170 



HARDWICKE'S SCIENCE - GOSSIP. 



[Aug. 1, 1867. 



remain perfectly flat, but is a little puckered 

 just where the mine is, and the mine, instead 

 of being a long slender gallery, begins slender 

 and gradually widens, the first portion of it remind- 

 ing one of a ram's horn or cornucopseia : this is of a 

 pale brown with the narrow end whiter : it then still 

 further increases in size till it occupies nearly half 

 the width of a bramble-leaf. The larva which forms 

 the mine is very different from the soft-looking 

 pale amber larva which forms the slender galleries ; 

 it is green, rather rigid-looking, with three pairs of 

 short anterior legs, and with the head black, and 

 two blackish marks on the back of the second 

 segment. When full-fed it does not quit the mine, 

 but changes within the bramble leaf to the pupa 

 state, and in two or three weeks' time the pupa 

 pushes its anterior end through the dry skin of the 

 mined leaf, and the little moth makes its escape. 

 "When its wings are expanded it is rather more than 

 a third of an inch, and the fore wings are of a 

 bright yellow, with a brownish margin along the 

 costa, and hind margin, and a round black spot 

 above the anal angle : this we call Tischeria 

 margined (fig. 175). 



In the month of June we may frequently find on 

 young oak-bushes that many of the leaves have ex- 

 tensive mines, occupying nearly a third of the leaf, 

 and the part mined is so completely cleaned out 

 that nothing is left but the two skins of the leaf, 

 and it hence has a very flimsy appearance : on hold- 

 ing one of these mined leaves up to the light, we 

 should perceive within it a mass of short dark grey 

 thread-like substances, being the excrement of the 

 larva; possibly in some of the leaves we might 

 succeed in finding the larva still there, a dull 

 whitish creature with no legs, but with a well- 

 defined head, his jaws being kept constantly at 

 work devouring the green portion of the leaf, 

 which imparts a greenish tinge to the dorsal vessel 

 running along the centre of its body (fig. 173). This 

 larva, when full fed, quits the leaf and descends to 

 the ground which it enters, and there spins a sub- 

 terranean cocoon, coated with particles of earth ; 

 within this cocoon it changes to the pupa state, 

 and it is not till the following month of May that 

 the imprisoned moth makes its escape and delights 

 to fly round the oak twigs in the sunshine. It is 

 a pretty glossy creature, about half an inch in the 

 expanse of the wings ; the fore wings are of a pale 

 golden green, with a faint appearance of two paler 

 spots, one on the inner margin beyond the middle, 

 the other midway between this and the tip of the 

 wing ; and scattered over the surface of the wings 

 are a few purple scales : the hind wings are rather 

 transparent pale purplish. This we call Micropteryx 

 subpurpurella . (There arc many species of this 

 same genus Micropteryx, which make similar mines 

 in birch-leaves.) The miners in the leaves of oak 

 are so numerous, that we frequently find several of 



the same genus happen to be oak-feeders, and it 

 is by no means uncommon to find that a single 

 oak leaf is mined simultaneously by half a dozen 

 different species. In the month of July we may 

 not unfrequently find oak -leaves which have nearly 

 the entire upper surface discoloured by a large, 

 white blotch ; these leaves are not transparent, for 

 the under side remains green as before, and the 

 white blotch is simply the upper skin of the leaf, 

 which has been loosened over a considerable area 

 by the operations of the mining larva within, and 

 which, having slightly shrunk, has caused the under 

 side of the leaf to curve a little upwards so that the 

 leaf no longer remains flat. On examining one of 

 the leaves closely, we shall see near the foot stalk 

 several short, slender, pale tracks running into the 



Fig. 173. Mined Oak Leaf, and Larva of Micropteryx 

 subpurpurella, enlarged. 



large blotch, just as if they were so many little 

 streams running into a large lake ; these are the 

 tracks formed by the individual larva; when young, 

 each of them making a separate path towards the 

 centre of the leaf, where they then proceed to 

 mine a large blotch in common : these larvse are 

 pale whitish green, with a darker green line down 

 the back, and with the head pale brown; when 

 nearly full-fed they become suffused with reddish 

 orange, and ultimately quit the leaf and spin small 

 cocoons, in which to undergo their change to the 

 pupa state. In a few weeks the elegant little moth 

 makes its appearance ; the expansion of the wings is 

 rather more than a third of an inch; the fore wings 

 are of a glossy brownish, with four oblique white 

 streaks from the costa, edged towards the base with 

 dark fuscous, and with two short whitish streaks on 

 the inner margin : this is called Corischtm Brongniar- 

 dettum (fig. 176). 



