A. N. Cheney, « Sea and River Fishing, Angling Notes, Caddis Worms », Forest and Stream, New York, vol. 50, n°18, 26 mars 1898, p. 247
A friend who had a trout lake in the Adirondacks told me that his keeper had noticed when a hole was cut in the ice that a bug or worm came to the opening in great quantities, and he desired to know what it was, as he had planted fresh-water shrimp in the pond, and he hoped the bug or worm of his keeper would prove to be shrimps.
I asked him to send me specimens, and soon afterward I met him in Albany one evening, and he handed me a bottle, tightly corked, containing what I recognized at a glance as the larvae of caddis fly, with movable case, for some caddis flies have movable cases and some fixed cases- the latter often observed on rocks in the water, if one takes the trouble to look for them. The bottle was passed around for the contents to be examined by several gentlemen in the club where we had met, and I then put in my bag and the same night went to New York.
The bottle was given to me in the evening, and I did not make a close examination of all that it contained, but I was quite sure that there were several specimens in the bottle. It was several days before I again looked at the contents of the bottle which had been all the time in my bag. When I did I was surprised to find but a single larva with an enormous case. The bottle had not be out of my bag, and the cork had not been removed after it came into my possession. My surprise was so great that I wrote to my friend asking if he knew positively how many caddis worms he had placed in the bottle. He said three or four, certainly three, and he thought there were four. This agreed with my recollection of what I saw at a hasty glance, and if true one caddis worm had eaten two or three others and had thus added the materials of their cases to its own- this in spite of the fact that the caddis worm is generally supposed to be a vegetable feeder. There were bits of case material in the bottom of the bottle, but no sign of more than one larva.
I took the worm from the bottle and pulled its case into bits and put worm and the materials of which the case was made back in the bottle, and in two hour’s time by the watch it had constructed a new case for itself, which practically covered its body ; but the case was thin in places, and not as long as before. At the end of two hours darkness came on, and my eyes were tired with watching the construction of the case (with naked eye and with a mgnifying glass), and I put the bottle away until the next day. Early in the morning the thin places in the case had been built upon and strengthened and the case lengthened, and I again sat down to observe the building of the case, for the worm was at work actively.
The materials of which the case was made consisted of bits of decaying bark and twigs, and green grasses, etc., all approximately of the same length. Some of the materials floated on the surface of the water and some settled at the bottom. The worm seized a bit of bark or other material in its mouth, assisting the opération with its feet, of which it has six on the anterior portion of its body, and apparently covered it with a secretion from one end to the other, and thus placed it in the case, where it remained. The secretion is really silk, and with this silk the material of the case is held firmly together. If the bit of twig, bark or grass was smooth and straight it was quickly fitted in place, but if irregular in shape it required a long time to fit the material to the satisfaction of the builder. One piece of bar kwas in shape like a letter Y, and to fit that particular addition took longer than half a dozen of straight pieces. It was tried in one place and then in another at the end of the sheath, tube or case ; it was turned over and over and turned end for end until my eyes ached from watching the opération ; but finally it was fitted and made fast. The Y-shapped piece of bark was for a brief moment of time taken by the worm in its mouth and manipulated with its feet as in the first instance, when i twas coated with silk, but wheteher for the purpose of spinning more silk to add to it I could not determine. One piece of green grass was taken by the worm apparently covered with spun silk , and then rejected without an attempt being made to ad dit to the tube. This was just before dark, and the next morning this same piece of grass was fixed to the sheath.
In adding material to the case the worm would at times extend itself more than half its length from the tube, and it seemed to be able to turn completely around on a longitudinal axis as it worked around the edges of the sheath, adding or fitting materials. this seemed the more strange as at the posterior end of the worm are two hooks which hold it firmly in the sheath or tube, and it would appear that they must prevent the worm from turning completely around. All during the operation of silk spinning and fastening the bits of material on the tube and extending its length the posterior part of the case where the material was thin was worked in convolutions, or perhaps oscillations is the better word, as though the worm’s silk factory was in full blast. When the heavy materials at the bottom of the water were added to the case the worm rose to the surface and added most of the floating materials, and then settled to the bottom, and for hours remained inactive except that occasionally it protuted its head. While at work and when more than half out of its sheath I noticed that the worm appeared to have light-colored filaments around the body back of the head and legs, and I assumed these to be a part of the silky lining of the tube ; but in this respect I must have been in error.
I cut the case open and examined the interior, finding it smooth and even as possible, the parts cemented with silk, but the light-colored filaments on the worm had, after death, lost their distinguishing color, and my glass was not strong enough for me to detect what they were, except that they were part of the worm and not part of the case lining. So I assumed that they must have been what scientists would have described as « external organs of respiration or membranous filaments covering the abdominal segments. » So we will let them go at that. I hope to get more caddis worms for observation (for I made all the use I could of my one poor spécimen), and find out for sure if they do prey upon one another, although the corked bottle would have seemed to settle the matter and it would if I were absolutely sure how many worms were put into the bottle.
Now as to the value of the caddis worm for fish food. In all stages of its development it is one of the very best fish foods. The illustrations herewith some various forms of caddis cases, composed of various materials-bark, sand, shells, sticks, straws, roots, seeds, etc., the caddis worm and a caddis fly. I say a caddis fly, for three are a number of species of caddis flies. In the illustration the fly is shown with wings extended, but at rest the wings fold lengthwise with the body.
Prof. Barfuth of the University of Bonn, examined the contents of the stomach of six trout, and found in the first four caddis cases ; in the second 136 cases ; in the third 585 cases ; in the fourth 116 cases, in the fifth 186 cases ; and in the sixth 115 cases. This will show what an important item of food the caddis fly is in its larval stage, and every fisherman who has seen the fly bursting its pupa case at the surface of the water,and rising in clouds, will understand how it furnishes vast quantities of food in its fly stages. The larva can easily be transplanted to water where it is not found, and as it is as rich in quality as it is abundant in quantity it will pay for transplanting to less favored waters ? While it may be true that the larva furnishes a greater amount of fish food than the perfect fly, from the very nature of its accessibility in the water, it should not be forgotten that in the fly stage the caddis fly, May fly, etc., bring trout up from the depths to feed at the surface, and thus are educated to become fly-taking fishes, to the joy of the fly-fishermen.
- N. Cheney, « Sea and River Fishing, Angling Notes, Caddis Worms », New York, Forest and Stream, vol. 50, n°18, 26 mars 1898, p. 247