February, '17] RICHARDSON: HOUSE-FLY FOODS 107 



Starch and two proteins, gliadin and glutenin make up the larger 

 part of wheat flour. I have already spoken of the unattractiveness of 

 starch. The present experiments concern the effectiveness of certain 

 proteins and the water soluble portion of white flour. 



By kneading white flour dough in water till practically all the 

 starch granules are detached, it is possible to prepare a substance 

 consisting largely of gliadin and glutenin known as crude gluten. 

 The crude gluten cannot be entirely freed of water soluble substances 

 by this method. Small amounts of crude gluten in water attracted 

 only six flies, in two experiments, while equal amounts of white flour in 

 water captured 332 flies. In view of the poor success of crude gluten 

 it did not seem advisable to try gliadin and glutenin separately. 



Solutions of the water soluble ingredients of white flour contained, 

 besides the starch granules in suspension, a number of water soluble 

 proteins, especially albumin and proteose, organic and inorganic salts 

 and small amounts of many other compounds. Three traps containing 

 solutions of 1 gram of total dissolved substance to 50 cc. of water 

 caught 2,112 flies. In other experiments three traps containing 1.35 

 grams each of dissolved material attracted 225 flies and 2.5 grams in 

 two traps, 855 flies. 



Solutions containing the water soluble ingredients without starch in 

 suspension gave with 0.1 gram concentrations in 50 cc. of water the 

 following results: three traps a total of 4 flies; two traps a total of 

 2,400 flies. 



The experiments indicate that there is something present in these 

 aqueous solutions of white flour which strongly attracts house-tlies. 

 Experiments which extended over a period of 67 to 75 hours were on 

 the whole more successful than those whose duration was shorter, 23 

 to 48 hours. These solutions improve on standing, apparently due to 

 the formation of certain fermentation products. 



Milk: — A few experiments were made on milk, prompted by the 

 fact that it is a uniformly good fly bait. Fre;sh milk was acidified 

 with dilute acetic acid till the caseinogen was precipitated. The 

 liquid portion was separated from the caseinogen, which held much 

 butter fat, by filtration. The caseinogen-fat mixture was unattract- 

 ive to house-flies in two experiments. Fat-free caseinogen caught 77 

 flies in one experiment while butter fat (ether extract) caught only 

 two flies. 



These tests indicate that fat-free caseinogen is somewhat attractive 

 to house-flies but are not conclusive. The experiments on carbo- 

 hydrates, as already stated, show that flies are not attracted to milk 

 sugar (lactose) in large numbers. 



