500 AN INTRODUCTION TO ENTOMOLOGY 



(Fig. 593). The body is elongated, somewhat flattened, and tapers 

 more or less toward each end ; the antennae are moderately elongated 

 and more or less serrate; the first and second ab- 

 dominal segments are not grown together on the 

 ■^^ \BV/' ventral side; and the hind coxsc are each furnished 

 'Jk y3lK ^^^^^ ^ groove for the reception of the femur. 

 -^wV /HPlA The ability to leap into the air when placed on 



their back, which is possessed by most members of 

 this family and by a few members of the following 

 Fig- 59 3 -—A family, is due to two facts: first, the prostemum is 

 Aeolus dorsalis Prolonged into a process which extends into a groove 

 natural size and ^^ ^^^ mesostemum; and second, the prothorax is 

 enlarged. loosely joined to the mesothorax, so that it can be 



freely moved up and down. When preparing to 

 leap, the beetle bends its body so as to bring the prosternal process 

 nearly out of the groove in the mesosternum ; then it suddenly 

 straightens its body, with the result that the prosternal process 

 descends violently into the groove; the blow thus given to the meso- 

 thorax causes the base of the elytra to strike the supporting surface, 

 and by their elasticity the whole body is propelled upward. 



Adult elaters are found on leaves and flowers, and are exclusively 

 phytophagous; the larvce live in various situations; most of them 

 are phytophagous, but some species 



The larvaj are long, narrow, Fig_ ^g_^_ 



worm-like creatures, very even in 

 width, with a very hard cuticula, 



and are brownish or yellowish in 



color (Figs. 594 and 595). They are Fig. 595. 



commonly known as wire-worms, a 



name suggested by the form and hardness of the body . 



Some wire-worms live under the bark of trees and in rotten wood ; 

 but many of them live in the gromid, and feed on seeds and the roots 

 of grass and grain. In fact there is hardly a cultivated plant that they 

 do not infest, and, working as they do beneath thesurface of the ground, 

 it is extremely difficult to destroy them. Not only do they infest 

 a great variety of plants, but they are very apt to attack them at the 

 most susceptible period of their growth, before they have attained 

 sufficient size and strength to withstand the attack; and often seed 

 is destroyed before it is germinated. Thus fields of com or other 

 grain are ruined at the outset. The appearance of these insects when 

 in the ground, as seen through the glass side of one of our root-cages, 

 is shown in Fig. 596. 



There is a vast number of species of click-beetles ; more than five 

 himdred have been described from North America alone. _ It is quite 

 difficult to separate the closely allied species, as there is but little 

 variation in shape and color. 



The larvae also show comparatively little variation in the general 

 form ; but in this stage the shape of the parts of the head and its ap- 



