XXXlll 



(Botydse), which sufficiently shows that the position which Doubleday 

 would assign to Aceutropus is in or near the Hydrocampidse. 



" It may possibly be remembered that, in a paper which the Society did 

 me the honour to publish in the • Transactions' for 1872 (pp. 121 and 281), 

 I adduced some arguments tending to show that there is really one species, 

 and one only, of this genus; and in a note on p. 156, the position is thus 

 summed up; — 'I am quite in accord with Ritsema when he says that 

 A. Hansoni, Garnonsii, Nevae, badensis and germanicus are not specifically 

 distinct from A. niveus ; but I go a step further, and say that A. latipennis 

 is identical with A. Hansoni.' Ritsema is now satisfied that A. latipennis 

 is identical with A. Hansoni, but still thinks that there are two species, of 

 which one (A. niveus, Oliv. = A. Garnonsii, Ciirt.) has a female with 

 rudimentary wings, and the other (A. latipennis, Moschl. = Zancle Hansoni, 

 Ste.) has a female with normally developed wings. Doubleday, in the 

 Supplementary Catalogue already mentioned, does not go into the synonymy 

 at length, but records one species only, under the name of A. niveus, giving 

 latipennis as a variety, thus : — 



AcENTROPUS NIVEUS. Kiveus, Olivier? 



latipennis, Moschl., var. 



" I am not able to throw any further light on the specific identity or 

 distinctness of the two forms. Ritsema, however, refers to his having found 

 many specimens, all males, at Arnheim, and to the capture at Huissen 

 (near Arnheim) of a winged female, which he recognises as A. latipennis. 

 ' By this capture ' (says he, at p. 15), * I am fortified afresh in the opinion 



that there are two species For it would be otherwise inexplicable that 



amongst the innumerable winged individuals captured by me at Overween, 

 not a single female occurred, and that I, by breeding from larvae coming 

 from the same place, obtained only females (in number already amounting 

 to fifteen), which were furnished with wing-rudiments and live in the water, 

 whilst the first specimen that is captured at Huissen, inside the house at a 

 lamp, is a female with well- developed wings.' I must confess that I cannot 

 follow this reasoning. Be it remembered that no difference is suggested in 

 the males from the different localities, and the supposed distinctness of the 

 species rests entirely on the possession by the females in the one case of 

 developed and in the other of rudimentary wings. From Arnheim and 

 Huissen, males, and one winged female captured ; from Overween, males, 

 and fifteen unwinged females bred. Ergo, two species ! Surely this is a 

 non sequitur. It is, in fact, a repetition of Brown's argument (with which 

 I dealt in the 'Transactions' for 1872, p. 142), that the winged female 

 occursjin one locality, and the apterous females in another locality. I can 

 scarcely see how the facts mentioned by Ritsema can be said to fortify any 



F 



