BITHYS QUERCUS. 251 



the latter rises higher than the former at its front edge ; the 7th and 

 8th abdominal segments are also less distinctly divided. Below the 

 spiracles each segment is produced into a flattened ridge, thus causing 

 the great proportional width ; the belly is flat ; a transverse section of 

 the larva would be almost triangular ; all the legs are short and well 

 under the body, the motion is even, almost gliding, the general 

 colouring is brown ; the centre of the back is fawn-colour, with a dark 

 brown dorsal line bordered with yellowish, which looks like a groove ; 

 the prothorax is edged with yellowish, and has a central brown spot 

 in front with a greyish patch, the mesothorax has a semicircular brown 

 patch with its curve behind, the metathorax has a similar patch, 

 but smaller ; on each of the segments, from the mesothorax to the 6fch 

 abdominal, there is, in the subdorsal region, a pale streak slanting 

 downwards and backwards, edged below with very dark brown, growing 

 wider and more intense backwards ; these streaks map off the centre 

 of the back ; below them the side is darker than the back ; the edge of 

 the ridge is yellowish ; some way above the ridge are the round, small, 

 dark-brown spiracles, placed in a hollow. On the 7th and 8th abdo- 

 minal segments the centre of the back is brown, the sides yellowish, 

 the hinder part of the 8th abdominal segment chestnut, the 9th 

 abdominal has a small, squarish, chestnut patch at the tip, bordered 

 with yellowish- white ; the colour under the ridge is reddish -brown, 

 just above the legs is a pale line ; the centre of the belly blackish ; the 

 true legs black and shining, with a fringe of bristles along them on 

 the outside, the prolegs soft pale brownish -ochreous (Hellins). 



Comparison of larvae of Bithys quercus and Euralis betulje. — 

 The fullgrown larva of B. quercus differs from that of E. betulae in 

 being comparatively flat, i.e., the dorsal ridges are flat, the slopes 

 flatter, especially above, so that they are convex instead of plane. 

 It agrees with that of It. betulae, however, in the narrowness of the 

 dorsal plane, i.e., in the ridges being very close, 03mm. or less, the 

 slopes being 3*7mm. on the abdomen, and widening out on the thorax, 

 forming an anterior " slope," though the larva is more rounded at the 

 ridges, etc., and therefore not so pronounced, in these respects, as that 

 of R. betulae ; especially the ridges do not run down to the marginal, 

 flange as in R. betulae. It differs from the larva of Strymon pruni in 

 the dorsal ridge being comparatively flat, rather, if anything, hollowed 

 in the middle of each segment, than acuminate, and is much the same 

 from the mesothorax to the 6th abdominal segment. The larva is 

 fairly constant in colour, and shows well the dorsal triangles, bounded by 

 a dorsal (yellow) line (i.e., ridge), the oblique line (yellow), and posterior 

 border of segment ; they are more or less marked from the mesothorax 

 to the 6th abdominal segment. For the rest, the colour is a rich oak- 

 brown, darker below triangles, with faint indication of a second oblique 

 line and yellow lateral line ; there is a yellow line just above the legs 

 (Chapman). 



Larva in the quiescent stage preceding pupation. — The larva 

 awaiting its moult is very different from the feeding larva. It is now 

 short, thick, and rounded, more the form of the pupa. It is red on 

 the back, green elsewhere, but very translucent, as if there were a 

 solid, central, whitish body surrounded by green fluid, and covered by 

 colourless skin, studded closely with black hair-points ; the pink back 

 is due to the white central material showing more distinctly on a back 



