24 



THE CLASS OF INSECTS. 



during flight. . The median area (Fig. 31a) is the largest. It is 

 in the grasshoppers and crickets sometimes modified to form a 

 musical organ, being 

 drum-like, as in the 

 (Ecanthus (Fig. 30), or 

 rasp-like, as in Archyp- 

 tera (Fig. 31a). Tlie 

 internal area (c) is tlie 

 smallest, and less dis- 

 tinctly marked tlian the 

 two other regions ; the musical file-like or- 

 gan of Plianeroptera curvicauda, a grass- 

 hopper (Fig. 32 d) is situated on this area. 

 The limits of the edges of the wing vary- 

 in almost every genus, and their comparative length affords 

 excellent generic characters. The front edge (Fig. 29) is called 

 the costal^ its termina- 

 tion in the outer angle 

 of the wing is called 

 the apex; the outer edge 

 is situated between the 

 apex and the inner an- 

 gle, between which and 

 the base of the wing is 

 the inner, or internal, 

 edge. These distinc- 

 tions are of most use 

 in describing the butter- 

 flies and moths. 



The Appendages of 

 Fig. 31a. ijiQ Head. These organs 

 are divided into two groups, 

 the first of which comprise the 

 sensory organs, i. e. the ocelli, 

 eyes, and antennae, wliich are attached to the region in front 

 of the mouth, or preoral region of the head. The second 

 group consists of the sensorio-digestive appendages, combining 

 the power of finding and seizing the food and preparing it for 

 digestion. They are inserted behind the mouth and belong 

 to the pastoral region of the head. 



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