Anonyme, The Christian Miscellany and Family Visitor, Londres, John Mason, 1875, p. 377-379.
Common as is the insect called the caddis-worm in many of our ponds and streamlets, and therefore know to many people, I can scarcely exclude the mention of it from this series, as it furnishes such a curious instance of building under water. It was become better know of late, throught the general introduction into parlours and conservatories of the aquarium, or aquavivarium, wherein fresh (or salt) water plants and animals can be kept and watched through its glassy walls. And really a globe which may be purchased for a few shillings and placed in the home for frequent observation, may be an object of more interest, and yield more instruction, than such huge affairs as the Brighton or the Crystal Palace Aquaria, especially if we take upon ourselves the agreable task of stocking it with what we get by our own exertions. There are numerous dealers who supply plants and various animal for these aquaria : and it is somewhat amusing to find persons bringing home ads curiosities sundry things which they might probably have obtained, with a small outlay of trouble, by visiting stagnant or running waternear their own dwellings. Until the introduction of these aquaria, I suppose the caddis worm was an object chiefly familiar to the angler, who was certainly not a friend to the insect, for by him it was ejected from its carefully-constructed home and, used as a bait. The entomologist kinder by necessity, as he could not pin the caddis-worm into his collection, when fishing for water-beetles or other insects, if he found a caddis would let it go again. I have written of the caddis-worm in the singular but i might have used the plural, for there many species ? differing much in size, but all like in their habit of forming habitations for themselves, though they choose a great variety of materials. In november or a little earlier, we may meet with the matured flies developed from caddis-worms, whose worm-like existence terminates in a brief life as winged insects. In that state they have received, in some districts where they most abound, the popular name of « Water-moths, « though they are very unlike moths in habit, and pretty nearly akin the rapacious Dragon-flies. But as they float about in the autumnal rains and winds they look rather inappropriate to the season ; more frequently, however, one notices the mat rest on the leaves of water-plants or on trees and palings near streams. But they all are furnished with four wings. Some species are on the wing at an earlied period of the year. Hosts of them are found in the warmer months, clustering about the lamps on the quays of Paris, proving that these insects are affected by that fascination of light which leads many others species to immolate themselves in candles and lamps. The antennae of most of the caddis-flies are beautifully ringed and the wings delicately veined; in repose they fold the wings back and close the antennae together. The parent insect lays her eggs either in the water or close to its surace. Figuier says that the eggs are enclosed in gelatinous capsules, which are something like the spawn of frogs in miniature. This swells, and adheres to stones, or other substances under water.
Ere long the young larvae appear, resembling minute black lines, and at once begin to form cases for their protection from the numerous « perils » that « do environ » juvenile larvae or grubs which have to live in water abounding with other insect’s and fishes. The fresh-water shrimp, by the way, common in brooks and ditches, is decidedly of a carnivorous turn, through in case of need it can be a vegetarian. My own observation do not convince me that Figuier is entirely correct, as I have detected feeding on the leaves of water-plants, not beneath, but just above the surface, Young larvae which I suspect would have proved to be caddis-worms; but unfortunately I failed to rear them.
Sooner or later the caddis-worm becomes a builder, and shows much skill in selecting its materials, as well as in putting them together. If the Young larvae live on leaves above the surface, they are of course comparatively safe; below they have but apoor chance, since the body of the creature is soft, except the head and the front segments, to which the six legs are attached, nor has it dexterity in swimming or agility in running. Its portable dwelling-place is therefore essential to its safety; and supposing we turn one out for the sake of experiment, (not very easy to do without hurting it, as it clings closely to the case by curved hooks along the body,) it is amusing to see how restless and uncomfortable it is until it can regain the old habitation or make a new one. Silk to them is instead of mortar;
It binds together admirably the materials they select. The commonest form of case we find- if not the most abundant, the readiest to our hand, as it occurs in shallow water easily dredged by the net- is constructed of stones and shells; and strangely enough, some of the latter will be be observed to have living occupants.
Those I believe are not so often chosen by the caddis-worm, as are empty shells, because the latter best suit its purpose, since it requires a counterpoise to its weight, which would otherwise be inconvenient. I have seen cases almost entirely formed of shells; but theses are less frequent, as is also a curious abode composed of short sticks or bits of stem, cut into regular lengths, and arranged in a spiral form. Occasionally the caddis-worm adds one or two stones to this, lest it should be too buoyant.
In some ponds one may bring up from the buttom, at a single dip, a score or two of small horn-like caddis–cases, composed entirely of sand. Other cases are constructed of miscellaneous vegetable substance, such as fragments of dead leaves, small seed-pods, etc. these, of course, suit the numerous caddis-worms that live on the stems of floating-plants. And the ingenuity with which these worms adapt their tenements to the circumstances of their life is remarkable.
Thus in a small aquarium a party of caddis-worm was introduced, having cases formed of shells and sand, therefore sufficiently heavy to prevent the insects rising much in the water. Some water-cress that had been growing in the aquarium was consumed by these and other of the inhabitants, and so it happened that only duck-weed remained for them to feed upon. As they were therefore compelled to come to the top, fromtime to time, they added a good deal of the duck-weed to their cases in order to make them lighter. Necessarily, as they increase in size they all have to lenghten and widen their dwellings.
They never voluntarily do this by quitting the old case and manufacturing one de novo. That this abode in open at both ends is obviously its « weak point » yet the health of the creature requires it to be so though a caddis-worm never turns entirely round in its habitation. The food of these insects is various.
They by no means confine themselves to a vegetable diet, but prey on small animal, living or dead. To their discredit it must be stated that they have no hesitation in attacking each other, not does this cannibalism always arise from necessity. With what might be termed sly spitefulness, a caddis will find out the extremity of a neighbour’s case, and make a charge there, rendering it difficult for the attacked caddis to defend itself.