The Caddis-worm and its houses

Elizabeth Mary Smee,  « The Caddis-worm and its houses», Londres, The Intellectual Observer : Review of Natural History, Microscopic Research and Recreative Science, vol. V,  , Groombridge, juin 1864, p. 307-317.

Amongst the vast world of animal life which, abounds in such profusion in the rivers and ponds of Great Britain, there are few creatures perhaps which will be found more interesting for observation than those insects which dwell at the bottom of the water whilst they exist in the imperfect or larva state. There are some of them which are doubly curious from their inhabiting houses of their own construction, and in which they may be seen walking about at the bottom of ponds or rivers.

At first sight it might seem highly improbable that larvas of any sort of insect should have the faculty of building houses wherein to dwell, but nevertheless it is perfectly true that there are some which have that power given to them, and so well is it employed, that often very beautiful houses are the results of their labour.

The larvae which form the subject of this memoir, belong to insects of the same order as the dragon flies, namely, the Neuroptera,* and to the family Phryganeide. They are more commonly known as caddis-worms.

The bodies of these so-called caddis-worms are, with the exception of their head, very soft ; in fact, exactly resembling  ordinary meal-worms. They are possessed of six feet, whoso uses, as will bo presently seen, aro employed in more ways than that of merely conveying them from one locality to another. They have also very strong jaws or mandibles, and short antennas, or feelers. At the end off the last segment or telum is situated two little hooks, which are curved or sharply pointed. These little hooks are strong, and are the chief weapons the larva employ in guarding their houses for their own use, for by them they are enabled to fastemthemselves in their houses, and thus resist the attacks of any enemy who many endeavour to pull them forcibly out of their abodes.

These cases or houses, which the caddis so tenaciously guards, are made of different materials, depending upon the locality in which it lives, and also the kind of substances it is able to procure. For instance, if the caddis inhabits still waters, such as ponds where water plants abound, or gently running streams, it will often use the leaves of those plants, and with them most ingeniously make for itself most comfortable and beautiful. The leaves are in this case arranged in such a manner that it would seem that not only comfort but also beauty of structure is considered. It is quite a curious sight to see these creatures walking about at the bottom of the water encased in these green portable houses, to which are usually attached a piece of stick or a stone to prevent the caddises and their dwellings from rising to  the surface.

Sometimes half a dozen many be seen at one time, and in each there is a slight difference of construction, according to the taste and convenience of the worms. It should be perhaps here added, that aftezr the house is completed to head and legs of the larva are the only part which is visible, the rest of the body being always kept encased in its domicile. But these green houses are not the only linds which are found in still waters. Other kinds may be seen which are made of very small stones, almost as fine as sand, and there are others again which are made up entirely of sticks, their lenght and size varying much.

In rapid streams, as cases made from leaves of water plants, and stones, so small as those just mentioned, would be speedily swept away by the current, we find that they are built of more solid and heavier kinds of materials. In such streams, if made of stones, the caddis cases are much larger and heavier.

One of the most curious of all the different kinds of houses or cases are those which are entirely made of shells of creatures inhabiting the same stream as the caddis-worms. These cases are frequently found to be constructed of shells of the Planorbis, a small snail, arranged in a most grotesque manner. Frequently  the creatures are alive in these shells employed by the caddis in making its house, and then when it walks about it carries the shelled animal, very much to the discomfort of the latter.

Such are the most frequent kind of caddis cases which are found in the rivers and ponds of Great Britain. But it by no means follow that the caddises are incapable of making them from other kinds of materials than those found in the water where they live. Indeed, they are able to employ various substances, although their capabilities for building are limited to a certain extent in regard to the material in its form. This was found by myself, from experiments tried with the creatures themselves. Having felt extremely interested in watching these caddises walking about with their differently constructed houses at the bottom of the water, I felt an intense desire to find out everything about them.

It was noticed that when the caddis was turned out of  its case and placed in asmall vessel of water containing the materials with which it was wished to form another, the larva would construct for itself a new house from those materials, provided they were within the limits of its capabilities.

As soon as the caddis-worms find themselves denuded of their houses, they commence forthwith with the materials that may be given to them, and build new ones, never stopping until the greater part of their bodies are encased.

