is usually carried out in one of the four following methods : firstly, 

 by addition of silk only, as, for example, Coleophora ibipennella ; 

 secondly, by the addition of portions of food-plant and silk, as 

 C. albitarsella ; thirdly, by addition of portions of food-plant without 

 visible silk, as C. lineolea ; and, fourthly, by quitting the small case 

 and making an entirely new larger case, as C. hemerobiella. The 

 individuals of a species invariably construct and enlarge their cases 

 by the same method. I have bred many specimens of C. ihipennella 

 and C. anatipennella^ both of which increase their cases by the 

 addition of silk only, but how they do it I have not yet observed. 

 The cases seem to grow gradually. I believe the larva spins inter- 

 mittingly at the margins of the case. \V^hen the larva of C. albitar- 

 sella is about to enlarge its case, it first, by means of silk, firmly fixes 

 the case on to the edge of a leaf of the food-plant, usually ground 

 ivy {Glecotna hederacea). It then mines out a more or less rhomboidal 

 space at this edge of the leaf, cuts out and joins together the two 

 then empty cuticles, which are already fast to the case, and eventually 

 lines the cuticles with silk. This is the way in which the case is 

 lengthened. As the larva grows not only longer but also stouter, it 

 requires at the same time to widen its case, or rather to make it 

 deeper. This is effected by cutting open the lower seam or margin 

 of the case and extending the margins by silk to the required depth. 

 This silken extension is pale in colour at first, but becomes darker 

 with age, though frequently a sharp keel of whitish silk may be seen 

 in quite old cases. At first sight the case of C. albitarsella appears 

 homogeneous, but if examined with a lens the added leaf-segments 

 may be easily observed, as well as the hairs which grow on their 

 surface, while the keel of the case will be found to consist of silk 

 only. In fact, the complete case really is formed of a silken tube 

 strengthened by segments of leaf cuticle laid saddle-wise in a row 

 over the back. 



C. lineolea, a common species feeding on the black horehound 

 {Ballota nigra), when about to enlarge its case, also fastens it 

 on to the edge of a leaf where the larva mines out a comparatively 

 large space-.-in fact, as far as it can conveniently reach without quitting 

 the case. This large piece is then added to the case, the larva 

 cutting it out of the leaf, and thus the case becomes both lengthened 

 and widened at one and the same time. The dentations of the leaf 

 included in the portion mined become the ornaments of the case. 

 The larva as soon as the new portion of the case is cut out from the 

 leaf walks off ; it does not wait to complete the lining. After the 

 larva has fed the case gradually becomes opaque, as though the 

 larva required a certain amount of food for the secretion of sufficient 

 silk to complete the lining. This method of case enlargement is 

 adopted by many species, such as C. onosmella, C. bicolorella, C. 

 viminetella, etc., but there is another method of case enlargement by 

 leaf fragments, which we can very well observe in such species as C. 

 juncicolella, C. genista, and C. saturatella. These species, feeding 



