OUTLINES OF ENTOMOLOGY. 53 



Beetles belonging in the Isomer A are sub-divided into five 

 tribes : 



I. Adephaga (carnivorous beetles), Land and Water Tigers, hun- 

 ters and trappers of other insects for the most part, although a few 

 species subsist on vegetation. In these the antennse are thread-like? 

 cylindrical, with the joints distinct. 



II. Clavicornia (Club-horns), having the antennae thickened 

 gradually or abruptly toward the tip ; feet with from one to five joints ; 

 small beetles of various habits. 



III. Serricornia (Saw-horns), having the antennae toothed or 

 serrated (in some few species also enlarged at the tip, much as in the 

 preceding tribe, but the species in other respects agreeing with the 

 members of this tribe). This group includes a great number of small 

 borers. 



IV. Lamellicornia (Leaf-horns), having the knob of the anten- 

 nae composed of several leaf like or blade-like parts, which the insect 

 can unfold or close up at will. This Tribe includes the largest insects 

 in the Order, most of which feed, often in the perfect as well as the lar- 

 vae state, upon vegetation, foliage, roots and decayed wood. 



Y. Phytophaga (Plant-eaters), mostly with thread- like antennae, 

 in some species very long, in others short and slightly thickened to- 

 ward the tip ; fourth and fifth joints of the feet consolidated, the former 

 minute. All the species feed on vegetation and many are extremely 

 destructive. 



Neither the Section Heteromera nor the Sub-Order E h y N- 

 CHOPHORA requires division into tribes for convenience of study. 



CHAPTER XY. 

 Order COLEOPTERA. Tribe I. Adephaga. 



CANNIBAL BEETLES. 



In this group of beetles we find mainly carnivorous species, many 

 of which prey especially on insects destructive to vegetation, and on 

 this account claim recognition as among our best friends. They also 

 merit consideration by their great beauty of form and color, and by the 

 grace and agility of their movements. The most important families are 

 the Tiger-beetles (Cicindelid.^), the Caterpillar hunters (Carabid^), 

 the Water-tigers (Dytiscid.^), and the Water- whirligigs (Gyrinid^). 



The Tiger-beetles received their popular name on account of their 

 ferocious habits, their swift movements and the stealthy manner in which 

 their larvae lie in wait for their prey. They are diurnal insects of 



