LYCAENA ARION. 337 



longitudinal rows of long curved hairs, one row being sub-dorsal, and 

 one lateral ; each row is composed of a single hair on each segment 

 from the fourth to the ninth inclusive, on which segment the sub- 

 dorsal series terminates ; the first three segments have each a set of 

 three sub-dorsal hairs, those on the first segment curving forwards : 

 the lateral series are likewise formed of one on each segment, and all 

 directed laterally and surrounding the extremities of the larva ; the 

 hairs have the bases of remarkable formation, resembling glass-like 

 pedestals with fluted sides. The entire upper surface of the body is 

 densely studded with extremely minute pyriform glassy processes; the 

 under surface is equally as densely clothed with very short stoutish 

 hairs. The head is ocbreous with dark brown markings in front ; the 

 prolegs dusky, and the claspers are unicolorous with the under surface 

 (July 27th, 1896). Full-grown (after hybernation)*; -583in. long. 

 Head extremely small, out of all proportion with size of larva. The 

 small black dorsal prothoracic disc now a mere speck. 



The head is set on a very flexible retractile neck which can be 

 readily protruded beyond the first segment while the larva is in 

 motion ; but when resting, the head is completely hidden and with- 

 drawn into the ventral surface of the segment. 



Dorsal view. — Both anterior and posterior segments are rounded, 

 the body gradually increasing in width to the 10th segment. The 

 segmental divisions are deeply cut, each segment being laterally 

 convexed. Side view. — First anterior and last three posterior segments 

 somewhat flattened dursally and projecting laterally ; second to ninth 

 segments humped dorsally ; the medio-dorsal furrow usual to Lycarna 

 larvae is, in avion, only indicated on the posterior half of each 

 segment ; the sides are sloping and convoluted to the spiracles ; the 

 lateral ridge is dilated, swollen and prominent, but rounded, and the 

 ventral surface is full and of a bulbous character; the rather small 

 feet are well provided with strongly-curved hooks. All other 

 structural details are as in the description given of the larva after the 

 third moult, in vol. xxxii., p. 105. But on examining the full-grown 

 specimen, I find that all the long dorsal hairs have been broken or 

 worn off short, leaving only a series of basal stumps. The colour is a 

 pale creamy ochreous, with a pinkish lilac tinge along the lateral 

 ridge, and surrounding both the first and last segments. When first 

 found, the entire skin had a shining distended appearance, as if too 

 tight for its obese proportions (Frohawk). 



The following is Chapman's account of the larva and its ontogeny 

 as worked out by him, and illustrated by his plates. In the four 

 instars of the larva, the heads in each stage seem to follow the usual 

 law of increase in size, the transverse diameter increases at each moult 

 by the same ratio, in this case about that of three to four. The actual 

 width of the heads, from a number of measurements at each stage, as 

 accurately as slightly distorted specimens (in some cases) allowed, were 

 first stage 0-30mm., second 0-40mm., third 0-54mm, fourth 0*72mm. 

 This diameter of head in the full-grown larva, of about three-quarters of 

 a millimetre, is remarkable. Avion is our largest British blue and this 

 diameter, 0-72mm., may be compared with that in medon l'Omm., 



* Four larvas found June 3rd, 1906, i.e., after hybernation, and all apparently 

 in last instar varied in length from -375in. to -5625m. in length (Ent., xxxix., p. 146). 



