By degrees

Emily Carter & Elizabeth Field, Nature Stories for Little Folk, Londres, Frederic Warme, 1904, p. 48 .

By degrees Libellula grew bolder, and she tried to drag some of the caddis worms out of their tubular houses, which they build so cleverly of sand or clay, with bits of gravel or leaves and twigs glued all over the outside; sometimes they will glue on a tiny shell with the snail still alive inside.