14 Gerald F. Hilt: 



Another jar containing a few inches of fresh matter. In a few 

 minutes the larvae migrated to the newer material, leaving the old 

 to be removed and replaced by a more abundant supply of fresh 

 food. 



In some cases the pupae were removed from the faecal matter, 

 washed in sterile physiological salt solution and transferred to 

 'moistened sterilized sand, but && this method did not appear to 

 possess any advantages over the simpler procedure of allowing 

 them to remain in the jar in which they had developed, it was 

 •discontinued. 



On the appearance of the first flies the metal clip and gauze 

 ■cage were fixed in position over the jar, and within a few hours 

 .sufficient flies were secured to bread from. The cage containing 

 Ihe newly emerged flies was then rapidly fitted to a clean empty jar, 

 iind food was introduced into it in the manner described. 



Food was given once or twice daily for about eight days, during 

 which period the flies were transferred on alternate days to clean 

 <jages and jars, and were kept as far as possible in a warm, sunny 

 :situation by day and near a radiator at night. Under these con- 

 •ditions they mated in four to six days after their emergence from 

 the pupae and oviposited about four days later. On the eighth day 

 the cage and its contents were transferred to a clean jar, containing 

 fleshly sterilized faeces, to which the flies had access until a suffi- 

 •cient number of eggs w^ere deposited. The flies w^ere then trans- 

 ferred to another similarly prepared jar for the production of more 

 -eggs, whilst the jar containing the first batches of eggs was covered 

 with paper and transferred to a warm situation. The eggs hatched 

 12-24 hours later, producing larvae which, like their parents, had 

 been reared exclusively on sterilized matter. It is obvious that any 

 chance of helminth infection in these " clean " larvae is almost, 

 if not quite absent, as shown also by the negative results of the 

 -examination of flies bred on such sterile faeces, and by the invari- 

 able absence even of moulds and such like from the jars. Such 

 larvae were used in all the experiments in which this species (Musca 

 •domestica) were concerned, excepting where the contrary is stated. 

 It may be mentioned here that the writer has succeeded in rearing 

 four generations of flies in the laboratory under these methods. 



Stomoxys calcitrans. 



The methods employed for obtaining the larvae of Stomoxys cal- 

 'citrans for experimental purposes differed from those outlined 

 :above only in the following details : — The adult caught flies did not 