Coloured glass, when broken up into small pieces, makes an extremely pretty case. The colours may be either sorted or mixed, for in either way the case is extremely pretty. With brooken pieces of glass the caddis builds very rapidly. In fact, I generally found that cases made from that material were constructed more quickly than when the worm was supplied with other substances. Why this was so I do not know ; however, glass is particulary adapted for the caddis to build with. If a case of a better sort of material than glass be desired, i twill be found that amethyst or cairngorn will answer the purpose well. But although the caddises are able to construct from either of these sorts of stones, yet I used to observe that when given to them the houses were always much slower in their constructions.

Cornelian, agates, and onyx are all capable of being adapted for cases, and lokk exceedingly well when finished, especially if used separately. A coral house makes a very grand-looking abode for a caddis, but as it is heavy, care should be taken that the pieces be selected from the most slender and thinnest part of a sprig of coral. Pices of marble broken up into tiny fragments can be successfully employed by the caddis. Shells, mother-of-pearl, when broken into small pieces, or small shells entire, are evy quickly made into suitable dwellings by caddises

I have had cases made from brass shavings, and also from gold and silver leaf. With the two last-named materials the worms experienced considerable difficulty, for they are unable to take up portions separately of gold and silver leaf, and they are obliged to roll themselves up in it in an irregular way.

Another material capable of being made into a caddie case is coralline. This substance forms a very curious dwelling. I had some constructed from pieces of a kind of coralline when dead, or rather when only the skeleton remained of it. These pieces of this dead or skeleton coralline are blanched, and are put together in such a manner that the case has an an appearance as if it had been the work of a basket maker, instead of that of a larva. But perhaps a more singular- looking case than even these wicker-work ones are those which are made from pieces of tortoiseshell, such as fragments of the teeth of a tortoiseshell comb. If these be given to a worm, it will be seen that it will arrange them crossways. In doing soi t will make its house slightly resemble a hedgehog whose bristles are erected. It seems astonishing that there is such a variety of form in the appearences of these different caddis cases. For what can be more unlike each other than cases made from fragments of the teeth of a comb, and that from the pieces of skeleton coralline ?

What also is more extraordinary, is, that the same worm which can build the basket-looking case can also construct the one resembling a hedgehog when its bristles are erected. In fact, if a caddis is able to make itself a case from any one of the substance already mentioned, it is able to build from all of them. For I have tried their capabilities in that way by giving a cadis a certain kind of material to construct its house, and as soon as it was completed I turned it out, and then give the same worm something different to work upon.

With these new materials it would commence building with as much case as it did with the former materials , although consisting of a totally different kind of substance from that which it employed in the formation of its previous case.

Although  these caddises are so wonderful  in being capable of forming cases for themselves of such a variety of structure, yet it is not eVery substance that they are able to employ for building materials. They are incapable of using anything  when existing in acertain form. For instance, although glass is an easy kind of material for a caddis to work with, yet if the form and surface of that glass be smooth and round, as in a small bead, the caddie will be totally unable to make a case from it. In broken glass the pieces arealways somewhat angular, and present no difficulty to the worm.

Generally, I may state that not only round beads, but every object which is rounded in form and smooth in surface, is unfit for building materials, whilst substances with angles and curves are quite fit for the use of a caddis-worm. There are some substances that exhale certain odours, which render them also quite unfit to be used. These scented materials are so highly noxious to the worms, that they often completely stupefy the creatures, and sometimes even cause their death. If pieces of pine wood be placed in a vessel, and if a caddis be kept amongst that wood, in a short time it become stupefied, and would ultimately die if suffered to remain. This stupefaction is caused by the turpentine which is contained in such large quantities in all kinds of pine wood.

Slate is another substance which caddis- worms are unable to employ for their building. I attribute this to a similar cause as that which prevents caddisfrom using pine wood, namely, the odour. In these cases, however, the substances does not cause any injury to the worms. The same obstacle arise with both coal and brick.

Although there are many kind of metals that can be employed by caddis-worms, yet there are some from which they are quite unable to construct their houses, such, for instance, as lead and copper. I have myself repeatedly endeavoured to get a caddis to use these metals just named, but it was always in vain ; although worms would try again and again to build from them, they invariably failed.

It will always bo found that if any caddis is not able to construct itself a house from any kind of substance which might be given to it, no other caddis  could form a house from the same material. Any number of caddises may be tried for that purpose, yet the results are always the same.

It has before been stated that the weight of caddis cases depends upon the locality that is inhabited by the worms, for it is found that the more rapid the streams, the heavier are the cases.

