264 



Journal New York Entomological Society. [Voi. xxiv. 



hcemorrhoidaUs Linnaeus, and, to some extent, clear up the uncer- 

 tainty concerning the reason why this fly is so obnoxious to horses. 



On July 7, Mr. R. W. Wells, the writer's assistant, brought in a 

 specimen of the nose fly captured just as it was about to "strike." 

 At the end of the ovipositor was a minute black object, apparently 

 an tgg. Dissection of the abdomen proved this to be true and the 

 peculiar shape of the egg at once suggested the cause of irritation 

 to horses. Fig. i shows that it consists of two parts, an enlarged, 

 laterally flattened portion and a slender, stalked portion. It seemed 

 likely that if the latter should be thrust into the nose or lips of a 

 horse, its penetration would undoubtedly cause a sharp pain sufficient 

 to account for the nervous and sometimes uncontrollable fear shown 

 by horses when the fly is " striking." The examination of several 

 horses fully substantiated the supposition. Some eggs were found 

 thrust in but a short distance, but most of them to the full length of 

 the stalk. Due to their minute size they were somewhat difficult to 

 discern, especially when the skin around the mouth was dark. They 

 were found principally in the upper lip, but also in the lower lip and 

 nostrils and doubtless may be inserted at other points near the mouth. 



Fig. I. Side and edge views of egg of Gastrophilns hamorrhoidalis. 

 Fig. 2. Outline sketch of egg of Gastrophilns hccmorrroidalis : (i) 

 Micropyle, (2) Cap in place and removed, (3) Developing embryo. 



Eggs dissected from the abdomen averaged 1.35 millimeters in 

 length, the stalked portion slightly more than .50 millimeter. Except 

 near the extremity of the enlarged portion, the chorion seems to 



