FAMILY GASTEROPHILID.E THE HORSE BOT FLIES 401 



authorities have placed it in the Acalypterie where it would seem to 

 belong on account of the shape of the second antennal segment. How- 

 ever, the species possess strong posterior calli and it is possible that the 

 family is, despite the antennal character, more nearly related to the 

 Mnscidae. 



The family contains bnt one genus, Gasterophilus Clark, and there 

 are three North American species. 



KEY TO THE NEARCTIC SPECIES OF GASTEROPHILUS 



1. Wings with dark spots intestinalis Degeer 



Wings without dark spots 2 



2. Discal cell closed beyond the first basal cell; apex of abdomen broadly 



reddish pilose haemorrhoidalis Linnaeus 



Discal cell closed almost oppo.'^ite the end of the first ba.^al cell; basal 

 cells of equal length; abdomen with whitish pile crossed by a black 

 median band veterinus Clark 



