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. 62, 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 vari- 

 ety of flying insects, mostly small forms, 

 but occasionally butterflies of considerable 

 size. The eyes of a dragon fly are remark- 

 ably large; the legs form a spiny basket, 

 probably to catch the prey, which is in- 

 stantly stripped and devoured, these opera- 

 tions being facilitated by the excessive 

 mobility of the head. The hemipterous 

 families Corixidae, Notonectidae (Fig. 225), 

 Nepidse, Belostomidae (Fig. 22), Naucoridae 

 (Fig. 62, D), Reduviidae and Phymatidae are 

 predaceous, with raptorial front legs and 

 sharp beaks. Some of the Pentatomidae 



(Fig. 274) are of considerable economic value on account of their predace- 

 ous habits. Most of the Neuroptera feed upon other insects. The Myrme- 

 leon larva digs a funnel-shaped pitfall, at the bottom of which it buries 

 itself to await the fail 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, ), 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 



253 



FIG. 274. Nymph of Podisus 

 macitlivcntris sucking the blood 

 from a clover caterpillar, Colias 

 phihdice. Natural size. 



