STRYMON PRUNI. 211 



pupa is suspended perpendicularly from a branch by its cremaster ; the 

 pupal stage lasting sixteen days. This also appears to be far too 

 general a statement ; one suspects that, in nature, pupation rarely 

 takes place on a branch at all. Lambillion compares the pupa in 

 form and colour with a large fruiting-bud of sloe (prunellier), and 

 says that it is difficult to discover. Borkhausen notes the pupal 

 stage as lasting fourteen days. Paul and Plotz observe that, in 

 Pomerania, the pupal stage lasts twenty days. Dixon fixes (in litt.) 

 its pupal period at fifteen days, and says tbat, on one occasion, he found 

 a pupa, the larva of which had evidently strayed, on whitethorn ; all 

 other pupas found, were on the sunny side of a drive, on blackthorn. 



Process of pupation and development op pupal form. — On June 

 8rd, 1907, at 7.30 p.m., a particular larva was observed laid up for 

 pupation, and presenting all the characters of shortening, thickening, 

 and especially heightening, since June 1st, at 9 p.m. The larva shows 

 slight, white, wrinkles down the incisions of the first three abdominal 

 segments. At 8 p.m. : Wrinkles now show in all the abdominal 

 incisions, and across between the first two pairs of dorsal humps ; the 

 pupal metathorax is very distinctly outlined in back part of mesothorax, 

 showing mesothoracic skin has been pushed back so far, but the larval 

 suture between the meso- and metathorax is not obvious, and it may 

 not be quite so far forward ; there is yet no slit in skin, and even no 

 drawing of the tracheal threads at the spiracles; this specimen shows, just 

 now very plainly, though in faint tints, two oblique lines on the 3rd to 6th 

 abdominal segments (downwards and backwards), one above spiracle 

 pale, edged below with darker ; the other, halfway between this and 

 humps, pale only ; the white area of pupal dorsum — prothorax, meta- 

 thorax, etc. — is clearly outlined through the larval skin as of an opaque 

 white area. 8.30 p.m. : Little change, white wrinkles across dorsa of 

 all abdominal segments. 8.37 p.m. : Skin split down back to end of 

 mesothorax, and tracheae drawing out. 8.43 p.m. : Skin halfway down 

 back, girth has fallen into place, and the front edge of mesothorax laps 

 over it very markedly. 8.47 p.m. : Moult completed a minute or so 

 ago. The skin is finally pushed off the last segment by quite a different 

 process from that by which the Papilionidae get rid of it. They leave the 

 skin adhering by claspers, and pull the tail out of it, afterwards pushing 

 it off. In this case, the skin has no hold by claspers, and is got rid of 

 by the extreme mobility of end segment, retracted and extended, and 

 pushed, first to one side, then to the other, until the skin, which, by 

 the stickiness of its inner surface, retains any folds and wrinkles given 

 it, and so continually contracts and does not expand, is pushed quite 

 off, and the tail is at liberty to seek the anal pad of silk. In this 

 specimen, the dorsal colouring is extremely brilliant, and the dorsum 

 of the 10th abdominal segment seems to be a solid plate, dark, but 

 with a red margin ; beneath it, immediately the skin was removed, 

 there appeared, when the segment was raised, a smooth surface, with 

 two raised red processes, exactly like claspers, and probably really them, 

 as regards the part of larval skin from which they come; a few minutes 

 later, this 10th abdominal plate faced backwards, i.e., posteriorly, in- 

 stead of dorsally, and then this ventral soft green area must have become 

 much contracted. In the earlier stage of the moult, the prothorax had 

 a very marked central notch on its front edge, as occurs in the larva. 

 [This is very marked in the larva of Somabrachys aegrota, so like, in 



