Hemiptera

Lore & Background

The name Hemiptera comes from the Greek words hemi (half) and ptera (wings), meaning 'half-wings,' since the forewings of many species are hardened and leathery at the base but membranous at the tips. Entomologists reserve the term bug for Hemiptera or Heteroptera, which does not include other arthropods or insects of other orders such as ants, bees, beetles, or butterflies. In some varieties of English, all terrestrial arthropods are colloquially called bugs. Many insects with 'bug' in their common name are in other orders; for example, the lovebug is a fly, while the maybug and ladybug are beetles.

Hemiptera is the largest order of hemimetabolous insects, containing more than 95,000 named species. Other insect orders with more species are all holometabolous. The majority of species are terrestrial, including a number of important agricultural pests, but some are found in freshwater habitats. These are usually members of the Nepomorpha and Gerromorpha infraorders, including water boatmen, backswimmers, pond skaters, velvet water bugs, and giant water bugs. Some terrestrial groups are also found near water, such as shore bugs and toad bugs.

The fossil record of hemipterans goes back to the Carboniferous (Moscovian). The oldest fossils are of the Archescytinidae from the Lower Permian and are thought to be basal to the Auchenorrhyncha. Fulgoromorpha and Cicadomorpha appear in the Upper Permian, as do Sternorrhyncha of the Psylloidea and Aleyrodoidea. Aphids and Coccoids appear in the Triassic. The Coleorrhyncha extend back to the Lower Jurassic. The Heteroptera first appeared in the Triassic.

Reader's Guide

Humans have interacted with Hemipterans for millennia. Some species, including many aphids, are significant agricultural pests, damaging crops by sucking the sap. Others harm humans more directly as vectors of serious diseases. The bed bug is a persistent parasite of humans, and some kissing bugs can transmit Chagas disease. Some species have been used for biological control of insect pests or of invasive plants. A few hemipterans have been cultivated for the extraction of dyestuffs such as cochineal and carmine, and for shellac. Cicadas have been used as food, and have appeared in literature since the Iliad in Ancient Greece.

The defining feature of hemipterans is their rostrum, or 'beak,' in which the modified mandibles and maxillae form a 'stylet' 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 predators. Both herbivorous and predatory hemipterans inject enzymes to begin digestion extra-orally. These enzymes include amylase to hydrolyse starch, polygalacturonase to weaken the tough cell walls of plants, and proteinases to break down proteins.

The forewings of Hemiptera are either entirely membranous, as in the Sternorrhyncha and Auchenorrhyncha, or partially hardened, as in most Heteroptera. The name 'Hemiptera' refers 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 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 or held flat on the back, with the ends overlapping. The antennae typically consist of four or five segments, and the tarsi of the legs have two or three segments. 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. Stridulatory sounds are produced among the aquatic Corixidae and Notonectidae using tibial combs rubbed across rostral ridges.

Did You Know?

• The name 'Hemiptera' means 'half-wings,' referring to forewings that are hardened at the base and membranous at the tips.
• Some hemipterans, such as kissing bugs, can transmit Chagas disease to humans.
• Many aphids are capable of parthenogenesis, producing young from unfertilised eggs.