106 



AKTHROPODA 



boatman (Notonecta) and the giant water bug (Belostoma) 

 are the two common aquatic members of this order. 



The pupil must remember that there is a wide difference 

 between bugs and beetles both in their external appearance 

 and habits. The most significant difference in structure is 

 in the mouth parts, which should be examined in some large 

 bug such as the squash bug. In this species the piercing 



FIG. 117. Squash bug viewed froiu the side and back; 6, beak used in piercing 

 and sucking the juice of the vines. Photograph enlarged three times. 



and sucking beak is more than a quarter of an inch long, and 

 is folded close to the ventral side of the body when not in use. 

 At the base of the beak is the labrum, while in a groove on 

 its upper part lie two pairs of hairlike processes, the shorter 

 of which are the mandibles, and the longer are the max- 

 illaB. The sheath inclosing these is made by the labium 

 and labial palpi. The bugs are capable only of piercing 

 and sucking food, and can not bite. 



