102 Journal of the Asiatic Society of Bengal. [N.S., XIV, 
two generations in each season. They are also very prolific, as 
a moth usually lays about two hundred eggs. 
During the cold season 1915-16 when I had only just 
begun working on a large scale and had many hundreds of 
moths from which to select, I found that great numbers in 
each group of families lived over eight days, so I decided to 
reject all those which lived under eight days. I continued m 
selection with regard to longevity through the hot weather of 
1916, and although it was quite warm in May and June a very 
fair number of moths lived over a week. However, in the 
generation reared in July, the moths of which cut out of their 
cocoons in August, I was surprised to find that nearly all the 
1916 and January 1917, many lived about twenty days. 
I watched this rise and fall in the vitality of the moths more 
closely through 1917 and found that it was repeated, for only 
a few moths lived over six days in August and September. 
It is well known that all insects complete their larval and 
pupal] stages quicker in the hot than in the cold weather ; Lam, 
however, not aware that the effect of the season on the length 
of the imaginal stages of insects has been recorded. It is well 
known that many beetles and cicadas live for years, but it is 
not generally known that moths, butterflies and mosquitos 
have quite a fair length of life. I have also found that 
butterflies kept in captivity live longer in the cold than in the 
rainy season. A specimen of Hypolimnas bolina which lived 
ninety-two days was caught on the 2nd November and died on 
the Ist February. 
The four families chosen to show the rise and fall in 
vitality during the seasons, were selected because they are des- 
January 1917 to April 1918 have been represented diagramati- 
cally in Tables I, 11, If, and IV. Diagrams I and II are of two 
families reared from March 1917 to April 1918, and Diagrams 
If and IV, which are of another branch of the same race, were 
reared from January 1917 to March 1918 and are also in their 
fifty-seventh generation. 
In these diagrams the figures on the base line show the 
number of moths, and the vertical lines above the figures show 
the number of days the moths have lived. These upright 
lines must be referred to the column of figures on the left 
