a 



a 



40 ENTOMOLOGY 



These endoskeletal processes serve chiefly for the origin of muscles 

 concerned with the wings or legs, and are absent in such wingless forms as 

 Thysanura, Pediculidas and Mallophaga. 



Some ambiguity attends the use of these terms. Thus some writers 

 use the term apodemes for apophyses and others apply the term apo- 

 deme to any of the three kinds of ingrowths. 



Legs. In almost all adult insects and in most larvae each of the three 

 thoracic segments bears a pair of legs. The leg is articulated to the 



sternum, episternum and epimeron and consists 

 of five segments (Fig. 60), in the following order : 

 'coxa, trochanter, femur, tibia, tarsus. The coxa, 

 or basal segment, often has a posterior sclerite, 

 the trochantine. 1 The trochanter is small, and 

 in parasitic Hymenoptera consists of two sub- 

 segments. The femur is usually stout and con- 

 spicuous, the tibia commonly slender. The 

 tarsus, rarely single-jointed, consists usually of 

 five segments, the last of which bears a pair of 

 claws in the adults of most orders of insects and 

 a single claw in larvae; between the claws in 

 most imagines is a pad, usually termed the 

 pulvillus, or em podium. 



Adaptations of Legs. The legs exhibit 

 a great variety of adaptive modifications. A 

 walking or running insect, as a carabid or cicin- 

 delid beetle (Fig. 62, A) presents an average 

 condition as regards the legs. In leaping in- 

 sects (grasshoppers, crickets, Haltica) the hind 

 femora are enlarged (B) to accommodate the 

 powerful extensor muscles. In insects that make 

 little use of their legs, as May flies and Tipulidae, 



these appendages are but weakly developed. The spinous legs of dragon 

 flies form a basket for catching the prey on the wing. Modifications of the 

 front legs for the purpose of grasping occur in many insects, as the terres- 

 trial families Mantidae (C) and Reduviidae and the aquatic families Belos- 

 tomidae and Naucoridas (D}. Swimming species present special adapta- 

 tions of the legs (Fig. 229), as described in the chapter on aquatic insects. 

 In digging insects, the fore legs are expanded to form shovel-like organs, 



a- 



FIG. 59. Transverse sec- 

 tions of the thoracic segments 

 of a beetle, Goliathns, to show 

 the endoskeletal processes. 

 A, prothorax; B, mesothorax; 

 C, metathorax; a, a, apoph- 

 yses; ad, apodeme; p, 

 phragma. After KOLBE. 



1 But on account of the ambiguous use of this last term, the name meron (Fig. 61), pro- 

 posed by Walton, is to be preferred. 



