4 CIRCULAR 2 4 7, U. S. DEPARTMENT OF AGRICULTURE 



the bait is used, water being added as it evaporates. The size of the trap will 

 govern the quantity of bait to be used and for the present it appears that 

 1 pint of bait to each cubic foot of the trap (inside measurements) is about 

 the right proportion. 



EFFICIENCY OF THE BOX-TYPE TRAPS 



The first traps were constructed and tested for eye gnats in April, 1928. As 

 has been stated, they were of glass in a wooden frame. After considerable 

 experimental work in devising entrances and shapes, a trap was constructed 

 that had essentially the same features as the traps mentioned here. It was 14 

 inches wide, 24 inches long, and 40 inches high. This trap took large numbers 

 of eye gnats, but observations indicated that better results were obtained by 

 darkening the lower part of the trap and placing a screen in the lower entrance 

 board. From October 17 to 27, 1928, this trap captured approximately 378 000 

 eye gnats on a ranch in Coachella Valley, Calif. A larger trap was constructed 

 (42 inches wide, 60 inches long, and 72 inches high), and from November 2 to 

 11, 1928, this trap captured about 988,000 eye gnats and 2y 2 gallons of flies of 

 various species. 



The work was continued through 1929 and 1930, and the present type of eye- 

 gnat trap was designed in October, 1930,. and tested during 15 months. It" is 

 believed that it will be suitable for use about schools and on ranches. Since 

 it has been determined that practically 100 per cent of the gnats entering the 

 traps are females capable of oviposition and that these may live in some cases 

 for more than three weeks, it would appear that gnat breeding may be con- 

 trolled to some extent by the use of these traps. 



Several tests which were run with the box-type blowfly traps using a large 

 amount of bait, in comparison with a number of the small cylindrical traps with 

 inner cones using relatively smaller quantities of bait, indicate that for sys- 

 tematic range trapping the cone traps are superior. However, where but one 

 trap can be maintained, the box-type trap should be very useful. 



During the tests, parasites of blowfly larvae and pupae were found to breed 

 in the trap, but not so freely as had been expected. 



The large concrete-base carcass-disposal trap was constructed at Menard, 

 Tex., March 13 and 14, 1930. The season's results for this trap were reported 

 by letter from H. E. Parish, agent of the Bureau of Entomology, January 11, 

 1931. The total catch of flies for the period of March 30 to October 31. 1930, 

 was 30 pounds 6 ounces, or 233.5 quarts. The amount of bait used was esti- 

 mated at 4,368 pounds. The flies were emptied from the trap four times during 

 the season. Of the total flies taken, 79.2 per cent were screw-worm flies, 

 CocJiliomym macellaria Fab., and 14.3 per cent were black blowflies, Phormia 

 regina Meig. 



CONCLUSIONS 



Tests of box-type traps as described herein indicate that under certain con- 

 ditions they may be of value in combating the screw-worm fly and other blow- 

 flies. 



The large concrete-base traps may be used to dispose of carcasses and gar- 

 bage in such a way as to make such refuse serve a useful purpose, especially 

 where it is not feasible to destroy carcasses or ranch garbage otherwise. 



The box- type trap may also be utilized to provide a continuous breeding place 

 for some of the parasites and predators of blowfly larvae and pupae. 



Data at hand indicate possibilities that this box-type trap will control the 

 breeding of the eye gnat to some extent, as well as diminish appreciably the 

 number of adult gnats. 



The tests also indicate that a windmill bait agitator installed in the box-type 

 trap may increase the catch of blowflies and does materially increase the catch 

 of eye gnats. 



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