The Chalcis Flies 



species of the genus Copidosoma are always parasitic within naked 

 caterpillars. Those of the genus Bothriothorax are always para- 

 sitic in small dipterous larvae. The economic importance of the 

 group is great. They are the most effective parasites of many of 

 our most injurious insects. For example, in a certain year in the 



<* 



Fig. 30. Chalcis ovata, Say. (Author's illustration.) 



cotton fields of Northern Florida 95 per cent, of the eggs from 

 which would have hatched the voracious cotton caterpillar were 

 killed by the minute Chalcidid parasite, Trichogramma pretiosa. 



Life History of a Chalcis Fly 



(Euplectrus corns tockii, 



It goes without saying that the full life of the internal-feeding 

 parasites of this group is very difficult and practically impossible 

 to follow so long as they are within the body of the host insect. 

 In our earlier consideration of the super-family Proctotrypoidea 

 we have given some general remarks upon the development of 

 all internal-feeding parasitic Hymenopterous larvae, and those re- 

 marks will apply in general to the Chalcis flies. There are some 

 of them, however, whose larvae do not feed internally. These are 

 especially those which are parasitic upon the larvae of gall-making 

 insects. If a gall be cut open, it is quite likely that there will be 

 found within it the larva of a Torymus (one of the Chalcis flies) 



57 





