Part 20
The boards should be kept in a frame made for the purpose. It should consist of a top, bottom, and two sides; the back and front should have the frames of doors attached by small hinges, and their centers covered with fine gauze, for the free passage of air; the sides should have small pieces of wood projecting from them, for the boards to rest on; which should be at such a distance from each other that the pins may not be displaced in pushing the boards in or drawing them out. The frame should be placed in a dry, airy situation.
=Braces.= These are merely small pieces of card, cut in the form exhibited, Fig. 36, attached to the butterfly and other insects; and also at Fig. 39. They are pinned down on the insects, to keep their wings, etc., in a proper state, till they acquire a set.
SETTING AND PRESERVING INSECTS.
Of the orders Coleoptera, Orthoptera, and Hemiptera. These are easily preserved.
They are killed by immersing in scalding water, and then laid upon blossom or blotting paper, for the purpose of absorbing as much of the moisture as possible; or they may be placed in a tin box, with a little camphor in it, near the fire, which soon kills them. This is, besides, of considerable effect in their preservation.
Insects of the genera _Gryllus_ (Cricket), _Locusta_ (Locusts), etc., have tender bodies, and are sure to shrivel in drying. The intestines should therefore be extracted, while they are yet moist, and skin filled with cotton, as directed with some of the spiders.
When Coleopterous insects are set with the wings displayed, the elytra should be separated, and the pin passed through their body near the middle of the thorax, as in Fig. 35. The wings are exhibited as in the act of flying, and are retained in this situation until they are quite dry, by the cord braces. The insects of this order should always have the pin passed through the right elytra on the right side, as shown at Fig. 37, that is, it should pass underneath, between the first pair of feet and the intermediate ones.
The legs, palpi and antennæ should be displayed in a natural order on the setting board, and retained in the position by means of pins and braces, as shown in Figs. 35, 37. These must be kept in that state, either longer or shorter, according to the insect and the state of the weather, as, if placed in a cabinet before they are quite dry, they are sure to get mouldy, and will ultimately rot.
Minute insects should be attached to cards with gum, as shown, Figs. 34 and 39, with the legs and other organs displayed. Entomologists generally adapt triangular cards as at Fig. 38, as less liable to hide the parts of the insects.
=Order Lepidoptera.= Mr. Haworth, in mentioning the tenacity of life in the Goat Moth, states that “the usual way of compressing the _thorax_ is not sufficient to kill this insect. They will live several days after the most severe pressure has been given there, to the great uneasiness of any humane entomologists. The methods of suffocation by tobacco or sulphur are equally inefficacious, unless continued for a greater number of hours, than is proper for the preservation of the specimens. Another method now in practice is better, and however fraught with cruelty it may appear to the inexperienced collector, is the greatest piece of _comparative mercy_ that can, in this case, be administered. When the larger Moths must be killed, destroy them at once by the _insertion of a strong, red-hot needle_ into their thickest part, beginning at the front of _the thorax_. If this be properly _done_, instead of _lingering through several days, they are dead in a moment_. It appears to me, however, that insects being animals of _cold_ and _sluggish juices_, are not so susceptible of the sensations we call pain, as those which enjoy a warmer temperature of body, and a swifter circulation of the fluids. To the philosophic mind it is self-evident that they have not such acute organs of feeling pain as other animals of a _similar size_, whose juices are endowed with a quicker motion, and possess a constant, regular and genial warmth.”
Butterflies are soon killed by passing a pin through the thorax. The pin passed through the thorax of small moths generally proves almost instantly fatal to them.
The best manner of preserving the minute species of moths is by pill-boxes, as above stated, each moth being kept in a separate box. We have found the following the best mode of destroying them:
A piece of flat hardwood is taken, and a circular groove cut in it, sufficiently deep to admit the mouth of a tumbler being placed within it. In the center of the wood, pierce a hole about a third of an inch in diameter in its center: place the pill box under this tumbler, with the lid off, and the insect will soon creep out; but whether it does so or not, a match well primed with sulphur is lighted and placed into the hole under the center of the tumbler, which will suffocate the insect in a few seconds. I have also found this an effectual method of killing the larger species of butterflies, and moths. In piercing them, the pin should be quite perpendicular, that no part of their minute frame should be hidden by its oblique position.
