GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. iLL 
Other than G. nasalis, which sometimes attaches in the pharynx, 
the first-stage larvee attach to various portions of the stomach and 
duodenum. In the stomach young larve have been removed from 
various locations, including both the cardiac and pyloric portions. 
The last-stage larve of all three species are found in the various por- 
tions. Gastrophilus intestinalis is confined for the most part to the 
mucosa of the left sac, though this species has been taken in the 
right sac and in the duodenum (see Table I). In the early stages 
some of the larve either change places of attachment or pass out of 
the horse undeveloped. With last-stage larve the indications are 
that, excepting G. haemorrhoidalis, they remain attached at one 
place continuously during feeding, as in early spring the number of 
larve and lesions upon the mucosa is the same. 
During the early spring or perhaps even in winter the larve of 
G. haemorrhoidalis move from the stomach and duodenum to the 
rectum where they may be found permanently attached in clusters. 
It is evident that they feed in this position, as lesions are sometimes 
present. Later when they move to the margin of the anus no lesions 
are present and apparently the larve only pause to become accustomed 
to air temperatures before dropping. 
There is no definitely periodic larval migration of G. haemorrhot- 
dalis, as some last-stage larve are found in the stomach and duode- 
num until early fall. Through the courtesy of Dr. L. Van Es, of the 
North Dakota Experiment Station, some post-mortem examinations 
were made at Fargo, N. Dak., and larve preserved according to 
their location within the animal. During the winter these larvee 
were found in the stomach, and on July 10, 1916, 3 larve; July 14, 
1916, 16 larve; and August 18, 1916, 2 larve were fully developed 
and in the same regions. This coincides with the findings at Aber- 
deen, S. Dak., although one last-stage larva was found in the stomach 
on September 8, 1916. 
POINTS OF LARVAL ATTACHMENT. 
When an opened stomach of a horse is examined, one is impressed 
by the contrast in the left and right portions. Around the entire 
organ a line of demarcation is represented by a prominent sinuous 
crest. In the left portion, which is often called the left sac, the 
mucosa is white, dry, resistant, and covered by a thick layer of 
epithelium. This covering is identical with that of the esophagus 
and may be considered as a widening of the esophageal canal. 
Dr. Guyot, in describing the mucosa of the left sac, says the struc- 
ture is analogous to that of the skin. It is dermo-papillary, with 
epithelium of the Malpighian type, but possesses a muscle, the 
muscularis mucosae, which is peculiar to it. The structure of the 
