Beetles 



55 



while we were taking it prisoner." These beetles have a narrow reddish- 

 yellow head and prothorax, and blackish-blue elytra. Of similar appear- 

 ance is Lebia grandis, the enemy of the Colorado potato-beetle, feeding 

 on its egg and larvae. Most abundant of the Carabids are the numerous 

 dull-black medium-sized species of Pterostichus (PI. IV), in which the pro- 

 thorax has a narrow, flat, projecting margin. Over one hundred species 

 of this genus have been found in this country. Harpalus is another large 

 genus with some very common species; H. pennsylvanicus is often found 

 in orchards eating the larvae of the codlin-moth and plum-curculio, ravag- 

 ing fruit-pests. A few Carabidi are not such good friends, Lugger record- 



FlG. 347. Predaceous diving-beetles (and back-swimmers, order Hemiptera) in water. 

 (From life; slightly less than natural size.) 



ing the fact that Agonoderus pallipes, a species abundant in Minnesota, 

 sometimes feeds on sprouting seeds of corn. 



Predaceous beetles of very different habitat are the Dyticidae, the carniv- 

 orous water- or diving-beetles. Three hundred species occur in this country, 

 and some members of the family are to be found wherever there are streams 

 and ponds. They vary in size from the large Cybister and Dyticus, an 

 inch and a half long, to small species of Hydroporus and other genera less 

 than a fifth of an inch long, but all are readily distinguishable from their 

 aquatic companions, the whirligigs (family Gyrinidae) (p. 25.7), by having 

 but one pair of eyes, and from the water-scavenger beetles (family Hydro- 



