A rare and beautiful example

Anonyme,  « Caddis Worms and Flies » in The Popular Educator : a Complete Encyclopaedia of Elementary, Advanced and Technical Education, vol. VI,  Londres, Cassell, 1888, p. 81-82.

Amongst the almost endless number of objects of interest which meet the eyes of the searcher after brook and river treasures few will be found to reward his investigations more ricnly, or open up a wider field for study and reflection, than the genus of neuropterous insects (Phryganea), to which the so-called caddis-fly belongs.A vast number of species have been described by naturalists as inhabiting the rivers and brooks of england. Some of these families of insects are comparatively local, whilst others appear to be common wherever suitable conditions for their sustenance and support are met with. Not only do the perfect insects or flies of different species vary in colour, tint, etc., but the larvae, who are accomplished buildersintheir way, adopt a style of architecture in accordance with the customs of the family to which the constructor belongs. P. fluviacornis, for example, from the egg dropped by the parent fly to the stil deeps of the brook pool, turns his attention to the collection of tiny fresh-water shells and minute particles of shell-like substances. These, by a process allied to that by which the silkworm forms its cocoon, are, so to speak, spun together. The glutinous filaments of web, as they are given off by the insect, adapt themselves to every inequality of the substance to be secured at the point intended to be next the chamber or tube, in which, when smoothly and evanly lined, the industrious and deft worm will find an abiding place. Shell after shell and particle after particle are thus added step by step the structure, and as the caddis-worm grows so he increases the bulk of his building materials, turning them with his ready claws until they are in a position to suit his requirements. But whilst we admire his constructive talent and skilful selection, truth compels us to state that P. fluviacornis is most dishonest and unscrupulous in his building operations. What should we say of a powerful potentate who, to build for himself a splendid mansion, seized on the dwelling-houses of other people, carried them off bodily, turned them upside down with the inhabitants in them, and then cemented one on the other until the tyrant’s stronghold was complete ? Such conduct, although highly reprehensive in the potentate, is most interesting and curious in a caddis-worm, who is perfectly indifferent as to whether the freshwater mollusk fixed on for building purposes is in his castle or not. If he is, he simply has to travel (from place to place at the will of his captor ; if not, the empty shell is taken immediate possession of, just as any other stray substance would bue.

Caddis-worms kept in a state of confinement, and deprived of the materials which their instinct teaches them to use, will, without hesitation, employ such substances as may be placed before them. Some curious and interesting results have followed experiments tried on the building powers of the caddis-worm. One specimen was, we are informed, furnished with particles of clear, transparent glass, and, as this was the  only substance to be obtained he in a short time constructed his dwelling tube of it. Though the transparent case thus formed every movement of the worm could be closely observed, and at length, on the completion of the tiny coat of crystal armour, the wearer was, with other wormsdiffrently clad, placed in an aquarium with a number of hungry and inquisitive sticklebacks, who at once made an attack on the plump, succulent-looking morsel just fallen amongst them. Like a set of pirates, they dashed at the coveted prize, but, to their confusion, discovered that instead of an unarmed and easily subdued victim they hadrun their stems against a formidable armour-clad, bristling with spikes, and armed at all points. So the pigmy fleet backed astern, and them sheered off in consternation and disgust, to seek more profitable cruising-grounds. Coloured beads, fragments de stained glass, particles of pearl shells, etc., are by the caddis-worm, when restricted in the matter of building material, worked up into tubes, or caddis houses, of the most curious and pleasing character- in fact they become, when vacated by the worm,  natural history specimens which most persons desire to possesss. Figs. 1 , 2 in the annexed illustration represent specimens of P. fluviacorniswhich have made use of materials of their own selection for the construction of their dwellings.

Then we have another noteworthy member of the caddis family in P.  rombira, who may be viewed in the light of a carpenter caddis. Sticks, fragments of bark, and strong splinters of wood, are his favourite materials. These he cleverly joins together, parallel to each other forming a kind of Liliputian fagot in which to dwell. Hence it is that the term fagot-worm has not unfrequently been applied to the whole caddis family. Fig. 3 represents one of these Liliputian log-houses. Then, again, we find a most eccentric worker, whose tribe confine themselves entirely to the use of sharp thorn-like spines of river-side, grass for the construction of their strongholds. These pointed and needle-like bars they lay transversely on each other row after row and tier after tier, in such a way that, as the cavity in the centre is made even and comfortable to reside in, all the points are caused to protrude from the outside. An American log hut is built much after the manner of thispeculiar kind of caddis tube, only that by the backwoodsman the ends of the logs are notched together and jointed, whilst by the worm the pointed spines are united by glutinous silk, and caused to stand roughly out most truly «  like quills on the fretful porcupine ; » and, found as fish are ythe inhabitants of these spiked castles, few care to risk being choked by interfering with them. Fig. 4 represents one of these spike-guarded dwellings.

Stratagem, as well, as the art of fortification, appears to be brought to bear by other members of the ingenious family under considerarion. If was search carefully amongst the water-weeds and lily-roots, we shall find some short thick cuttings of stout grass blads joined at the edges, pefectly green, fresh, and as though snipped from the parent stem. Let us examine them closely, and we shall find that within these fragments of longitudinally-arranged grass blades is a tubular cavity, and in it a worm of retiring habits, who withdraws his head to the secret recess which he has formed for himself, and which no fish of ordinary intelligence would look twice at. Fig. 5 represents one of these grass tubes.

A search amongst the rough pebble stones will not unfrequently be rewarded by the discovery of a tiny trumpet-shaped caddis tube composed entirely of minute particles of river sand. A rare and beautiful example of this trumpet, or rather tusk-like form of tube, is to be found in the British Museum ; it is know as the Dentalium nigrum, from its tooth or tusk-like forms, and almost black colour. Fig. 6 represents one of these whilst Fig. 7 shows the more common tusk-shaped tube found in most English rivulets and streams.

 

 

Anonyme,  « Caddis Worms and Flies » in The Popular Educator : a Complete Encyclopaedia of Elementary, Advanced and Technical Education, vol. VI,  Londres, Cassell, 1888, p. 81-82.