256 



COLLEGE ZOOLOGY 



plants could not exist without insects. An 

 interesting example is furnished by the 

 Smyrna fig which could not be grown in 

 California until the minute fig insect (Fig. 

 448) was introduced to pollenize the 

 flowers. 



Predaceous insects 



Predaceous insects are of benefit because 

 they devour vast numbers of other insects, 

 most of which are injurious. Ground beetles, 

 tiger beetles, antlions, and lady beetles, all 



Hymenopteran ovipositing in on aphid (Homoptero) 



Cocoons (pupae) of a braconid 

 fly (Hymenoptera) on the larva 

 (hornv/orm) of the tomato 

 sphinx moth (Lepidoptera) 



^^^ 



Hymenopteran 

 ovipositing in egg 

 of codling moth 

 (Lepidoptera) 



Pyrgota fly (Diptera) 

 ovipositing in abdomen 

 of June beetle (Coleoptera) 



Figure 155. Some insects that show a parasite-host relationship. It is roughly estimated that 

 there are about 11,000 species of parasitic insects in North America. Insects are probably their 

 own worst enemies. (After U.S. Department of Agriculture Yearbook, 1952.) 



shown in Fig. 154, are common types. The 

 Australian ladybird beetle (Fig. 154) was 

 introduced into California because it was 

 known to devour the fluted scale and to 

 protect successfully the orange and lemon 

 trees from this species. Other predaceous 



species have also been introduced with favor- 

 able results. 



Insects that live as parasites (Fig. 155) on 

 other insects are also beneficial to man. 

 They usually lay their eggs in the larvae, and 

 the young that hatch from these eggs 



