John Ellor Taylor, Half-hours in the green lanes : a book for a country stroll, Londres, W. H. Allen, 1884, p. 41-45.
Fishes, the larvae of dragon-flies, and water-beetles have a sharp recollection of the juiey sweetness of a caddis-worm deprived of its shell ? You can hardly get a more taking bait for fresh-water fish, than such a denided larva. Hence the absolute necessicity for such a protection as is obtained by forming a case of dead shells, sand leaves, twigs, &c., which more than compensates for the natural softness of the body. The head and the first three segments of the body are hard and horny- a most useful fact in theeconomy of these creatures, seeing that thses are the parts necessarily required to be thrust forth in obtaining food. The rest of the body is soft, and at the extremity are a series of hooks by means of which the caddis-worm can take firm hold of its dwelling. The swelling or humps, on the body, which fill the case, help also to prevent the body being forcibly dragged out. In looking out for these interesting objects, you will not fail to find one species, the Phryganea grandis(Fig. 25), whose case is invariably formed not of shells, but of pieces of leaves and other vegetable matters so cemented together that they form a cylindrical tube. You will notice that the pieces are arranged spirally, either from left to right, or from right to left, generally the former. The tubes are of nearly equal diameter throughout, and the larva of this species has the power of turning itself inside, and thus of presenting its head at either end as it may wish. Not less common than this species of caddis-fly, are the larvae of another genus, named Limnephilus, or « pond-lover. » One of them (L. rhombicus,Fig. 26) uses pieces of moss, cut lengths of rushes, grass, etc., and arranges them in a transverse and oblique directions, so as to form quite bulky masses. Another common species (L. flavicornis) is not at all particular as to what materials it uses in forming its cases, as the following sketches will show. Shells are employed very abundantly, and most of the caddis-worm cases to be met with in any ditch or tarn, are the work pf this particular species. Indeed, the flavicornisseems to be exceedingly capricious in its selection of building materials. At one time it will choose only seeds, at another only shells or grains of sand. The shells are often fastened together even when their inmates are yet alive, and the latter have to put up with this forcible captivity till such time as the larva shall be transferred to its next or winged stage of existance, and the cementing material binding the elements of its former case together, shall be dissolved away.
Another common form of cadis-worm case is made by an allied species L. lunatus, which , like the species of an allied genus, Anabolia nervosa, makes its tube of fine sand, or the equally fine fragments of fresh-water shells. In both these species, the case has attached to it smal twigs or other pieces of wood, as balancers. These twigs often extend far beyond one end of the tube. In hunting for these « small deer », it is more than probable you may come across another species of caddis-worm called Limnephilus pellucidus (Fig.35), whose case is formed of entire leaves, or large pieces usuallyof willow or poplar. Sometimes, it is composed of pieces cut out from the stems of bulrushes, etc., and flatly laid over each other, so as to form broadish masses. In the interior of theses is the slender tube containing the larva. The leavers, etc., form a capital protection, and you have to pull the pieces quite from each other before you can fully decide that they were formed as worm-tubes. We have also caddis-cases of yet other species, with straight or curved tubes, sometimes gradually tapering to one end. Such are the cases of Sericostoma, Setodes, etc., They are formed of sand, or very small stones, neatly cemented together. Some species of Steodes make delicate little tubes, entirely formed of silky secretion, without any admixture of extraneous objects. Not uncommon in ditches and tarns, is the caddis-tube of the Molanna angustata (Fig. 38). It will be met with most abundantly in ponds having a sandy bottom. The tube is long, broad, and rater flattened, and his composed of fine sand grains cemented together. The upper surface, at the front end, projects over the larva, so that it forms an ingenious covering whenever the larva is forced to protrude its head in searchj of food. These larvae generally live on vegetable matters, although they have been said to be not indifferent to the ova of fishes, etc., The mechanism of the tubes of caddis-worms is geologically speaking, very ancient ; for similar cases are found in such abundance in the Miocene strata of Central France, that actual rocks are composed almost wholly of theur remains.