590 



ZOOLOGY 



SECT. 



provided with hooks or spines for rupturing the nectaries of 

 flowers. 



Appendages of the thorax. Each of the segments of the 

 thorax bears a pair of five-jointed legs; the terminal section or 

 tarsus being made up of a number of short segments and ending 

 in a pair of claws, often with an adhesive pad or sucking disc 

 between them. In accordance with differences in the uses to 

 which they are put, considerable differences are observable in the 

 form of the legs in Different groups of Insects. In most they are 

 adapted for walking, and are long and slender ; in some they are 



FIG, 479. Mouth parts of the Diptera. A, of Tab anus ; B, of Culex. Lettering as in pre 

 ceding figure ; oc. ocellus. (From Lang.) 



expanded to enable them to act as swimming paddles: in some 

 the first pair are prehensile, and develop a sub-chelate extremity ; 

 in others again the legs, or the first pair of them, are stout and 

 adapted for burrowing. In addition to the legs the meso- and 

 meta-thorax may each bear a pair of wings. The wings are thin 

 transparent expansions of the integument of the body, supported 

 by a system of branching ribs or nerviwes consisting of chitinous 

 material with branches of the tracheae, nerves, and tubular diver- 

 ticula of the body cavity. In most Lepidoptera the wings are 

 opaque, owing to their being covered with numerous overlapping 

 microscopic scales, to which the various colours of the wing are 



