STATES OF INSECTS. (Jmago.) 345 
by keeping apart the sexes of a grasshopper, their lives 
were prolonged to eight or nine weeks, instead of two or 
three, their ordinary length; and under similar circum- 
stances Ephemera, which usually perish in a day, have 
been kept alive seven or eight. It is in consequence of 
this very curious fact, which has not received from phy- 
siologists the attention that it merits, that many butter- 
flies and other insects, which, when excluded from the 
pupa in summer, perish in less than a month, live through 
the winter, if excluded late in the autumn, and the union 
of the sexes does not ensue. It is probable that the great 
age to which Baker’s Blaps, Rosel’s Cetonia, and Esper’s 
Dytiscus attained, was owing to their being virgins when 
taken, and subsequently kept from any sexual inter- 
course. A parallel case happens in the vegetable king- 
dom :—if annual plants are kept from seeding, they will 
become biennial ; as, likewise, if they are sown too late 
in the year to produce seeds. 
In the case, however, of the earlier or later exclusion 
of the imago, another agent has probably some influ- 
ence. Buffon found that, other circumstances being alike, 
the silkworm-moths placed in a northern, lived longer 
than those exposed to a southern aspect: whence it ap- 
pears that the stimulus of heat shortens the lives of in- 
sects, and consequently that cold tends to lengthen 
them. 
It must be observed too, that as the death of the fe- 
male insect does not take place until all the eggs are ex- 
cluded, the term of her life, though usually short in the 
majority of species, which lay their whole number at 
once, is proportionably long in those which, like the 
queen-bee, have a longer period assigned them for this 
