PLEBEIUS ARGUS. 221 



003mm. to 0-Oomm., rarely more, carved, and well-spiculated. The 

 bases are rather flat ; a central dome, from the top of which the hair 

 rises, has round its margin twelve to fifteen or more, short, upstand- 

 ing spikes, forming a very beautiful object. Along the side of this 

 band is a pale area in which one hardly sees the skin-points and the 

 hair-bases, which are colourless, though of much the same structure, but 

 apparently softer texture and more easily deformed in mounted 

 specimens; this band is little more than one hair wide, but these hairs 

 are large (to 0.3mm. long), a,nd the setas of i and ii are to be found 

 amongst them if at all. Then comes a wide area, practically, one 

 may say, the rest of the larva, in which, but with local variations, the 

 skin-points are not black, but very visible, the hairs curved, thick, 

 about 0-05mm. long, with colourless bases, but the lenticles very 

 conspicuous by being nearly black. In the spiracular region are 

 patches with black hair-bases, and, again lower, places with nearly 

 invisible hair-points. In the marginal region are again some long 

 hairs (0-3mm.) ; these, and those lower, have much longer, slender 

 bases, with little trace of the stellate structure so conspicuous above. 

 The honey-gland (0 , 45mm. long) is surrounded by a cloud of lenticles, 

 and has, at each end, five or six special hairs clubbed or ballooned. 

 The lenticles in front of the gland are largely displaced by hair-bases, 

 with hardly a trace of hairs ; they are, however, rather obsolete hairs 

 than modified lenticles. When the honey-gland is expanded, it shows 

 a colourless membrane, in the middle of which are four circles, like 

 large, pale, narrow- bordered lenticles, with some intermediate 

 structures. The fans on the 8th abdominal segment each show the 

 bases of twenty to thirty hairs, but I have not succeeded in mounting 

 a specimen to show its details. In a mounted skin it generally 

 shows a circle, about 0-25mm. across, with a ring of hairs round 

 it. In one specimen these are very ordinary straight hairs, thick, 

 about 0-14mm. long, and about twelve in number, forming a striking 

 object when all fall together at the centre. In most specimens, how- 

 ever, the hairs are shorter, 0'03mm. to 0-05mm., thick and curved ; 

 they are in a region with well-coloured bases. This illustrates the 

 great variability in detail, noted in previous skins (after the first); one 

 may further, in this connection, note a specimen in which the obsolete 

 hair-bases are very numerous behind the honey-gland as well as in 

 front. The pads of prolegs have nine hooks, alternately large and 

 small (the longest about 0-08mm. long). The anal claspers have 

 twelve or fourteen on the forward pad, one or two less on the posterior; 

 in other specimens seven and eight books are found on a pad of the 

 claspers, so here again is variability, and, in another, fifteen and nine 

 on the front and back pads of the claspers (Chapman). 



Variation of larva. — When hatched, the young larvse are colour- 

 less, or of the faintest ochreous tint; as they grow in the first stadium, 

 they become rather darker, and gradually develop markings which are, 

 at the end of the stage, very pronounced and distinct. In the second 

 instar they are very dark brown, with a good deal of paler marbling, and 

 look rough from the prominence of the hair-bases, but, as they grow, 

 they show much more distinctly the colour and markings. Amongst 

 the larger larvae there is a considerable amount of colour-variation, and, 

 when about half-fed, the sparkling of the hair-bases, especially along the 

 white dorsal flanges, is more marked than when they are nearly full- 



