202 BRITISH BUTTERFLIES. 



creature with very large prothorax, and meso- and metathorax 

 also large. Hairs long, a double dorsal series (i ?) form two long high 

 crests down the back, and the lower series also are in line as flanges or 

 crests when the larva is looked at end on. It is very deep brown ; head 

 black. I have not ventured on a more profound examination yet, having 

 only the one example. It leaves the egg by eating an exactly circular 

 hole on top, involving apparently just the whole of the inner smooth 

 flat surface. March 8th: Appeared to eat a little yesterday, but to-day 

 looks as if dead, or nearly so. March 9th: Is certainly dead; it has all 

 along had a very peculiar outline, owing to the largeness of the thoracic 

 segments, equal to nearly the rest of the larva, and especially the bulk 

 of the prothorax, more expanded even than one would expect were a 

 moult imminent." When the larva is in its last two stadia, its slow 

 gliding motion is very remarkable ; the anal prolegs are pushed forward 

 as far as possible, and this forward movement is followed by each pair 

 of prolegs in turn, and then by the true legs, so that a wave seems to 

 run from segment to segment along the body. When not moving, 

 the legs are retracted, and the larva rests almost flat upon the surface 

 of a leaf; when in motion, the anal segment is slightly raised. 

 The movements of the larva give some variation to its tint, for, 

 whilst the larva at rest is very uniformly green, in motion there is 

 a distinctly darker green, mediodorsal, line, traceable from the head to 

 the anus, making the central furrow appear darker than the ground colour ; 

 this darkening is, of course, largely due to the food in the alimentary 

 canal. The larva? can be beaten from blackthorn during the day, 

 being very hard to find by searching at this time, for they appear to 

 hide very successfully, assimilating to the colour of the leaf, whilst they 

 feed and move freely during the night (Tutt). Russell notes (Ent. Bee, 

 viii., p. 104) that, towards the end of May, 1896, he made a long search 

 in the haunts of S. pruni for larvae, but, although he could beat them 

 without difficulty, he only succeeded in finding one by searching, so 

 that he concluded that they must hide very successfully ; yet, the one 

 he did take was not at all difficult to see. It was quite fullfed, reclining 

 on the topmost sprig of a blackthorn bush in a curved position, 

 stretched at full length, and not humped — apparently feeding. In 

 confinement, larvae kept in the dark in small tin boxes, fed freel}\ 

 Russell believes the larva? rest quietly by day on the upperside of a 

 leaf, that their colour assimilates well with that of the leaf, and that 

 they move and feed during the night. Raynor notes (in litt.) : " The 

 larva? are fullfed about May 20th. They seem chiefly to frequent the 

 taller blackthorns in the denser parts of the wood, and are, therefore, 

 difficult to beat, unless one can bend the upper branches down right over 

 the umbrella. In Monk's Wood, on May 19th, 1904, nearly all the larva? 

 of S. prion' beaten were fullfed, whereas a single larva of Ruralis betulae 

 obtained was only just hatched." Dixon insists [Ent. Rec, x., pp. 110- 

 111) that the proper way to obtain the larva? (and pupse) of S. pruni is by 

 searching, and not by beating. He states that, in 1897, he visited a 

 well-known haunt for this species, where the bushes had been beaten 

 so unmercifully that, not only were the terminal and lateral shoots 

 broken, but the bark, and the stout steins themselves, had been cut off 

 or injured by the strokes, and he very pertinently asks, what must 

 have been the result on any larva or pupa in the line of the stroke, this 

 having been the effect on the wood. He insists that a careful study 



