1884.] 245 



THE LARYA OP HEBYA SERVILLANA AND ITS HABITS. 

 BT JOHN H. WOOD, M.B. 



In the spring of last year I was mucli interested by finding, in the 

 shoots of sallow, a larva that in the end proved to be this species. I 

 am aware that in this I can lay claim to no discovery ; Mr. Bond has 

 already stated that it feeds in sallow, and Herr Anton Schmid says, in 

 a swelling in sallow shoots, but as neither observer, so far as I know, 

 ^as given any particulars, nor entered into a description, I have put 

 together the following notes, which will, I hope, render fairly clear the 

 (Economy of this scarce species, and at the same time enable Entomo- 

 gists to meet with it more readily than hitherto. 



The larva forms a symmetrical swelling, I mean by that an 

 enlargement running equally round all sides of the stem, on the shoots 

 of the broad-leaved sallow {Salix cupreti) in those localities where the 

 shrub occurs among young undergrowth in woods. The swelling is 

 oval in outline, with a circumference, at the widest part, barely half as 

 much again as that of the sound stem ; it measures 8 or 9 lines in 

 length, and occupies the site of a bud, extending, usually, as far below 

 it as above it, and, in most cases, without intei'feriug with its 

 vitality. The circumstance of its position, combined with its gentle 

 outline and moderate girth, render it a somewhat inconspicuous object, 

 and liable to be mistaken for the natural thickening that occurs at the 

 origin of the buds ; this is especially likely to be the case whilst the 

 leaves are on, but in the winter months its recognition is not difficult, for 

 the eye runs over the naked twigs, and quickly distinguishes the sym- 

 metrical swelling caused by the larva from the one-sided one of the bud. 

 In its attack on the tree the insect invariably selects shoots of the year, 

 and when these are vigorous, and such are the ones usually chosen, no 

 injury is done beyond the production of the enlargement, but when 

 weaker shoots are attacked or the mine is placed too near the end, then 

 the part beyond ceases to grow, acquires a stunted appearance, and, at 

 length, dies, becoming in the course of the winter black and shrunken. 

 The point where the larva enters is just where the apex of the bud 

 touches the stem, and this is so generally the case as to lead to the 

 conclusion, that the moth is guided by the bud in laying her egg, and 

 deposits it at this particular spot. At first, communication is main- 

 tained with the outside, and the frass is thrown out and caught on the 

 parts below, but before the larva has ceased to feed, the opening gets 

 closed up, and its site marked by a small brown scar, through which 

 the perfect insect eventually breaks. The mine is cylindrical, short 



