440 COMPARATIVE ANATOMY .CHAP. 



Order 5. Plecoptera (Perlaria). 



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

 Hind body 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-like larvre live in water, with tracheal gills, apneustic. The tracheal 

 gills often persist in the imago. Pcrla (Fig. 317, p. 456), Nemura. 



Order 6. Corrodentia. 



Insects without, or with 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 in the workers. Some Psoeidce and the 

 Mallopliagct are wingless. The compound eyes are wanting in the Mallopliaga. The 

 Avings of the winged Psoeidce are glassy, areolate, and like those of the Hymen- 

 optera. Young forms Thysanura-like. Termitidce (white ants, which form communities, 

 Termcs, Calotermes) ; Psoeidce ( Troctcs, Psocus, book lice ; Mallophaga, parasites feed- 

 ing on the fur of animals or feathers of birds ; Trichodectes, 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. Thrips. 



Order 8. Rhynchota. 



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

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

 Compound eyes are wanting in the parasitic Rhynchota. 



Sub-Order 1. Phytophthires. 



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

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

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

 Aphidce : with 2 pairs of membranous wings, generally wanting in the female ; Aphis, 

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

 Aspidiotus. 



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

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



Sub-Order 3. Heteroptera (Hcmiptera), Bugs. 



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

 their points. Hind-wings membranous. Geocores (land bugs : Hydrometra, Halo- 

 bates, Pentatoma, Coreus, Corizus, Alydus, Pyrrhocoris, Lygaeus, Miris, Capsus, 

 Acanihia [bed-bugs], Reduviis, etc.) Hydrocores (water -bugs : Nepa, JRanatra, 

 Naucoris, Corixa, Notonccta, etc.) 



