14 



larval food is usually but not always necessary for the deposition of 

 eggs. According to the writer's observations, eggs laid on a dry 

 surface (that is, one that is neither damp nor greasy) do not hatch. 



FECUNDITY 



Swammerdam (73, p. 74) dissected an adult female and found that 

 the ovaries contained 256 eggs. In 1861 Taylor (75, p. 609) reported 

 that nearly 300 eggs were laid, but more recently published data 

 show much smaller numbers. The average number of eggs laid by 

 females in Murtfeldt's experiments (53, p. 173) was 30, and several 

 dissections made by Sakharov (67) gave an average of 64 eggs, a 

 maximum of 84, and a minimum of 44. 



Sakharov computed the probable increase of the cheese skipper 

 in Astrachan, basing his computations on an average of 60 eggs per 

 female and assuming the resulting progeny equally divided as to 

 sex. Starting with a pair of flies in April, he estimated that the 

 total progeny of five generations (the minimum number during the 

 Astrachan summer) amounted to 50,279,860. 



With two generations a month at Washington during the sum- 

 mer, and at least double the average individual reproduction figures 

 used by Sakharov, it is apparent that the cheese skipper is poten- 

 tially extremely prolific in climates like that of the District of 

 Columbia. The limited food list of this species, together with the 

 care which is usually taken to guard edibles and dispose of carrion, 

 prevents the enormous increase of which the species is capable. 



Table 2 details some of the oviposition records made in 1921 on 

 several foods at Washington, D. C. 





Table 2. — Oviposition records of Piophila casei on various food materials at 

 Washington, D. C, in 1921 



Date 



Date 

 mated 



Day after matog and number ' Longevity 



Total 



eggs 



Remarks 



emerged 



1st 



2d 



3d 



4th 



5th 



6th 



7th Male 



Fe- 

 male 



June 1 



June 1 



1 



1 



6 



6 



18 



18 



18 



18 



18 



28 



28 



28 



July 7 



7 



7 



8 



8 



13 



13 



13 



13 



13 



87 

 

 55 





 99 



91 











Days 

 3 

 3 

 7 

 3 

 5 

 7 

 4 

 6 

 6 

 7 

 3 

 6 

 3 

 3 

 8 

 4 

 5 

 5 



8 



Days 

 4 

 4 

 4 

 5 

 6 

 3 

 2 

 2 

 5 

 4 

 3 

 4 

 2 

 2 

 3 

 2 

 2 

 2 

 6 

 2 



178 



99 



55 











175 



43 



86 



203 



159 



61 



128 



129 























65 







85 











On lean ham. 



1 











Do. 



1 













Do. 



6 















On dried beef. 1 



6 

















Do. 



18 



95 

 43 

 85 

 78 

 93 

 30 

 128 

 68 



80 













On lean ham. 



18 













Do. 



18 



1 

 87 





 31 













Do. 



18 



5 

 66 



11 



22 







Do. 



18 







Do. 



28 











Do. 



28 













Do. 



28 



61 













Do. 



July 7 













On lean Smithfield ham. 



7 

















Do. 



7 

















On Smithfield ham fat. 



8 

















Do. 



8 

















Do. 



13 



65 















On lean Smithfield ham. 



13 















Do. 



13 



85 













14 1 7 



7 3 



8 1 3 



Do. 



13 













Do. 



13 













Do. 



i Dried beef aud Smithfield ham are unsuitable as food for adults and larva? because they contain com- 

 paratively little water. 



