﻿86 BULLETIN 1369, U. S. DEPARTMENT OF AGRICULTUEE 



EFFECT OF BURIAL ON LARV^ AND PUP^ 



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 larvae and pupae occur would destroy many of them. 



Several mature larvae and freshly formed pupae of H. lineatuTn 

 were buried in sand and black clay soil, at depths of from 2^4 to 4 

 inches. In most instances the larvae 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 pupae 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 larvae 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 larvae 

 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 larvae are destroyed 

 in this way, since often a large percentage of the grubs leave the 

 hosts in the barns. 



Some larvae of H. hovis 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 pupae 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 supplied 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. lineatuon,^ but less against H. hovis. 

 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. 



