I i 8 INSECT LIFE. 



1. The body as a whole. Observe its evenly 

 rounded outlines, and consider how well fitted it is 

 for gliding through the water. 



2. The antennae. These are inserted immediately 



in front of the eyes, and are threadlike in 



^ 



form, each consisting of twelve similar seg- 

 ments (Fig. 95). The form of the antennae is 

 an important characteristic of these insects, 

 for by it they can be distinguished from the 

 FlG " water-scavenger beetles, which they closely 

 resemble in general appearance. 



3. The hind legs. These are fitted especially for 

 swimming, being long and more or less oarlike ; the 

 tarsus is flattened and fringed with hairs, and the 

 segments of it taper evenly from its base to the 

 claws. Make a drawing of one of these legs. 



4. The middle legs. These do not differ greatly 

 from the usual form of the legs of insects, except 

 that in the males of certain species the first three 

 segments of the tarsus are much wider than the 



o 



others and furnished with cushions beneath. 



5. The fore legs. In the females these legs are 

 also of the usual form. But in the males of our com- 

 mon larger species the first three segments of the 

 tarsus are dilated and form a circular disk, upon the 

 under side of which are little cuplike suckers. These 

 suckers differ in size and arrangement in different 

 genera ; Fig. 96 represents a tarsus of Dytiscus (Dy- 

 tis'cus). 



6. Examine the fore legs of all of your pinned 

 specimens of the larger diving-beetles and separate 

 the sexes of each species. 



7. If your collection is sufficiently full, you will 



