58 NEW YORK STATE MUSEUM 
species, because we are thereby able to ascertain to some extent 
the limiting agencies controlling them, and the more that is 
known along these lines concerning various forms, the more 
accurate will be our judgment as to their possible range. The 
present year has been marked by the presence in abundance of 
several interesting species, three of which are mentioned below. 
The reason for their occurrence in great numbers is probably 
found in unusually favoring weather conditions, particularly in 
the more than normal warmth. A study of the monthly mean 
temperatures during the growing season in the Hudson river 
valley for this and the preceding four years bears out this con- 
clusion somewhat. The following tables, compiled from the 
records of the New York state weather bureau and from those 
of the New York section of the national weather bureau, show 
this fairly well. ; | 
Monthly mean temperature of the Hudson valley region 
May June July August September 
SOMA eRe ome fer aks conc 59 64.3 73.6 68.6 61 
SOS ee ak lear ss 57.3 68.8 Tl TLRS) 65.9 
ELIS ON eather avs neiawerers 59'..7 70.3 C2 AL 70.8 61 
BOGOR Cyd) Neus cae 58.1 69.2 74.1 Toon 66.1 
OMe oe ap vectra Vee 57.6 69.1 74.7 71.4 63.2 
June in 1899, 1900 and 1901 was markedly warmer than in 
1897 and 1898 and July in both 1960 and 1901 was warmer than 
the same month in 1897 , 1898 and 1899, and this higher temper- 
ature is more marked in August 1900, which is just about the 
time of year when many insects would respond most readily to 
the influence of heat, specially those in the caterpillar stage, 
and the more than normal. warmth would tend to produce 
greater vigor than usual in this latitude and a consequent 
increase in numbers the present year. The increased warmth 
of the last two years is still better shown in the table of monthly 
means of Albany, compiled from the same sources as the pre- 
¢eding table. 
Monthly mean temperature of Albany 
May June July August September ; 
USOT. co her eae 59 G5 75 70 63 
BOS eve Hise ee wiles 58.2 69.8 75 73 60.6 
Bike Be Maries iS WS, We Liha 6O Falk Ta ays 72.3 61.4 
BODO re van aa ieee 57.9 70.5 74.6 74.7 67.7 
BDU) lrreey, tk oes di etane ents do), 1 10.2 75.8 72.8 65 
