Insects of Britain and Ireland: orders

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L. Watson and M. J. Dallwitz


Bugs, Aphids, Frog-hoppers, Pond-skaters, Water-scorpions, Water-boatmen, Cicadas, etc.

Adult insects. Terrestrial (mostly), or aquatic (some Heteroptera); nearly always found near water (some forms), or not particularly associated with water. Predatory (with many Heteroptera feeding on invertebrates), or phytophagous (all Homoptera being plant feeders, with Sternorrhyncha and Fulgoroidea predominantly in phloem, Cicadoidea and Cercopoidea in xylem, Cicadelloidea specialising variously in phloem, xylem or parenchyma, and phytophagous Heteroptera feeding on parenchyma, seeds or pollen; most are associated with Angiosperms, but some feed on cryptogams, and a few are mycetophagous), or parasitic (some Heteroptera); when parasitic, ectoparasitic on mammals (a few), or ectoparasitic on birds, or parasitising invertebrates only; conspicuous ‘jumpers’ (many Homoptera), or not ‘jumpers’; voluntarily emitting sound (by stridulation, notably in Reduviidae, or by other means in cicadas), or mute. Small to large; with hardened ‘elytra’ (q.v.), representing the fore-wings, or without elytra; capable of flight, or flightless; when winged, with one pair of propellant wings (the hindwings). Body dorsiventrally flattened. Head more or less prognathous (in most Heteroptera), or hypognathous to opisthognathous (in most Homoptera); prolonged into a rigid beak (via the extended, rigid and downward-to-backwardly directed labrum). Mouthparts well developed; suctorial; piercing; highly modified (consisting of two pairs of hinged, piercing ‘stylets’, comprising the mandibles and maxillae, both of which lack palps, resting in an elongated, dorsally grooved, rostrate labium: see the accompanying illustrations, and the more detailed description below). Antennae conspicuous, or inconspicuous; more or less simple, or complex (for example, often elbowed or articulated); 4–5 segmented (Heteroptera), or 3–10 segmented (Hemiptera). Compound eyes present and well developed. Ocelli 0, or 2, or 3. Wings when present, i.e. usually, four; of similar texture in both pairs, or markedly differently textured in the two pairs (the fore-wings usually completely or at least proximally harder than the hind-wings). Fore-wings membranous, or leathery, or membranous and leathery (commonly basally leathery and distally membranous). Hind-wings smaller than the fore-wings to larger than the fore-wings; markedly broader than the fore-wings, or no broader than the fore-wings; folded in repose, or not folded in the resting insect. Wings with numerous cross-veins, or with few cross-veins; more or less naked. Wings of the resting insect closed and directed backwards; held roof-like over the abdomen, or not held roof-like. Thoracic legs present (usually), or absent (in mealybugs and scale insects). Tarsi 1–3 segmented (erminating in 1–3 claws, or clawless). Abdomen conspicuously appendaged at the rear (e.g., the respiratory tubes in aquatic forms), or not conspicuously appendaged; with long terminal bristles, or not spectacularly appendaged; lacking clearly visible cerci; apparently 8–11 segmented (with much diversity of structure - segment 1 or 1 and 2 being sometimes reduced and closely associated with the metathorax, and 10 being usually modified as the anal tube), or 2 segmented.

Larvae. Larvae terrestrial, or aquatic; with three pairs of segmented thoracic legs; without ventral abdominal prolegs. Development of larva into adult gradual; exopterygote; not involving a pupal stage.

Classification. Subclass Pterygota; Division Endopterygota.

British representation. 61 families, described individually in the accompanying data set; genera about 540; about 1650 species.

General comments. The remarkable mouthparts incorporate two pairs of long, slender, sclerotized, flexible stylets, representing highly modified mandibles and maxillae. The stylets lie in a groove in the elongated, 1–4 segmented labium, which serves as a guide. The mandibular stylets almost enclose the maxillary pair, and are apically serrated for piercing and drilling. Longitudinal grooves in the apposed maxillary stylets form two separate channels, and during feeding salivary secretions are pumped down one while liquid food is sucked up the other. Some phytophagous forms, in particular the aphids, operate this device with remarkable precision to locate the phloem of the host - a capacity involved in the natural and experimental transmission of plant viruses, and capitalized upon by plant physiologists collecting phloem contents.

Illustrations. • Representative hemipteran: Acanthosoma haemorrhoidale. For numerous images of Hemiptera, see the ‘Families of British Hemiptera’ data set. • Acanthosoma haemorrhoidale (detail: B. Ent. 28). • Acanthosoma haemorrhoidale (dissections: B. Ent. 28). • Acanthosoma haemorrhoidale (legend+text: B. Ent 28). • Ranatra linearis (Shaw and Nodder, about 1802). • 'The Great Surinam Nepa' (Exotic species, Shaw and Nodder, about 1798).

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. Insects of Britain and Ireland: orders. Version: 16th May 2016.’.