(2) Pseudoneuroptera.—Biting mouth parts, wings of equal size, thin, not folded up (dragon-flies, hair and feather lice, termites).
(3) Rhynchota or Hemiptera.—Mouth parts formed for puncturing and sucking; wings alike, or the anterior wings may be thickened, parchment-like at their base (plant lice, cicadæ, bugs and true lice).
(4) Neuroptera.—Biting mouth parts; wings alike, thin; metamorphosis complete (ant-lions, lace-wing flies, etc.).
(5) Trichoptera.—Licking mouth parts; anterior wings narrow, posterior wings longitudinally folded, both ornamented with little hairs; the larvæ are worm-like in form, live in water, and breathe through tracheal gills (may flies, etc.).
(6) Lepidoptera.—Suctorial mouth parts; wings covered with scales (butterflies).
(7) Coleoptera.—Biting mouth parts; anterior wings thickened and differ in colour, appearance and function from the thin, folded posterior wings (beetles).
(8) Hymenoptera.—Mouth parts for licking and biting; the wings alike, membranous (ichneumon flies, ants, wasps, bees, humble bees).
(9) Diptera.—Mouth parts formed for puncturing, sucking or licking; posterior wings degenerated (gnats, flies, gadflies, fleas).
(10) Strepsiptera.—Anterior wings shortened; the female without wings and living parasitically (fan-wings).
The parasites of man occur amongst the Rhynchota, Coleoptera, and amongst the Diptera.