308 ENTOMOLOGY 



The Myrmeleon larva digs a funnel-shaped pitfall, at the bot- 

 tom of which it buries itself to await the fall of some unlucky 

 ant. The Chrysopa larva impales an aphid on the points of 

 its mandibles and sucks the blood through a groove along 

 each mandible (Fig. 45, E), the maxilla fitting against this 

 groove to form a closed channel. Several families of Coleop- 

 tera are almost entirely predaceous. Among aquatic beetles, 

 Dytiscidae are carnivorous both as larvae and imagines, Gyrin- 

 idae subsist chiefly upon disabled insects, but occasionally eat 

 plant substances, and Hydrophilidse as larvae catch and devour 

 other insects, though some of the beetles of this family (H. 

 triangularis , for example, Fig. 226) feed largely if not en- 

 tirely upon vegetation. Of terrestrial Coleoptera, the tiger 

 beetles (Cicindelidae) are strictly predaceous upon other insects. 

 The Cicindela larva lives in a burrow in the soil and lies in 

 wait for passing insects; a pair of hooks on the fifth segment 

 of the abdomen serves to. prevent the larva from being jerked 

 out of its burrow by the struggles of its captive. The large 

 family Carabidae is chiefly predaceous ; these " running 

 beetles " both as larvae and adults easily overtake and capture 

 other terrestrial insects. The Carabidae, however, are by no 

 means exclusively carnivorous, for many of them feed to some 

 extent upon fungus spores, pollen, ovules, root-tips and other 

 vegetable matter, as Forbes has found; Harpalus caliginosus 

 eats the pollen of the ragweed in autumn ; Galerita janus eats 

 caterpillars and occasionally the seeds of grasses; Calosoma, 

 however, appears to be strictly carnivorous, feeding chiefly 

 upon caterpillars and being in this respect of considerable eco- 

 nomic importance. As a whole, Carabidae prefer animal food, 

 as appears from the fact that, when canker worms, for in- 

 stance, are unusually abundant they form a correspondingly 

 large percentage of carabid food, the increase being compen- 

 sated by a diminution in the amount of vegetable food taken 

 (Forbes). CoccinelHd larvae (excepting Epilachna, which 

 eats leaves) feed almost entirely upon plant lice and consti- 

 tute one of the most effective checks upon their multiplication ; 



