82 Ohservations on the Habits of Certain Flies 



concrete to bind. A two inch layer of concrete was spread over the sand 

 and six roughened slates were sunk into it; and a land drainage pipe 

 one foot long and six inches in diameter was then placed upright on 

 each of the slates on to which it was carefully cemented. When the 

 cement had set the hole was filled in with earth to the level of the top 

 of the pipes. A layer of sand was then spread round the mouths of the 

 pipes and a second lot of pipes was cemented on to the first lot with a 

 fresh layer of cement, which was sloped up to the pipe to ensure covering 

 the joint completely. This process was continued until there were four 

 tiers of pipes, i.e. until there were six holes six inches in diameter and 

 four feet deep, from which no larvae could escape save upwards. The 

 pipes were then numbered as shown in the diagram. 



Fig. 6. 



Many C. eri/throcephola females were placed in a large muslin cage 

 (Graham-Smith, 1914, PI, XIX, fig. 3) with bodies of four guinea-pigs 

 and of one large rabbit, which had been dead for several days, in order 

 that they might thoroughly infest the carcasses with their eggs. 



On May 2nd the body of a dead guinea-pig, which was swarming 

 with larvae of Calliphora, was dropped into each of holes 1 and 2, which 

 were then filled in with loam — the soil in 1 being loosely packed, but 

 that in 2 tightly. On May 4th similarly infested remains were placed in 

 3, 4, 5 and 6; the first two being filled with sand and the last two with 

 clay. Nos. 3 and 5 were loosely filled, but 4 and 6 tightly packed. The 

 contents of 2, 4 and 6 were packed by filling them by degrees and 

 ramming each lot of soil down with a long wooden pole. 



A trap to catch any flies which might emerge was constructed over 

 each pipe. A small piece of wood, with a half-inch hole in the middle, 

 and to which muslin was tacked (Fig. 5), was supported on four wires, 



