348 Insect Architecture. 



wall ; but it abandoned at the least three or four of these in 

 order to begin others, till at length, as if compelled by the 

 extreme urgency of the stimulus of its approaching change, 

 it completed a shell of shining brown silk, woven into a close 

 texture. Had the grub remained within the narrow clay cell 

 built for it by the mother bee, it would, in all probability, 

 not have thus exhausted itself in vain efforts at building, 

 which were likely to prevent it from ever arriving at the per- 

 fect state a circumstance which often happens in the arti- 

 ficial breeding of insects. This bee, however, made its 

 appearance the following spring. (J. E.) 



Besides silk, the cocoons of many insects are composed of 

 Other animal secretions, intended to strengthen or otherwise 

 perfect their texture. We have already seen that some cater- 

 pillars pluck off their own hair to interweave amongst their 

 silk ; there are others which produce a peculiar substance for 

 the same purpose. The lackey caterpillar (Clisiocampa 

 neustria, CURTIS) in this manner lines its cocoon with pellets 

 of a downy substance, resembling little tufts of the flowers of 

 sulphur. The small egger, again (Eriogaster lanestris, GER- 

 MAB), can scarcely be said to employ silk at all, the cocoon 

 being of a uniform texture, looking, at first sight, like dingy 

 Paris plaster, or the shell of a pheasant's egg ; but upon being 

 broken, and inspected narrowly, a few threads of silk may be 

 seen interspersed through the whole. In size it is not larger 

 than the egg of the gold-crested wren. It has been con- 

 sidered by Brahm a puzzling circumstance, that this cocoon 

 is usually perforated with one or two little holes, as if made 

 by a pin from without ; and Kirby and Spence tell us that 

 their use has not been ascertained.* May they not be left as 

 air-holes for the included chrysalis, as the close texture of the 

 cocoon might, without this provision, prove fatal to the ani- 

 mal ? Yet, on comparing one of these with a similar cocoon 

 of the large egger-moth (Lasiocampa quercus), we find no air- 

 holes in the latter, as we might have been led to expect from 

 the closeness of its texture. We found a cocoon of a saw-fly 

 (Trichiosoma), about the same size as that of the egger, 

 * Brahra's Ins. Nat. 289, and Kirby and Spence's Intr. iii. 223. 



