5i3 
(figs. 3, 4), and the actual size is shown in fig. 1. . The larvae or 
maggots hatch from these in periods varying from eight hours to 
three to four days; the average time may be given as twelve hours, 
but when laid in fermenting materials the incubation period is 
reduced to a minimum of eight to twelve hours. 
“ The number of eggs laid by a single fly averages from 120 to 
140. More than one batch may be laid during the life of the fly, but 
this question has not been definitely settled. 
“2nd Stage. —The larva or maggot (fig. 9) resembles that of the 
common ‘bluebottle-fly,’ or ‘Blow-fly’ ( Calliphora crythrocephala ), 
but is much smaller, measuring when fully matured nearly half an 
inch in length, and is distinguished also by certain anatomical 
characters. It is essentially a vegetable feeder; animal matter is 
eaten only, so far as one has been able to gather, when in the form of 
human faeces. It was never found feeding on the carcases of dead 
cats and dogs or of birds and fish remains.* 
“ They thrive and mature most rapidly, and are always most 
abundant in fermenting materials; but they can also mature in 
non-fermenting substances during warm weather, though under such 
conditions they do so very slowly. In stable manure they are 
generally most numerous a few inches below the surface, and 
undoubtedly work their way upwards day by day into the fresh 
material, a few hours (five to six) after it has been added to the 
previous accumulation. This marked habit is evidently due to the 
excessive heat which is engendered in the lower strata of the manure. 
“ h'nder the most favourable conditions as to temperature and food 
supply they mature in five to eight days ; but, where fermentation 
does not take place, this stage, even in hot weather, may be 
prolonged to several weeks (six to eight). In middensteads the fully 
matured larvae crawl away to the sides or to the top of the wall or 
framework of the receptacle ; in ashpits they locate themselves in 
various materials as well as ashes, but are evidently partial to old 
bedding, paper and rags, usually in or near the centre of fermentation. 
After emptying the alimentary tract of organic matter, pupation 
takes place rapidly, and the third stage is reached. 
" 3 r d Stage. The pupa or chrysalis (figs. 7, 10, n) is at first of a 
Pale yellowish colour, but rapidly changes to bright red, and finally 
t° a dark chestnut colour. It is somewhat barrel-shaped, and varies 
. * Taschfiibcrs in l88o, states that he found eggs on the carcases of dead 
umals, but does not indicate that the larvae will breed in such substance. R. JN. 
CG 
