106 



Richardson (C. H.). A Chemotropic Response of the House-Fly 



{Musca dotnestica, L.). — Science, Lancaster, Pa., xliii, no. 1113, 

 28th April 1916, pp. 613-616. 



This paper gives a prehminary account of experiments carried out 

 in New Jersey to determine the response of the house-fly to certain 

 organic and inorganic compounds which occur as products of fermenta- 

 tion of horse manure. In the first experiments, various compounds 

 were exposed in wire fly-traps, the latter being placed in situations in 

 which flies were always present, but never extremely abundant. 

 Positive results were obtained only with ammonium hydroxide and 

 ammonium carbonate. The flies were attracted in large numbers 

 to ammonium carbonate, the best results being obtained when water 

 was added to the compound, since it prevented the deposition of the 

 less volatile ammonium acid carbonate. Since water and carbon 

 dioxide were not attractive to flies, it was concluded that ammonia, 

 the remaining constituent of ammonium carbonate, was the stimulating 

 agent. The percentage of females caught in the ammonium carbonate 

 trap amounted to 90- 7. Traps baited with food materials maintained 

 near the first experiment showed that females were especially attracted 

 by this compound, though they were not especially abundant in that 

 spot. 



Further experiments were conducted to determine whether fresh 

 horse manure which did not volatilise ammonia would induce 

 oviposition and whether such manure, when again giving off ammonia, 

 would attract the female fly. Fresh manure was treated with dilute 

 hydrochloric acid to convert the free ammonia into the chloride, which 

 is non-volatile at ordinary temperatures. As a result it was found 

 that the lots which volatilised ammonia from ammonium carbonate 

 were more than four times as attractive as untreated acidulated lots 

 placed from 1 to 2 feet away, and 20 times more attractive than 

 acidulated lots placed at distances of from 25 to 50 feet. In one 

 experiment in which an acidulated manure lot stood on each side of a 

 dish containing ammonium carbonate and Avater, 12 egg-masses were 

 deposited upon the acidulated manure, while none were found in 

 acidulated manure controls 30 feet distant. The oviposition response 

 was roughly in an inverse ratio to the distance from the source of 

 ammonia. Experiments with timothy chaff conducted in a similar 

 manner showed that chaff which produced ammonia induced 

 oviposition ; larvae w^ere able to develop normally in this medium. 

 Pine sawdust was less attractive and the larvae died soon after hatching. 

 Oviposition in cotton and on filter paper occurred in the presence of 

 combinations of ammonium carbonate and water with valerianic and 

 butyric acids ; without these acids the response was practically 

 wanting. The fact that some o\aposition took place in distantly 

 removed controls of the acidulated manure series showed that certain 

 flies went a short distance from the source of ammonia in order to place 

 their eggs in a favourable substance, or else that they were attracted 

 by the odour of ammonia and came by chance upon the controls. 

 A certain power of discrimination between substances valuable or 

 useless as food for the larvae was exhibited in some cases. Butyric 

 and valerianic acids both occur in manure and have previously been 

 shown to increase the attraction of ethyl alcohol to Drosojihila 

 ampelophila. 



