496 MISS O. C. LODGE ON THE 



Yet in these experiments, at no time were all the flies caught, 

 but only a proportion of them. This was, however, only to be 

 expected, judging from the catholicity of their tastes ; yet they 

 have their likes and dislikes. 



It was found that the attractiveness of most substances vai^ied 

 at different times. The weather appeai-ed to influence them — as 

 a ru.le fewer flies were caught on dull days than on sunny ones. 

 Possibly, also, flies of different ages and sexes have different likes 

 and dislikes, all of which would afiect the numbers caught and 

 the attractiveness of the baits. 



Ill, Poisons for Flies. 



These experiments were made with the object of tryino' to 

 discover a substance which would be poisonous to flies — especially 

 house-flies — and harmless to man. It should not be distasteful 

 to the flies, otherwise they will not come to feed, and unless 

 cheap and easily obtained will not be suitable for general use. 



The following methods of testing the diflferent substances were 

 employed : — 



(i.) To expose an attractive bait, to which the poison had been 

 added, in a place where the flies were free to come and 

 feed, or not, as they liked. 



(ii.) To test the poison on flies which were confined, and must 

 either eat it or starve. 



(i.) Accoiont of Ex2nriments on Poison-baits when Free Flies 

 ■were used. 



These experiments were carried out in the greenhouse. The 

 flies used were chiefly house-flies, though a certain number of 

 blow-flies from traps were released fi-om time to time. 



The substances used were generally placed in large saucers, in 

 sunny places on the floor. They were then watched, to see 

 whether after feeding, («) the flies fell over immediately, ■ 

 apparently dead, or {h) crawled for a distance and then fell 

 over on their backs, or (c) whether they flew away apparently 

 unharmed. When the two former occurred, as many of the 

 " corpses " as could be found were collected and kept till the 

 next day, to see if they would recover. 



It was thus possible to obtain some idea of the effect of 

 the different substances on the flies, and also to see whether 

 their addition made any difference to the attractiveness of the 

 baits. They were generally added to mixtures of casein, banana, 

 sugar, and water. Contiols for comparison were arranged for 

 each series of expei'iments. 



A list of the various tiubstances used, together with a summary 

 of results, is given on p. 497. 



