140 THE ENTOMOLOGIST. 



the original Gracilarian mine. Brongniardellum, on the contrary, 

 makes a very large Gracilarian mine, and in its later stages 

 feeds entirely on the parenchyma so exposed, never in any way 

 extending the mine, a habit which is exactly that of Lithoculletis. 

 In separating these two species generically, the name Coriscium 

 I fancy adheres to cuculipennellum. For brongniardellum we 

 have the name Acrocercops, provided by Wallengren, whose 

 diagnosis is founded entirely on imaginal characters. 



In the European Lithocolletis we have a very homogeneous 

 group ; all of which have three Gracilarian instars, and all 

 pupate in the mine. Amongst even these there is great variety 

 of habit, both as to the mine itself, the way in which the larva 

 contracts the thin epidermal cover, and in the pupating habits. 



Lithocolletis typically separates merely the cuticle when in its 

 Gracilarian stage, and thereafter eats the parenchyma so exposed, 

 meantime contracting the cuticular roof by the silk spun on it. 



There are, however, some, and possibly a good many, varia- 

 tions and complications of this habit, of which I may refer to 

 one or two. 



Lithocolletis stettinensis mines in alder leaves. It is stated to 

 mine on the upper side, but in" one respect it might be more 

 correctly described as mining on the lower. It possesses three 

 instars with flat Gracilarian head, and during these it mines not 

 immediately below the cuticle, but at a lower level ; rather, how- 

 ever, above the middle of the leaf, and leaving the ribs of the 

 leaf in the lower half. When, however, in the fourth instar, 

 with ordinary head, &c., it commences to eat; it attacks, not the 

 thick lower layer, but the thin layer of green parenchyma that 

 is attached to the upper cuticle, first eating in a longitudinal 

 line, and as it clears off the parenchyma, spinning silk on the 

 denuded upper cuticle. 



The habit of corylifoliella is perhaps in some degree inter- 

 mediate between this and the ordinary habit. Corylifoliella, as 

 its first effort, enters a similar layer of the leaf to that in which 

 stettinensis mines ; but apparently, whilst still in the first skin, 

 leaves this position and mines beneath the upper cuticle, and 

 continues to work in both these mines, one above the other, for 

 some time, a valvular slit in the veil of intermediate parenchyma 

 affording access from the one mine to the other. It, however, 

 leaves the deeper mine of comparatively small size, and extends 

 the subcuticular one to large dimensions. When it assumes an 

 ordinary head it eats the lower parenchyma, there being in fact 

 no parenchyma attached to the upper cuticle. The round piece 

 of intermediate tissue is separated from its attachment to the 

 floor of the mine, and, dried up to a very flimsy scale, is attached 

 to the cuticle forming the roof of the mine, and is covered over, 

 with it, with the silk that contracts and pulls together the roof 

 of the mine. 



