the stronger building. But the necessary materials are seldom near
at hand: you have to go and fetch them, you have to move your
position, an effort which has been avoided until now. With this
object, the caddis worm cuts its moorings, that is to say, the
rootlets which keep the cylinder fixed, or else the half-severed
leaf of pond weed on which the cone-shaped bag has come into being.

The worm is now free. The smallness of the artificial pond, the
tumbler, soon brings it into touch with what it is seeking. This
is a little faggot of dry twigs, which I have selected of equal
length and of slight thickness. Displaying greater care than it
did when treating the slender roots, the carpenter measures out the
requisite length on the joist. The distance to which it has to
extend its body in order to reach the point where the break will be
made tells it pretty accurately what length of stick it wants.

The piece is patiently sawn off with the mandibles; it is next
taken in the fore legs and held crosswise below the neck. The
backward movement which brings the caddis worm home also brings the
bit of twig to the edge of the tube. Thereupon, the methods
employed in working with the scraps of root are renewed in
precisely the same manner. The sticks are scaffolded to the
regulation height, all alike in length, amply soldered in the
middle and free at either end.

With the picked materials provided, the carpenter has turned out a
work of some elegance. The joists are all arranged crosswise,
because this way is the handiest for carrying the sticks and
putting them in position; they are fixed by the middle, because the
two arms that hold the stick while the spinneret does its work