When a caddis is turned out of its house, the whole surface of its body is covered  with air-bubbles. Now, if these creatures are placed under these circumstances in running water, they speedily rise to the surface and float, until at last they die from exhaustion in their struggles to regain the bottom of the water.

This being then the use of the cases to the caddises, let us now see the manner in which they construct them. It is, indeed, an interesting sight to watch them during the progress of their building. The worms commence by placing together a number of pieces of the substances they wish to employ. These are then cemented loosely together, so as to make a foundation for building its subsequent structure. These first pieces that are used as a foundation are always cast off before the completion of the edifice. The cement used by the caddis in fastening the pieces of its house together, is a secretion which proceeds from its mouth. Wit hit the different pieces are fixed together in the most perfect manner. This cementanswers the same purpose to the caddis-worm as the mortar The Caddis-Worm as the mortar which is used by the bricklayer in the construction of his buildings. After the foundation has been formed, the caddice proceeds by lifting up with its feet a piece of the material it :is employing for its building. This is turned on every side, either in order to discover whether the [piece will or will not suit, or else to  find out which is the side that will best fit into the space required for it. If the piece is found to answer all the purposes required by the caddis, it is cemented into the space reserved for it by this secretion, which as I have stated before, proceeds from its mouth. If, however, the piece does not suit the space, that piece is instantly rejected, and another one is taken up by the worm in the same manner as the previous one Was. Sometimes the caddis is obliged to take up several pieces before it is able to meet with one fit for the purpose. This makes the task of building extremely tedious and laborious. Indeed, with the creature’s slender legs it seems marvellous that it is able to take up the diferent pieces with them, particularly when heavy ones are selected, which is the case when the worms inhabit rough waters;

For in those localities the  materials are principally large stones, or else thick heavy bits of wood, which must render the building extremely laborious. The building is continued by the caddis in the manner just described without stopping, until it has succedeed in rearing a house according to its taste. When it is completely finished, the whole body of the worm is encased in it, with the exception only of its head and legs, and these even are capable of being drawn into its building, either for ts pleasure or for their protection at the appearance of danger.

The caddises are exceedingly fond of the houses which they take so much pains to build, and it is often very troublesome to deprive them of their habitations. They fasten themselves into the end of their houses by the means of those two little little hooks which have already been alluded to, and by the aid of which they are enabled to bid defiance to any enemy who might try to denude them of their abodes. When the caddis is once hooked into its case i twill often suffer itself to be torn into two rather than allow itself to be dragged out. The obstinate resistance on the part of these caddis-worms often offers some difficulty when it is wished that they should build another case.

But it will be found that caddises will creep out of their cases, if slightly irritated by gently pushing a pin into the end of their case. By this method both case and worm will escape damage and injury.

Now caddises are able to make more than one case for themselves when former ones are destroyed. When I tried some experiments with them, I found that five was about greatest number I ever obtained from one caddis. The last one was not nearly so strongly or firmly cemented together as the first one.  After the fifth one was made, the caddis, when turned out of it, would invariably bury itself under the heap of the materials given to it without even trying to make another case. It seems that the secretion used for cementing the parts together was entirely used up and failed to be further produced. But although five was found to be the greatest number obtained from one caddie yet it should be stated that if the worms were captured as soon as they were hatched, and experiments tried with them, I believe they would be able to make more than that number. Frequently they did not succeed in making so many as five cases.

I have seen the small caddises just hatched, building their tiny houses as early as the beginning of January ; of course being then very little creatures, the materials they are only able to employ must be of the smallest description, like sand, etc., for with larger or heavier materials they would not have the strength to take the particles up with their then tiny feet. As they grow sot hey must enlarge their house, always building until the creatures cease to grow larger ; but in what way they expand the circumference of their dwelling I have not been able at present to observe.

The time taken for a caddis to construct a case varies very much. With some substances a cadis takes more than double the amount of time and labour that it does with others, for with some materials they finish their work in about twenty-four hours, with others again it takes more than a week to do it. It has been already stated, that cases made from broken pieces of glass, jet, shells, or marble, were very much quicker in their construction than when the worms were supplied with either amethyst, or cairngorm, or coral. A shorter time is always taken in the early part of the season, for as the period approaches for the larvas to turn into the pupa state, they require a much longer time to build.

