86 BULLETIN 1369, U. S. DEPARTMENT OF AGRICULTURE 
EFFECT OF BURIAL ON LARVZ AND PUPZ 
It is difficult to say just what degree of control is effected through 
plowing. From reports on the abundance of grubs in cattle in the § 
Central States in the eighties as compared with the number of grubs 
in the same regions now, it apears that there has been a decrease in 
abundance. Many think that the restriction of pastures to compara- 
tively small areas and more general and intensive cultivation are 
largely responsible for this. It is reasonable to suppose that plowing 
fields where larvee and pup occur would destroy many of them. 
Several mature larve and freshly formed pupe of H. lineatum 
were buried in sand and black clay soil, at depths of from 2% to 4 
inches. In most instances the larve worked their way to the surface 
in a short time and pupated on top of the soil. In the black clay the 
flies emerged in about the normal time and pushed out of the soil 
even when the pupe were buried to a depth of 4 inches. In the fine © 
sand, however, the flies were found to have emerged and worked up- 
ward about half an inch from the puparia, where they died and were 
found later with a comparatively hard cell of sand formed around ~ 
them. 
Many larve in pastures undoubtedly become covered with manure 
as are those that drop in barns and are shoveled out with the dung. 
To test the effect of burial under such conditions four mature larvee 
were placed on a board and a large fresh cow dropping was laid on 
them. None of them moved from where they were placed. Three 
of them died without pupating and the other died as a half-developed 
fly. This preliminary test probably indicates that burial in fresh 
cow manure is very destructive and that many larve are destroyed 
in this way, since often a large percentage of the grubs leave the 
hosts in the barns. 
Some larve of H. bovis buried from 1 to 6 inches in both clay and 
sand came to the surface, while others pupated near where they were 
buried. Some flies emerged from pupe buried to a depth of 6 inches, 
but apparently the burial below 3 inches was detrimental, especially 
if the soil was very moist. 
PROTECTION OF CATTLE BY HOUSING AND NATURAL BARRIERS 
There are abundant examples of the great reduction of infestations 
effected by housing the herd during the periods of fly activity. Some 
dairymen leave their barns open or provide sheds which the cattle 
can enter when attacked by the flies. The flies, however, have con- 
siderable opportunity to deposit eggs on the cattle before they can 
get into the buildings. Such an arrangement has the advantage of 
allowing the cattle to excape from continued annoyance and fright, 
which is inevitable when no protection is afforded. Since the flies 
will oviposit in the broken shade supphed by trees, the presence of 
woods in a pasture will not greatly reduce infestation, but is bene- 
ficial in that the worry to the catttle is lessened. Streams afford 
effective protection against H. lineatum, but less against H. bovis. 
The excitement, however, is greatly relieved and milk flow main-_ 
tained when cattle have access to streams or ponds. There is danger 
of some injury to cattle, however, from standing in mud and water 
for long periods when weather is favorable for continued fly activity. 
