Insects of Britain and Ireland: orders

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L. Watson and M. J. Dallwitz

Hymenoptera

Bees, Ants, Wasps, Sawflies, Icnneumons, etc.

Adult insects. Social, constituting organized colonies (ants, many bees and wasps), or not social (the rest); predatory, or phytophagous, or imbibing nectar, or saprophagous, or consuming stored produce, or mycophagous, or parasitic; parasitising invertebrates only (but including many blood-suckers and parasites of insects and other arthropods); voluntarily emitting sound (commonly, for example by rubbing a specialized area of the fore-wings over the cenchri, or rubbing files or scrapers on overlapping terga over one another), or mute. Minute to large; capable of flight (usually), or flightless (there being rather numerous forms where wings are either lacking or deciduous); when winged, with two pairs of propellant wings (nearly always), or with one pair of propellant wings (the hindwings being vestigial in some Mymaridae). Body more or less cylindrical to laterally flattened. Head hypognathous. Mouthparts usually well developed; of the biting type, or adapted for both biting and sucking (in the Apoidea); not piercing; conforming to the generalized biting type to highly modified (mandibles are always present, but mouthparts range from the generalized biting type in Symphyta and supposedly primitive Apocrita to combined chewing and sucking adaptations in the Apoidea. In the latter, the laciniae of the labium constitute the glossa (tongue), which becomes lengthened in relation to collecting nectar, the other mouthparts being elongated to constitute a proboscis on which the glossa is borne. On the other hand, some parasitic Hymenoptera exhibit some reduction in mouthparts components). The clypeus not transversely divided and bulbous above as in Psocoptera (q.v.). Antennae conspicuous, or inconspicuous; simple, or complex; 9–13(–30) segmented. Ocelli 0 (or more or less aborted, e.g. in some Sphecidae and the workers of many ants), or 3 (nearly always). Wings four; nearly always of similar texture in both pairs (with some tiny Mymaridae being exceptional, in having the hind-wings reduced to linear stalks and lacking the membrane). Fore-wings membranous; with a pterostigma, or without a pterostigma. Hind-wings smaller than the fore-wings; 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; not fringed. Wings of the resting insect held above the body, with their upper surfaces more or less apposed, or outspread, or closed and directed backwards. Thoracic legs present. The body and legs of wingless adults without scales. Tarsi (3–)5 segmented. Abdomen conspicuously appendaged at the rear, or not conspicuously appendaged (but of these, many Apocrita are equipped with a terminal, retractile sting); exhibiting a conspicuous ovipositor, or not spectacularly appendaged; with cerci clearly visible at its tip, or lacking clearly visible cerci. Abdomen of females with an exserted ovipositor, or with no exserted ovipositor. Abdomen apparently 2–10 segmented (there being much diversity re fusion of tergites, sternites, and segment 1 being associated with the metathorax in bees, ants and wasps); with no rudimentary abdominal limbs.

Larvae. Larvae terrestrial; feeding in the open, or clandestine feeders; phytophagous, or saprophagous, or mycophagous, or parasitic (on Arthropods), or feeding on food gathered and stored by the adults (in many Apocrita, being animal or plant material in different families: e.g., Apidae, Pompilidae, Formicidae); with three pairs of segmented thoracic legs (in externally feeding Symphyta), or without segmented thoracic legs (Apocrita and boring, tunelling and mining Symphyta); with ventral abdominal prolegs (in externally feeding Symphyta), or without ventral abdominal prolegs (Apocrita and boring, tunelling and mining Symphyta); with paired anal prolegs, or without anal prolegs (often, sometimes even when ventral prolegs are present). The abdominal prolegs without crochets. Larvae brightly coloured (some Symphyta), or drab (mostly). Larval head with a well sclerotized capsule (Symphyta), or without a well sclerotized capsule (or much less heavily sclerotized, in the maggot-like larvae of Apocrita). Development of larva into adult involving marked metamorphosis; endopterygote; involving a pupal stage.

Pupae. Pupae without a puparium; always without articulated mandibles; usually with free appendages.

Classification. Subclass Pterygota; Division Endopterygota.

British representation. 66 families, described individually in the accompanying data set; genera about 1100; about 6700 species.

Special features. Without the ‘neck’ characteristic of Raphidioptera. The wingless adults not larviform, with only obscure thoracic segmentation.

General comments. The adults are found everywhere: in and on the ground, on vegetation (especially on flowers), hawking for prey, drinking or gathering mud around ponds and streams, etc. Most adults seem to feed to some extent on nectar or honey-dew, but many parasitic species suck the juices of their hosts, as well as depositing eggs in or on them. They are mostly diurnal or crepuscular, but parasitic wasps with nocturnal hosts are themselves nocturnal, and are generally of distinctive appearance, being pale coloured and with unusually large compound eyes and ocelli.

Illustrations. • Representative Hymenoptera. For numerous illustrations of Hymenoptera from Curtis, Saunders, Cameron and other classic works, see the ‘Families of British Hymenoptera’ data set. • Coelinius anceps (Curtis) (Yellow-bodied Ichneumon: B. Ent. 289). • Adults and larvae (Cynipoidea, Formicoidea, Vespoidea: Lubbock 1890). Cynipoidea. Formicoidea. Vespoidea.


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. delta-intkey.com’.

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