STRUCTURE, GROWTH AND ECONOMICS OF INSECTS 4I 



2. Polyphagous endophagous species which are themselves sub- 

 ject to severe competition and meet with many adverse factors, e.g., 

 ScutelUsta cyanea, etc. 



3. Predators with special victims, e.g., many lady-birds. 



4. Polyphagous predatory species; Calosoma. 

 Entomophagous insects include members of the Coleoptera,Hymen- 



optera, Diptera, Hemiptera and Neuroptera. The coleopterous mem- 

 bers are the lady-bird beetles, murky ground-beetles, and tiger-beetles. 



The lady-birds are small, convex, nearly hemispherical beetles, 

 generally red or yellow and spotted. Their antennae or feelers are 

 club-shaped, and their tarsi are apparently three-jointed. They feed 

 upon small insects and the eggs of larger species, and are specially 

 valuable for keeping plant-lice in check. 



The larvae of lady-birds are quite active and hunt for their prey. 

 Some bear spines, while others are protected by fine white down. 



Ground-beetles {CarabidcB) are active forms that live on the surface 

 of the ground. They are usually black, but some have bright colors. 

 They hide under stones or boards in the day-time but leave their 

 shelters at night. They destroy large numbers of caterpillars, such as 

 cutworms, canker-worms, tent-caterpillars, and the grubs of curculio. 

 The larvae feed underground on the larvae of leaf-feeding insects. 



The ground-beetles have thread-like antennae, five-jointed tarsi, 

 and legs fitted for running. 



Tiger-beetles {Cicindelidce) are carnivorous insects, and are most 

 active in the day time. Their activity, markings, and stealthy habits 

 have given them their common name. In structure they are closely 

 related to the ground-beetles, and like them have thread-like antennae 

 and five-jointed tarsi. 



The larvae of these beetles live in holes in the ground and prey upon 

 unwary insects. They have large heads, immense jaws, long sprawling 

 legs, and two prominent humps on the back. 



The Hymenoptera possess several very important beneficial forms, 

 mostly parasites: 



Ichneumon-flies {I chneumonidce) vary greatly in size, and the females 

 of some species possess a protruding ovipositor. A common ex- 

 ample is Megarhyssa (Thalessa) a very long tailed ichneumon, which 

 bores a hole in wood infested with pigeon Tremex borers and deposits an 

 egg beside the larval Tremex (Fig. 41); other common ichneumons are: 



