6 



BRITISH BUTTERFLIES. 



usually a slight depression surrounding the micropyle proper, of which 

 mention has already been made. It may be well here to remark that 

 whilst the Urbicolid (Pamphilid) group of skippers tends to smooth eggs, 

 forming rather more than a hemisphere, those of the Hesperiid group 

 are hemispherical, with well-defined, clearly-cut, strongly projecting 

 longitudinal ribs, which give them an appearance much more resembling 

 that of the eggs of Argynnids than the other skippers. We have already 

 noted that, in the same group, the Thymelicids have fiat eggs, super- 

 ficially like those of many moths, except that the micropylar axis is 

 upright. The number of ribs running from the base to the apex varies 

 considerably, in the Vanessids they may be reduced to eight, and 

 rarely have more than twelve, in the Coliads there may be as many 

 as thirty or forty. 



The eggs of butterflies are usually of a pale yellow or pale greenish 

 colour when first laid, but those with transparent shells change their 

 colour very rapidly, the tint becoming quickly that which will best 

 preserve each in the position in which it is laid. It is usually placed on 

 a leaf, and then hatches in a few days, but if the eggstage lasts for any 

 length of time, the position chosen is on a twig or other permanent 

 part of the plant. The egg of Euchloe card amines is pale yellow when 

 laid, becomes deep orange in about twenty-four hours ; and remains of 

 this tint till just before the larva hatches, when the embryo can be seen 

 coiled up within the transparent eggshell. Other eggs change from 

 yellow to pink, or brown, or pale salmon, and then to greyish in 

 different species. As the young larvae mature within the egg, there is a 

 considerable change observable inside in those of many species, due to the 

 development of the embryo within. These changes can, in some of the 

 more transparent-shelled species, be readily traced under a microscope, 

 e.g., Pararge megaera, Nemeobius lucina, etc. Those British butterflies 

 whose eggs go through the winter are few in number, viz., Argynnis 

 adippe, Thecla w-album, T. pruni, Zephyrus betulae, Z. guercus, Urbicola 

 comma, Adopaea lineola and Thymelicus acteon. The hybernating 

 stage of Lampides boetica is very uncertain. The old myth of the eggs 

 of Aporia crataegi (teste Rennie and other authors) going over three 

 winters and then hatching, is absurd. 



The eggs of butterflies are usually laid singly, rarely more than 

 two or three on a leaf, but a few British species, e.g., Aporia crataegi, 

 Pieris brassicae, Melitaea cinxia, M. athalia, M. aurinia, Vanessa io, 

 Aglais urticae, F/ugonia polychloros, and Euvanessa antiopa, and many 

 of their Continental and exotic allies, lay their eggs in clusters, either 

 as regular rows or irregular heaps, on a twig or the upper- or under- 

 side of a leaf. Some of the Polygonias lay their eggs upon each other 

 in a string, as it were, from three to ten eggs in a single file. 



Eggs are subject to many dangers after being laid. A particular 

 group of Hymenoptera, called Chalcids, lay their eggs inside the eggs 

 of lepidopterous insects, and find within them sufficient nutriment to 

 come to perfection ; in fact, a do/en or more perfect Proctotrupids some- 

 times emerge from a single moderate-sized egg, having passed their 

 entire existence within, and obtained the whole of their nutriment 

 from the contents of, this tiny receptacle. 



It has already been noted that the egg consists of an outside shell 

 and its protoplasmic contents. After fertilisation, the time varying 

 much with the species, the contents begin to thicken visibly and to 



