OUR INSECT FRIENDS 



367 



FIG. 371. Caterpillar from which 

 larval parasites are emerging. The 

 adult chalcid fly is shown on right. 



birds," which with their larvae prey 

 upon plant lice and scale insects; 

 syrphus flies (Fig. 368), whose young 

 have a similar diet; the lace-winged 

 fly (Fig. 369) or aphis lion, some 

 wasps and others. 



(6) There are parasitic forms which 

 lay eggs on or in other insects or their 

 eggs. The most notable group of 

 parasites is the Ichneumonidce (Fig. 

 370 illustrates a large species), a hyme- 

 nopterous family containing over 10,000 

 species, all parasites. The Chalcididce 

 (Fig. 371), also belonging to the Hyme- 

 noptera, includes about 4000 species. 

 The Braconidce and the Proctotrypidoe. 

 The members of the latter family are 

 very small, and are chiefly parasitic on 

 eggs of insects. Among the Diptera we 

 have the bee flies (Fig. 372) and the 

 Tachinidce, very abundant in number 

 of species. Their white eggs are fre- 

 quently seen on tent caterpillars and 

 army worms (Fig. 373). 



(c) Among the indirectly beneficial 

 insects we ought also to include several 



Fin. ?72. S. orens, a bombyliid or bee fly. The larvse of some members of the family 

 are parasitic in the egg pockets of grasshoppers; a, larva; 6, head of same from the side; 

 c, same from the front; d, preanal spiracle. (After Riley.) 



