But what are these singular moving objects ?

AnonymeThe Methodist new connexion magazine and evangelical repository, Londres, William Cooke, 1855, p. 196.

But what are these singular  moving objects?

They look like bits of sticks, and yet there is evidently life in them. These are the tubes of a singular grub, well know to anglers by the name of caddis worm, and to naturalists as the larva of the four-winged flies, in the order Trichoptera. These beautifully constructed tubes will amply repay a careful examination. Pieces of reed or grass, or straw, or wood, are cut into convenient lengths, as the work proceeds, each piece is carefully joined and cemented to its fellow, and then, as if by way of finish, a broad is added longer than the rest, to shade the doorway over head, so that the insect may be seem from above. But a more laborious structure is reared by another of these little aquatic architects. In the construction of his cell he makes choice of the tiny shells of young fresh-water mussels and snails to form a movable grotto, and as these shells are for the most part inhabited, he keeps the poor animals close prisoners, and drag them, without mercy, along with him. These grotto-building grubs are by no means uncommon in ponds ; and in chalk districts, such as the courntry about Woolwich and Gravesend, they are very abundant. Raising our eyes from earth upwards, we are owerwhelmed with admiration at the grandeur and magnificence of the Works of the Creator.