272 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



and the old trap one fly. With dried blood moistened with Avater the 

 new trap captured 28 and the old trap 12. Combined, the new trap 

 captured 41 and the old trap 13 in the two tests. 



TABLE n 



Date, : 

 December, Material used 



1&13 



Percent- 

 Flies killed I age of 

 total 



17 Cobalt (1) water (20) and bread [ 101 47 



17 Formalin (1) water (10) and bread: I 78 36.2 



17 Cobalt (1) water (20) and dried blood 20 9.3 



17 ' Bichromate of potash (10 dms.) water (2 oz.) and bread | 16 7.4 



18 FormaUn (1) water (10) ". i 259 41 



18 i Alcohol (1) and water (20) j 253 40,2 



18 Cobalt (1) and water (20) ! 104 16.5 



18 Bichromate of potash (10 dms.) and water (2 oz.) 13 2.1 



Conclusions from the Experiments 



Vinegar in itself is an excellent bait for a fly trap but when used 

 with sugar or bread its attractiveness to flies is greatly increased. 

 Equal parts of vinegar, sugar and water appear to be approximately 

 as attractive as equal parts sugar and vinegar. An attractive com- 

 bination poisonous to flies can be made with formalin and vinegar 

 but further tests are necessary to determine the best proportions. 



Formalin (40 per cent) difl^ers greatly on different days in its at- 

 tractiveness to flies. This variation is evidently not due directly to 

 temperature conditions, and it suggests the possibility of the flies 

 themselves differing from day to day in the degree of the sensitive- 

 ness of the sensory organs. Formalin, as is well kno\ATi, makes an 

 excellent fly poison when combined with other substances. The 

 usual dilution of the commercial or 40 per cent formalin at the rate of 

 about one part to about ten parts of water seems to be as good as at 

 any other rate. Beer, milk and bread, in the order named, are excel- 

 lent materials to use with formalin, increasing its attractiveness many 

 times. The addition of sugar increased the attractiveness of the for- 

 malin solution but not to a satisfactory degree. 



Commercial alcohol (95 per cent) and water at the rate of one to 

 20 appears from the experiments to be of about equal value with 

 formalin and water mixed at the rate of one to ten, both as to attrac- 

 tive power and killing effects. The addition of sugar to the alcohol 

 mixture gave a more marked increase in the attractive power than 

 did the addition of sugar to the formalin mixture. Beer and alco- 

 hol did not make an attractive mixture, while the addition of bread 

 to alcohol and to alcohol mixtures increased the attractive power 



