INSECTS BENEFICIAL AND BEAUTIFUL 251 



late victim as a roof. Some of these will probably be 

 found during the search for plant lice. 



The Chalcis Flies.' — These are the smallest of the parasitic 

 Hymenoptera. They are generally black with metallic 

 luster, but a few are yellow. Slingerland writes of one 

 of them : 



It would seem that the codling-moth's egg, not quite so large as 

 a common pin's head, would escape the eye of the enemy, but many 

 of them do not. In June, 1896, we were surprised to find that quite 

 a number of the eggs we saw had a peculiar black appearance. 

 These were placed in cages, and a few days later the mystery was 

 explained. For instead of little apple-worms hatching from them, 

 there appeared fully developed adult insects, the surprising number 

 of four coming from a single tiny egg in some cases. It is wonder- 

 ful to think of four perfect animals having been born in, and having 

 obtained sufficient sustenance to develop into perfect insects from 

 the contents of such a tiny thing as the egg of a codling-moth. In 

 figure 138 is shown a greatly enlarged picture of this pretty little 

 parasite, v/hich is of course an exceeding small creature, yet it is 

 easily visible to the naked eye.^ 



Many of the Chalcis flies are parasitic on the scales 

 and on the eggs of other insects. To keep watch for 

 them will add interest to many of our lessons. 



The Syrphus and Tachina Flies. — Though related to the 

 ichneumons only by their parasitic habits, these may be 

 considered in this connection. Both belong to the fly 

 family proper, since they have but a single pair of wings. 



The syrphus flies are the ones we all have wondered 

 about from our infancy. They are par excellence the 

 flies of bright sunshine and flowers, where they disport 



1 M. V. Slingerland. "The Codling-Moth," Bulletin 142, Cornell 

 University Agricultural Experiment Station, 1898, p. 37. 



