78 



NEW YORK STATE MUSEUM 



Cool weather the first ten days in June, so far as conditions at 

 Nassau and the elm leaf beetle are concerned, is very likely to be a 

 continuation of earlier unseasonable weather and therefore to mean 

 little more than a delayed development, and temperatures rarely 

 drop the last of June to such an extent as to do more than som3what 

 retard biological processes. Generally speaking, the critical psriod 

 is limited to the ten days from June nth to 20th, inclusive. It will 

 be seen by referring to the tables given above, that the maximum, 

 minimum and effective temperatures for mid- June in both 19 12 and 

 1914 are markedly lower than the average for the decade tabulated, 

 with the possible exception of the year 1907, and here we have, 

 especially in minimum temperatures, an approximation to con- 

 ditions obtaining in the two years mentioisd above, though it should 

 be noted that the effective temperatures for the ten days under con- 

 sideration exceed the average for the decade, conditions by no means 

 obtaining for the same period in 1912 and 1914. It should also be 

 noted in connection \vith the 1907 records, that the temperatures for 

 the first period are considerably lower than the normal, and conse- 

 quently it is evident that the season was an exceptionally late one, 

 the low temperatures of the first part of June simply checking develop- 

 ment without any special hazard to insect life. 



There is a question as to what point should be taken as the bio- 

 logical zero in endeavoring to ascertain the effect of temperature 

 upon animal life, and in this instance we have based our calculation 

 upon two points and present below a comparison of data thus secured. 



Comparison of deficiency in temperature units for June nth to 20th 



I9I2 

 43° 



1912 



55° 



1914 

 43° 



41.6 



41.6 



31-6 



30.5 



31-8 



32.5 



41.2 



75-5 



33-2 



I9I4 



55° 



Maximum temperatures 

 Minimum temperatures . 

 Effective temperatures . 



31.6 

 36.8 

 70.5 



It will be seen by referring to the table, that so far as maximum 

 and minimum temperatures are concerned the units are nearly 

 identical, whether we start at 43° or 55°. This is far from the case, 

 however, when we come to the effective temperatures, there being 

 a much greater discrepancy when zero equals 55° than if we start 



