62 INSECTS INJURIOUS TO VEGETABLES 



or less surrounded by webs and leaftissues offering little or no 

 barrier to the effects of the poison. In addition, clean cultural 

 methods, including late plowing in the fall followed by deep 

 plowing in spring, and the burning of all waste material and 

 weeds, are of service in controlling this pest. Early planting is 

 useful as a safeguard for some crops. 



LEAF-BEETLES 



Leaf-beetles (Chrysonielidcc) are among the most important 

 groups of insects, economically speaking. Many of them select 

 in the larval stage single species or plants of the same or 

 similar botanical families, but the beetles are more inclined to 

 be omnivorous, and some devour nearly all forms of vegetation. 

 Their larval habits are variable, but a considerable proportion 

 subsist on plant tissue on the external surface of leaves. A 

 smaller number develop in mines which they construct in the 

 leaves or in the roots, in fruits and seeds, and even in flower 

 heads and in stems. A familiar example of a leaf-beetle larva 

 that lives externally on leaves is the Colorado potato beetle, and 

 of the root-feeders are the corn root-worms. An example of 

 those which live in seeds is the twelve-spotted asparagus beetle. 

 Such as feed on the outer surfaces of leaves are more or less 

 grub-like, with six true legs and a proleg at the posterior ex- 

 tremity. Their colors are often well marked, red or yellow, 

 with rows of black spots as in the case of the Colorado potato 

 beetle. The root-feeders, however, are pale, frequently white 

 and elongate, even threadlike in form. 



The greatest amount of injury is generally due to the hiber- 

 nated beetles on young and tender plants before they have made 

 good growth. Some species, indeed, cause little trouble after 

 this period, while others, like the Colorado beetle, occasion 

 losses of greater or less extent throughout the growing season 

 of the plants which they affect. 



Our most common omnivorous leaf-beetle is the twelve- 



