breeding season 95 



Location of Breeding Place. 



The female flies, as a rule, prefer to deposit their eggs on 

 substances oi- heaps ot breeding material exposed to the light. 

 General observations on the occurrence of the larvae have shown 

 that fewer larvae are found in pr-'poition as the situation t»f the 

 substance in which they are living is further away fi'om the 

 light. Felt (1910) has demonstrated experimentally that the 

 absence of light has a very marked influence on the ovipositing 

 impulse of the fly ; the darker the situation was, the fewer were 

 the number of flies which were to be found there. The fact that 

 flies are disinclined to penetrate a dark place to ovij)osit has 

 some practical significance in thcii- eontioj. 



Breeding Season. 



All my experiments and observations on the breeding habits 

 of the house-fly indicated the important fact that, if suitable 

 larval food were present and the temperature of the surrounding- 

 air were sufiiciently high to permit the prolonged activity of 

 the flies, the female house-flies will deposit their eggs and the 

 larvae will develop at any time of the year. Under ordinary 

 circumstances, however, the condition regarding temperature is 

 not satisfied in temperate climates during the whole year round. 

 Consequently, we find that in the temperate region the breeding 

 season is confined to the period June to October; exceptional 

 circumstances may extend this period a few weeks earlier or 

 later. During these months, as the breeding and activity of the 

 house-fly is directly dependent upon the temperature, the gi-eatest 

 breeding activity takes place during the hottest months, July, 

 August and September. 



During the winter months, under natural conditions, the 

 outside temperature will not permit breeding to take place, but 

 under such conditions as are found, for example, in warm stables 

 and cowsheds, restaurants and kitchens, female flies may be 

 often found either ovipositing or able to do so. On dissecting 

 such flies I have found mature ova in the ovaries and living 

 :spermatozoa in the spermathecae. I have obtained eggs from 



