530 AN INTRODUCTION TO ENTOMOLOGY 



Family CHRYSOMELID^ 

 The Leaf-Beetles or Chrysomelids 



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

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

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

 length ; and the front is not prolonged into a beak. The legs are usu- 

 ally short, and are furnished with tarsi of the same type as those of 

 the preceding family (see Fig. 634, p. 524). 



Although we are unable to cite any characteristic that will in- 

 variably distinguish these beetles from the preceding family, the 

 student will rarely have any difficulty in making the distinction. 

 The beetles of the genus Dondcia, 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 antennse, 

 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 larvas feed. Many 

 of the larvas 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 Ameri- 

 can species are known. The following illustrations will serve to show 

 the variations in form and habits. 



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



leaf -beetles that are liable to be mistaken for ceramby cids . They are of 



elongated form, with slender antennae (Fig. 647). They measure 



from 6 mm. to 1 2 mm. in length, and are of a 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 are found on the leaves of the same 



Fig. 647. plants. We have many species, but they resemble one 



another so closely that it is difficult to separate them. 



The three-lined lema, Lema trilinedta. — This insect is common, 

 feeding on the leaves of potato. The beetle is 6 mm. long, yellow, with 

 three black stripes on the wing-covers. The eggs are usually laid in 

 rows along the midrib on the lower side of the leaves. The larvae 

 feed on the leaves, and can be easily recognized by a habit they have 

 of covering their backs with their own excrement. They transform 

 in the ground in earthen cells. There are two broods each year; 

 the second hibernates in the ground as pupae. 



The asparagus-beetle, Crioceris aspdragi. — This is a small red, 

 yellow, and black beetle, that gnaws holes into the heads of young 



