PREOVIPOSITION PERIOD OF THE HOUSE FLY, 13 
SUMMARY. 
From the experiments reported in this paper it is seen that the 
shortest record for the preoviposition period was one of about 24 
days and the longest, one of 23 days, with most of the records falling 
on the fourth, fifth, sixth, ninth, twelfth, and fourteenth days after 
emergence. 
It is shown that the temperature has a very decided influence on 
the length of the period. 
Other factors influencing this period are humidity, the kind and 
quality of the food of the adults, and the kind and quality of the 
larval food with its resulting effect on the size and physiological con- 
dition of the adults. In the experiments with isolated pairs of flies 
very few results were obtained, which suggests that the association 
of a number of females in the process of egg laying is the normal 
habit and that isolation has an inhibiting effect. 
Copulations were observed as early as the first day after emergence 
and as late as the forty-seventh day. No copulations have been 
noted when the air temperature has been below 55° F. 
The maximum record for longevity was 70 days, and the minimum 
was one day or less. The average of the records of some 3,000 flies 
was slightly over 19 days. 
LITERATURE CITED. 
Bisuorp, F. C., Dove, W. E., and Parmay, D.C. 
1915. Notes on certain points of economic importance in the biology of the house 
fly. Jn Jour. Econ. Ent., v. 8, No. 1, p. 54-71. 
Boapanow, E. A. 
1903. Zehn Generationen der Fliegen (Musca domestica) in verinderten Lebens- 
bedingungen. Jn Allg. Ztschr. Ent., Bd. 8, p. 265-267. 
GRIFFITH, A. 
1908. Life history of house flies. Im Public Health, London, v. 21, p. 122-127. 
Hewirt, C. G. 
1910. The house fly. 195p.,22pl. The University Press, Manchester, England. 
Howarp, L. O. 
1911. The house fly, disease carrier. 312 p., 39 fig. Stokes and Co., New York. 
Perarrs, L. M. 
1914. The relation of temperature to insect development. Jn Jour. Econ. Ent., 
v. 7, No. 2, p. 174-179. 
