270 



BENEFICIAL INSECTS. 



already living' in the hodv of a caterpillar ; we then have one ichneumon 



parasitic upon another, a 

 singular phenomenon, which 

 checks the too g-reat increase 

 of the beneficial insects 

 (fi g. oil o) . Ichneumons also 

 lay their eggs in such small 

 insects as aphides, and even 

 in the eggs of insects. 

 One species lays its eggs in 

 the eggs of the moth-borer 

 of sugarcane and the eggs 

 of many insects are thus 

 destroyed. 



Besides the ichneumons, 

 there axe the parasitic flies, 

 a large group of Dtftem 

 which behave very similarly 

 to the ichneumons. These 

 flies (fig. 325) resemble 

 house-flies and are common 

 in the fields. They lay 

 their eggs on caterpillars, 



and other insects, the maggot that hatches destroying the caterpillar. 



As in other flies, the full grown 



maggot forms a brown seed-like 



pupa (fig. 324) usually coming 



out of the caterpillar before it 



does so. A species of parasitic 



fly lays its eggs on the Bombay 



Locust and another on the Red 



Cotton Bug. 



As a rule every species of 



parasite is found only on one or 



a few insects. The parasite 



of the Cotton Stem-borer is not 



the same as that of the Moth- 

 borer of sugarcane. Parasites 



that we rear from distinct insects are usually distinct themselves, though 



the same parasite may be found in two species of insects which are 



very much alike. Every abundant caterpillar and very many beetle 



Fig. 325. 



Fli/ vJiose mar/qot is a, parasite on leaf-eating 



cateiyillars. (^Magnified.) JPufa 



belotr, itatwal size. 



FiO. 326. 



The parasite of tie maggot of tlie Sice^Siem 

 Fly. {Magnified.) 



