GASTBOPHILUS HAEMOKRHOIDALIS AND OTHER BOTS. 27 



a horse is grazing or otherwise protected from ovipositions. She 

 usually comes from a distance and strikes at the lips. Her quick 

 flight seems to be distinguished by the male, who attempts to mount 

 her before she oviposits, but the momentum of the two usually carries 

 the couple to some distant place so quickly that one can not tell 

 whether copulation actually takes place upon the wing or whether 

 they fall to the ground. At any rate, they fly for some distance. Ap- 

 parently the sexes always meet at the horse, the males awaiting the 

 approach of the females. At times the male encounters an adult 

 female .of G. intestinalis about the horse, and these two may be ob- 

 served to fall upon the grass at the feet of the horse, usually separat- 

 ing within a few seconds. 



PREOVIPOSITION PERIOD AND OVIPOSITIONS. 



Just how soon after emergence copulation takes place is not 

 definitely known, but it is certainly less than 18 hours. Adults 

 emerging during the night copulate by noon of the following day 

 and will oviposit during that afternoon. They will not oviposit in 

 captivity. On five occasions in which flies emerged normally during 

 the night, males and females were kept in a box with glass sides and 

 with green foliage. By noon in each case some w T ere observed to 

 copulate and w T hen liberated in the afternoon would oviposit. Their 

 wings were colored with red ink, and when captured they could be 

 identified easily. Under favorable conditions ovipositions took place 

 as soon as adults were liberated, usually about 3 hours after copula- 

 tion. After a lapse of a few minutes they were never to be col- 

 lected about the same bunch of horses, which is probably due to the 

 migration of adults and to the movements of the various horses upon 

 which they oviposit. 



A determination of the egg-laying period is important in that it 

 shows the value of destroying adults at different times during this 

 stage, but with such short preoviposition and longevity periods and 

 the inability of flies to feed, the indication is that the flies oviposit 

 throughout their existence. Dissections of females reared to adults 

 indicate that they develop from 134 to 167 eggs, the usual number 

 possibly being near 150. 



Unlike G. intestinalis, which may stand in midair and consecu- 

 tively deposit 15 or 20 eggs at one time, often placing two or more 

 upon one hair, G. haemorrhoklalis deposits but one at a time and 

 only one upon a hair. It leaves the animal for about one-half minute 

 or longer after ovipositing, but not for so long a time as does 

 G. nasalis. It never oviposits upon any other portion except the 

 lips, preferably the portions moistened by saliva. The stalk portion 

 of the egg is inserted in the pore of the skin at varying depths, but 



