N'OTES 0\ PHORODESMA (cOMIB.ENa) PUSTULATA, HUFN. 171 



the leaves of the foodplant. The difference is practically the same 

 that we often tind between moths that emerge the same season and 

 those that hibernate as pupie. The cocoon that has to be occupied 

 during winter must not be amongst the leaves of the foodplant, but 

 have a more permanent position. The cocoon of O. antiqua is occu- 

 pied during the winter, but, as it happens, not by a pupa, but by eggs. 

 The cocoon of 0. i/onostinma amongst the foodplant requires, how- 

 ever, that the leaves be drawn together and an outer network made to 

 support it. The station on the cocoon proper is, however, always 

 reserved for the moth, but the access of the male is more and more 

 hindered, till it happens that he has to force his way through the 

 loose outer network. The step from this to ( K aurolinibata is rather 

 a long one, but still very obvious. Let the outer cocoon be gradually 

 made stronger and also smaller. Let the male moth, as this process 

 progresses, learn to force his way through the gradually stronger 

 impediment. We get at length the outer cocoon (or the inner portion 

 of it), like a' second cocoon upon the first, the moth emerges from the 

 one into the other, and into this the male is able to force his way. It 

 is only one step further for these two cocoons to become to all appear- 

 ance really one, there would remain, however, the original wall of the 

 original inner cocoon as a diaphragm between the two chambers of 

 the cocoon, and we have then exactly the structure and habits of O. 

 ainoliiiihata. 



Since the female of O. splaullda is more specialised than that of 

 0. anrolhnbata, we may suppose it to be derived from the latter, i.e., 

 from some form not very essentially different from it or its more 

 immediate ancestors. It is not so easy to picture the steps by which 

 the modifications occurred as it is to see as it were the change from 

 O. gonostifpna to U. aiirulimhata. As a very probable route, however, 

 we may suppose the diaphragm to be lost, as a complication and a 

 waste of energy and material. We may also suppose that the female 

 moth acquired the method of opening the cocoon for the ingress of 

 the male by modification of her method of passing from the one 

 chamber of the cocoon to the other We want, however, some inter- 

 mediate species to enlighten us, just as O. fiouostiijma does as between 

 (>. anti(]i(a and O. nuroUwhata. 



The point that is perhaps of the greatest interest and importance 

 in this explanation is in the remarkable diaphragm of the cocoon of 

 O. aiirolimhata, proving to have a distinct and intelligible ancestry, 

 and not in being a new structure whose origin is quite mysterious. It 

 warns us that many other extraordinary and aberrant structures that 

 are utterly puzzling, nevertheless have probably a simple and rational 

 origin if we only had the necessary clue for their investigation. 



(To be conthined. ) 



Notes on Phorodesma (Comibaena) pustulata, Hufn. ^ {irith plate). 



B> Key. C. E. N. BURROWS. 

 It was not without considerable hesitation that I reluctantly con- 

 sented to read a paper this season, as I share with other aged persons 

 the feeling that it is the duty of the younger generation to come 



* Read before the City of London Entomological Society, March 17th, 1903. 



