104 Journal of the Asiatic Society of Bengal. [{N.S., XIV, 
parents have not always been recorded as they have on the 
whole been short-lived. However, in the 49th generation in 
Diagram I both parents lived ten days, and in the 48th 
generation in Diagram III the paternal parent lived nine days 
and the maternal twelve days. 
lance at the Diagrams shows that the rise and fall 
in the vitality of the moths are not always connected with the 
duration of the larval and pupal stage, for the moths which 
emerged in January and February lived longest and had a 
larval and pupal stage of sixty-three days only, while those 
which emerged in March, after passing through a larval and 
pupal stage lasting eighty days, lived about the same number of 
days as:‘those which emer in May and June, which had a 
larval stage lasting forty and thirty-eight days respectively. 
From this it appears that if the moths cut out at the end of 
the cold weather they will not live very long, although they 
e effects of temperature and moisture on insects have 
been shown in a number of most carefully conducted experi- 
ments by Tower on beetles, and fully described in his valuable 
work “An Investigation of the Evolution in Chrysomelid 
Beetles of the Genus Leptinotarsa.”” In his experiments Tower 
used the larvae of Liptinotarsa decemlineata and subjected 
many thousands of individuals to varying conditions through 
the larval and pupal stages till the adult insect emerged. As he 
gives the mortality percentages in each experiment, it is 
were taken after the beetles emerged, and not after their death, 
so the death-rate given was taken during the larval and pupal 
stage and not in the imaginal instar. 
However, the mortality percentages are very interesting. 
{In one of his experiments to determine the effects of a high 
average deviation of temperature on over ten thousand beetle 
larvae the death-rate was 99 per cent. In this experiment the 
403°C 
er experiment in which Tower subjected over six 
thousand beetle larvae to a large decrease in the average 
temperature, about 13:4°C below normal, the death-rate 
