Acentropus. 139 



water. And Speyer lias pointed out that several of the 

 peculiarities of the male appear to have for their object 

 the facilitating a short sojourn and an onward movement 

 in the water. The front of the body^ he says^ is rela- 

 tively very strongly built; the wings are narrow, 

 pointed, firmly fastened, almost fin-shaped, and when at 

 rest bent backwards, and the scales lie smoothly on, and 

 are fixed uncommonly fast ; and, finally, the large and 

 long palpi would be a hindrance to motion under water 

 if they had extended forwards instead of being directed 

 backwards. In short, Speyer explains the peculiarities in 

 mode of life and organization of Acentropus, by regarding 

 it as the representative of an older branch of the original 

 stock of moths, the other members of which branch have 

 disappeared ; the primitive insect forms must be sought 

 in water, the atavi of the Lepidoptera rose from the 

 water to the land, and adapted themselves to terrestrial 

 and aerial life ; and Acentrojnis, the most distinctly 

 aquatic of all known moths, is, from this point of view, 

 the primeval type, the nearest extant representative of 

 the grand ancestor of all the Lepidoptera. 



But to return from the region of speculation to the 

 domain of fact, I say that, knowing what we do know of 

 the habits of Acentropvs, I have no great difl&culty in 

 accepting Reutti's account of the apterous female, or 

 rather of the female with rudimentary wings, for it is of 

 the intermediate form that Reutti speaks. And I go a 

 step further — for if the winged male can exist underwater, 

 whether he voluntarily, as Brown thinks, descends like 

 Orpheus in quest of his Eurydice, or whether, as Reutti 

 records, he is dragged down by the female, like Hylas 

 by the water-nymph, there can be no reason why the 

 winged female should not have the same habit as her 

 unwinged sister ; it is less vmlikely that the winged and 

 unwinged should be two forms of the female of the same 

 insect, having the same sexual habit, than that they 

 should be the females of two different insects with males 

 undistinguishable by the eye, one of which indulges iu 

 aerial, and the other in aquatic, copulation. 



This brings me to the question which it is the main 

 object of this paper to open for discussion ; namely, how 

 many known species are there of the genus Acentropus ? 



For six and twenty years after, Westwood mated Acen- 

 tropus and Zancle, but one species of the genus was 



