e
backs of cows. Mixtures of cottonseed oil and pine tar containing from 10
to 50 per cent of the latter substance were found by investigations in the
Bureau of Animal Industry to have a marked repellent action against flies
when applied lightly every day. A too free application of tar mixtures and
other preparations containing phenols is liable to cause poisoning; hence
care should be observed in this regard.

Jensen (1909) recommends the following formula, which is said to protect
cows for a week:

Common laundry soap 1 pound.
Water 4 gallons.
Crude petroleum 1 gallon.
Powdered naphthalin 4 ounces.

Cut the soap into thin shavings and dissolve in water by the aid of heat;
dissolve the naphthalin in the crude oil, mix the two solutions, put them
into an old dasher churn, and mix thoroughly for 15 minutes. The mixture
should be applied once or twice a week with a brush. It must be stirred
well before being used.

THE STABLE FLY (STOMOXYS CALCITRANS).[13]

This fly very closely resembles the house fly, but, unlike the latter, it
is a biting fly. It is common about stables and often enters dwellings,
especially in cloudy weather. According to Noe, it is the agent of
transmission of a parasitic roundworm of cattle
(_Setaria labiato-papillosa_, see p. 529). This fly has been shown capable
of transmitting anthrax from diseased to healthy animals, and under some
conditions it may transmit surra, a disease caused by a blood parasite
which affects horses, cattle, and other livestock.

The annoyance suffered by cattle and horses from stable flies is much
lessened if the stables are darkened.

The screening of doors and windows, however, is preferable, as ventilation
is not interfered with as it is in darkening stables. For milk cows
coverings made from burlap (double thickness), including trouserlike
coverings for the legs, may be used when the flies are very numerous and
troublesome. One of the fly repellents mentioned above may be applied to
cattle to protect them from stable flies. The Hodge flytrap fitted to the
windows of dairy barns is a useful means of destroying stable flies. The
United States Bureau of Entomology has found that a mixture of fish oil (1
gallon), oil of pine tar (2 ounces), oil of pennyroyal (2 ounces), and
kerosene (1/2 pint) is fairly effective for a short time when applied
lightly, but thoroughly, to the portions of animals not covered with
blan