THE GENUS ACRONYCTA AND ITS ALLIES. 131 



seizing strongly the loose silk of the bottom of the cocoon, and 

 this is always done so effectually, that it is only with great care 

 and pains that the silk can be unravelled, without damage to 

 the pupal spines. The spines are arranged on the tridens 

 formula, i.e., with 2 dorsal and 6 (3 on each side) ventral 

 spines. They are curved so as to be hooks rather than spines, 

 the dorsal curved downwards and the ventral upwards. The 

 latter are, however, not so terminal as in tridens, but are spread 

 round a semicircle, so that the outer ones are lateral rather 

 than terminal. The, roughly speaking, round boss, on which 

 the spines are situated, is separated at its base from the rest of 

 the pupa by a shallow groove ventrally, but dorsallv by a deep 

 channel or incision, so cut into it that the basal portion of the 

 boss has a thin round margin over it, with a smooth surface, 

 passing down to the dorsal spines, which is somewhat shield- 

 shaped. The pupal margin of the incision presents a series of 

 longitudinal ribs or buttresses, four on either side, with indica- 

 tion of a minute one in the intervals between them. 



When the moth emerges, it leaves very little trace of an 

 opening in the outer diaphragm, but there is always a little 

 wool rubbed off the moth to be observed in the opening. If 

 the pupae are kept too dry, the moth is unable to force the 

 outer diaphragm, either because this becomes too hard and 

 dry, or because the moth has no spare fluid to soften it, the 

 moth then perishes in the outer chamber. 



The larva appears to eat almost anything arboreal, is perhaps 

 even more omnivorous than psi; but I have little doubt it is 

 correctly named, in so far that in the wild state it is fonder of 

 alder than anything. It is very widely distributed and supposed 

 to have its headquarters in the New Forest ; I fancy it is as 

 abundant here as anywhere. My friend. Dr. Wood, finds a larva 

 or two most years, and I have twice taken it here on birch. 

 On only one occasion have I searched for it, and then Dr. 

 Wood and myself (really looking ostensibly for Cerura bicuspis, 

 which we did not get) each took two larvae off alder. 



Alni feeds up the most rapidly of any species I have bred. 

 In each skin it occupies four days in feeding, one or two days in 

 moulting, with a few extra days in the last skin. One month 

 is all the time spent as a larva when the season is reasonably 

 warm. 



( To be continued) 



