454 The Mdiniri' Htap kihI the Ilini.^t- I'hi 



ChiirlophUn cilicriim Rdi. ... 14 



Hydiuliiea armipes F. ... ... (5 



Spp. ? 1 



To those who have kept in touch with much of the woik recently 

 carried out in connection with the Hy problem, perhaps the most striking 

 feature of the foregoing results will appear to be the small number of 

 flies obtained from the oxpori mental heaps. Having some two dozen 

 traps in constant use T fullv exjx'cted that some assistance would 

 certainly be required in t he mere mechanical work of counting and sorting 

 the flies taken. 



Thus in Dr Gordon Hewitt's experiments in Canada in 1913' a 

 cubic vard of untreated manure used as a control experiment produced 

 13,332 flies. Large as this number is it appears almost trifling when 

 compared with the figures given by Messrs Cook, Hutcliison and 

 Scales-. In their Table V, control heaps consisting of 4 bushels of 

 manure (b cubic feet) are cited as having contained 342.771, 38.5,403 

 and 273,.520 pupae respectively. Whether such numbers are liable to 

 occur in this country I have no records to enable me to decide, though 

 doubtless numbers comparable to the^e might occur in say a crowded 

 city area. The most heavily infected manure I was able to obtain, in 

 quantitv about 14 cwt. (see Experiment II), produced only some 865 

 flies, of which 798 were M. domestica. The wet summer of 191 -J may 

 perhaps account to some extent for the results obtained, though 

 Experiment If was carried out in comparatively fine weather. The 

 flies obtained in this expeiiment weic however quite .sufficiently numerous 

 to emphasize the admitted dangei- of uncontrolled manure heaps in close 

 proximity to dwellings, and we may at once turn to the consideration 

 of the results as applied to heaps under more rural conditions. 



Experiments I, 111 and IV, with horse and mixed manures, produced 

 only three examples of M. domestira. During the early part of the 

 season this fly was by no means common, and even later in the summer 

 it was not found to occur in great numbers in or near the laboratory. 

 It was not obtained from garden refuse. A small quantity of horse 

 manure (Experiment X\'II) became rather heavily infected at the 

 laboratory though this was undoubtedly due to its having stood for 

 some davs actually in the laboratory, and a few flies first attracted 

 into the rooms had soon found the material so conveniently at hand. 



' Journal of Ecotiomic Entomoloijit. vol. vii. No. 3, p. 281 et seq. 1914. 

 2 U.S. Dtpt. of Aijricullure, But. 24.j, July 1915. 