The larger insects of this order are set by braces chiefly. A single one should in the first place be introduced under the wing, near the thorax, as shown in Fig. 36, and a longer brace extending over the wings. These should not bear upon the wings, but be ready to rest gently on them, when required. The wings are now elevated to their proper position by the setting needle, and other braces are used as necessity dictates. The feet and antennæ are extended and kept in their places by means of pins, in which operation small braces are also occasionally used.
The French entomologists set butterflies, moths, and sphinges, on a piece of soft wood, in which they have excavated a groove for the reception of the body, as deep as the insertion of the wings. They are otherwise preserved as above directed.
In the larger butterflies, moths, and sphinges, the abdomen should be perforated, its contents extracted, and then stuffed with fine cotton, after having been washed internally with the solution of corrosive sublimate. Indeed, the cotton should also be rubbed with arsenical soap before being introduced, as these insects are particularly liable to the attack of smaller insects, such as the mite.
Several of the moth tribe are extremely liable to change their color some time after they have been placed in a cabinet. This change is frequently occasioned by an oily matter which is common to many of them. This first makes its appearance in small spots on the body, but soon spreads itself over the abdomen, thorax, and wings; and ends in a total obliteration of all the beautiful markings. A method which has been sometimes successfully adopted is to sprinkle all the wings with powdered chalk, and holding a heated iron over it; the chalk absorbs the grease, and may then be blown off by means of a pair of small bellows. Another way of applying the chalk, and perhaps the better of the two, is to throw some powdered chalk on the face of a heated iron, and then put it into a piece of linen cloth, and apply it to the body of the insect; the heat of the iron will soften the grease, and the chalk will absorb it.
Another method is to hold a heated iron over the insects for a few minutes, and then to wash the spotted or greasy places with ox-gall and water, applied with a camel-hair pencil, and afterwards wash it with pure water, and dry it by an application of blotting paper, and when perfectly dry imbue it with the solution of corrosive sublimate. But grease seldom appears where the contents of the abdomen have been removed.
=Orders Neuroptera, Hymenoptera and Diptera.= The Dragon Flies (_Libellulæ_) are frequently very difficult to kill, being powerful and nervous animals. When caught they should be transfixed through the sides, and it sometimes becomes necessary to put braces on their wings to prevent them from fluttering while in the hunting box. They may also be killed sometimes by placing them under a tumbler and suffocating them. Some entomologists put them in scalding water for an instant.
The contents of the abdomen should always be removed from Dragon Flies, otherwise it will become black and shining through the skin, and destroy the beautiful bands with which they are ornamented. They can be stuffed with cotton or a small roll of paper introduced. If these precautions are attended to, the insect will preserve the perfect beauty of its living state.
The other species of these orders soon die after being transfixed. They may be set by braces and pins, as represented in Figs. 35 and 37.
Some of the _Dipterous_ insects are very perishable in point of color after death, particularly in the abdomen, the skin of which is very thin. The only way of remedying this is to pierce the abdomen, and after taking out the contents the cavity should be filled with a powdered paint the same color as the living subjects, which will shine through and give it all the appearance of nature.
METHOD OF RELAXING DRIED INSECTS.
Insects frequently get stiffened before the entomologist has leisure to get them set; and it usually happens that those sent home from foreign countries have been ill set, and require to be placed in more appropriate attitudes after they have fallen into the hands of the scientific collector. They may be relaxed and made as flexible as recently killed specimens by the following simple process, from which they can receive no injury: Pin them on a piece of cork, and place the cork in a large basin or pan of tepid water, and cover the top tight with a damp cloth, taking care that it is sufficiently high not to injure the insects. In most cases a few hours is sufficient to restore them to their original flexibility, so that they may be easily put in their proper positions. In some instances, three or four days are necessary to relax them thoroughly, so as to set the wings without the risk of breaking them; no force whatever must be used with any of the members. When set up, after being relaxed, they must be treated in exactly the same manner as recent specimens.
