2QQ I September, 



the leaf, packing the shell behind it with its dejecta. But the point 

 that concerns us at the present moment is, that in the great majority 

 of cases the moth is b\'^ no means indifferent as to where on the leaf 

 she places it. I have noted the matter in 41 different species, in all 

 of which the observations have been many times repeated and on 

 many separate occasions, and in only four of them have I found the 

 position of the egg to be inconstant. Even these four ought perhaps 

 to be reduced to three, if w^e exclude salicis, which is scarcely a true 

 exception. On the rough leaved willows {Salix cinerea and capred) it 

 lays on the under-surface of the leaves, but in the smooth leaved 

 species {S. alha) on the upper-surface : the reason apparently being, 

 that in the former plants, although the leaves are clothed below with 

 a thick woolly covering, the hairs stand on end, and the moth is able 

 to push her ovipositor between and reach firm ground ; whereas in the 

 latter the covering is not only extremely dense, but is also brushed 

 close down upon the surface, and so the upper-side is selected instead, 

 where the hairs are not as thick. In the other 37 some degree or other 

 of choice is shown by the parent insect. It may be merely the 

 selection of one side of the leaf in preference to the other, or the 

 choice may be still more precise and extend to a particular part of it, 

 as the extreme edge, the shelter of a protecting rib on the under side, 

 or the corresponding sulcus on the upper-side. In some cases there 

 is good and sufficient reason for the selection. The larva of apicelJa 

 passes the early part of its life in the stalk of the aspen leaf ; the egg 

 must, therefore, be laid upon the stalk, and there it is that we find the 

 empty shell, at the foot of the small sw^elling produced by the larva. 

 In like manner the egg of intimella must be sought for on the stalk of 

 the Bedford willow {8. HusselUana), or on the upper-surface of the 

 midrib of the great sallow (S. capo-ea^, for this larva also burrows 

 into the stalk or midrib of its food-plant, and only in the latter part 

 of its life extends its mine into the blade. Again, regiella and igno- 

 hilella blotch the lobes of the hawthorn leaves. The mines of both 

 begin as galleries which run along the margin, ensuring by this means 

 the subsequent advance of the blotch inwards, that is, from the margin 

 to the centre, for if it advanced in the opposite direction, then one or 

 other of two misfortunes would be liable to happen ; either the larva 

 might reach the enrl of the lobe prematurely and find its supply of 

 food exhausted, or the flow of sap might be so cut off, that the end of 

 the lobe would wither and die, and the larva run the risk, as before, of 

 perishing of starvation. Hence their instinct leads them to start the 

 body of their mines from the edge. The eggs of both are laid on the 



