14 INSECT A. 



are small in most insects and difficult to make out. The 

 ventral or sternal portion (PI. I., Fig. 5,^') consists of a 

 hard, crescent-shaped ridge (which here extends into a 

 blunt tubercle {d') at the middle), a soft, pliable mem- 

 brane (^), and a stiffened posterior margin (/). 



The prothorax moves freely, apparently only con- 

 nected with the middle segment, or mesothorax (PL I., 

 Figs. 3, 7, ^"), by soft skin. While this is true of the 

 back, the sternal and lateral connections (PI. I., Figs. 

 5, 6, sut) are immovable, lying back of the pliable 

 membrane. PL I., Fig. 6 represents the prothorax 

 with a portion on one side cut away, exposing the 

 fleshy membrane (<:'), the chitinous margin (/), and 

 the spiracle (i"^), which will be described farther on. 

 Practically, however, the prothorax is independent of 

 the mesothorax, and also of the head, as it is only 

 connected with the latter by fleshy membrane and 

 two chitinous jointed bands which extend downward 

 on either side of the face. With the exception of 

 these bands, the neck yields readily to pressure. The 

 weakness of this part of its armor sometimes costs the 

 locust its life. The sharp, dry grass-blades are as 

 dangerous as steel-pointed spears to the naked skin, 

 and when one accicientally enters between the plates 

 of the cheek and the prothorax, it readily pierces the 

 soft neck, so that the insect is impaled and often dies. 

 One such unfortunate is figured by Morse.^ Such parts 

 can be used to show pupils the suitability of the horny 

 crust to resist collisions while in flight, and the con- 

 stant attrition of the grass and other vegetation. A 



1 First Book of /.oology, p. 91. 