We must again caution the entomologist to be careful that he applies the solution of corrosive sublimate to all his species, otherwise there is little chance of their continuing long without being attacked by the mite; they ought to be frequently imbued.
Mr. Waterton, who has studied deeply the subject of preserving animal substances, and applied them not only in our own country, but also under the influence of a tropical climate, makes the following observations on the preservation of Insects: “I only know of two methods,” says he, “to guard preserved insects from the depredations of living ones. The first is, by poisoning the atmosphere—the second is, by poisoning the prepared specimens themselves, so effectually that they are no longer food for the depredators. But there are some objections to both these modes; a poisoned atmosphere will evaporate in time if not attended to, or if neglected to be renewed; and there is great difficulty in poisoning some specimens on account of their delicacy and minuteness. If you keep spirits of turpentine in the boxes which contain your preserved specimens, I am of opinion that those specimens will be safe as long as the odor of the turpentine remains in the box, for it is said to be the most pernicious of all scents to insects. But it requires attention to keep up an atmosphere of spirits of turpentine; if it be allowed to evaporate entirely, then there is a clear and undisputed path open to the inroads of the enemy; he will take advantage of your absence or neglect, and when you return to view your treasure you will find it in ruins. Spirits of turpentine poured into a common glass inkstand, in which there is a piece of sponge, and placed in a corner of your box, will create a poisoned atmosphere and kill every insect there. The poisoning of your specimens by means of corrosive sublimate in alcohol, is a most effective method. As soon as the operation is properly performed, the depredating insect perceives that the prepared specimen is no longer food for it, and will forever cease to attack it; but then every part must have received the poison, otherwise those parts where the poison has not reached will still be exposed to the enemy, and he will pass unhurt over the poisoned parts till he arrives at that part of your specimen which is still wholesome food for him. Now, the difficulty lies in applying the solution to very minute specimens without injuring their appearance; and all that can be said is, to recommend unwearied exertion, which is sure to be attended with great skill, and great skill will insure surprising success.”
I am convinced that there is no absolute and lasting safety for prepared specimens in zoölogy from the depredations of insects, except by poisoning every part of them with a solution of corrosive sublimate in alcohol.
Mr. Waterton is of opinion that tight boxes with aromatic atmospheres are not to be depended upon in the preservation of insects. He says: “The tight boxes and aromatic atmospheres will certainly do a great deal, but they are liable to fail, for this obvious reason, viz.: That they do not render forever absolutely baneful and abhorrent to the depredator that which in itself is nutritious and grateful to him. In an evil hour, through neglect in keeping up a poisoned atmosphere, the specimens collected by industry and prepared by art, and which ought to live, as it were, for the admiration of future ages, may fall a prey to an intruding and almost invisible enemy, so that, unless the solution of corrosive sublimate in alcohol is applied, you are never perfectly safe from surprise. I have tried a decoction of aloes, wormwood and walnut leaves, thinking they would be of service on account of their bitterness. The trial completely failed.”
Many entomologists are satisfied with possessing the insect in its perfect or image condition. But it is exceedingly interesting to be able to trace these through their different states of existence from the egg to the perfect insect. Besides, we are certain to produce the insects in the highest state of preservation when we breed them ourselves, and it is besides very interesting to have the eggs of the different species as well as the caterpillar and pupa.
=The Eggs of Insects.= The eggs of insects preserve their form and color in a cabinet, in general, without much trouble. Swammerdam had a method of preserving them when they appeared to be giving way. He made a perforation within them with a fine needle, pressed out their contents, afterwards inflated them with a glass blow-pipe, and filled them with a mixture of resin and oil of spike.
