Removal of Objects.—For the removal of portions of decayed weed, and other small noxious bodies, from the bottom, a glass tube of ¼ or ½ inch diameter, open at both ends, will be found very useful. Place a thumb or finger on the top of the tube, and thrust it down over the object to be removed, then remove the finger, and the matter will rise in it. Lift the tube up to the surface ofthe water, then place the finger on again, and lift the whole away. The advantage of this plan is, that no disturbance is occasioned. A pewter spoon bent to a right angle, and attached to a stick is very useful for lifting up objects that are too large for the dipping tube.
Density of the Water.—Evaporation causes the pure water to escape from the Aquarium, and hence there is a constant tendency to increase of density—in fact, if left alone, the water in the tank soon gets too salt. To prevent this, additions of pure spring or distilled water must be made from time to time, and the amount regulated by a specific gravity bubble, which it would be as well to leave at all times floating in the tank. This instrument registers the density much more accurately than the hydrometer, for it is more delicate in its determination of a balance. I find it expedient to use two bubbles of different specific gravities—one which just floats when the water is sufficiently fluid, and another which just sinks when it is sufficiently saline. The movement of either indicates at once the exact cause, and enables the aquarian to regulate the density to perfection.
Green Stain.—I have never been troubled with confervoid growths in tanks filled with artificial water, though the same water has been in use during periods of from a few months to two years. When it occurs, the mollusks are the natural remedy, the sponge the artificial one. But a strange affection—which I think is most common in spring—is the sudden occurrence of a green turbidity, which destroys the translucence, and for which neither sponge nor winkle can afford a remedy. It is not agrowth on the side of the vessel, but a green stain pervading the water, as if a green colouring matter had been dissolved in it. Mr. Gosse says, "it is vegetable in its origin, and arises from an infinite number of the spores (or seeds) of greenAlgædispersed through the fluid, and held in suspension there." Mr. Gosse further says, "I know of no cure for this," but he quotes Mr. Lloyd's experience as demonstrative of its curability by placing the water "in a dark closet for two or three weeks."
From the experience I have had in this matter, I have no hesitation in saying that thefilterwill be found an instantaneous remedy; the water need not be drawn off at all, but kept filtering through charcoal by frequent filling of the filter from the surface. In May last, a tank of mine became suddenly opaque, though otherwise in excellent order. The collection was valuable, and a disturbance of it would have been attended with risk. I suspended an old flower-pot half filled with fresh charcoal and sea-side grit above it, and set the filter to work. As fast as the filter ran out, I filled it again from the tank, without disturbing anything, and a change for the better was perceptible in an hour. Two days after, the water was as bright as ever, and the stock in the finest possible condition, owing to the brisk æration they had gained by the experiment.
Feeding.—Anemones generally do not require feeding, though the Daisy and the Dianthus will greedily partake of small fragments of oyster and minced mutton, and some other kinds will occasionally eat of the same food; but I cannot recommend the beginner to feed Anemones, for, ina well managed tank, Infusoria are sufficiently abundant to provide them with all they require, and food not eaten soon decays, unless speedily removed. Crabs and prawns positively require feeding, and Madreporesmaybe fed for amusement. Small fragments of the lean of raw meat should be given, or the flesh of a cooked prawn, and twenty-four hours afterwards, the undigested morsels should be removed.
The Syphonis a simple affair enough. In using it, place the short end below the surface of the water in the tank, and apply the mouth to the longer end, and draw till the water flows; it will then continue to flow as long as the short end is kept under water. If you object to promote aquarian science by means of suction, first fill the syphon with water, and apply a finger to each end, and so turn it over, and withdraw the fingers when the short end is dipped beneath the surface of the water in the tank. Mr. Lloyd sells a syphon expressly for the purpose, which the aquarian should possess.
Purchase of Specimens.—There are now many dealers in Aquarian stock, but very few of them supplymarinestock in any variety. I have my readers' interest only at heart when I suggest, that no one should attempt to set up an Aquarium without first paying a visit to the establishment of Mr. W. Alford Lloyd, of No. 20, Portland Road, Regent's Park, where choice may be made from a stock consisting ofthousandsof specimens, supplied, as, the oyster shops say, "fresh every day." Mr. Lloyd was a labourer in the field years before the Aquarium became popular, and his experience, attained by patient study, is now at the service of all who need advice or assistance inanydepartment of the subject.
