THE GENUS ACRONYCTA AND ITS ALLIES. 277 



Viminia rumicis and V. venosa. — With regard to the close 

 relationship of rumicis and venosa, Mr. Farren informs me that 

 so common a species as rumicis is not found in the habitats of 

 venosa, though one would suppose that stragglers would certainly 

 from time to time occur. Indeed, Mr. Tutt informs me that 

 a well-known Fen collector did take a specimen of rumicis last 

 summer, and brought it to him as something very rare and 

 unusual. 



Cuspidia alni. — I bred a large number this year in order to 

 get for figuring the form (in extra 5th skin) intermediate 

 between the early and adult plumage, but not one occurred. 

 " He that will not when he may," etc. In former broods as 

 many as 5 per cent, have occurred. These were from long 

 domesticated and somewhat inbred ancestry. Those this year 

 were direct from wild specimens. I think it is very probable 

 that the domestication had produced a tendency to their 

 variation in the direction of reversion. 



I had entirely omitted from my former notes a circumstance 

 of some importance and interest, viz., the strong odour that 

 the adult larva of alni emits when irritated. It can also do so 

 slightly in the previous skin. The odour is suggestive of an 

 escape of ordinary illuminating coal gas. A friend of chemical 

 and engineering experience to whom I submitted some examples 

 says the odour is that of carburetted hydrogen. The scent 

 is emitted most strongly when the larva is ready to search for 

 a place to pupate in. It is so strong that I have several times 

 wondered whether there was not an escape of gas in the room 

 in which the larvae were. It is perhaps proper to suggest that 

 this odour is protective, and in this sense associated with the 

 brilliant "warning" colour and conspicuous station (on the 

 middle of the upper surface of a leaf) of the larva. 



In reference to a record that the function of the spathulate 

 hairs is to eject the chips made by the larva in excavating its 

 pupating cavity, there is no doubt that an odd grain thereof 

 may sometimes be so ejected, but this is rare and purely acci- 

 dental. I have observed scores of larvae engaged in this 

 operation, and they all use the thoracic legs and the head bent 

 down as a sort of scoop to drag out the debris, which they do 

 at intervals, after having made a certain quantity. Rarely 

 also a portion will be brought out held by the jaws. In 

 forming the outer operculum of the burrow the larva will use 

 anything it can get hold of, but it distinctly prefers to break off 

 a httle fresh material from the surface about the opening to 



