40 



HARDWICKE' S SCIENCE-GOSSIP. 



that the broad black dorsal band now becomes brown I 

 from the head (inclusive) to the point formed by I 

 what the Rev. J. G. Wood calls the "St, Andrew's 

 Cross," on the fourth, and also on the last segment. 

 It is in changing" from the third to the fourth skin 

 that the larva experiences the greatest difficulty in its 

 ecdysis, often being unable to throw off its old skin, 

 especially when "stung," and consequently dying, 

 foreign aid rarely being of any assistance. 



In the fourth skin, the eighth segment is black all 

 over, with just a little green above the prolegs ; 

 there is a minute black spot on the second segment 

 with a white centre; the "ears," jagged, black to 

 dark-brown ; tails black, red just before the tips, 

 with scarlet tentacula, legs black ; head dark, shining 

 black; there are also dashes of light-brown just 

 above the legs on the seventh and ninth segments : 

 the eleventh and twelfth segments are brown under- 

 neath, while the thirteenth segment is brown on each 

 side of the belly. The larva in this skin is three- 

 fourths of an inch in length, and the "ears " begin to 

 disappear. 



The fifth skin varies from the last only in that the 

 black is darker generally, all the spiracles are black 

 with a white centre, and that the green, which covers 

 the whole of the body, except that occupied by the 

 spiracles and dorsal area, is of a beautiful grass-green 

 and remarkably pretty. The larva is now fourteen 

 lines in length. 



The sixth and last skin differs materially from its 

 predecessors. The brown on the back becomes very 

 light and most pleasantly mottled with white. The 

 brown on the dorsal portion of the second segment, 

 being quite greeny, appears to fade gently into the 

 yellowish-green of the sides. The spiracles are of a 

 vivid [white surrounded by black ; there is a white 

 line between the brown of the dorsal and the green of 

 the lateral, area. The hump on the fourth segment 

 is reddish. The second segment is extended into 

 prominences on each side of the head, in the place 

 where]the ears, which have now entirely disappeared, 

 once were, giving the front of that metamere a 

 square appearance, on which prominences are two 

 black spots. The head is chestnut-brown, black at 

 the | sides, [and decidedly smaller than the second 

 segment, into the red "front "of which it maybe 

 withdrawn at the will of the larva, this being its 

 natural position when at rest. The legs are yellow 

 and black ; the prolegs are green with black at the 

 extremities ; the tails are white and black, the black 

 part being rough and scabrous ; the dorsal tails are 

 black ; and the thirteenth segment is black above. 



There appear to be, as far as my observation serves 

 me, but [six skins to this larva, although the last 

 certainly varies considerably in accordance with its 

 age, and also in different specimens. In some, the 

 brown spot on the eighth segment is very small, i.e., 

 a very small patch of it, and in others the whole 

 segment is completely covered. Some individuals 



are almost white or very light, whilst in [others a 

 great density of colouring is manifest. Again, when 

 the skin is "young" — i.e., only just changed — the 

 top of the second segment is the same as the rest of 

 the back, but when old it becomes harder and 

 shinyer, or whiter, or again in other specimens, 

 blacker. In some examples the head is brown 

 nearly all over, whilst in others it has a broad black 

 band along the top and sides ; but it is always shiny. 



The larva may be found from the beginning of 

 June to the end of August, although rarely after the 

 beginning of the latter month, as they then ascend 

 the tree to a height of seven or eight feet, and, being 

 almost wholly green (except the dorsal band, which 

 may very easily be mistaken for the mid-rib of the 

 leaf or for a twig by the uneducated eye) are very 

 difficult to spot, and when "spotted" the leaf on 

 which the specimen is feeding must be taken with it, 

 for this insect possesses marvellous "powers of 

 grip," as is ably set forth by Mr. E. A. Butler, in 

 the December (1892) number of " Knowledge," 

 where my readers will find a microscopical illustra- 

 tion of the hooks on the prolegs of Smerinthtis tilice 

 (the lime hawk-moth) magnified sixteen diameters, 

 to which insect D. vhucla bears a close relationship 

 in this particular. 



When the larva is about to become a pupa, it is 

 exceedingly curious to note that, in common with the 

 majority of other larvae, it invariably emits a ver- 

 milion frass, and the bright grass-green of its lateral 

 area turns to a dull, dirty, purplish-brown, harmonis- 

 ing beautifully with the colour of the trunk of the 

 tree, down which it has to climb in order to select 

 a suitable situation for its wintry abode. In confine- 

 ment, it then becomes exceedingly restless, and if 

 bark, etc., be not supplied it, will "spin up" among 

 the dead leaves and frass, whence doubtless it would 

 emerge in due course, having completed its pupa 

 state, as fine an imago as though it were at large on 

 the stately trunk of some lordly poplar, ancient willow, 

 or water-loving sallow. 



The chrysalis of D. vimda is rather small, com- 

 pared with the size of the larva and imago, being 

 about an inch and a quarter in length ; of a claret 

 colour, having the antennae short and thick, the legs 

 visible, and the eyes and very small proboscis pro- 

 minent. The spiracles are very obvious, and the 

 extremity of the body, or anal apex is rounded. Its 

 ecdysis takes place on the trunks of those trees on 

 which the larva has lived, viz., poplars, willows, and 

 sallows, placed in the order of merit ; but I have not 

 noted that it affects the Lombardy poplar more than 

 the aspen, as stated by Mr. Merrin in his " Lepi- 

 dopterists' Calendar." When full-fed, the larva, as 

 above described, changes in colour, and seeks some 

 place in which it may be secure from the " stormy 

 blast " of winter cold. Having found this, he at once 

 begins to gnaw away the bark, and to bring it round 

 in front of him, between himself and the outer air, 



