PREOVIPOSITION PERIOD OF THE HOUSE FLY. 9 



Table III. — Correlation between the average mean temperature and the length of the 

 preoviposition period of the housefly. 



Average 

 mean tem- 

 poratures 

 in 2° inter- 

 vals. 



Length of the preoviposition period in days. 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



16 



17 



18 



19 



20 



21 



22 



23 



82° to 84°.. 

 80° to 82° 

 78° to 80° 

 76° to 78°.. 



1 



2 

 1 



1 

 1 

 1 







































2 



















1 





















2 



1 



1 



1 















1 

















1 

























74° to 76° . . 







1 



1 













2 









1 

















72° to 74°.. 







3 





1 



2 

 4 



1 

 1 

























70° to 72°.. 













1 

























68° to 70° . . 











1 





























66° to 68°.. 















1 

 2 





2 







1 



















64° to 66°.. 

















1 



4 





1 

 1 

 2 













1 



62° to 64°.. 



















1 



4 

 4 





1 



i" 



1 

 1 



1 







60° to 62°.. 





















1 



3 





1 





58° to 60°.. 







































































To represent this relation graphically the average of the average 

 mean temperatures for all the records of a given length has been taken, 

 and the following figures obtained: 



Length of 

 period. 



Number of 

 records. 



Average of the 

 average mean 

 temperatures. 



Days. 





° F. 



2i 



1 



82.5 



3 



3 



80.9 



4 



4 



79.5 



5 



3 



79.2 



6 



6 



74.9 



7 



1 



78.5 



8 



2 



75.2 



9 



10 



71.2 



10 



4 



67.1 



11 



6 



65.8 



12 



8 



68.1 



13 



1 



67.3 



14 



9 



63.9 



15 



1 



66.7 



16 



2 



68.8 



17 



5 



65.8 



18 



1 



59.1 



19 



2 



62.3 



20 



1 



63.5 



22 



1 



61 



23 



1 



65.1 



Figure 1 shows the curve obtained by plotting these figures. The 

 broken line in the figure is the hyperbole which is the nearest approach 

 to the actual experimental curve. If it is true that "the curve 

 expressing the increase in rate of development is a true hyperbole" 

 (Peairs, 1914), one must seek for an explanation of the many devia- 

 tions from the true curve which are seen in the experimental curve. 

 It is of course probable that if the accumulated effective temperature 

 for each period were worked out, the resulting curve would show a 

 much closer approach to a true hyperbole. 



