Insects of Britain and Ireland: orders
Adult insects. Mainly saprophagous and mycophagous (and and feeding on other decay-related micro-organisms), or predatory (a few, e.g. Friesia species feed on tardigrades and rotifers), or phytophagous (e.g., a few consuming pollen and a few consuming plant roots); conspicuous jumpers (via an elongate, forked springing organ beneath the fourth abdominal segment). Minute to small (rarely exceeding 5 mm); flightless. Body dorsiventrally flattened to more or less cylindrical. Head prognathous to hypognathous. Mouthparts well developed; adapted for both biting and sucking; not piercing; highly modified (elongated, adapted for grinding and sucking: the mandibles slender, the maxillae complex, the labium reduced, labial and maxillary palps lacking in the adults). Antennae conspicuous to inconspicuous (variable, sometimes modified as grasping organs in males); simple; 4–6 segmented. Compound eyes present and well developed (but composed of eight or fewer omitidia), or vestigial or absent. Ocelli 0–16 (the distinction between compound eyes and ocelli here being indistinct). Thoracic legs present (and 4-segmented, comprising coxa, trochanter, femur and tibio-tarsus). The body and legs of wingless adults bearing scales (sometimes), or without scales. Tarsi reduced to pretarsal claws terminating the tibiae (the tibia ending in a pair of claws). Abdomen more or less conspicuously appendaged at the rear (via the paired bristles of the springing organ, which however is not strictly terminal, being borne beneath the fourth abdominal segment); with long terminal bristles, or not spectacularly appendaged; lacking clearly visible cerci; apparently 6 segmented; exhibiting rudimentary abdominal limbs (in the form of specialised appendages, a bilobed tube on segment 1, a bifurcate retinaculum on segment 3, and the bisetose springing organ on segment 4).
Larvae. Larvae with three pairs of segmented thoracic legs; without ventral abdominal prolegs. Development of larva into adult gradual; apterygote; not involving a pupal stage.
Classification. Subclass Apterygota (but sometimes treated as a Class, equivalent in status to the Insecta).
British representation. Entomobryidae, Hypogastruridae, Isotomidae, Neelidae, Oncopoduridae, Onychiuridae, Poduridae, Sminthuridae, Tomoceridae; genera about 55; about 305 species.
General comments. Minute, primitive, soft-bodied, phytophagous or saprophagous arthropods, with only 6 abdominal segments. The integument sometimes bears scales rather than the more usual hairs.
Illustrations. • Axelsonia, Anurida (Imms 1957). Axelsonia. Anurida maritima, dorsal (left) and ventral views.
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’.