(9) Coleoptera.—Four wings, the front pair hard and horny (elytra), meeting in a line over the back and covering the delicate hind pair; mandibulate; metamorphosis complete.
[There are two other well-known arrangements, namely, Packard’s and Brauer’s, of recent date, but the one given here, which is based on Linnaeus’ grouping by Dr. Sharp, is by far the simplest.—F. V. T.]
Order. Rhyncota.[361]
The lower lip forms a long thin tube that can be turned back (rostrum), and within which lie the setaceous mandibles and maxillæ; the first thoracic segment is not united with the two posterior ones; the anterior wings are usually leathery as far as the centre.
(a) Rhyncota aptera parasitica.
Family. Pediculidæ (Lice).
The lower lip is transformed into a projecting rostrum provided with barbed hooklets in which the hollow extensile sucker (maxillæ and mandibles) is situated; no wings; no metamorphosis; only simple eyes; the antennæ are five-jointed, the feet possess hook-like terminal structures; the barrel-shaped eggs (nits) are deposited on the hair of the host.
[The lice or Pediculidæ are also known as Anoplura and Siphunculata.
[They have been split up into a number of families and sub-families and a number of genera, but as far as this work is concerned it is best to retain the single family Pediculidæ.
[Only the three species mentioned here are common parasites of man, but now and then horse and cattle and sheep lice, Hæmatopinus, may cause transitory annoyance.—F. V. T.]