THE SENSE REACTIONS OF FLIES. 151 



The experiments were carried out in a laboratory, the average temperature of which 

 •was 17 '5° C. The eggs, maggots, etc., were kept in a glass cylinder covered with 

 muslin. The maggots and flies were fed on banana, and the casein, sugar, banana 

 and water mixtures. In many cases the maggots were isolated as soon as they 

 had pupated, being placed in small glass bottles inside the cylinder. 



The eggs were found laid on the inside of a banana skin (Plate XI, fig. 2)* on the 

 13th August 1916. The maggots hatched out from the 14th to 17th August. They 

 began to pupate on the 25th and 26th August and all had pupated by 4th September. 

 The flies began to emerge on the 7th, the largest numbers emerging together on 

 23rd and 24th September, while all had emerged by the 3rd October 1916. 



Summary. 



1. There appears to be a general similarity in the tastes of the different species 

 with regard to various chemicals and foods ; the tastes of Musca domestica and 

 Phormia azurea, in many cases, being found to approximate most nearly. 

 It will be interesting to discover whether there is a closer correspondence between 

 the sense-organs of these flies than between these of other species. 



2. These experiments emphasise the extreme curiosity of house-flies, and again 

 show the catholicity of the'ir tastes and the difficulty of finding any substances which 

 will either attract or repel all those that come near it. The mineral and tar oils 

 seem to be amongst the most repellent substances. With regard to poisons, good 

 results were obtained with sodium iodate, large numbers being killed when very 

 small amounts were used, although it did not always attract many flies. Sodium 

 iodate has the disadvantage of being very expensive. But further experiments 

 require to be made before any definite conclusions can be arrived at as to the 

 importance of the iodates of sodium and other metals as poisons for general use. 



3. House-flies were not found to show any colour-preference. 



4. For house-flies the optimum temperature was found to be between 36°-44° C, 

 the maximum and minimum between 55°-58° C. and 10°-13° C, respectively. 



5. It appears that curiosity plays an important part in causing house-flies to come 

 to baits and to investigate traps, etc., although the senses of smell and to a less 

 extent that of sight are also concerned ; the former, however, to a much less extent 

 than it is with blow-flies, and it appears to be most used when the flies are close 

 to the baits. 



* The eggs of Fannia were invariably found laid singly on the insides of banana skins, 

 while those of Musca were found either on the cut surface or sides of the banana, or in 

 the cracks between the pulp and the skin. 



