THE CONTROL OF FLIES IN THE EGYPTIAN CAMPAIGN. 301 



in the proportion tibbin 6, sand 1, with water, was formed over it. This set quite 

 hard and practically imprisoned all flies which might be breeding out in the trench. 

 In some districts mud or clay was available for this purpose. Fly maggots which 

 hatch out in the trench crawl in between the sandbags forming the revetment and 

 pupate there. The flies which hatch out may burrow their way out diagonally from 

 the trench through the loose sand. To avoid this the mound was extended for an 

 extra 18 inches all round the trench. 



Major E. E. Austen recommended the following method of dealing with this, which 

 is very effective. A piece of canvas soaked in crude tar oil is stretched over the 

 trench about six inches below the surface, extending to 18 inches all round it. A 

 second trench about six inches deep is made round the trench and a foot from the 

 edge of it. This is filled with sand mixed liberally with cresol and tightly packed. 

 The whole is then covered over with a mound. In this way any flies which emerge 

 laterally are trapped. 



The danger of open shallow trenches cannot be too greatly emphasised. On 

 inspecting, some days later, areas in the desert which had been temporarily occupied 

 by bivouacing troops, newly hatched flies were found running about the sand in 

 hundreds. By digging in the sand at certain places where shallow trench latrines 

 and pits for unburnt refuse had been, shoals of pupae were found. It is absolutely 

 essential so to localise sanitary areas for latrines and refuse, that they may be readily 

 and efficiently treated. 



The author has found large numbers of flies breeding out from latrine trenches 

 which, although they had been covered with a box latrine, had been afterwards 

 carelessly filled in. The flies hatch out and make their way through several feet of 

 the loose desert sand. An open trench 5 feet deep was used for three days and then 

 filled in with 4 feet of the desert sand without any further treatment. Flies were 

 found emerging from this trench 10 days afterwards, and numbers of pupae were 

 found 18 inches down, in the sand with which the trench had been filled. On 

 examination, two weeks later, of latrine trenches filled in as described above, pupae 

 have been found in the top layer formed of crude tar oil and sand, but they were 

 small, malformed, and had failed to develop. 



Native lafrines. — A large number of native labourers are employed with the troops, 

 and the deep-trench system of latrines is in force for them. These are covered with 

 flat, squat, fly-proof covers having self-closing lids. By strict policing and super- 

 vision this system works satisfactorily. One native is always on duty at the latrines 

 as policeman. The danger from indiscriminate defaecation by individuals in the 

 open is very great, and strict orders to prevent this are necessary, especially with 

 large bodies of native labourers. 



Several casual deposits defaecated on the soft desert sand by native labourers 

 were kept under observation. Flies collected on the faeces almost immediately. 

 The surface of the deposits soon dried in the hot sun, forming a hard coating, but 

 there was enough moisture below this for the fly ova to hatch out. On the third day, 

 numbers of maggots were present in the faeces, which were thoroughly disintegrated 

 by them in two or three days, the whole being turned into a dry, powdery heap. The 

 larvae, which were small and ill-fed, burrowed down into the loose sand, where they 



