24 ON ENTOMOLOGY. 



of the stones, indeed, may be accounted for from this species living- in 

 streams where, but for the weight of its house, it would to a certainty 

 be swept away. For this purpose it is probable that the Grub makes 

 choice of larger stones than it might otherwise want, and therefore also 

 it is that we frequently find a case composed of very small stones and 

 sand, to which, when nearly finished, a large stone is added by way of 

 ballast. In other instances, when the material is found to possess too 

 great specific gravity, a bit of light wood or a hollow straw is added to 

 buoy up the case. It is worthy of remark, that the cement used in all 

 these cases is superior to pozzolana (a cement prepared of volcanic 

 earth or lava), in standing water, which is indissoluble. The Grubs 

 themselves are also admirably adapted for their mode of life, the portion 

 pf their bodies, which is always enclosed in a case, being soft like a 

 Meal Worm or Caterpillar, while the head and shoulders, which are for 

 the most part projected beyond the door-way in search of food, are firm, 

 hard, and, consequently, less liable to injury than the protected portion, 

 should it chance to be exposed. We have repeatedly, says Rennie, 

 tried experiments with the inhabitants of those aquatic tents to ascer- 

 tain their mode of building. We have deprived them of their little 

 houses, and furnished them with materials for constructing new ones, 

 watching their proceedings from the laying the first stone or shell of the 

 structure. They work at the commencement in a very clumsy manner, 

 attaching a great number of chips to whatever materials may be within 

 their reach, with loose threads of silk, and many of these they never use 

 at all in their perfect building. They act, indeed, much like an unskil- 

 ful workman, trying his hand before committing himself upon an in- 

 tended work of difficult execution. The main intention is, however, to 

 have abundance of materials within their reach, for after their dwelling 

 is fairly begun they shut themselves up in it, and do not again protrude 

 more than half of their body to procure materials ; and even when they 

 have dragged a stone, a shell, or a chip of reed within building reach, 

 they have often to reject it as unfit for use. 



Before we began to study the habits of insects, says Rennie, we 

 found upon a lilac twig in the neighbourhood of London a singular pro- 

 duction, which we took for a very delicate Fungus, and supposing it not 

 to be common we carefully preserved the specimens ; but we have since 

 learned, with no little surprise, that these are the eggs of the lace- 

 winged Fly, (Chrysopa Reticulata). Reaumur says, that several 

 naturalists have described them as Fungi, which is not to be wondered 

 at, for they consist of a small oval greenish white head, similar to the 

 apple mould, with a white transparent stem, more than an inch high, 

 not thicker than a human hair, but much more stiff and rigid. About a 

 dozen of these eggs are deposited in a single and sometimes in a double 

 line upon the leaves and branches of elder, and other trees and plants 

 abounding with aphides, upon which the Grubs feed when hatched. The 

 footstalks of these eggs are formed by the mother Fly attaching a 



