70 
ward Into Oklahoma was found to be 60 to 75 miles during March and April, 
125 to L50 mile- in May. and L50 to 200 miles in June 
it was found thai approximately J percent of the cottontail rabbits in 
certain Localities In Texas were Infested with screwworms. Numerous infes- 
tations also occur in deer, coyotes, opossums, and other wild animals. Wild- 
life qoI only Buffers tan it also serves as a reservoir for the reinfestation of 
domestic animals by this fly. 
Investigation <>!' the relative economic importance, in the Southeastern 81 
of tl)«- various species of wound-invading blowflies other than the primary 
screwworm fly {Cochliomyia americana < '. and P.) show that species of PhormiOt 
Lucilia, and CaUiphora and GocHUomyia maceUaria J", are involved in about 
13 percent of the cases in domestic Livestock. Heavy infestation i»y these 
s, which often follows from <; to 10 days after the attacks of the primary 
screwworm fly, may kill the infested animal quickly. Studies on the Lethal 
< ffeel on animals of larvae of C. americana and C. maceUaria indicate thai the 
effect of the former Ls approximately four or five times as great as that of the 
latter. 
Work on the biology, habits, and control of the primary screwworm fly has 
been greatlj accelerated by the development of a method of rearing stocks of 
larvae on an artificial medium. Heretofore the rearing of these llh-s has 
required the ase of Large numbers of Live laboratory animals. 
In the work of developing more effective screwworm Larvicides and repel- 
lents, over 200 different chemicals and mixtures have been tested. Some of the 
many materials tried as larvicides which gave promising results are a mixture 
of benzol and carbon tetrachloride containing 10 percent of ground derris root. 
soluble pine oil and 5 percent of nicotine, wormseed oil, and phenothiazine 
dust. In small-scale tests ground derris root, rotenone, Or derris resinate added 
to pine-tar oil appears to be more effective as a fly repellent than pine-tar oil 
alone. 
Considerable attention has been given to the study of the biology and i 
of preventing infestation of the Gulf coast tick, one of the most important 
predisposing causes of screwworm attack. It has been found that the meadow- 
Lark Ls the principal host of the immature stages of this tick. Mixtures of pine- 
tar oil with rosin residue and sulphur applied to the ear- of animals have a 
more lasting repellent action against the tick than other materials tested. 
THE SCREWWORM IN PTJEBT0 BIOO 
r rii>' true or primary screwworm {CocMiomyia americana) was found to be 
widely distributed over the entire island of Puerto Rico, from sea level to the 
highest mountains, and to he a serious problem. Wounds, if neglected, were 
gore to he infested with maggots within a few days. The high valuation of 
catth' per head in Puerto Rico and the fact that all animals are under daily 
observation, with consequent quick treatment, keep the screwworm from being 
more serious, particularly in the case of cattle belonging to the Larger owners 
and SUgar cent ralS. This fly normally oviposits only in wounds of living animals. 
Twelve continuous generations were reared on wounded guinea pins during the 
period October 13, 1935, t<> September L966, showing that 13 generations develop 
during an entire year. Breeding, although somewhat retarded, continued 
throughout the winter, during which the lowest recorded temperature was 56 r 
The season of greatest activity was during May, June, and .inly. No evidence 
of parasitization was observed. 
HORSE HOTS 
Further Investigation on methods of controlling horse bots has shown that 
the warm-water treatment of the parts of the animal's body Infested with the 
Qasterophilus intestinalis Degeer Ls effective in destroying more than 
80 percent of this stage of the parasite, even when the air temperature Ls ns 
blgh as 82 F. 
INS! ( T PARASITES or sin l P 
The investigations on the biologies ami metho 
botfly, slieop tick, ami sheep and goat Lice were 
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