298 BEITISH BUTTERFLIES. 



dome, and the segmental incisions show markedly, especially on the 

 upper edge of the dorsal ridge. The hairs look like a pale covering 

 surface, at some angles of a greenish-grey tint, this hue being particu- 

 larly noticeable if looked at frontally. The spiracles are very distinct, 

 especially looked at from above, from which direction, too, one can 

 still trace distinctly the upper row of oblique stripes. As maturation 

 takes place, a marked change is noticeable in the thoracic region ; a 

 distinct area, commencing on the mesothorax, directly behind the 

 prothoracic spiracle, on either side, developing a clear' green tint, 

 which spreads over the lateral area of both the mesothoracic and 

 metathoracic lateral areas as far as the subspiracular flange. By the 

 end of the second day, these areas have extended to just beyond the 

 1st abdominal spiracles, and leave no doubt that they represent the 

 developing pupal wings (July 13th, 1907). 



Comparison of larv^ of Ruralis betuljE and Klugia spini. — 

 [Both the larvas here noted are in last instar but neither fullgrown.] 

 The larva of Ruralis betulae has, in the extreme, the Lycsenid character 

 of dorsal flanges approximating and straight slopes. In these specimens 

 the flanges or ridges along the 2nd to 7th abdominal segments are little 

 more than 0-2mm. apart, the slope (on the 2nd abdominal) being 

 quite 3-3mm. high and with the very slightest convexity. The oblique 

 lines are very marked, crisply outlined, but narrow. In certain lights 

 they suggest that they are raised ridges, but this is not so. On the 

 1st abdominal segment the dorsal ridges diverge, each being straight, 

 to the middle of the prothorax, where they are 2'2mm. apart, then 

 converge slightly and join the marginal flange in front. The 

 included triangle is nearly flat, sloping down as it widens to the flange 

 border of the prothorax. The larva is pure light green with yellow 

 lines (dorsal, oblique, lateral, and some minor ones chiefly in spiracular 

 region less easy to describe). Head deep brown, so as to look black, 

 but graduating in pale rufous or ochreous over greater part of less often 

 exposed vertex. The larva of Klugia spini is very different. It has 

 the great hood of the mesothorax and the depression of the prothoracic 

 plate. The dorsal ridges are l*2mm. apart, not very prominent; slopes 

 about 2-2mm. It resembles R. betulae in the outline of dorsal ridges on 

 lateral view, viz., a straight line cut into by incisions, but with the crest of 

 hairs wanting, except at the extreme portion of angle, neither of the 

 species with the humped outline of Strymonpruni and Edwardsiaw-album. 

 The colour is deep blue-green, and the hairs (very short) have a sparkling 

 yellow appearance(in R.betulae they are less conspicuous, and silvery rather 

 than golden). Head black throughout. The lines are blurred, hardly 

 visible, and consist of a yellow mark, apparently so deep in the tissues 

 as to be quite obscured. This specimen has no reddish colour. The 

 constant absence of such colour in R. betulae also is probable, several 

 specimens having been examined. The slopes of K. spini are slightly 

 waved, not so smooth as in R. betulae, but are not convex. This com- 

 parison was made because the larvae were available, but K. spini is 

 almost of the Callophryid or " rubi " section, and not nearly allied to 

 R. betulae, so that it is less valuable than it might be (Chapman). 



Foodplants. — Prunus spinosa (Ochsenheimer, etc.), the general food 

 in western and central Europe; Prunus domestica (Ochsenheimer, etc.), 

 a common food throughout central Europe, more common than sloe in 

 eastern Europe ; Prunus padus (Caradja); apricot (Blachier, Stange, 



