BUREAU OP ENTOMOLOGY. 221 



simply of the removal of the domestic hosts of the adult tick from 

 the infested areas, and such a plan appears to be more adaptable 

 to stock-farming conditions and practices in the Bitter Root Valley. 

 A campaign of destruction against the Columbian ground squirrel 

 and other rodent hosts of the immature ticks has been conducted, 

 and as a result of two seasons' efforts it is estimated that the normal 

 squirrel population has been reduced from 60 to 75 per cent. 



Owing to the prolonged life cycle and its complications in this 

 species of tick, the effect of the control work is difficult to determine. 

 The examination of 376 ground squirrels during the season gave an 

 average infestation of 0.42 nymph per squirrel as compared to 0.69 

 per squirrel in 1915, and 4.8 per squirrel under normal conditions 

 as determined in 1910 and 1911 — a reduction of 92.3 per cent of 

 the normal and 40 per cent of the 1915 average. The occurrence 

 of human cases of spotted fever during any one season is not a 

 reliable index of the effect of the control work, since there may be a 

 considerable variation under normal conditions and the number of 

 cases is never large. It is of interest, however, to note the develop- 

 ment of only one case during the present season in the area in which 

 the operations have been conducted. 



The house fly. — The work on the house fly has been continued 

 along the same lines as in previous years. The experiments on the 

 chemical treatment of manure resulted in finding a mixture of cal- 

 cium cyanamid and acid phosphate which was fairly effective when 

 used in proper amounts. Demonstrational work with maggot traps 

 was continued. An improved type of flytrap was worked out, and nu- 

 merous baits were tested and compared as to their effectiveness. The 

 most attractive baits were found to be beer, vinegar in sweetened water, 

 banana, and milk. A series of experiments was begun to get exact in- 

 formation as to certain poisoned baits in which such substances as for- 

 malin and sodium arsenite were used. A large number of experiments 

 and observations were made on the question of the hibernation of the 

 house fly, with the result that, in the latitude of Dallas, Tex., it was 

 found to pass the winter in the larval and pupal stages. In the 

 latitude of Washington circumstantial evidence indicates that here, 

 also, the immature stages are the overwintering forms, though final 

 direct proof is still lacking. 



Insects affecting packing establishments. — Investigations of in- 

 sects in relation to packing establishments operated under the meat- 

 inspection service of the Bureau of Animal Industry were continued 

 throughout the year in cooperation with that bureau. An agent 

 visited a considerable number of plants in the Western States where 

 the fly problem is of much importance, in some localities continuing 

 throughout the year, owing to the mild winter climate. Suggestions 

 were made to the inspectors in charge which enabled them to take im- 

 mediate steps toward improving the fly situation in their respective 

 establishments. Studies were made of methods of preventing the 

 breeding of flies under the particular conditions found to prevail in 

 and around packing houses and a considerable cumber of experiments 

 with methods of destruction of the adult flies were conducted. As a 

 result of tests a very satisfactory trap was developed, as well as im- 

 proved baits and methods of trap operation, and the information put 



