BUTTERFLIES AND THE ACT OF EGG-LAYING. 



and V. optilete, and adds " two days previously there had been over a 

 foot of snow." In view of the date it is certain that all these species 

 had survived burial under even this depth of snow. Unfortunately 

 Mr. Curwen does not tell one how long the snow had lain. 



Mr. A. L. Earl (vol. xxviii., p. 54), records a " twelve hours 

 thunderstorm with six inches of snow " on July 26th, 1913, at 

 Pontresina, which put him to flight ; but Mr. H. J. Turner (vol. xxix., 

 p. 161), notes on August 17th, 1914, the following species which had 

 " successfully weathered " twenty-four hours incessant snow-fall : — A. 

 niobe, A. aglaia, P. brassicae, E. ijoante, E. tyndarus, E. mdampas, A. 

 medrm, and a doubtful H. alveus. 



I think no more need be added to show that all Alpine species, no 

 matter what their season of flight, may be subjected to these conditions 

 and are (as a whole, not individually) quite unaffected by them. This 

 being so, is it unlikely or unnatural, that the 2 can lay under similar 

 circumstances ? 



Then there is another remarkable point to note. All the species, 

 which first attracted my attention by their readiness to lay in pill boxes 

 are, it may be remembered, Erebiid species. Now Dr. Chapman, whose 

 experience in obtaining butterfly ova is probably second to none, writes 

 (Ent. Rec, vol. xxiii., p. 233) of Erebiid species, that they are " often 

 difficult to induce to lay eggs." This, of course, means in captivity, 

 in as natural surroundings as Dr. Chapman could provide for them ; 

 yet, shut up in boxes, they show a far greater readiness to lay than 

 other speeies. What does this suggest ? What, but that the condi- 

 tions under a net bag with light and food plant, are not as natural to 

 these species as those of the box. We may take it that the' inability 

 to fly is disconcerting in the former case, but compatible in the latter. 

 The only natural circumstances which would, in any degree correspond 

 with the position of the butterfly in the box, are those experienced by 

 the buried butterfly. It probably often has, when buried, the additional 

 incentive of foodplant, lacking in the pill box, but again it often may 

 not ; and the fact that eggs are so freely laid on the sides of the box, 

 suggests to me that the buried insect may often lay on a rock. The 

 two principal elements wanting in the pill boxes are, of course, 

 moisture and the lower temperature, but this does not seem to affect 

 the Erebias. Possibly it accounts for the Alpine Lycfenids and 

 Hesperias not having, in my experience, laid in the pill boxes ; but I 

 must add that I have not at all so frequently had these species enclosed 

 for a sufficient length of time. 



The most unexplainable hypothesis which has to be conceded, if we 

 maintain that Alpine species possess this faculty, is that it can be con- 

 served by a species, although only required intermittently, lying in 

 abeyance for long periods. For example, in many seasons if the 

 weather be fine, a given species will be able to lay its eggs without 

 having recourse to this faculty, especially in a series of fine seasons, 

 perhaps ten might pass in succession without the necessity arising ; 

 but, in the eleventh if required, the insect must be in full possession 

 of the faculty which has passed down to it, although unrequired and 

 unexercised by ten generations, if it is to benefit by it. 



Although this hypothesis is perhaps nor. one one would readily 

 accept, yet I think we find some support for it in the fact that on rare 

 occasions lowland species of butterflies will lay an egg or two in a box. 



