many hemipterans can produce sound for communication. The "song" of male cicadas, the loudest of any insect, is produced by tymbal organs on the underside of the abdomen, and is used to attract mates. The tymbals are drumlike disks of cuticle, which are clicked in and out repeatedly, making a sound in the same way as popping the metal lid of a

Fire bugs are often known for causing an extreme damage to crops

jam jar in and out.

Stridulatory sounds are produced among the aquatic Corixidae and Notonectidae (backswimmers) using tibial combs rubbed across rostral ridges.

Metamorphosis[]

Hemipterans are hemimetabolous, meaning that they do not undergo metamorphosis, the complete change of form between a larval phase and an adult phase. Instead, their young are called nymphs, and resemble the adults to a greater or lesser degree. The nymphs moult several times as they grow, and each instar resembles the adult more than the previous one. Wing buds grow in later stage nymphs; the final transformation involves little more than the development of functional wings (if they are present at all) and functioning sexual organs, with no intervening pupal stage as in holometabolous insects.

Defense mechanisms[]

Assassin bugs inject their prey with a fluid that dissolves their inner tissues as it enters the blood vessels!

Hemiptera form prey to predators including vertebrates, such as birds, and other invertebrates such as ladybirds. In response, hemipterans have evolved antipredator adaptations. Ranatra may feign death (thanatosis). Others such as Carpocoris purpureipennis secrete toxic fluids to ward off arthropod predators; some Pentatomidae such as Dolycoris are able to direct these fluids at an attacker. Toxic cardenolide compounds are accumulated by the heteropteran Oncopeltus fasciatus when it consumes milkweeds, while the coreid stinkbug Amorbus rubiginosus acquires 2-hexenal from its food plant, Eucalyptus. Some long-legged bugs mimic twigs, rocking to and fro to simulate the motion of a plant part in the wind. The nymph of the Masked hunter bug camouflages itself with sand grains, using its hind legs and tarsal fan to form a double layer of grains, coarser on the outside. The Amazon rain forest cicada Hemisciera maculipennis displays bright red deimatic flash coloration on its hindwings when threatened; the sudden contrast helps to startle predators, giving the cicada time to escape. The coloured patch on the hindwing is concealed at rest by an olive green patch of the same size on the forewing, enabling the insect to switch rapidly from cryptic to deimatic behaviour.

Cicadas can sometimes become a nuisance when in large numbers.

Some hemipterans such as firebugs have bold aposematic warning coloration, often red and black, which appear to deter passerine birds. Many hemipterans including aphids, scale insects and especially the planthoppers secrete wax to protect themselves from threats such as fungi, parasitoidal insects and predators, as well as abiotic factors like desiccation. Hard waxy coverings are especially important in the sedentary Sternorrhyncha such as scale insects, which have no means of escaping from predators; other Sternorrhyncha evade detection and attack by creating and living inside plant galls. Nymphal Cicadoidea and Cercopoidea have glands attached to the Malpighian tubules in their proximal segment that produce mucopolysaccharides, which form the froth around spittlebugs, offering a measure of protection.

Parental care is found in many species of Hemiptera especially in members of the Membracidae and numerous Heteroptera. In many species of shield bug, females stand guard over their egg clusters to protect them from egg parasitoids and predators. In the aquatic Belostomatidae, females lay their eggs on the back of the male which guards the eggs. Protection provided by ants is common in the Auchenorrhyncha.

Agricultural threat[]

Large clumps of aphids can harm or even kill plants.

Although many species of Hemiptera are significant pests of crops and garden plants, including many species of aphid and scale insects, other species are harmless. The damage done is often not so much the deprivation of the plant of its sap, but the fact that they transmit serious viral diseases between plants. They often produce copious amounts of honeydew which encourages the growth of sooty mould. Significant pests include the cottony cushion scale, a pest of citrus fruit trees, the green peach aphid and other aphids which attack crops worldwide and transmit diseases, and jumping plant lice which are often host plant-specific and transmit diseases.

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