Insects of Britain and Ireland: orders

DELTA home

L. Watson and M. J. Dallwitz


Including Megaloptera (Sialidae); excluding Raphidioptera. Green Lacewings, Brown Lacewings, Alder-flies, Stinkers, Stink-flies, Dusty-wings, Sponge-flies, Wax-flies.

Adult insects. Nearly always found near water (the Sialidae and Sisyridae having aquatic larvae), or not particularly associated with water. Predatory (on slow moving, soft bodied arthropods - aphids, psyllids, etc.). Small to medium sized; capable of flight; with two pairs of propellant wings. Head hypognathous. Mouthparts well developed; of the biting type; not piercing; conforming to the generalized biting type (with the apical segments of the labial and maxillary palps sensory in function and often swollen). Antennae conspicuous; simple; 15–35 segmented (‘many-segmented’). Ocelli 0 (usually absent), or 3 (but vestigial only, in Osmylidae). Wings four; of similar texture in both pairs. Fore-wings membranous. Hind-wings more or less similar in size to the fore-wings, or larger than the fore-wings (Sialidae); markedly broader than the fore-wings, or no broader than the fore-wings; folded in repose (at least in Sialidae, where the hind-wings have an expanded anal field), or not folded in the resting insect (all the rest?). Wings with numerous cross-veins (mostly), or with few cross-veins (e.g. Conwentzia); conspicuously hairy, or more or less naked; exhibiting ‘corneous dots’ (sometimes, according to text-books, but details not recorded), or without ‘corneous dots’; fringed, or not fringed. Wings of the resting insect closed and directed backwards; held roof-like over the abdomen. Tarsi 5 segmented. Abdomen not conspicuously appendaged; lacking clearly visible cerci; apparently 9 segmented (Chrysopidae), or 10 segmented (even then with sternite 1 reduced).

Larvae. Larvae aquatic (those of Megaloptera-Sialidae and Neuroptera-Sisyridae having abdominal gills, the latter being predatory on fresh-water sponges), or terrestrial (the rest); feeding in the open; predatory; with three pairs of segmented thoracic legs; without ventral abdominal prolegs; with paired anal prolegs (i.e., often with one or two terminal abdominal suction discs, which in Osmylidae are identical with those of Lepidoptera), or without anal prolegs. The abdominal prolegs bearing crochets (e.g., Osmylidae), or without crochets. Larval head with a well sclerotized capsule. Development of larva into adult involving marked metamorphosis; endopterygote; involving a pupal stage.

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

Classification. Subclass Pterygota; Division Endopterygota.

British representation. Chrysopidae, Coniopterigidae, Hemerobiidae, Osmylidae, Sialidae, Sisyridae; genera 18; 56 species.

General comments. Often emitting an odour when handled. The wings sometimes bear ‘corneous spots’, cf. Trichoptera (Riek, 1970).

Illustrations. • Chrysopa abbreviata Curtis (Chrysopidae. Short-winged Green Lacewing, Golden-eye: B. Ent. 520). • Chrysopa abbreviata (detail, dissections: B. Ent. 520). • Chrysopa abbreviata (B. Ent. 520, legend+text). • Chrysopa abbreviata (B. Ent. 520, text cont.). • Coniopteryx Curtis, = Conwentzia psociformis (Curtis): Coniopterygidae. Psocus-like Powdered-wing: B. Ent. 528). • Conwentzia psociformis (B. Ent. 528, legend+text). • Conwentzia psociformis (B. Ent. 528, text cont.). • Hemerobius fimbriatus Curtis (Bordered Brown Lacewing, Hemerobiidae), = Megalomus hirtus: B. Ent. 202. • Hemerobius fimbriatus Curtis (Bordered Brown Lacewing, Hemerobiidae), = Megalomus hirtus: B. Ent. 202, legend+text. • Hemerobius fimbriatus Curtis (Bordered Brown Lacewing, Hemerobiidae), = Megalomus hirtus: B. Ent. 202 text cont.. • Nathanica fulviceps, Sisyra fuscata, Wesmaelius concinnus: Stephens VI, 1835. • Drepanepteryx phalanoides: Stephens VI, 1835.

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.’.