VARIATION OF VANESSA lO, L. 171 



far disturbed it as to get a fair view of it in its retreat. Its advance 

 was such, as I judged on this further examination, as to amount to 

 about three-quarters of the length of the pupa, or so as to bring the 

 wing-tips to about the usual level of the head. There was no question 

 of the pupa being ready to emerge, as the whole of the head and wings 

 were pale in colour, though with the opaque aspect of commencing 

 maturity. It seemed as if the object might be to obtain some sun- 

 shine, but it might have been regarded as a provision for keeping the 

 opening above from being closed by the further growth of the plant, 

 i.e., of the leaf-bases surrounding the opening, or again perchance to 

 escape some exudation of sap into its cocoon. 



On June 8th, the moth emerged, and the empty pupa- case was 

 well above the cocoon, if its puparium can be so called, and if the 

 disturbance it had undergone from my examinations, and the short 

 journeys of the pupa itself had left what might be called its upper 

 end. On close examination, however, it was found that the pupa- 

 case was 10-5mm. long, and that the cremastral end of the pupa-case 

 was 11mm. from the base of the excavation forming the puparium. 

 The cremaster of the pupa was firmly held by a silken cable, which 

 was stretched straight, and descended 5mm. or 6mm. before it was 

 merged in the other silken spinning, lining (very weakly) the puparium. 



The pupa-case was not, therefore, at liberty to leave its tube 

 further than it had done. The cable seems to hold the pupa from 

 further advance when the imago is leaving it, otherwise the imago 

 would fail to escape and would drag the pupa-case with it. A similar 

 provision exists in many Tortricids whose pupa-cases leave the 

 puparium. 



The interest of this curious habit is by comparison with other 

 Platyptiliids. In Gilhueria (ochrodacti/la), etc., we have the usual 

 plume habit of a fixed external pupa. In I'latt/ptilia {i/onoflactt/la) an 

 enclosed pupa that does not, however, emerge. Neither does AJaina 

 uiirrodactyla (an Alucitid), also an enclosed pupa. Though the 

 structure of the plume pupa is that of the Incompletae, this retention 

 of the typical habit of the incomplete pupa is certainly rare in the 

 group. A not dissimilar habit in (Kri/ptilas, which has a similar larval 

 existence, is associated with a loss of cremastral hooks, and seemed to 

 me to be possibly a re-acquired habit, it may, however, be by immediate 

 descent from some relative of F. ralndarti/la. 8ome Oxyptilids have 

 the usual plume external habit of pupation. 



This primitive habit, characteristic of the incomplete pupa, is a 

 strong point, which I was not aware of, when urging that the 

 Platyptiliids were the most ancestral group of plumes that I had 

 examined, in support of that view. 



Variation of Vanessa io, L. 



By T. REUSS. 

 {Concluded from p. 141.) 

 It might throw some light on these different results from the etiect 

 of "contrasts of temperature" on pupii? from wild-grown British 

 larvse, when I say that broods of I'fl/n'x.sa io (or V. urticae) reared under 

 stimulating contrastless temperature conditions from the early stages 

 will often vary from the type, but among themselves the individuals of 



