er 
ngs 
» ‘ 
THK CATTLE GRUBS OR OX WARBLES 63 
was greatly reduced in the middle of the day, increasing again in 
the middle of the afternoon. 
The number of larve recorded as dropping in the earlier morn- 
ing hours is undoubtedly too small, as fewer examinations were 
made between 8 and 9 a. m. than in later periods, and a much 
smaller number still between 7 and 8 a. m. It is believed, how- 
ever, that by adding all of those which may have dropped between 
7 and 9 a. m. the total would not nearly equal the number which 
dropped between 9 and 10 a. m. Of the 269 larvee the hour of 
emergence of which was noted with considerable accuracy, 140, or 
52 per cent, left the host between 8 a. m. and noon, and 129, or 48 
per cent, between nocn and 6 p.m. There is undoubtedly a greater 
disparity than these percentages indicate, as the number of hours 
in the forenoon period was smaller than the number in the after- 
noon. Also, as stated above, some warbles that dropped in the 
early morning hours were not recorded. 
The percentage of grubs dropping in the night was compara- 
tively small. Considering the entire 392 larve upon which 
the writers have records, only 88, or 22.4 per cent, dropped out 
during the 12 hours from 6 p. m. to 7 a.m. Asa matter of fact, 
this percentage is too high, as in it are included larve which on 
several occasions were found to have dropped from animals when 
they were first examined in the morning; sometimes this examina- 
tion being made as late as 8 or 9 o’clock. 
From their observations and the study of the data accumulated 
the writers are led to believe that the activity of the host has 
much to do with the dropping of the larve. Feeding of the 
animals usually took place between 8 and 9 a. m. and up to about 
that time the animals were comparatively quiet, usually lying 
down. In the noon period following the morning feeding they 
again became quiet and lay down much of the time, until 4 or 
5 p. m., when feeding again took place. Just how activity of the 
host should influence the dropping of the larve it is not easy 
to see. Possibly the muscular movements stimulate them. There 
is a possibility also that the warming up of the back of the 
animals by the sun following the cool night may tend to stimulate 
dropping. In the instances cited by Glaser it appears that feeding 
took place very early in the morning and hence his observations 
may tend to substantiate this hypothesis. 
DISTRIBUTION OF THE LARVA ON THE BACKS OF CATTLE 
As is well known, the larve occur in the greatest numbers along 
each side of the spinous processes from the shoulder to the hip bones. 
In diagraming the backs of hundreds of cattle the writers have 
observed that this distribution is very irregular, sometimes several 
larve being in one group and the rest of the back comparatively | 
free, while in other cases they are widely scattered over the entire 
area. It seems certain, however, that this is simply a matter of 
chance. In summarizing their figures on the distribution of the 
larvee the writers find that about 50 per cent of them occur in the 
region of the dorsal vertebre and the other 50 per cent in the 
lumbar region. As a rule they are more concentrated in the area 
over the last three ribs. Although it is not unusual to find grubs on 
