[4] Entomologists reserve the term bug for Hemiptera or Heteroptera,[5] which does not include other arthropods or insects of other orders such as ants, bees, beetles, or butterflies.

[a] Many insects with "bug" in their common name, especially in American English, belong to other orders; for example, the lovebug is a fly[9] and the Maybug and ladybug are beetles.

Many aphids are capable of parthenogenesis, producing young from unfertilised eggs; this helps them to reproduce extremely rapidly in favourable conditions.

[25] The cause of the disparity in the analyses is suggested to be the long branch attraction effect in phylogenetic analysis, due to rapidly evolving DNA regions.

These enzymes include amylase to hydrolyse starch, polygalacturonase to weaken the tough cell walls of plants, and proteinases to break down proteins.

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.

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.

[35] 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 jam jar in and out.

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

[40] Hemipterans make use of a variety of modes of locomotion including swimming, skating on a water surface and jumping, as well as walking and flying like other insects.

Treehoppers can attain a take-off velocity of up to 2.7 metres per second and an acceleration of up to 250 g. The instantaneous power output is much greater than that of normal muscle, implying that energy is stored and released to catapult the insect into the air.

[46] Cicadas, which are much larger, extend their hind legs for a jump in under a millisecond, again implying elastic storage of energy for sudden release.

Most Heteroptera also feed on mesophyll tissue where they are more likely to encounter defensive secondary plant metabolites which often leads to the evolution of host specificity.

[55][56] Phloem sap is a sugary liquid low in amino acids, so insects have to process large quantities to meet their nutritional requirements.

[58] A striking adaptation to a very dilute diet is found in many hemipterans: a filter chamber, a part of the gut looped back on itself as a countercurrent exchanger, which permits nutrients to be separated from excess water.

[59] The residue, mostly water with sugars and amino acids, is quickly excreted as sticky "honey dew", notably from aphids but also from other Auchenorrhycha and Sternorrhyncha.

There are further stylets on the maxillae, adapted as tubular canals to inject saliva and to extract the pre-digested and liquified contents of the prey.

[41] The first known hemipteran to feed in this way on vertebrates was the extinct assassin bug Triatoma dominicana found fossilized in amber and dating back about twenty million years.

Faecal pellets fossilised beside it show that it transmitted a disease-causing Trypanosoma and the amber included hairs of the likely host, a bat.

[66] Ants may also protect the plant bugs from their natural enemies, removing the eggs of predatory beetles and preventing access by parasitic wasps.

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.

[47] 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.

[90] Additional uses of this traditional product include the waxing of citrus fruits to extend their shelf-life, and the coating of pills to moisture-proof them, provide slow-release or mask the taste of bitter ingredients.

[93][94] Bed bugs mate by traumatic insemination; the male pierces the female's abdomen and injects his sperm into a secondary genital structure, the spermalege.

Insects have a high protein content and good food conversion ratios, but most hemipterans are too small to be a useful component of the human diet.

[99] Among the bugs, cicadas in particular have been used as money, in folk medicine, to forecast the weather, to provide song (in China), and in folklore and myths around the world.

[100] Large-scale cultivation of the oil palm Elaeis guineensis in the Amazon basin damages freshwater habitats and reduces the diversity of aquatic and semi-aquatic Heteroptera.