ANATOMY AND PHYSIOLOGY 



FIG. 60. 



tb 



Some ambiguity attends the use of these terms. Thus some 

 writers use the term apodemes for apophyses and others apply 

 the term apodeme 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 seg- 

 ments (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 subseg- 

 ments. The femur is usually stout and 

 conspicuous, 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 empodium. 



Adaptations of Legs. The legs ex- 

 hibit a great variety of adaptive modifica- 

 tions. A walking or running insect, as a 

 carabid or cicindelid beetle (Fig. 62, A) presents an average 

 condition, as regards the legs. In leaping insects (grasshop- 

 pers, 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 



Leg of a beetle, Calo- 

 soma calidum. c, coxa; 

 cl, claws; f, femur; s, 

 spur; fi-t 5 , tarsal seg- 

 ments; tb, tibia; tr, 

 trochanter. 



1 But on account of the ambiguous use of this last term, the name meron 

 (Fig. 61), proposed by Walton, is to be preferred. 



