30 BULLETIN 597, U. S. DEPABTMEXT OF AGKICULTITBE. 



eggs upon the moist portions incubated in from 5 days to a slightly 

 longer period. 



September 9 was preceded by two unfavorable days for oviposition 

 and was itself very favorable, but was followed by rain and cloudy 

 weather until September 15. At this time black eggs were found 

 upon the dry portions of the lips, while upon the moist portions 

 the eggs were reddish with whitish tips. Due to the scarcity of 

 adults, the eggs were not plentiful at this time, and a few days 

 later one only could be found, upon the dry portions of the lips. 



Due to the comparatively long period during which the eggs re- 

 main attached upon the dry portions of the lips of horses, which is 

 particularly due to the protection of the thick, coarse hairs surround- 

 ing them, it is believed that one could be misled easily as to the 

 most favorable places of deposition of the adults. 



GASTROPHILUS NASALIS (Linnaeus). 



SYNONYMY. 



Oestrus nasalis Linnaeus. 1761. 

 Oestrus veterinus Clark, 1797. 

 Oestrus salutiferus Clark. 1815. 

 Oestrus clarkii Leach, 1817. 

 Gastrus nasalis Aleigen. 1824. 

 Oestrus duodenalis Schwab. 1S40. 

 Gastrophilus nasalis Schiner. 1861. 



OVIPOSITIONS AND LONGEVITY. 



The female Gastrophilus nasalis often appears from the grass 

 about the fore legs of a grazing animal, strikes under the jaws, re- 

 mains a few seconds, and during that time deposits an egg about 

 midway upon the hair. The adult then leaves, completely disap- 

 pearing in the distance, but within a minute or two a similar oviposi- 

 tion may occur, except that the adult approaches from a distance. 

 The presence of a person about the head of an animal does not inter- 

 fere with egg deposition, and the fly may be caught with the hand 

 when it alights upon the hairs underneath the jaws. It may also 

 be observed to deposit upon the fore legs or the flanks. Dissections 

 of the abdomen of reared females show that they are capable of 

 depositing from 480 to 518 eggs. The attachment of these, as may 

 be seen by referring to figure 3. <r-, extends to almost the entire length 

 of the egg, and being attached about midway upon the hair, numbers 

 are concealed unless the hair is brushed aside in making examina- 

 tions. Often eggs may be observed near the end of the hairs, but 

 this usually occurs after great numbers have been deposited. Then 

 it is possible to find two or more eggs upon one hair. As yet the 

 method of ingress of the larvae has not been determined. Dr. C. H. 

 T. Townsend thinks that the larvae burrow through into the mouth 



