Grotto building

Jammes RennieAlphabet of Scientific Angling for the Use of Beginners, Londres, Willliam Orr, 1833, p. 34-35.

One of the grubs in question form a prety case of whithered leaves glued together lengthwise, but leaving an opening sufficiently large for the inhabitant to put out its head and shoulders when it wishes to look about for food. Another emplous pieces of reed cut into convenient lengths, or of grass,, straw, wood, &c., carefully  joining and cementing,, each piece to its fellow, as the work proceeds ; and he frequently finishes the whole by adding a broat piece longer then the rest to shace his door-way over head, so that he may not be seen by any fish above. Another of these aquatic architects makes choice of the tiny shells are for the most part inhabited, he keeps the poor animals close prisoners, and drags them without mercy along with him. These grotto buiding grub are by no means uncommon in ponds ; and in chalk districts, such as the country about Woolwich and Gravesend, they are very abundant.

One of the most surprising instances of their skill occurs in the structures of which small stones are the principal materials. The problem is to make a tube about the width of the hollow of a wheat-straw or crow-quill, and equally smooth and uniform. Now the materials being small stones full of angles and irregularities, the difficulty of performing this problem will appear to be considerable, if not insurmountable: yet the little architects, by patiently examining their stones and turning them round on every side, never fail to accomplish their plans. In other instance when the materials are found to possess too great specific gravity, a bit of light wood, or a hollow straw, is added to buoy up the case. The grubs themselves are admirably adapted for their mode of life, the portion of their bodies which is always enclosed in the case being soft like a mealworm, or garden-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.