I have no interest in this matter beyond doing justice to my reader, and beg to add that Mr. Hall, of City Road, has supplied me with marine stock of high character, and that I can recommend him as an honest and intelligent naturalist, though, on marine matters he will not attempt to compete with Mr. Lloyd, for the latter has now the name, the trade, and the organization, and since he keeps everything, so he can supply everything of the commonest or rarest kind, in the highest condition.
THE BOOK OF THE AQUARIUM.
THE WATER CABINET.
CHAPTER I.
CONSTRUCTION OF CABINETS.
Distinctions between the Cabinet and the Aquarium.—The Aquarium has not only spread abroad a love for Natural History, it has also increased the facilities for the study of nature by removing the difficulties which have hitherto attended the preservation, for any length of time, of living specimens of aquatic life. The tank had scarcely taken its place among the resources for pleasureable recreation, and scientific study, when the field of culture extended itself, and every variety of minute life found in the waters, came to have its share of attention for the general profit and delight of the studious. The ordinary tank was found insufficient for the wants of the aquarian, and wherever a large vessel was to be seen stocked with fresh water fishes or marine objects, a collection of small jars, phials, or show glasses, was pretty sure to be found also. In an aquarium, we may group together many dissimilar objects; but it must be evident to the most superficial observer, that when immersed in a large body of water with other creatures, many objects are ill-placedfor examination, especially if we use the microscope. Hence, where the study is pursued with any degree of ardour, some special arrangements are necessary to enable us to keep in a healthy state, and in a way that admits of close scrutiny at any moment, such of the smaller aquatic objects as most commend themselves for beauty or scientific interest. Many beginners, unable to resist the temptation of a jar of beetles, or a collection of larva, and having no other means of keeping them, have placed them in the tank to mingle with the stock of finny creatures, and have thereby either lost the better part of the collection or have been compelled to break up the stock and begin anew. I have already suggested that a few species of water beetles, and aquatic larva, may be safely preserved in an aquarium; but an aquarium is by no means the best place for them, if we wish to study their habits closely, or investigate their mechanism and economy by the aid of lenses: all insects, many mollusks, larva, and other small objects should be kept apart, and a collection of such objects is what we mean by a Water Cabinet.
To the genuine student, there is really more for remunerative study in such a collection than can be found in the Aquarium, though the tank, whether river or marine, will always prove most attractive as an ornament, and because it requires less care and study, will be pretty sure to retain the greatest number of admirers. But the Aquarium and the Cabinet are distinct things; they cannot be combined in the same vessel, and, though a Water Cabinet is but another form, or rather a series ofseparate and smaller aquaria, the uses and economies of each are in a great measure distinct. It is possible to cultivate either without the other, though we should generally expect to find them in company, the Cabinet being a growth or extension of the Aquarium.
Construction of a Cabinet.—Ingenuity, under the control of circumstances, will devise many modes of preserving the smaller specimens of aquatic life, and I shall here describe a plan which I think will be found most generally useful, particularly as it may have a very simple form, and be produced for a very trifling outlay; or may be elaborated into a noble piece of furniture for the adornment of an elegantly furnished room.
The frontispiece represents a series of shelves fitted into a carved framework, the lower portion of which forms a table with drawers. My own cabinet, which is a simple affair of stained deal, is made after the model of the one here represented, but without ornament of any kind; and if I describe its measurements, it may serve as a guide to any who may desire to have one constructed of a similar pattern, though, as a matter of course, the plan admits of endless modifications to suit the means of the student, or the position in which such a cabinet is to be placed.
The table measures nineteen inches from back to front across the centre drawer; and from back to front across the two side drawers, twelve inches. On this is placed a row of seven-inch cylindrical glasses of clear flint glass, and in the centre, behind the jars, stands a twelve-inch bell glass aquarium, to be stocked with choice fishes or superfluous cabinet specimens. The first shelf has abreadth of eight inches to receive a row of six inch glasses; the second shelf a breadth of five inches, and the jars upon it measure four inches in diameter. The top shelf is only three-and-a-half inches wide, and the glasses on it measure three inches across the top, and, two-and-a-half at the base; the jars of this size, in my own collection, are of a tapering form, half an inch narrower at the bottom than at the top, though I am not aware whether such is the usual form of the small vessels. The entire framework has a breadth of about thirty-two inches, and a height, from the floor of the room to the level of the top shelf, of about sixty-six inches.
