348 NUMERICAL PREPONDERANCE OF THE MALES IN ODONATA, 



was a picked specimen, I propose to leave him out of account, 

 both as regards his early date of appearance and as affecting the 

 numerical ratio of the sexes. We then have the following 

 remarkable result — remarkable, I mean, in view of the supposed 

 numerical inequality of the sexes — that out of 100 nymphs 24 

 bred out, and of these exactly half were males and half females. 



With other species I had not the same success in breeding. 

 The nymphs of Ischnura delicata, of which I had about a score, 

 nearly all fell victims to the rapacious nymphs of larger species. 

 Of four which emerged, two were males and two females. 



It would be interesting to breed a large number of nymphs of 

 other common species in order to see whether the result given by 

 Lestes Leda is really typical of the generality of species. Of 

 this, however, there can be very little doubt. To my mind, the 

 experiment proves the ratio of the numbers of the sexes to be 

 one almost of equality in any given species. 



The other fact to be noticed is that the females of L. Leda 

 appear before the males (leaving out of account the selected 

 specimen). The first female appeared on Aug. 8th and the first 

 male on Aug. 27th, nearly three weeks later. This has to be 

 borne in mind when collecting. In the early part of the season 

 I have always found the females of species before the males. It 

 seems probable that the females fly early near their breeding 

 places and later on retire into the bush or conceal themselves in 

 the herbage, only appearing again in company with the males for 

 oviposition. This, then, would account for collectors who are 

 out in mid-season only obtaining a few females. 



There is one subfamily, the Aeschnince, which appears to be an 

 exception to the general rule. In this subfamily the number of 

 females captured is nearly always equal to, if not actually in 

 excess of, the number of males. Thus out of 38 specimens taken 

 by me last season, 18 were males and 20 females. There were 

 twelve species represented; in four cases I did not obtain the 

 male, and in four cases also I failed to obtain the female. In 

 this case, then, the rule of numerical equality of the sexes is 

 borne out in collecting. The reason appears to be that they are 



