346 STATES OF INSECTS. 



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 Ceto- 

 nia, and Esper's Dytiscus attained, was owing to their 

 being virgins when taken, and subsequently kept from 

 any sexual intercourse. A parallel case happens in the 

 vegetable kingdom : — if annual plants are kept from seed- 

 ing, 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 proportion ably long in those which, like the 

 queen-bee, have a longer period assigned them for this 

 important office. Huber affirms, that he had certain 

 proofs that she was engaged for two years in laying eggs, 

 all impregnated by a single sexual union a ; and in the 

 a Huber i. 106. 