If it be wished to keep caddisiworms for the purpose of watching these  creatures constructing their cases, i twill be found to be advisable to let each worm have a separate place to work in. They are so extremely quarrelsome towards each other, that if you denude several worms of their houses, and place them together in a vessel of water containing materials for them, you will find that instead of beginning to build they will commence a most deadly warfare with each other, their animosity never being appeased until some one stronger than the rest succeeds in killing them off. After this the survivor will commence his house as if nothing had happened. The best way is to let each caddis have a small jar of river water for itself, and which should contain the substance it is wished its house should be built of. The water should be changed daily, so as to let the caddis have always a fresh supply of  oxygen, and also to keep the materials bright and clean which it employs. When the period arrives for these larvas to become pupas they gradually lose their activity, until at last they withdraw their head and legs entirely into, their cases, and remain in a completely dormant state for a short time until their last transformation, when they burst open their cases, and rise to the surface of the water in their new and glorious forms of perfect flies. They dry their wings and skim along the surface of the water, their instinct leading them to perform their new career as if they had been accustomed to that state of existence all their lives.

The period in which the transformation from larvas into flies takes place does not always fall at the same time at different parts of the country. In the south of England it generally occurs about the middle of May.

The colour of the fly is brown. It is possessed of four wings, which are equally long, and very much resemble network. Whilst at rest the wings are placed longitudinally. It has also long antennae. The flies always keep near the water. Their great enemies in all states of their existence are trout, with other fish, who devour them freely ; the trout even eat cases and all of the caddis ; although they greatly prefer them withou the stones andsticks which cover the bodies, as then they consider them exceeding dainty morsels, and in that condition they are thus found a killing bait by the angler.

But caddis-worms are equally as rapacious as the trout themselves. They have really a tremendous appetite, taking into consideration their size. I have observed that if this was not satisfied they were never sufficiently nourished to be able to undergo their final transformation, but would die whilst existing in the pupa state. When I kept these creatures I used to feed them on pieces of uncooked meat, which they would eargerly seize from my fingers, and ravenously devour.  It used to surprise me to see how much such small animals could manage to get through at a meal. They will also eat a common house-fly, the wings, legs, and head being alone rejected as unfit. But meat, if that be cooked, no caddis will offer to touch, however hungry hem ay be. It is only whilst the caddises are in the larva state that they are so carnivorous. When living in the streams their food consists of the numerous creatures that exist there, as insects, polyps, mollusks, and they have even the reputation of eating the ova of trout.

But after taking into consideration the leathery case and the roundness and smoothness of the ova, and the difficulties which they must present to the caddises, I am inclined to doubt the assertion that they cause in any way their injury.

I have placedthe ova of trout in the same vessel with caddises, but never knew one to  be eaten, and even have know a caddis to incorporate ova into its case. But with the other-named creatures I myself have been an eyes-witness of their rapacity. Indeed, as far as the mollusks are concerned, caddis-worms seem to consider them as extremely delicate food, judging from the amount of them they consume when they can get the opportunity to do so. I will here give a little anecdote to prove this, and also to show in what manner I discovered their rapacity in that way.

I had some fresh-water mussels, belonging to the family Mytilacece, and called the Dreissena polymorpha. They were given to me rather as curiosities, and which I kept in an aquarium, containing, amongst other things, caddis-worms. After a short time I found to my mortification a great number of my mussels were dead, as I at first thought although I was surprised that I never found any trace of the dead creatures, their shells being always open and clean. This state of things went on for a few days, my shells, or rather their inhabitants, vanishing in a most mysterious and unaccountable manner ; until one day I saw a caddis walk deliberately up to one of the mussels, whose respiratory orifices were protruded from the partly open shell of the mussel, which was enjoying itself in the nice bright water of my aquarium, not dreaming that there was any danger so near to it.

Well, as soon as the caddis had reachedclose to the mussel, it seized hold of the siphoned orifices, which are the respiratory orifices of the mussel, and then devoured the poor creature up. Beginning with the part that it first attacked, and continuing its havoc until the shell, or rather the two shells (for mussels are possessed of two shells), were completely emptied. Other caddises were also discovered demolishing others of the same kind of mussel, after a similar manner as that just described.

The mussels which are mentioned here are natives of northern and eastern parts of Europe. They were first discovered in England in 1824, in the Commercial Docks, and have beeb supposed to have been brought to England amongst some timber.