The breadth and height of the window, in which the cabinet is to be placed, must have the first consideration, with any one who may intend to construct such a piece of furniture; the respective sizes of the vessels must be an after consideration, because, unless the whole be so adapted, as that it shall enjoy a full share of uninterrupted daylight, very little progress can be effected, especially if the growth of the more delicate forms of aquatic vegetation be attempted.
In the absence of a properly constructed set of shelves, a few plain ones may be fitted up in a window. A single strip of deal, on brackets, would afford room for a dozen jars, and in these by judicious grouping, specimens of from fifty to a hundred kinds could be kept, whether for observation by the naked eye, or the microscope.
Glasses.—In common with many aquarians I used phials and confectioners' show-glasses for a considerable length of time; but to preserve the uniformity of thecollection, I should recommend cylindrical glasses of flint glass of the form represented in the engraving. Chancing to unearth a number of such glasses, at the warehouse of the Messrs. Phillips, of Bishopsgate Street, I have since abolished theolla podridaof acid bottles and phials, with which I had previously been content, and now use no other kinds, and I think their strength and clearness of colour must commend them to the student, as the best that can be had for the purpose. The cost of them is a shilling a pound, though common show-glasses may be had at ninepence a pound. If there is much dust in the room where the cabinet stands, a strip of green gauze might be stretched on light cane frames over each row of glasses.
The jars are intended for the reception of separate or grouped species, and the bell glass may be an ordinary aquarium or a receptacle for theomnium gatherumof general collecting. My jars are now (July, 1856,) stocked with minute aquatic plants, beetles of several species, diving spiders, water worms, and mites, larva of beetles and flies, tadpoles in progress of transformation, mollusks of choice kinds, and spawn of all kinds, removed from the tanks. The bell glass contains a miscellaneous assemblage of duplicates of all kinds, such as water weeds for renewal of tanks, tadpoles, leeches, whirlwigs, mollusks, crustacea, and infusoria for the microscope. Species that do not agree, may be introduced to the bell glass for the sake of teaching us the nature and incidents of the strife maintained in the great world out of doors; the battle may there have its way, and we may study destruction with asmuch profit as we may the momentary creation by which the system of nature is maintained in its completeness. In fact, the bell glass is a reservoir into which we may dip for almost anything we want to fill up vacancies in the jars, and in the proper tanks, and to which we may consign the superfluities of a day's collecting; having first assorted, and set apart such as are wanted for separate observation and study.
CHAPTER II.
COLLECTING AND ARRANGING SPECIMENS.
Implements for Collecting.—Most of the ordinary productions of ponds and brooks may be purchased of the dealers, especially beetles, larger kinds of larvæ, water spiders, and tadpoles; but very little progress can be made in the study of this branch of natural history, without personal visits to the fishing grounds.
An hour spent in dragging a brook or pond, will do more towards stocking a cabinet with wonders than a hundred purchases. To the pleasure of an excursion is added the intellectual profit of learning the nature of the haunts, and many of the habits of the creatures obtained; every haul of the net will bring forth from the oozy bottom, an immense variety of the most curious kinds of life.
Nets, for the purpose, are easily obtainable. At least, two kinds will be necessary, namely, a small hand net attached to a short rod, or made to slip on a common walking stick, and a larger one for a long rod, or for hauling with a line. The small net should be of a fine mesh, and for convenience of carriage, may be fitted on a jointed ring of brass, so as to fold together. The large net need not be very fine in the mesh, but it should be very strong, both in the texture and the fittings, and should be lined inside with muslin so as to prevent the escape of the smallest game. Every variety of pond and drag-nets may be obtained of the dealers in fishing-tackle, at prices varying from one to five or six shillings, and of a quality that may be depended on for serviceableness. Some water-cord, a jointed rod or walking stick, and a few earthen jars, or live bait cans, make up the stock of implements, the whole of which, with the exception of rods, may be packed into a basket in which suitable divisions are made, and transported easily. Living in the neighbourhood of many prolific brooks and ponds, I have very little experience in the carriage of specimens, and, indeed, seldom use more than a single jar, and a single net at one time; but I should suggest to those who have to travel a distance for the pleasure of beetle fishing, to provide themselves with a basket or box, made after the fashion of the baskets in which bottles are sent out by vintners, the divisions being fitted with stone jars; and one division left the whole length of the basket, for nets, scissors, a pair of forceps, and a few small phials. Each vessel should have a lid of perforated zinc, toprevent the escape of objects during transit; the jolting of a railway train or coach might otherwise waste the contents. The stone jars used for the purpose, should have a cord attached round the rim of each for convenient handling at the brook side.
