Til E TYPHOID FLY, OB HOUSE PLY. 3 1 
Strange as it may seem, an exhaustive study of the conditions 
which produce house Hies in numbers has never been made. The 
life history of the insect in general was, down to L873, mentioned in 
only three European work- and few exact Pacts were given. In L873 
Dr. A. S. Packard, then of Salem, Mass., studied the transformations 
of the insect and gave descriptions of all stages, showing thai the 
growth of a generation from the egg slate 1 to the adult occupies from 
lo to 1 I days. 
In lsi).') the writer traced the life history in question, indicating 
that L20 eggs arc laid by a single female, and that in Washington, 
in midsummer, a generation is produced every LO days. Although 
numerous substances were experimented with, he was able to breed 
the fly only in horse manure. Later investigations indicated that the 
fly will breed in human excrement and in other fermenting vegetable 
and animal material, hut thai the 1 vast majority of the Hie- that 
infesl dwelling houses, both in cities and on farms, come from horse 
manure. 
In L907 careful investigations carried on in tin 1 city of Liverpool 
by Robert Newstead, lecturer in economic entomology and para- 
sitology in the School of Tropical Medicine of the University of 
Liverpool, indicated that the chief breeding places of the house fly 
in that city should he classified under the following head-: 
(1) Middensteads (places where dung is stored) containing* horse 
manure only. 
(2) Middensteads containing spent hops. 
(3) Ash pits containing fermenting materials. 
He found that the dung heaps of stables containing horse manure 
only were the chief breeding places. Where horse and cow manures 
were mixed the Hies bred less numerously, and in barnyards where 
fowls were kept and allowed freedom relatively few of the house 
llie> were found. Only one midden containing warm -pent hops was 
inspected, and this was found to be as badly infested as any of the 
.-table middens. A great deal of time was given to the inspection of 
ash pit-, and it was found that wherever fermentation had taken 
place and artificial heat had been thus produced, such places were 
infested with house-fly larvae and pupae, often to the same alarming 
extent as in -table manure. Such ash pits as these almost invariably 
contained large quantities of old bedding or straw and paper, paper 
mixed with human excreta, or old rags, manure from rabbit hutches, 
etc. or a mixture of all these. About 25 per cent of the ash pits 
examined were thus infested, and house flies were found breeding 
in smaller uumbers in ash pits in which no heat had been engendered 
by fermentation. The house fly was also found breeding by Mr. 
stead in certain temporary breeding places, such as collection- 
