CHAPTER X 



INTERRELATIONS OF INSECTS 



Insects in general are adapted to utilize all kinds of organic matter 

 as food, and they show all gradations of habit from herbivorous to carniv- 

 orous. The many forms that derive their food from the bodies of other 

 insects may conveniently be classed as predaceous or parasitic. 



Predaceous Insects. Among Orthoptera, Mantidae are notably 

 predatory, their front legs (Fig. 64, C) being well fitted for grasping and 

 killing other insects. The predaceous odonate nymphs have a peculiar 

 hinged extensible labium with which to gather in the prey. The adults 



catch with surpassing speed and precision 

 a great variety of flying insects, mostly 

 small forms, but occasionally butterflies of 

 considerable size. The eyes of a dragon 

 fly are remarkably large; the legs form a 

 spiny basket, probably to catch the prey, 

 which is instantly stripped and devoured, 

 these operations being facilitated by the 

 excessive mobility of the head. The 

 hemipterous families Corixidae, Notonec- 

 tidae (Fig. 227), Nepidae, Belostomidae 

 (Fig. 23), Naucoridae (Fig. 64, D) Redu- 

 viidae and Phymatidae are predaceous, with 

 raptorial front legs and sharp beaks. 

 Some of the Pentatomidae (Fig. 277) are 

 of considerable economic value on account 



of \heir predaceous habits. Most of the Neuroptera feed upon other 

 insects. The Myrmeleon larva (ant-lion) digs a funnel-shaped pitfall, 

 at the bottom of which it buries itself to await the fall of some 

 unlucky ant. The Chrysopa larva (aphis-lion) impales an aphid on 

 the points of its mandibles and sucks the blood through a groove 

 along each mandible (Fig. 46, ), the maxilla fitting against this 

 groove to form a closed channel. Several families of Coleoptera 

 are almost entirely predaceous. Among aquatic beetles, Dytiscidae 

 are carnivorous both as larvae and imagines, Gyrinidae subsist chiefly 



270 



FIG. 277. Nymph of Podisus 

 maculiventris sucking the blood 

 from a clover caterpillar, Colias 

 philodice. Natural size. 



