GASTROPHILUS HAEMORBHOIDALIS AND OTHER BOTS. 



DISTRIBUTION IN THE UNITED STATES AND PROBABLE 

 DISPERSION. 



Becently Mr. F. C. Bishopp, in communication with a large num- 

 ber of horse breeders, has determined some facts on the distribution 

 and other points, especially in regions adjoining the district where 

 G. haemorrhoidalis is known to occur. This information will be 

 published later. It will suffice to say here that G. haemorrhoidalis 

 occurs in sufficient numbers to warrant the adoption of control 

 measures in the Dakotas, Montana, and northern Wyoming. Accord- 

 ing to Dr. C. Gordon Hewitt, Dominion Entomologist, the species 

 extends over a considerable area in the Dominion of Canada. Two 

 of the species, G. intestinalis and G. nasalis, are found throughout 

 the United States where horses are present. G. pecorum is not 

 known to occur in the United States. 



The constant migration of the larvae of G. haemorrhoidalis to the 

 region of the anus and their dropping, which occurs over a long 

 period, indicates that the principal means of dispersion is through 

 the movement of infested horses. During the past few years 

 large numbers of horses, which have been purchased in the 

 infested district for European 

 army purposes, were concentrat- 

 ed at certain points until more 

 could be assembled for shipment. 

 This occurred at times when 

 larvae were normally dropping 

 and allowed ample time for this 

 species to become established. 

 Although the adults may not 

 have appeared in sufficient num- 

 bers to attract attention in new 

 districts, this will undoubtedly 

 occur in the near future. 



The comparatively short dura- 

 tion of adult life and the func- 

 tions of the adults restricted to 

 depositing eggs indicate that 

 little dispersion takes place by 

 actual flight. In the nose-fly 

 district there has been a slow but gradual spread of the species each 

 year, as verified by hundreds of statements from farmers and horse 

 breeders. 



1*5: 



Fig. 3. — Gastrophilus eggs attached to hairs : 

 a, G. haemorrhoidalis and hair removed 

 with root; 6, G. intestinalis; c, G. nasalis. 

 Greatly enlarged. (Original.) 



LARVAL COLLECTIONS AND REARING TECHNIQUE. 



An insectary was located in Aberdeen, S. Dak., where all types 

 of farm and city operations concerned with the use of horses could 