Pond fishing.—Every variety of stream or stagnant pond may be fished to advantage; but the specimens obtained from clear running brooks will, in general, differ greatly in character from those which the drag net brings from a dark still pool. Ponds which have formed in gravel pits, are generally well stocked with newts, mollusks, and tadpoles; but for the varieties of the beetle family, old ponds in meadows, and which are the resorts of cattle, are the best; ditches and rank brooks are the usual haunts of caddis worms, diving spiders, polypes, and the more beautiful varieties of water bugs; but every locality has its special attractions only to be learnt by experience.
Supposing that you have made a halt beside a pleasantly shaded brook, with hedge sparrows, robins, and black-caps warbling about you. You prepare by selecting a suitable spot free from brushwood, and where the edge of the water may be reached without danger. The first thing to be done is, to fill a few jars with clear water, and to throw into each a few strips of any common water-weed, of which callitriche is always the best, and most generally attainable. If the water is very foul it will be better to travel a little distance for a supply, because the specimens are wanted as cleanly as possible, and if thrown into clean water when caught, their own motions will tendto cleanse them, and fit them for the glass jars at home. The shore should be fished first, and the operation should be conducted with as much quiet as possible; any disturbance will be sure to drive away many of the livelier creatures. Take a small net attached to a walking stick or short rod, and thrust it out from you as far as possible over the water; then quickly dip and draw it towards you, and land it at your feet at some little distance from the edge of the water. Sort out the contents of the haul into separate jars, though, as you cannot have as many jars as the kinds which the net will bring up, a little judicious grouping will be necessary. Spawn of all kinds may be placed together in the same jar with mollusks, tadpoles, caddis worms, and colymbetes; most beetles must be kept by themselves, on account of their voracity, as must also the several kinds of carnivorous larvæ, such as those of theDytiscus, and the dragon fly, and water worms of the genusNais.
When the sides have been well fished, the deeper water may be operated on by means of the drag-net, and the produce disposed of in the same way.
On arriving home, sort over the jarsseriatim, and dispose of the specimens according to the capacity and arrangement of your cabinet. The glass jars should be each furnished with a few tufts of some growing weeds, and with clear water. Some of the specimens will require to be washed to remove offensive matter, and some few will need a bottom of small pebbles, and a jar nearly filled with healthy vegetation.Anacharis,Myriophyllum,Nitella,Chara,Riccia, and choiceConfervoids, are thebest for the cabinet, on account of the limited space in which they must be kept, and the elegance they impart to the collection. In the larger jars it would be well to keep some tufts of vallisneria in order to propagate it to supply vacancies in the tanks. When the stock has been housed in the cabinet, whatever is left may be transferred to the bell glass for further examination. It would be better not to wash or disturb the refuse weed and sediment of the collecting jars, but to throw the whole into the vase. After a few hours it will settle down, and a lens will assist in the detection of whatever curiosities may swarm out of the refuse weed. Objects for the compound microscope may in this way be obtained and preserved in plenty.
CHAPTER III.
THE STOCK.
I have already indicated some of the varieties best suited for the cabinet, but will here briefly enumerate those which form the leading features of attraction, leaving the development of the collection to the perseverance of the student. The great division ofColeopterawill furnish by far the largest number of showy species, all of them interesting and lively creatures, many of them possessed of great beauty. The ravenousDytiscus marginalisanddimidiatus, with their strong hooked claws, and brightly bronzed elytra; and the pretty, docile, and harmlessColymbetes, with its shining silver breast-plate, and jet black limbs and elytra, must take the first place among the beetles for beauty of form and colour. The large,harmlessHydrous piceus, the livelyNotanecta,Gyrinus, andNepa, are essential to the collection.
Among the larva, those of the Caddis fly should be kept in abundance, on account of the amusement afforded by their strange habits and their remarkable metamorphosis. Larva of the Dytiscus, known as the Water Tiger, of the Dragon fly, the gnat, the May fly, and of the two-winged fly,Stratiomys Chamæleon, the pretty blood-worm, which is the larva of theChironomus plumosus, a very pretty gnat, with feathered antennæ; and the telescope-tailed grubs ofHelophilus pendulus, which, in its larva form, is one of the most curious examples in the cabinet, and, in its imago, is frequently mistaken for the honey-bee.
