i6 4 THE STUDY OF INSECTS 



The two-spotted oberea, Oberea bimaculata, is sometimes a serious 

 pest, boring in the canes of blackberry and raspberry. The larva re- 

 sembles that of the preceding species. The adult (Fig. 

 288) is .about h of an inch in length and of a dee]) black 

 color, except the prothorax, which is yellow. There are 

 usually two or three black spots on the pronotum, but 

 frequently these are wanting. 



The red milkweed-beetles, Tetrabpes. 

 - There are several species of bright red 

 beetles that are common on milkweeds (Asclepias). 

 These belong to the genus Tetraopes. Our most com- 

 mon species (Fig. 289) is T. tetraophthalmus . In this 

 species there are four black spots on each wing-cover, and the antennae 

 are black and not ringed with a lighter color. The larva bores in the 

 roots and the lower parts of the stems of milkweeds. 



Family Chrysomelids 



The Leaf-beetles or Chrysomelids 



The leaf-beetles are so called because they feed upon the leaves of 

 plants both as larvae and adults. They are usually short-bodied, and 

 more or less oval in outline ; the antennas are usually of moderate length ; 

 and the front is not prolonged into a beak. The legs are usually short, 

 and are furnished with tarsi of the same type as those of the preceding 

 family (see Fig. 279, p. 161). 



Although we are unable to cite any characteristic that will invariably 

 distinguish these beetles from the preceding family, the student will 

 rarely have any difficulty in making the distinction. The beetles of the 

 genus Donacia, described below, are the only common ones that are 

 liable to be misplaced. In other cases the more or less oval form of the 

 body, and the comparatively short antennae, and the leaf-feeding habits, 

 will serve to distinguish the chrysomelids. 



The leaf -beetles are nearly all comparatively small, the Colorado 

 potato-beetle being one of our larger species. 



The eggs are usually elongated and yellowish, and are laid upon the 

 leaves or stems of the plants upon which the larvae feed. Many of the 

 larvae live exposed on the leaves of plants; others that live in similar 

 situations cover themselves with their excrement; some are leaf -miners; 

 and a few, as the striped squash -beetle, bore in the roots or stems of 

 plants. 



This is a large family, of which nearly one thousand North American 

 species are known. The following illustrations will serve to 

 show the variations in form and habits. 



The long-horned leaf-beetles, Donacia. — These are the 

 common leaf-beetles that are liable to be mistaken for ceram- 

 bycids. They are of elongated form, with slender antennae 

 (Fig. 290). They measure from | to f inch in length, and 

 metallic color — either greenish, bronze, or purplish. The 

 lower side of the body is paler and is clothed with very fine hair which 

 serves as a water-proof coat when the insect is submerged. The larvae 

 feed upon the roots or in the stems of aquatic plants; and the adults 



