Some differences in the reported lengths of the life cycle can be 

 attributed to varience in environmental factors, such as temperature. 

 Melvin (1934) studied the duration of incubation periods when house fly 

 eggs were incubated at different temperatures. Incabation periods 

 ranged from 51.45 hours at 15-0 C to 3.05 hours at 40.6 C. At 42.8 C, 

 no eggs hatched. 



In fresh poultry manure, a temperature of 27.0 C and a moisture 

 level of 60 to 75% proved optimal for larval development (Miller et a!., 

 197^) • In horse manure, larvae showed no i 1 1 effects when the tempera- 

 ture reached 45.0 C, out as the temperature approached 48.9 C, they 

 began to migrate out. At 54.4 C, larvae died within 1 min, and at 

 60.0 C, death was instantaneous (Allnut, 1926). 



The pH of the larval medium may also change cycle length. Erofeeva 

 (1967) determined the optimum pH for house fly larval media to be between 

 7 and 8. This is also the pH of day old poultry manure (Beard and 

 Sands, 1973). 



Another temperature dependent variable that changes the length of 

 the life cycle is the fly's ability to overwinter. Early investigators 

 were unable to determine in which stage M. domestiea overwintered 

 (Hewitt, 1914; Graham- Smi th , 1916), but it is now known that the house 

 fly can overwinter in all of its developmental stages (Graenberg, 1971). 

 Breeding occurs throughout the year in warmer climates where tempera- 

 tures are 18. C or above (James, 1947; Greenberg, 1971). 

 Fecund i ty 



At 5 to 7 days of age, the female house fly has mated and is ready 

 to begin laying eggs (James and Harwood, 1369). A female may lay up to 



