10 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. 
during the time when larve were naturally dropping with excreta. 
The numbers do not show the maximum infestations of larve that 
may have been present. Many of the dead horses examined had 
been subjected to various environments prior to the autopsies and are 
not representative of infestations found when horses have spent the 
entire previous summer in pastures. 
TABLE I.—Gastrophilus findings in post-mortem examinations of horses at Aber- 
deen, S. Dak., 1915-16. 
Larve in stomach. Larve in duodenum. 
Horse Spent summer. 
sp. small. 
sp. small. 
Larve in rectum, G. 
G. intestinalis. 
G. nasalis. 
G. haemorrhoi- 
dalis 
Gastrophilus 
| G. intestinalis. 
G. nasalis. 
G. haemorrhoi- 
dalis 
Gastrophilus 
haemorrhoidalis 
Total number larvee. 
July 24 | Inpasture.................. 
Aug. 3 Farm work i 
1 Includes 1 G. intestinalis temporarily attached in colon. 
2 Includes 1 G. intestinalis temporarily attached in rectum. 
LARVAL MOVEMENTS WITHIN THE HORSE. 
When a post-mortem examination is made, the larve usually are 
found quiescent, although occasionally some may be observed to move 
the posterior end slightly. The smaller larve show more activity 
than do well-developed ones. 
