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AN EXAMINATION OF THE SENSE-REACTIONS OF FLIES. 



By Olive C. Lodge. 



(Plates VIII^XL) 



Comparatively little experimental work appears to have been done to determine 

 the likes and dislikes of flies, and the ways in which the different species respond to 

 stimuli affecting the senses of smell, sight, touch, taste, and the perception of the 

 differences of temperature and humidity. 



It is self-evident that the more completely the ways in which flies behave under 

 different conditions are understood, the more possible it is for effective remedial 

 and preventive measures to be devised and carried out ; especially is this important 

 in the case of those flies which are known to be agents in the spread of intestinal 

 diseases. 



One of the objects of this investigation was to test many different substances 

 with a view to finding some which would so stimulate the senses of flies that all 

 those approaching would be immediately attracted or repelled. If some such 

 substances could be found, they would be of extreme economic importance, and should 

 they be poisonous to the flies as well, their practical value would be increased. 



The two obvious methods of investigating the sense-reactions of flies are : — 



(1) To examine and compare the position and morphology of the sense organs, 

 more particularly those situated on the antennae and mouth-parts ; (2) to test 

 various poisons, smells, colours, etc., on flies of different species, and to notice how 

 they react towards them. 



The second method was followed in this investigation, in which there are two 

 main points to be considered : — (a) The observation of the likes and dislikes of 

 flies, and the general way in which they react to sense-impressions ; (b) the 

 determination of the sense or senses involved in these reactions, and to find out 

 whether they are due to sight, smell, etc. 



To this end experiments were made to find out : — 



(I) The likes and dislikes of flies, with regard to, (a) various foods, (b) various 

 chemicals, (c) different colours, (d) variations in temperature, and (e) variations 

 in humidity. 



(II) Their behaviour when different substances, either freely exposed or covered 

 in various ways, were presented to (a) normal flies, (b) flies with their antennae 

 removed, and (c) flies with their eyes covered. 



The behaviour of the two sexes was particularly observed, since any difference 

 of reaction of the sexes in this respect might be of use in considering economic 

 measures. 



The work was undertaken for the Zoological Society of London, to whom my 

 thanks are due for the facilities which they afforded me. It was carried out at the 

 Imperial College of Science and Technology, during the summer and autumn 

 of 1916. 



The flies principally used were those which from their habits were likely to be 

 concerned in the spread of intestinal diseases, viz. : Musca dotnestica (house-fly), 



(C478) d2 