They have been carried to the River Lea, and increades plentifully in the reservoirs and even in the water-pipes of the New River Company in the Green Lanes. By their fertility they have become almost a nuisance, and I may confidently suggest to the New River Company the importation of caddis-worms into their reservoirs as a means for their extermination.

Now after all that has been stated on the variety of struc’tures of caddis cases, it should be borne in mind that however i great may seemingly appear to be the difference  between thedifferent cases, such as between the wicker-work house of the caddis and that which was made from the teeth of a tortoise- shell comb, yet the general design of those house sis identically the same. For instance, if they be compared together i twill be seen that all the cases are made of the same shape, namely, in that of a tube, and that the same smooth surface is found to exist in the interior of those houses. The only difference between them consists in the manner in which the pieces of the material are arranged, and not in the design of the whole. The design upon which the case is madeis derived from instinct, which is implanted into the organisation of the creature by nature, which leads them to construct cases of such a uniformity of plan as was said in an analogous case by Gilbert White in his Natural History of Selborne, that « the God of Nature is their secret guide. » As soon as the creature is hatched it commences building a house without experience andwithout knowledge, and without even requiring to be taught, and which is as perfect in its structure as if it had the most extended experience and the most correct knowledge, and the same plan will also be observed in all instances.
Instinct then does not proceed from the operations of the mind but is something which is implanted into the nature of the creatures as a part of their organization, and which causes them to act upon that idea that has been umplanted.

With respect, however, to the choice of each stone, the caddis is guided by a particular adaptation of each piece for its purpose, and to that extent acts as well as man could do under similar circumstances. Whilst the design of the case is clearly instinctive, as much reason is shown in the choice of materials as man could exercise under the same conditions.

In these pages I have endeavoured to point out simply the principal features of that wonderful instinct which is possessed by the larvae of that order of insects commonly know as caddis-worms. The facts which I have mentioned were all ascertained by trying experiments with them. For, as I have said at the commencement of this paper, the experiments were carried on solely from an intense desire to know what were the capabilities of these curious creatures. But I feel convinced that more can be learnt of them, and it is in the hope that others may be incited to the same object that this account has been written, which contains that which I myself have learnt through my own observations made upon creatures obtained from the streams in our garden at Wallington. That it was attended with great amusement. I need hardly add. Should any one wish to discover more about them, let them try experiments themselves with these creatures. In the month of April they will find in the rivers the caddis-worms in a most active state, each busily employed in building their differently-formed cases.



Description of Plate

-Fig. 1. Case of a caddis, found in the river where the current is slow. It is built of small stones, attached to a long strip of wood, which balances the weight of the stones.

-Fig. 2. Case of a caddis found in rought waters. This is much heavier than the former.

-Fig. 3. Case of a caddis when the larva wasturned out of its former one, and was supplied with the teeth of a tortoishell comb.

-Fig. 4. Case as taken out of the river where the stream is moderate. It is formed of the shells of planorbis aand shells.

-Fig. 5. Case made of jet. It should be added the same larva made five cases from this same material.

-Fig . 6. Case made of the filings of brass.

-Fig. 7. Case made of sprigs of red and white coral, and will be seen to be a heavy one.

-Fig. 8. Case made from broken pieces of different-coloured glass.

-Fig. 9. Case as existing in the river, it consists of small stones and strips of wood, one of which is much longer than the other.

-Fig. 10. Case of caddis made of silver leaf.

-Fig. 11. Case of caddis when the larva was supplied with pieces of coralline. It will be seen that the pieces are put together in such a manner that the case bears a great resemblance to basket-work.

-Fig. 12. Case made when a caddis was supplied with pieces of amethyst.

-Fig. 13. Caddis case constructed of pieces of cairngorm.

-fFg. 14. Case made a willow shavings.

-Fig. 15. Case of a caddis from a gently running stream ; it consists of small stones attached to two long sticks.

-Fig. 16. Case made when the caddis was supplied with red coral. It will be seen that it closely resembles the one which is made of the red and white coral.

-Fig. 17. Case made of broken pieces of green glass.

-Fig. 18. Case formed of cornelian.

-Fig. 19. Case made of broken pieces of shells.

-Fig. 20. Case from the river, which consists of small stones with one stick attached.

-Fig. 21. Case of caddis-worm as taken from the river. There is a cherry stone attached to one side of the case.

-Fig. 22 Case of caddis made of small stones, to which is attached a long strip of wood.