IV. INSECTA: HEXAPODA, ARCHIPTERA 



419 



inal somite; two or three additional pairs appear in other genera. The cerci 

 or large 'bristles' are also regarded as abdominal appendages. 



Sub Order I. THYSANURA (Bristle-tails). Body elongate, with long 

 bristles (cerci) at the hinder end. Lepisma saccharina* silver fish, common 

 among old books and papers, does considerable damage. Campodca* (fig. 365). 

 ^racl^lis* lapyx* with caudal forceps. Sub Order II. COLLEMBOLA 

 (Spring-tails). Compressed forms in which two jointed appendages bent under 

 the body serve as a spring, throwing the animals (one to three mm. long) for- 

 wards. Podura*; Anurida, maritima,* in tide pools; Achor elites nivalis* snow 

 flea. 



The recently discovered group of PROTURA may be mentioned here. 

 They lack antennae, have the first leg directed forwards and tactile, twelve 

 abdominal somites, appendages on first three, two thoracic spiracles. Europe 

 and India. Acerentonioti. 



Order II. Archiptera (Pseudoneuroptera). 



These represent the primitive forms of winged insects. The elongate body 

 usually bears the cerci of the Thysanura. The wings are delicate and trans- 

 parent, supported by a close network of nervures, both pairs being very closely 

 alike. The mouth parts are of the typical biting kind, the labium frequently 

 deeply cleft. These points of primitive structure are correlated with a primi- 

 tive, usually hemimetabolous development. The distinction between larva 

 and imago is largely one of presence or absence of wings, although larval organs 

 like gills (Amphibiotica) may occur. Frequently the development is direct 

 when the adults, as in some Termites and the Psocicke, are wingless. 



FIG. 464. Termes ftavipes* white ant (from Riley). a, larva; b, winged male; c, 

 worker; d, soldier; e, queen;/, pupa. 



Sub Order I. CORRODENTIA. Larvae distinguished from the imagines 

 by difference in size and, in the winged forms, by lack of wings. Best known 

 are the TERMITID.^; (Isoptera), or white ants, which must not be confused with 

 the true ants (Hymenoptera). Like the true ants, they have a well-developed 

 social state, their communities resembling each other in many details as the 

 'guests' (termitophiles), the mushroom gardens, etc. They differ from the ants 

 in the similar segments of the body, the character of the mouth parts, the hemi- 

 metabolous development and by the fact that the workers include both males 



