1918. | The Vitality of Silkworm Moths. 103 
which gives the number of days. The length of the uprights 
always noted as these moths are usually rejected. When the 
moths have lived wnder a certain number of days I have shown 
the uprights as broken. However, they are all known to be 
dead on the first day on which the longer-lived moths were 
noted as being alive 
t is apparent from a study of these diagrams, that there 
is always a pronounced rise in the vitality of the moths in 
the cold season and a fairly sudden drop in the rainy season. 
It is always lowest in either August or September, but in March, 
April, May and June it remains almost stationary, being neither 
high nor low. Diagram I shows a fairly regular rise and fall, 
highest in December, when many moths lived fourteen, fifteen, 
and seventeen days, and one ninteen days; lowest in August, 
when only six moths lived five days and the remaining eighty- 
four lived three days and under three days. In March, April, 
and June the vitality was fairly high, but in October it was 
lower than might have been expected. Diagram II shows a 
greater rise and fall than that which occurred in the vitality of 
family represented in Diagram T. It was, as usual, highest 
ecember, rising to twenty days, but the greatest drop was 
in ge Bete har. not August, when it fell very low, none of the 
moths out of one hundred and fifty-eight living more than 
three days. In October the degree of vitality remained much 
the same as that shown in Diagram 
The two families the longevity of which is represented in 
greatest drop in September. There is an unusual rise in April 
when one moth lived fifteen days, two fourteen days, and seven 
twelve days. 
In Diagram III the rise and fall in the vitality seems very 
gradual, the rise is slightly higher than usual and the fall is not 
as low as shown in the other Diagrams. It is lower in August 
than in September as pa one moth lived seven days in a 
while seven lived seven days in September, seven lived s 
days. and fifteen lived five days, cigs only five lived six 
dz ys and three lived five days in Au 
The unusual rise in the August Oe shown in Dia- 
am III may probably be due to the greater longevity of the 
parent moths from which it is descended. In fac t the families 
represented in Diagrams III and IV are from a ach longer- 
lived branch of the race than that from which the families 
represented in Diagrams I and II are descended. In all the 
generations given in the Diagrams the length of days the 
maternal parents lived is indicated by an arrow. The paternal 