The drag-net will also bring out many curious water-mites, than which there can be no more interesting subjects for the microscope, or prettier objects for ordinary observation. While writing this, I have before me several specimens of the beautiful mites,Hydrachna geographicaandabstergens(Müller), in a jar ofNitella; they are ever in action, treading the water as if it were air, with a kind of motion that cannot be termed swimming, but rather a walking or dancing, maintained with the greatest ease at any level, or at the bottom of the vessel. Another, and much more showy one, is the bright carmine-coloured miteLimnochares holosericea(Latreille), of which I find an abundance in a neighbouring brook. Its pretty, spidery motions, and vivid colouring, render a jar, containing a dozen specimens, very attractive to the eye of a student of nature.
DIVING SPIDER AND NESTS.
DIVING SPIDER AND NESTS.
The Diving Spiders are amusing, and should be kept in plenty in large jars, well stocked with healthy weed; and the curious Raft Spider may also be preserved in a shallow vessel, closely covered with gauze. Aquatic Spiders are most abundant in clear brooks and ditchesnear rivers; the small tributaries of the Lea, and the dykes that abound in the marshes at Tottenham, supply me with specimens whenever I seek them.
Among the water-worms most easily obtained, the hair-likeGordius aquaticus(Linnæus), and the curiously-formedNais, may be recommended as curious and interesting. The latter requires a bottom of sand in which to burrow, and should be covered with only a few inches of water. When it takes to its new home, it plunges its body into the sand or mud, and extends its telescope-tail upwards to the surface for air, adapting its length to the depth of the water.
The generation and development of reptilia and mollusca may be better studied by the use of jars for the specimens, than by their immersion in the aquarium. Tadpoles, the larva of newts, and the spawn of mollusks, may be preserved in the cabinet for purposes of study, much better than in the tank; each species being separate in a bright and portable vessel, every minute change can be observed, and a lens applied at any time, or the specimens removed for close inspection without difficulty. I find it a good practice to remove any spawn, which may be deposited on the large vessels, to the small jars on my shelves. There the littleLymneaandPlanorbisare developed in hundreds, without molestation; and if increase of Paludina vivipara be required, a jar is at once converted into a breeding tank by throwing a couple into it, with a bunch ofCallitriche, and any vegetable waste from the tanks. In the aquarium, the young mollusks are devoured almost as soon as they are born; and thepleasing spectacle of their increase, coming forth from the gelatinous mass in hundreds, like minute beads of gold, is lost without the aid of the cabinet in which to rear them. The young of most species of univalve mollusks are vagrant in their habits, and the jars in which spawn is hatched should be closely covered with perforated card or gauze, fitting closely by means of India rubber rings.
Since it is unnecessary in this work to give a classified history of the several creatures that may be kept in water-cabinets, I shall devote the remainder of the space at my command to notices of a few of the most attractive and best known species, and to a few hints on the general management of the cabinet.
CHAPTER IV.
LARVA.
The great class of insects comprises many remarkable and diverse forms, among the 560,000 species which Dr. Imhoff estimates to be now known to naturalists. Yet, various as they are, it is by no means impossible to define what are the distinctive features by which this class is separated from those which approach it in conformation and habits. A true insect has the body divided into three parts—the head, the thorax, and the abdomen. It has never more than six legs, and these are attached to the thorax. The segments of the body seldom exceed thirteen in number, one of which forms the head, three the thorax, and the remaining nine the abdomen. Thepossession of one or two pairs of wings gives them their prominent characteristic to the eye, but it is the successive metamorphoses that arrests universal attention, and calls forth the admiration and wonder of mankind. In the progress of an insect from the minute egg to its completed form, we see the most remarkable series of developments which animal life ever displays in all its endless procession of forms—the egg, the worm, the chrysalis, the fly—a strange unfolding, for the first time accurately observed by Swammerdam, who detected, under the wrinkled skin of the disgusting worm, the complete outline of the lovely butterfly.
