407 



the same phenomenon might not occur in this couutrj', and it is 

 one that it would be interesting to discover. 



Another circumstance coiniected with the subject we are con- 

 sidering, wliich has not been satisfactorily explained and needs 

 farther investigation, is the foct of a large proportion of the females 

 of many fjcpidoptera, especially those of the larger Sphingidce, 

 when bred in the autumn, being perfectly barren. Some have 

 thought tliis to he a provision of nature, in the case of double brooded 

 species, to meet the circumstance of the scarcity of the right sort 

 of food for the larvse, if hatched in large numbers, at a season 

 whun the leaves are about to fall. But this can hardly be sus- 

 tained ; it having been observed by others that though " the 

 females of some species are mostly barren when disclosed in the 

 autumn, in cases where there are two distinct broods of a species, 

 a vernal and an autumnal brood, both are fertile." * It is clearly 

 a physiological phenomenon only to be elucidated by a series of 

 observations continued for several years, and extended to a large 

 number of species, all particulars respecting time, place, character 

 of the season, condition and sex, being carefully noted down. 



Another remarkable phenomenon in the history of insects, and 

 well worth the attention of the local naturalist is the fact of the 

 extreme disproportion of the sexes in some species, so far beyond 

 anything that occurs in the higher animals. It is allied to the 

 phenomena before treated of, so far as it may be due to 

 parthenogenesis or perliaps to dimorphism. Instead of the 

 sexes being pretty equally balanced in numbei-s, as we might 

 be led to expect, in certain cases we find the males largely 

 predominating over the females, or on the contrary the females 

 over the males. Mr. Darwin, in his last work on the 

 " Descent of Man," has gone very closely into this subject, 

 and collected a large number of instances in point.t " From 

 various sources of evidence, all pointing to the same direction, he 

 infers that with most species of Lepidoptera, the males in the 

 imago state generally exceed the females in number, whatever 



• Ent. Trans., 2nd Scr., vol. 4., Proceed, pp. 72, 73, t Vol. 1, 



pp. 309-314. 



