June, '14] MORRILL: HOUSE-FLY BAITS AND POISONS 269 



were also counted. In one case, when formalin was used in the trap, 

 dead flies outside several cages were counted and were found to rep- 

 resent only 5.3 per cent of the total killed and captured alive. In 

 the other experiments those which escaped after feeding on the poison 

 were not taken into consideration. 



The principal results of the cage or fly trap experiments are pre- 

 sented in Table I. In order to group the different bait materials 

 for convenience in making comparisons, wherever a combination was 

 tested, an extra listing in the table has been made for each ingre- 

 dient with the exception of water. Commercial formalin (40 per cent) 

 mixed with water at the rate of one part to ten was included in all 

 of the tests except those made on one day, December 12, and this 

 mixture provides a good basis for comparisons with the other materials. 

 The figures given represent the percentage of the total catch each dsiy. 



In addition to the tests included in the following table several 

 others Avere made. In one series the following fly collections were 

 recorded: Beer, 527; sweet milk, 268; sour milk, 268; decayed banana, 

 228; fresh banana, 135; cheese, 107; fresh orange, 99; cane sugar, 

 43; decayed apple, 26; fresh apple, 5. 



To test the killing efteets of those substances used as poisons in 

 the fly trap experiments a third series was made with the poisonous 

 bait exposed in watch glasses outside of the traps and resting on papers 

 to facilitate the counting of the dead insects. 



Bichromate of potash was included with the other materials on ac- 

 count of its endorsement in a newspaper dispatch concerning a Kan- 

 sas state board of health bulletin. Whether or not the substance was 

 recommended as a fly poison in the bulletin referred to the writer has 

 never ascertained. It is evident, however, that it is of little value as 

 compared with formalin, cobalt and alcohol. 



One series of experiments was made with tanglefoot fly paper to 

 determine whether it was practicable to increase the attraction this 

 paper has for flies. Dried blood moistened with water and placed in 

 a watch glass near the center of- a sheet attracted 465 flies as compared 

 with 324 flies attracted to a nearby sheet which was lightly sprayed with 

 40 per cent formalin, and 230 flies attracted to an untreated sheet. 

 In another instance a sheet of the fly paper with a small piece of banana 

 near the middle attracted 363 flies, as compared with 350 attracted to 

 a sheet having dried blood rubbed into the sticky surface, 283 attracted 

 to an untreated sheet, 266 attracted to a sheet treated with bichro- 

 mate of potash and 210 to a sheet treated with cobalt. In these four 

 tests where substances were added an equal area near the middle 

 of the sheet was treated in each case. Dried blood moistened with 

 water and decayed banana were tested by treating a square inch of 



