440 COMPARATIVE ANATOMY chap. 



Order 5. Plecoptera (Perlaria). 



Insects Avith incomplete or gradual metamorphosis, with biting mouth parts. 

 Hind bodj' generally with 2 long cerci. Both pairs of wings large, veins forming 

 large meshes, the hinder pair often broader than the front pair, and partly foldable. 

 The Thysanura-\i\i& larvre live in water, with tracheal gills, apneustic. The tracheal 

 gills often persist in the imago. Fcrla (Fig. 317, p. 456), Kcmura. 



Order 6. Corrodentia. 



Insects without, or ivith gradual metamorphosis, with biting mouth parts. 

 Wings often wanting. In the Termites they are finely membranous, and in the 

 sexual animals deciduous. They are wanting iu the workers. Some Psocidce and the 

 Mallophaga are wingless. The compound eyes are wanting in the MalloiiJiaga. The 

 wings of the winged Psocida: are glassy, areolate, and like those of the Hymen- 

 optera. Young forms ThijsanuraAike. Tcrmitiilre (white ants, which form communities, 

 Termes, Calotermes) ; Psociihc {Trades, Psocus, book lice ; Mallophaga, parasites feed- 

 ing on the fur of animals or feathers of birds ; Trichodcdes, Philopterus, bird lice ; 

 Liotheum). 



Order 7. Thysanoptera sive Physopoda. 



Insects with gradual metamorphosis, the larval form very like the imaginal. The 

 last larval stage goes without food. Sucking mouth parts. The claws of the short 

 feet with the adhering lobes of the tarsus changed into a protrusible vesicular 

 apparatus. Wings very narrow, with reduced veining, with long fringed edges, 

 often wanting or rudimentary. Only 3 or 4 pairs of stigmata, one or 2 on the thorax, 

 one on the first and one on the eighth ring of the hind body. Nervous system con- 

 centrated. Thrip}S. 



Order 8. Ehynchota. 



Insects with gradual metamorphosis (in the males of the Coccida: complete meta- 

 morphosis). Mouth parts form a proboscis adapted for piercing and sucking. 

 Compound eyes are wanting in the parasitic Ehynchota. 



Sub-Order 1. Phytophthires. 



With two pairs of membranous wings. Generally wanting in the female. The 

 Ooccidce have only fore-wings, the hind-wings being changed into halteres. Fam. 

 Psyllidce : with 2 pairs of wings (fore-wings parchment-like) ; Psylla, -Lixia. Fam. 

 Aphid u: : with 2 pairs of nrembranous wings, generally wanting in the female ; Aphis, 

 Chermes, Schizoneura, Phylloxera. Fam. : Ooceidcc, scale insects ; Coccus, Lecanium, 

 Asjndiotus. 



Sub-Order 2. Pedioulidse (Aptera), Lice. 



Without facet eyes and without wings. Pediculus, Hccmatopinus, Phthirius. 



Sub-Order 3. Hcteroptera {Hemiptera), Bugs. 



Four wings (seldom wanting). The anterior horny wing-oovers are membranous at 

 their points. Hind-wings membranous. Geocores (land bugs : Sydroonetra, Salo- 

 hates, Pentatoiiia, Coreus, C'oriziis, Alydus, Pyrrhocoris, Lygaciis, Miris, Capsus, 

 Acanthia [bed-bugs], Eeduviis, etc.) Hydrocores (water -bugs: Kepia, Eanatra, 

 NoAicoris, Corixa, Notonecta, etc.) 



