stock are seldom completely free from insects. Outbreaks do occur, 
but there is usually no markedly reduced infestation the following 
year, except in the case of the screw-worm in the Northern States, 
which are inveded in some years. 
The injury that insects do to livestock is usually not so apparent 
as injury done to plants. The grower may see his livestock fighting 
flies, but not understand that losses in weight and milk will result. 
House flies, stable flies, horse and deer flies, cattle grubs, lice, 
and screw—worms cause reduction in yield due to fighting and run- 
ning from them and reduced feeding. In addition, hides and meat are 
damaged by cattle grubs, and wool and mohair of sheep and goast by 
lice and sheep ticks. 
Cattle 
Cattle grubs are distributed over the entire United States, but 
especielly in the North, where two species are involved. They 
cause losses in cattle in three ways: 
(1) Damage to hides. A large proportion of the hides taken 
during the grub season (6-8 months) have five or more 
grub holes and are classed as No. 2 grade. The grower 
takes the loss, but is seldom aware of the degrading. 
(2) Loss of meat in dressed carcasses. Buyers down-grade 
cattle purchased during grub season. Two or three 
grubby animals in a lot are reported to lower the price 
of the entire lot as much as $5 per head in some stocke 
yards, 
(3) Running from flies. Cattle occasionally jump, run, and 
stampede over or into fences and injure themselves 
during the heel fly season (2=l; months). The loss in 
weight and milk preduction among cattle severely attacked 
is estimated at 10-20 percent. 
The average annual loss in cattle due to the cattle grub is 
estimated at $100 million. 
Lice cause beef and dairy animals to rub and lick or bite then- 
selves. Lousy animals are unthrifty and do not utilize feed for 
proper gains. Little information is available on the reduction 
of weight gains or milk production due to lice. Snipes 1/ showed 
7/ Snipes, B. Thomas. 1948. One=treatment control for cattle 
lice. Agr. Chem. 3(9): 30=-3h. 
- 153 - 