This metempsychosis may be studied in its several strange details by the aid of the Water-Cabinet. The first condition of the newly-hatched egg is that known as the grub, or caterpillar—scientifically called thelarva. The larva generally bears no earthly resemblance to theimago, or perfect insect, into which it is to be hereafter developed, but leads a life of sensual enjoyment—it eats, eats! it is gluttony concentrated in type and act. It changes its skin several times, slips one coat off and acquires a new; growing, and eating, and changing garments, till, like man himself, it seeks a temporary tomb, from which it is to soar to the skies like a soul liberated. This second form is popularly known as the chrysalis, or aurelia, scientifically called thepupa. In this form the insect remains in a state of complete or partial torpidity for a few days, weeks, or months, according to the particular species.
The day of its deliverance arrives, its bonds burst, andit comes forth "a thing of beauty" to sport in sunbeams, and, for but a brief season, lead a life of joy—
"Fluttering round the jasmine stems,Like winged flowers or flying gems."
But beauty of the high poetic kind is not the inheritance of every member of the class insecta; and the water-cabinet presents us with many that have but analogical resemblances to the typical structure of the moth or the fly, though the naturalist finds beauty in a beetle, and points of profound interest in a maggot or grub.
Since larva are distributed through at least three elements, being, according to the species, inhabitants of earth, air, and water, the breathing apparatus arrests our attention, as constituting a distinct feature in the anatomy of the insect. A caterpillar may be regarded as all stomach, and the cravings of this immense digesting tube easily account for the voracity of larva of all kinds. In the larger animals, the food is elaborated into blood, and brought to the lungs to be oxygenated by means of contact with the air, but the insect does not breathe at the mouth, but at the other end, or by means of tubes arranged along the sides of the body. In a caterpillar there are usually eighteen of these tubes, the orifices of which may be seen in action. These tubes all run into two larger lateral tubes, or wind-pipes, arranged one on each side of the body; and from these lateral tubes innumerable smaller ones diverge, and convey air to the vessels in which the digested food is contained, and thus supply it with oxygen. Swammerdam was the first who successfullyanatomised this class of animals, and to him we are indebted for the microscopic anatomy of grubs, and a revelation of their inner economy generally.
The Dragon Fly,Libellulidæ(Leach), a well-known summer beauty—the mere mention of which is always sufficient to set one's heart beating for rustic coolness, and the hushed music of the beechen shades—is, in its larva form, an interesting object for the cabinet. Between the larva and the imago of this insect, the difference is striking indeed; as a lady, not addicted to scientific studies, once characterised the larva—using Pope's lines—as,
"A monster of such hideous mien,That to be hated needs but to be seen."
But the gauze-winged and gaily-coloured fly merits all the praise bestowed upon it by the French, who call themDemoiselles, so light, fairy-like, and visionary are its form and movements. Scientific writers have applied many descriptive names to it, such asCalepteryx(pretty wing),Puella(girl),Sponsa(bride), andVirgo(virgin). The larva of the dragon fly exhibits, in a very striking manner, the mode of respiration in aquatic insects. It is not an active creature; for though it has six legs, it seldom uses these except in the capture of prey; its locomotion is chiefly performed by the tail in the action of breathing. When thrown into a jar with some fragments of weed and a few light chips, these will be seen to be drawn towards the tail of the creature, by the current occasioned by the absorption of water; and then again driven off, with considerableforce, as the water is again ejected. The quantity drawn into the body by this hydrostatic action must be considerable, since the dimensions of the larva regularly change with the breathing action, the body becoming collapsed when the stream is ejected, and again swelled out with the suction that follows. If it be thrown into water, tinged with cochineal, and then quickly removed again into clear water, the coloured stream will be seen to be projected several inches, and with force sufficient to propel the creature forward by a series of successive jerks.
Besides the act of breathing, then, this anal pump has locomotive uses; and it also aids the creature in obtaining food by drawing minute creatures towards it in a manner similar to those animals which are furnished with cilia.
