Without any regularity

Rev. William Bingley, Useful Knowledge or a Familiar Account of the Various Productions of Nature, Mineral, Vegetable and Animal, vol. II, Londres, Gilbert & Rivington, 1852, p. 502.

Of the larva itself, only the head and six legs are to be seen, the other parts being concealed in a case, which, as in the three examples given in the cut, is sometimes a piece of straw, at others a mass of leaves united without any regularity, while some for mit of pieces of wood all glued together and mixed with small shells or stones ; the construction of these cases, however is very various.