Lettre de Miss M. E. Smee

Elizabeth Mary Smee, « Letter from Miss M.E. Smee », The Annals and Magazine of Natural History, 3e série, vol. 12, Londres, 1863, p. 399-402.

Letter from Miss M. E. Smee

The following letter, relating to the habits of the Caddis-worm (larva of Phryganea), addressed to Dr. Gray by Miss M. E. Smee, was read to the Meeting: -Feb. 19, 1863

“My Dear SIR, – I have ventured to send for your inspection a box containing cases made by the Caddis-worm, the worms of which were collected by myself from that part of the Wandle which runs through our garden at Wallington.

“I found, on examining the natural cases, that they were made of different materials. For instance, some were constructed of small stones finely glued together, others of sticks, and some were formed of sticks and stones combined. Again, some were made of leaves of water-plants, and I observed that others were formed of the shells of creatures which inhabited the same stream.
“As I had never seen or heard of these Caddises before, I felt much astonished that creatures somewhat resembling maggots, and living at the bottom of the river, should live in houses built by themselves, and yet that these houses should differ so greatly in their construction. Indeed I was so interested that I determined, if possible, to discover the capabilities which these creatures possessed of forming different kinds of dwellings under different circumstances. I very much desired to know whether they could construct cases from other kinds of materials, besides those usually existing in the river in which they lived.
“To ascertain the fact, I accordingly turned the worms out of their natural cases, and gave them different substances to work upon; but I found that they had not an equal facility with every material; for whilst with some they formed cases which were attended with good results, with others they entirely failed.
“The worms succeeded well when they were supplied with pieces of glass, amethyst, cairngorm, cornelian, onyx, agate, coral, coralline, marble, shells, jet, brass shavings, gold-leaf, silver-leaf, when existing as small fragments.
“When, however, the worms were supplied with round objects, they invariably failed; and although I have repeatedly tried them with small glass beads and other round objects, I never found that with these they were capable of forming a case.
“But these Caddises also failed to make themselves houses from other causes than that of the roundness of an object; for I found that if these creatures were placed among materials strongly scented, or which contained poisonous matter, not only were they unable to build with them, but in most cases the substances proved fatal to the worms. When I tried them with pine-wood, my Caddises would in a short time become completely stupefied from the turpentine contained in the wood, from which they often never recovered. With pieces of coal, brick, or slate they never succeeded in making a case, although these substances did not cause their death. The reason for their failure I attributed to some kind of odour which might have emanated from these different materials. With painted or varnished objects they also failed. Not every kind of metal was suitable for their buildings; for neither with tin, or lead, or copper did they succeed. I found that if one Caddis was not able to make a case out of any one kind of material, no other Caddis could succeed, although I might try several others with the same material.
“After a Caddis had made two or three houses, I used to give it something fresh to work upon, and often times I supplied it with a totally different material. With these new substances it proceeded to build as quickly as before, constructing its new habitation according to the shapes of the pieces it had then to deal with.
“The maximum amount of artificial cases I could get any Caddis-worm to make was five, the last one being very brittle, the parts being scarcely glued together. After they had built so many houses, if turned out of the last house, they would simply bury themselves and remain in a quiescent state. But I think that if the Caddises were procured early in the year, the number of their cases might be considerably increased.
“It is a most curious sight to see these little creatures building their houses, beginning by cementing a number of pieces loosely together. This is merely used as a foundation for building its subsequent structure; for it is always cast off before the house is completed. After they have laid the foundation, they proceed by lifting up each piece of stone, or whatever the material may consist of, with their feet, turning it on all sides to discover whether it will fit into the space, and if it does not, as is frequently the case, that piece of stone is instantly rejected, and another is tried after the same manner, until they succeed in finding a suitable piece, when it is cemented to the other stones by a secretion which I ascertained proceeded from their mouth.
“When their house is made, the body of the creature is completely encased; their heads and feet alone protruded.
“In their natural state, the weight of these cases varies much. They are twice as heavy, and made of more solid materials, when the creatures inhabit rapid streams than when they live in still waters. The reason of this difference is, I suppose, to enable themselves to keep, by the weight of their cases, at the bottom of the water.
“I noticed that, after the Caddis-worms were turned out of their cases, air-bubbles appeared on the surface of their bodies. If placed under these circumstances in running water, these air-bubbles would cause the creatures to rise to the surface and there float until they died from exhaustion, caused by their hard endeavours to reach the bottom. According to the roughness of the water, so must be the weight of their cases.
“When in the pupa-state, their heads and feet are entirely withdrawn into their cases; and they remain in a dormant state, neither eating nor moving, until they turn into files, their cases being more or less split in the act of transformation.
“I used to feed some of my Caddises whilst in the larva state with small pieces of raw meat, which they ravenously devoured; they would even eat a common house-fly, leaving only the wings, head, and leg; but however hungry they might be, yet they never could be induced to touch cooked meat.
“ I found it was quite necessary for the Caddises to have plenty of food whilst in the larva state, to enable them to have strength to undergo the transformation.
“Trout are the great enemies of the Caddises, as they eat them up, cases and all, in every stage of their existence; but they consider the worms without the cases as especially dainty morsels.
“On the 24th of January this year, I observed that the Caddises were just hatched; and although some were so small that they were only visible with a lens, yet every one was busily employed in making its little house.
“They have grown so quickly that, since that date, they are now quite conspicuous at the bottom of the river.
“The box I send to you contains in the centre the cases made from the various materials I gave to the worms, and encircling the artificial cases are the natural habitations as taken from the river.
“Trusting you will find them worthy of your inspection,
“Believe me to remain,
“My dear Sir,
“Yours faithfully,
“ELIZABETH MARY SMEE.”
“To Dr. Gray, F.R.S.,
of the British Museum.”

“P.S. The Caddises are so excessively pugnacious that I am always obliged to keep each in a separate vessel. If that precaution were not taken, instead of peaceable constructing their houses, a fierce warfare would be carried on between them, which would result in the death of the weakest party. After one was killed, the survivor would set about building its house. I generally kept about thirty small white earthen jars at a time, each being filled with water, and containing a single Caddis-worm, with the particular material of which I wished its house to be constructed.
“The Caddises are provided with two little hooks, situated one on each side of the tergm. These little hooks are curved and sharply pointed. With these they securely fasten themselves in their houses, by which extra strength is given to resist their being torn from their cases. At firs, on account of these hooks, I experienced some difficulty in turning them out of their habitations. Indeed, I was often so unfortunate as to break and consequently spoil their cases; or sometimes, after catching the creature by its head and trying to pull it forcibly out, I have know the creature to retain its hold so firmly by means of its hooks, that its body has been pulled in two rather than it would let go its hooks and suffer its house to be taken from it. At last I found that when a pin was gently pushed into the end of the case, the slight irritation would cause the Caddis to crawl entirely out of its house, and thus I was enabled to preserve the case without causing injury to the worm.”