But the microscope reveals a still more curious fact, in the anatomy of this larva, which has been most faithfully described by Kirby and Spence. The under lip, when closed, entirely conceals the mouth, and it not only retains, but actually seizes, the animal's prey, by means of a very singular pair of jaws with which it is furnished. Conceive your under lip (to have recourse, like Reaumur, on another occasion, to such a comparison) to be horny instead of fleshy, and to be elongated perpendicularly downward, so as to wrap over your chin, and extend to its bottom—-that this elongation is there expanded into a triangular convex plate, attached to it by a joint, so as to bend upwards again and fold over the face as high as the nose, concealing not only the chin and the first mentioned elongations, but the mouth and part of the cheeks. Conceive, moreover, that to the end of this last-mentionedplate are fixed two other convex ones, so broad as to cover the whole nose and temples—that these can open at pleasure, transversely, like a pair of jaws, so as to expose the nose and mouth, and that their inner edges, where they meet, are cut into numerous sharp teeth, or spines, or armed with one or more long sharp claws—you will have as accurate an idea, as my powers of description can give, of the strange formation of the under lip in the larva ofLibellulina, which conceals the mouth and face, precisely as I have supposed a similar construction of lip would do yours. You will probably admit that your own visage would present an appearance not very engaging, while concealed by such a mask; but it would strike still more awe into the spectators, were they to see you first open the two upper jaw plates, which would project from the temples like the blinders of a horse; and next, having, by means of the joint of your chin, let down the whole apparatus and uncovered your face, employ them in seizing any food that presented itself, and conveying it to your mouth. Yet this procedure is that adopted by the larvæ of the dragon-fly, provided with this strange organ. While it is at rest, it applies close to and covers the face. When the insects would make use of it, they unfold it like an arm, catch the prey at which they aim, by means of the mandibuliform plates, and then partly refold it, so as to hold the prey to the mouth, in a convenient position for the operation of the two pairs of jaws with which they are provided. The form of this masked jaw is represented, but not very clearly, in Rennies' "Insect Transformations," p. 164.
TRANSFORMATION OF THE DRAGON FLY.1. The Fly just emerging. 2. The Fly nearly free, and forming an arch. 3. The Fly liberated, and with its body bent, to hasten the drying of the wings
TRANSFORMATION OF THE DRAGON FLY.
1. The Fly just emerging. 2. The Fly nearly free, and forming an arch. 3. The Fly liberated, and with its body bent, to hasten the drying of the wings
When its season of larva life is over, it retires to the bottom of the vessel to repose, and becomes a pupa. When the crumpled form of the gaudy fly begins to expand within, and to knock at the door of its sepulchre, the pupa quits the watery element for ever, and betakesitself to the dry land, or to the slip of cork placed in the jar for its use. There, the apparently painful process of its unfolding takes place, and the fly slowly emerges. The envelope bursts asunder, and the head of the lovely, but bloodthirsty damsel, emerges to the light. Next appear the legs, not in action, but gathered up to the breast, as if in spasm, and, for a time, the effort is suspended, and the helpless, half-formed beauty hangs back her head, as if languid with the exhaustion of pain. Once more she pants for freedom, sighing to sun herself in the blue ether, and another struggle is made. This time she clutches at the pupa case with a convulsive grasp, and drags forth the whole of her delicate body from the grave, and there remains motionless, still clinging to it, as if contemplating the baseness of her origin—for beauty is ever the offspring of the dust. She is free at last—but, ah! how helpless. Her wings are damp, and closely folded, and would not yield to the wish for flight, even were she already possessed of the power to stir them into action. She is on the threshold of a new world—a creature born of the dust, just escaped from the dust; and now as we watch her wings dry and expand, away she goes—a thing of light and loveliness soaring heavenward. Like the mortal ark, out of which the spirit of man escapes, we may, without losing sight of the disparity of the subjects, speak of the chrysalis of the dragon fly as—
"A worn-out fetter, which the soulHas broken, and thrown away."
DRAGON FLIES.a.Virgin Dragon Fly—Calepteryx Virgo.b.Green Dragon Fly—Æshna varia
DRAGON FLIES.a.Virgin Dragon Fly—Calepteryx Virgo.b.Green Dragon Fly—Æshna varia
THE GNAT—Culex pipiens(LINNÆUS)
In the operation of dragging, many curious larva are brought out, and the mud should be searched carefully for them before washing the net for another cast. The larva of the gnat is one of the most interesting of these, and during summer may be obtained in hundreds if a little ofthe brook water be dipped to fill the jar with, and a few light weeds thrown in to supply oxygen. These larva are the produce of eggs deposited in a curious manner.
