22 nru.K'i; PUERTO BIOO EXPERIMENT STATION 
sorb sufficient arsenic through the skin to cause death. This usually 
occur- when the preparation is applied as a spray and the dilutions 
arc made by persons unfamiliar with the danger involved. The 
dilution- stipulated l>y the manufacturer must be closely 1<>11. . 
A recommended dilution of 1 part of the stock solution to 155 part- 
id' water is much less concentrated than the 1- to 3-percent solution 
of a disinfectant ordinarily used in the stable. 
Prevention. — The most feasible method of control usually 
reduce the infestations t<> a minimum by routine dipping of cattle 
;i- often a- accessary. Individual premises can he freed of ticks 
and maintained tick-free by proper dipping and quarantine meas- 
ures, hut cattle raised on these premises would he nonimmune t«» 
tick fever and thus the owner would he handicapped in selling ani- 
mal- other than for meat purposes. 
The complete eradication of the cattle tick from the island would 
enable dairymen to hrim: in pure-bred animal- for replacements 
and to improve the native stock without danger of death from 
tick fever. 
Further information concerning treatment, eradication, and the 
diseases transmitted by this tick i- available in various bulletins 
published by the United State- Department of Agriculture. 
HORNFLY 
The hornfly < H<i> n,<it<>hni serrata) (tin. 2, F) i- a bloodsucking fly 
that attack- cattle and also horses. This fly i- about one-half the size 
of the common house fly. It is easily determined by it- size and 
by the fact that it always bites or suets blood with it- wings spi 
and with the head toward the ground and in the same direction as 
the hair of the animal. 
Lifi history. — The fly deposits it- eggs in fresh cow manure, 
larvae remain in the manure for :'> t<> 5 days before they burrow into 
the drier -oil underneath to pupate. The adult fly emerges in 1<» t.» 
II day- after the eggs are deposited. 
Importance. — In the southern coastal area of Puerto Rico this 
fly i- very common and a very serious pest of cattle. Attacks 
myriads of these flic- are common. In the wet coastal area- it is 
considerably Less important, hut it i> common at times, and control 
measures are necessary. 
Symptoms <in<I lesions. — The fly puncture.- the -kin and sucks 
blood. The loss of blood is considerable where it attacks in large 
numbers. Animal- sometimes lacerate the -kin of the Hank- with 
their horns while fighting the fly. 
Treatment. — A spray consisting of a kerosene extract of pyre- 
thrum i> very effective in destroying these flies. Spraying morn- 
ing and evening protects the animal from infestation and greatly 
reduces the number of flies. 
Prevention. — The manure collected from stables should t> 
in fly-tight pit- or bins or spread immediately on fields. In dairy 
1 CHAPIN, B M FKVKi; TICKS \M> METHODS OF EftADI- 
,•' \_ Farmers' Bui. 1067, '■'<- pp.. Ulus. 1919. 
M'.iu.i ::. .1. R n- b rsvBB U.S. Dept. A-r Farmers' Bui. 1625. :'.<» pp., illus. 
StilbSj G w. Jr. w\ :\ cattle. I'.s. Dept. Agr. Circ. i~.4. i<» pp 
