294 BRITISH BUTTERFLIES. 



the prothorax is nearly straightly transverse. The dorsum of the thorax 

 between the ridges is without hairs ; the rather large prothoracic 

 plate is smooth and shining, but hardly otherwise distinguishable. 

 The ridges carry a line of hairs, rather brownish, in front spiculated 

 and curved backwards, about four large ones and some smaller ones 

 on abdominal segments, five on mesothorax and six or seven on 

 prothorax, the largest about 0-5mm. long. The margin of the ridge 

 seen from the inner side is yellow. Each hair seems to have a yellow 

 bulbous base, in addition to the yellow line. The lateral flange 

 running all round is yellow, and has, on each segment, eight or nine 

 long hairs and a good many short ones, all white and rather glistening, 

 giving a hazy appearance to the margin ; the longest of these is about 

 0'5mm. Besides the dorsal and lateral flanges are two oblique lines 

 (downwards and backwards) on this slope, the lowest just above spiracle 

 and sundry yellow spots in the intervals. On the metathorax, the 

 lower line is horizontal ; on the mesothorax, both are. The spots are 

 fewer, the area being less, and on the prothorax is only a spot or two. 

 In compensation some yellow longitudinal lines appear dorsally on the 

 thoracic segments between the flange lines. The oblique lines similarly 

 dwindle posteriorly, and on the 10th abdominal segment are only two 

 longitudinal lines, a little wider apart than to correspond with the 

 dorsal flange lines. The head is black, shining, about 07mm. across. 

 On the slopes there are a number of very minute (microscopic) hairs, 

 disposed over the green area, almost in rows along the margins of 

 segments. April 17th : Eating vigorously. Now 10mm. long. The 

 special form of the larva consists in the extreme flatness of the 

 " slopes," the extreme narrowness of the dorsal ridge (ridge rather than 

 ridges, they are so close together), the flatness of the front slopes 

 (thoracic dorsum), and the angular appearance resulting. The lateral 

 flange (on lateral view) is a straight line, and the dorsal yellow line or 

 flange descends to it, from the angle on the 2nd abdominal segment, in 

 a straight line in either direction. A mounted larva-skin in the third 

 instar shows a prothoracic plate about 0'6mm. across, a little angular, 

 but fairly round and quite circular on its posterior border. It has 25 

 or 30 very minute hairs and half-a-dozen lenticles. The hairs round 

 the front are very numerous and fairly long, generally about 0-2mm., 

 but up to 0-4mm., two or three between the plate and spiracle longer. 

 One of the large spiracles appears to have a lenticle in its margin, the 

 other to have three. There is also a lenticle attached to the posterior 

 margin of each of the abdominal spiracles. (This incorporation of a 

 lenticle into the margin of the spiracular plate has already been noted as 

 more extended in the case of Bithys quercus.) There are several lenticles 

 near the spiracles and also just below the dorsal ridges, but elsewhere 

 they are rare and solitary. A feature of the abdominal hairs is that 

 there is a row of short (about 0-14mm.), ordinary, spiculated hairs along 

 the margins of the segments, on the slopes, but on the slope between 

 these are scattered hairs of less than half the length, smoother outline, 

 thickened in the middle and with rounded end, forming peculiar club-like 

 batons. On the prolegs the outer line of small hooks has about thirteen 

 crochets, each of the pads has ten or eleven, much larger and, though in 

 a single row of two alternating sizes, there is a clear hiatus between the 

 two pads. Fourth (last) instar (April 26th, 1906, moulted April 25th): 

 12- 5mm. when resting a day before the last moult; 13-2mm. (16mm. 



