276 Cheiiiotropic Responses of Insects 



alcohol and acetic acid were found more attractive than the aqueous 

 solutions of these substances. Crude gluten from wheat flour was not 

 attractive. The water soluble portion, with or without starch in suspen- 

 sion, was decidedly attractive. Several experiments with milk indicated 

 that fat-free caseinogen is attractive while butter fat is not. In 1918 

 Miss Lodge published a paper on the sense-reactions of flies — mainly 

 those species likely to be concerned with the spread of intestinal diseases. 

 The experiments were conducted indoors, and the different substances 

 were tested both upon free flies and those confined in glass cylinders 

 provided with muslin tops. The authoress states that the most suitable 

 medium for the experimental tests was found to be equal parts of casein, 

 sugar and banana, to which a solution of the substance to be tested was 

 added. In all cases, therefore, an extraordinarily complex chemotropic 

 substance was utilised, to which was added various other chemical agents 

 of varying complexity. The results showed that, although many of the 

 substances attracted a certain number of Diptera present in the room, yet 

 none were so attractive that all the flies went to them. Pyrethrum extract, 

 added to the medium already described, proved very attractive to 

 Calliphora, ammonia proved attractive to Phormia azurea, ammonia and 

 honey to Musca domestica ; the latter insect was also attracted by honey 

 and methylene blue, 1 per cent, nicotine, ammonium carbonate, and 

 other substances. The addition of an aqueous solution of skatol was 

 attractive to Calliphora and Scafophaga; camphor attracted Calliphora 

 and also honey, the latter substance was attractive also to Lucilia caesar. 

 As a control the casein mixture was adopted and this substance proved 

 more attractive to Calliphora and Lucilia than any other reagent when 

 added to it. Mineral and tar oils proved to be powerful repellents, the 

 essential oils were, on the whole, repellents. Davidson (1918) states that 

 12 per cent, glycerine, and 5 per cent, sugar to which was added 1 per 

 cent, sodium arsenite proved a successful poisonous attractive agent for 

 flies during the Egyptian campaign of the late war. Parker (1918) found 

 a combination of beer and oatmeal proved a most attractive substance 

 for the females of various Diptera frequenting privy vaults in Montana. 

 In the foregoing summary of the literature bearing upon Chemo- 

 tropism we have included the more important papers but it makes no 

 pretence of being exhaustive. A further object of this resume is to 

 emphasise the fact that no systematic quantitative work has yet been 

 attempted, and most of the observations so far recorded concern particu- 

 lar species only. A large number of chemical substances are sufficiently 

 volatile to merit adequate trials, and it is our intention during these 