The gnats repair to the water soon after day-break, and commence an operation of a truly naval kind, such as would have delighted the savage heart of Peter the Great, could he have witnessed it in the midst of his dreams of achieving naval power. In fact, the mother gnats construct rafts of eggs, and each egg is added as a separate timber of the vessel, till a boat-like structure is produced. The skill as well as the necessity of the construction is well tested by the fact that each separate egg would of itself sink to the bottom, whereas being protruded one by one into the angle formed by the hind legs which serve as stocks for the future vessel, and successively glued to each other by the fluid which exudes with them, they gradually assume, under her guidance, a neat boat-like form of about three hundred minute pyramidal eggs.
"The most violent agitation," says Kirby, "cannot sink it, and what is more extraordinary, and a property still a disideratum in our life-boats, though hollow it never becomes filled with water, even though exposed."
The grubs at last come forth, and lead a very merry sort of life under the shadow of the sedges. Placed in the jars they appear at first sight like newly hatched fry of fishes, but we soon detect the segments of their pellucid bodies, and, as might be expected in water larva, they breathe at the wrong end, and hence most of their merry movements are performed between the surface and thebottom; every time they descend they carry with them a minute bubble from the surface. Under a good lens the pretty creature changes its form considerably, and comes out in the pantomime style, with huge horns, goggle eyes, and starched frills of shaggy hair; but then the tail becomes the object of attraction, and we watch the breathing action of the curious funnel which breaks away at an angle from the last segment of the body.
LARVA OF THE GNAT, NATURAL SIZE AND MAGNIFIED.
LARVA OF THE GNAT, NATURAL SIZE AND MAGNIFIED.
Swammerdam first observed that the breathing tube and tail are both anointed with oil, and that if the larva is handled roughly the oil is removed, and the grub "can no longer suspend itself on the surface of the water. I have, on these occasions, observed it put its tail in itsmouth, and afterwards draw it back, as a water fowl will draw its feathers through its bill to prepare them for resisting water." I have now (July, 1856) some thousands of the larva of this and other species of gnats, and they are the most lively creatures in my collection. The flies come off in large numbers, and escape through the open window; or, if the window be closed, they swarm on the glass, and keep up a musical humming, closely resembling that of a swarm of bees at a distance.
LARVA OF STRATIOMYS.
LARVA OF STRATIOMYS.
A more elegant example of this kind of breathing apparatus is seen in the grub of the two-winged fly,Stratiomys Chamæleon. The funnel tail spreads into a beautiful star of thirty distinct rays, and with this structure,the creature suspends itself to the surface of the water, as if it were a ceiling, and as it moves to and fro its changes of position may be noted by the shifting of the dimple on the surface.
In the little gnat,Corethra plumicornis(Meigen) we have some further examples of the peculiar conformation of the larva, to enable it to respire in the water; but the larva is so transparent that it requires an expert microscopist, and an effective instrument to work out the details as represented by Reaumur and Dr. Goring. The larva of this species is plentiful in our brooks, and worthy of close scrutiny by the aid of the microscope. Just now the gnats are abundant in meadows near streams, and to them we are indebted for that soft humming which has been appropriately termed the "music of the wild," and on which good old Gilbert White exhausted his ingenuity to find an explanation. The social communities of these ephemeral creatures are strictly music parties, and whenever we suffer them to assemble about our heads, when rambling in the hedgerows, we are entertained by their fairy-like performances.Expertum est.
The Case FlyPhryganea grandis.—There are several species in the family ofPhryganea, which is the only tribe in the orderTrichoptera, but such strong resemblances exist between the several members of the family that some entomological experience is necessary to enable the student to distinguish them. In an aquarium, the caddis worms are very amusing, and since they thrive there, they are very suitable additions to the happy family. We see them busy at the bottom, adding fragments ofweed, pebbles, minute shells, even if the snails within them are alive, and any small debris that their fingers can seize hold of. Last season I had amongst a large number of cads, one that had his case nearly destroyed by accidentally falling from the table. I removed from him what remained of his case, and threw him into a jar with a soldier plant and a fewLymnea. He set to work to repair his tabernacle, and theLymneahelped him, for they nibbled a plant ofStratoidesinto shreds. These shreds the cad gathered, and every day he added a fresh piece, so that, in about ten days, he appeared in a suit of green, his clothes bulged out to an enormous size, and everywhere studded with points and corners, the most comical sight that could be imagined. Since he could find nothing of a small neat pattern, he took what he could, and became a perfect Jack in the green, nearly an inch and a half in length, and thicker than a carpenter's lead pencil.