A. D. Imms and M. a. Husain 275 



cent, of 95 per cent, ethyl alcohol in water was a good attractive agent. 

 Sucrose was found to be a valuable addition to various baits, sometimes 

 increasing their attractive properties 10-20 per cent. According to 

 Richardson (1916) the female house-fly is strongly attracted towards 

 manure for purposes of oviposition, food being only a secondary object. 

 He exposed a number of liquids and found that ammonium carbonate 

 was the most attractive. Small amounts of water and carbon dioxide, 

 both constituents of ammonium carbonate, were not sought after by the 

 flies, and it was concluded that the other constituent, ammonia, was the 

 real attracting agent. Of the flies attracted only 7-6 per cent, were males. 

 His experiments indicated that manure which was liberating ammonia 

 was more attractive than fresh manure. Richardson was successful in 

 inducing oviposition on a mixture of moist Timothy chaff and ammonium 

 carbonate, whereas the chafE alone produced no result. In experiments 

 conducted with moist sterilised absorbent cotton, ammonium carbonate 

 exercised practically no chemotropic stimulus for oviposition, but was 

 effective when traces of butyric acid were added: valerianic acid was 

 attractive to a lesser degree. Crumb and Lyon (1917) investigated the 

 question more fully, and produced evidence suggesting that carbon dioxide 

 is the chief stimulant for oviposition, giving an 82 per cent, higher stimulus 

 than ammonia. Richardson (1916) conducted some further experiments 

 with reference to the attraction of Diptera to ammonia and found that 

 it attracted various species. Those which respond to this stimulus are 

 known to spend at least part of their lives in some form of animal excre- 

 ment. The response is not always a simple one as was shown in his earlier 

 investigation. In this same paper Richardson remarks that he was 

 unable to induce Stomoxys calcitrans to oviposit on cotton wool soaked 

 in valerianic acid, although Howlett was successful with this experiment 

 in India. In 1917 Richardson conducted a series of tests with reference 

 to the house-fly, using a wide range of substances placed in fly traps. 

 A number of carbohydrates were tested in solution and, on the whole, 

 they did not prove very attractive : lactose attracted the largest number 

 of flies and starch the least. Dextrin also caught a comparatively large 

 number of flies, but sucrose was consistently a poor attractive agent. 

 In using alcohols and acids he found that 4 per cent, amylic alcohol gave 

 better results than ethyl alcohol. Ethyl alcohol in 4 per cent, strength 

 was more attractive than in 10 per cent, concentration; 10 per cent, 

 acetic acid gave better results than 4 per cent. Succinic and lactic acids 

 exhibited some attractive qualities in two experiments. Maltose, lactose, 

 sucrose and dextrin in 4 per cent, solutions of amylic alcohol, ethyl 

 Ann. Biol, vi 19 



