44 



MXIDUOUS FRUIT INSECTS AND INSECTICIDES. 



Table XLV. — Incubation periods of first-brood eggs; summary of Tables X LIU and 



XLIV. 



Table XLYI. 



. I oerage mean temperature during incubation of first brood of eggs, 1911; 

 summary of Table XLIII. 



Effect of temperature upon time of incubation. — One of the greatest 

 factors affecting the time of incubation is the temperature. This is 

 fully shown from the results of the temperature records for the time 

 of incubation both for the first and second broods of eggs as brought 

 out in the curve of figure 15. 



Because of the similarity of results obtained, the two broods of 

 eggs are here considered together. The same methods of computing 

 results have been followed as for the spring brood of pupae (p. 10). 

 In Tables XLIII and LVII the average mean temperature is given 

 for the time of incubation for the different sets of eggs. These data 

 have been summarized into averages under the respective days of the 

 hatching periods. (Tables XL VI and LX.) The curve of figure 15 

 has been plotted from these combined data, and shows a marked 

 shortening of time under a prevailing high temperature and a pro- 

 longation of time under prevailing low temperature. 



Taking our readings directly from the curve of figure 15 we get the 

 following average degrees of temperature for the different number of 

 days of incubation: 



4days=83.6° F. or 28.7° C. 



5 days=77.0° F. or 25.0° C. 



6 days=72.8° F. or 22.8° C. 



7days=^70.0° F. or 2L.1°<\ 



8 days=67.5° F. or 19.7° C. 



9 days=65.5° F. or 18.6° C. 

 10 days=64.0° F. or 17.8° C. 



11 days=62.7° F. or 17.0° C. 



12 days=61.8° F. or 16.6° 0. 



13 days=61.2° F. or 10.2° C. 



14 days=f)0.fi° F. or 16.0° 0. 



15 days=60.1° F. or 15.6° 0. 



16 days=59.8° F. or 15.4° C. 



