28 



Liood of this species in a season, for Hart's specimens issued im 

 August and September, while I have bred specimens which is- 

 sued in July. This is a very small insect, and passes its immature 

 stages inside the eggs of the fly, one specimen in each egg. At 

 a certain place in Medina County, Ohio, where the eggs of the 

 black horsefly were common, it was found that many of the- 

 masses remained plump long after others had sliriveled because 

 of the larvae hatching from them. An investigation showed that 



,._i 



Pig. 15. — Horsefly egg-parasite. I'liniiiirux /<//<.;»/r')/((.v. miicli i-nlarged. (After 

 Hart, Bull. Ills. State Lab.. Volume IV.) 



the forniei- contained many pai-asitized eggs, soiiu' masses liavin.rf 

 r.early every specimen in this condition. A numbei- were col- 

 hcted and ])ut into small vials, where, in the course of a couple 

 of weeks, hundreds of the parasites issued. A\1iat 1 have ob- 

 served regarding this minute species proves to my mind that 

 it is of much importance in lessening the numbers of horseflies 

 whose eggs it infests. It has not been observed in Louisiana, but 



