Acentropus. 143 



females with rudiments of wings, which, for brevity, we 

 will call apterous *) were found at Glanville^s Wootton ; 

 but it is equally true that winged females were found at 

 Glanville's Wootton. Curtis and Dale took the two 

 forms of female together ; and though the London col- 

 lections do not contain a single apterous specimen, there 

 is no lack of amply winged females from Glanville's 

 Wootton. Then, what is the state of affairs at Burton- 

 on-Trent ? Brown bred the apterous female, but never 

 " had an opportunity of studying its habits in a state of 

 nature ; " in a recent letter, he writes, " I may further 

 add, that it is my firm conviction that winged females, 

 with wings so ample as those found in London, cannot 

 exist amongst our examples without their having been 

 seen." But to this I reply, that M'Lachlan has a female 

 with wings as ample as any of those found near London, 

 and this female, he assures me, was captured by himself, 

 not in the Trent, it is true, but in the Canal, at Burton. 

 So that in both the localities in England, in which the 

 apterous females have occurred, the winged form has 

 likewise occurred. It is true that (so far as I know) 

 near London the apterous form, and on the Lake of 

 Constance the winged form, has not yet been found ; but 

 negative evidence of this sort is of very slight value. 

 Finally, Ritsema found a number of pupae near Haarlem 

 in 1870; from these only two females emerged, and one 

 had rudimentary, the other well-developed wings. Was 

 one of these Garnonsii, and the other Hansoni ? two 

 species out of the same batch of pupas, or two forms of 

 the female of one and the same species ? There are 

 females without any trace of wings, females with rudi- 

 ments of wings, and females with ample wings ; and if 

 these forms occur together, and the males are all alike, 

 it seems to me that we require something more than the 

 difference in the alar development of the female sex, before 

 we can assert that there is more than one species. I sub- 

 mit that unless some other distinction can be pointed out, 

 beyond the greater or less growth of wing of the female 

 sex, the old view is the sound one, and Hagen was right 

 when he regarded the winged and the unwinged females 

 only as two forms of the same species. 



* " A semi-apterous form of the female," is M'Lachlan's expression 

 (InteU. ix. 132). 



