70 THE ENTOMOLOGIST. 



but that various circumstances tend to upset this equal propor- 

 tion. Among men, mammals in general, birds, fish, &c., various 

 conditions occur from equality to great preponderance of one sex 

 or the other, and equally various circumstances seem to deter- 

 mine these conditions. Among Lepidoptera various conditions 

 in the numerical proportions also occur ; in silk-moths the 

 females are said to be bred in excess ; in Rhopalocera the general 

 impression of collectors is that males are produced in excess. 

 We are not here concerned with the actual production of males 

 or females, but of their arrival to the state of sexual maturity ; 

 so that what we have to examine is this impression of collectors. 

 Two views may be taken — (1) that owing to differences in habits, 

 times of appearance, &c., of the two sexes, this impression of 

 collectors is a mistaken one ; (2) that this impression is a true 

 one. The former view was taken by Mr. Stainton, the latter by 

 Mr. Bates, in the discussion before the Entomological Society in 

 1868. It seems probable that thei'e is truth in both views, so 

 long as each is not applied to Rhopalocera in general. No doubt 

 if the two sexes of a species have different habits, &c., collectors 

 who are ignorant of those habits would very likely gain a wrong 

 impression of the numerical proportion of the sexes ; but if such 

 a disparity in the habits does not exist, it is an unwarrantable 

 position to ignore the repeated assertions of collectors. Now, 

 with the genus Erebia I do not think there is any great difference 

 in the habits of the sexes. Whenever I have taken a female of 

 the species that I have collected (and I have taken many), I have 

 done so generally unwittingly until the capture has been made, 

 and usually I have caught females flying on the same ground 

 with males, from which they are indistinguishable in general 

 appearance, flight, &c., and conspicuousness. Then again, even 

 supposing that the females do lie hid more than the males, or 

 occur at different periods, it would be rash to suppose that a 

 collector of even moderate attainments does not state or even 

 understate the numerical disproportion of the sexes by the col- 

 lections he brings home ; for, knowing the supposed rareness of 

 the females, he will always retain them when they are caught, 

 whereas he will continually pass by or let go the commoner 

 males. Considering the abundance of many species of Erebia, I 

 think that the collections brought home probably understate the 

 numerical disproportion of the mature sexes. 



The proportions given to the species considered afterwards 

 are derived from my collection, and from the collections in the 

 British Museum. Here again the risk run is one of under- 

 statement, for in the latter collection many specimens have been 

 ejected, and these will be sure to have been mostly males, owing 

 to the scarcity of females for representing types. 



In applying the methods, that have now been discussed at 

 some length, to actual data derived from the genus Erebia, my 



