:3G2 
('. aORDOX IfEWITT. 
manner. The larvjB of some species breed in human and other 
excrement, others breed in decaying vegetable substances, 
while certain species breed in water, especially when polluted 
Avith sewage, and these aquatic species have the spiracular 
apparatus modified accordingly. Although a form, Phlebo- 
tamus, which occurs in Southern Europe, has blood-sucking 
habits, the British species have no such annoying habits, and 
are of little importance in their relation to man. 
IV. Physiology. 
1. The Influence of Food, Temperature, and Light. 
Food. — Mention has already been made in the second part 
of this work of the influence of food on the development of the 
laiwte; the experiments which Avere carried out showed that 
the larvte develop more rapidly in certain kinds of food, such 
as horse-manure, than in others. It has yet to be discovered 
Avhat are the chemical constituents Avhich faA'our the more 
rapid development. It Avas found that insufficient food in the 
larval state retarded development and produced flies which 
Avere subnormal in size. BogdanoAV (1908), in an interesting 
experiment, fed M. domestica through ten generations on 
unaccustomed food such as meat and tanacetum in different 
proportions, and he found that the resulting flies did not show 
any change. 
Temperature. — The influence of temperature on the 
development of the larvae has been shown also. A high 
temperature accelerates the development of the egg, larva 
and pupa. Temperatiu’e also affects the adult insect; they 
are most active at a high summer temperature, and cold 
produces an inactive and torpid condition. They are able, 
hoAvever, to withstand a comparatively Ioav temperature. 
BachmetjeAv (1906) Avas able to submit M. domestica to as 
loAV a temperature as — 10° C., and vitality Avas retained, as 
they recovei’ed Avhen brought into ordinary room temperature. 
Uonhoff (1872) performed a number of experiments previous 