=The Larvæ, or Caterpillars.= The easiest way of destroying the Caterpillar is by immersion in spirits of wine. They may be retained for a long time in this spirit without destroying their color.
Mr. William Weatherhead had an ingenious mode of preserving larvæ. He killed the caterpillar, as above directed, and having made a small puncture in the tail, gently pressed out the contents of the abdomen, and then filled the skin with fine dry sand, and brought the animal to its natural circumference. It is then exposed to the air to dry, and it will have become quite hard in the course of a few hours, after which the sand may be shaken out at the small aperture and the caterpillar then gummed to a piece of card.
Another method is, after the entrails are squeezed out, to insert into the aperture a glass tube which has been drawn to a very fine point. The operator must blow through this pipe while he keeps turning the skin slowly round over a charcoal fire; the skin soon becomes hardened, and, after being anointed with oil of spike and resin, it may be placed in a cabinet when dry. A small straw or pipe of grass may be substituted for the glass pipe. Some persons inject them with colored wax after they are dry.
=The Pupa.= When the insects have escaped from their pupa skin, the skin usually retains the shape and general appearance it did while it contained the insect. It is therefore ready for the cabinet, without any preparation whatever. But if the animal has not quitted its envelope, it will be necessary either to drop the pupa into warm water, or to heat it in a tin case before the fire; the former mode, however, is the best, and least liable to change the colors of the pupa.
METHOD OF BREEDING INSECTS.
=Breeding Cages.= These must be made of oak, or other hard wood, as pine is apt to kill the caterpillars from its strong smell of turpentine. The best form for these is represented in Fig. 32. The sides and front are covered with gauze; a is a small square box, for the reception of a phial of water, for placing the stalks of plants in, on which it is intended the caterpillars are to feed. The most convenient size for a breeding cage is eight inches in breadth, four deep, and one foot in height. It is not proper to place within a cage more than one species of caterpillar, as many of them prey upon each other. Indeed, animals of the same species will devour each other if left without food. The caterpillars of insects, for the most part, will only eat one particular kind of food, so that it is better to have no more than one sort in a cage.
There must be at the bottom of the cage earth to the depth of two inches; this should be mixed with some fine sand and vegetable earth, if possible, to prevent it from drying. The cages should be kept in a cool cellar or damp place, because many insects change into the pupa condition under the earth; so that it would require to be somewhat moist, to prevent the destruction of the animal. The shell or case of the pupa also becomes hard, if the earth is not kept moist; and, in that event, the animal will not have sufficient strength to break its case at the time it ought to emerge from its confinement, and must consequently die, which but too frequently happens from mismanagement.
Some seasons are more favorable than others for the production of caterpillars, and to keep each kind by themselves would require an immense number of cages, as well as occupy much time in changing the food, and paying due attention to them. To obviate this, some persons have large breeding cages, with a variety of food in them, which must be cleaned out every two days, and fresh leaves given to the caterpillars; as, on due attention to feeding, the beauty and vigor of the coming insects will much depend.
The larvæ of insects, which feed beneath the surface of the earth, may be bred in the following manner: Let any box that is about three or four feet square, and two or three feet deep, be lined internally with tin, and a number of very minute holes be bored through the sides and bottom. Put into this box a quantity of earth, replete with such vegetables as the caterpillars subsist on, and sink it into a bed of earth, so that the surface may be exposed to the different changes of the weather. The lid should be covered with brass or iron network, to prevent their escape, and for the free admission of air.
The young entomologist should obtain a cabinet of about thirty drawers, arranged in two tiers, and covered in with folding doors. There is a great convenience in this size, as the cabinet is rendered more portable, and at the same time admits of having another of the same size, being placed above the top of it, as the collection increases, without injuring the uniformity, and thus the drawers may be augmented to any extent. It is immaterial whether the cabinet is made of mahogany or oak; sometimes they are constructed of cedar, but seldom of pine, or any other soft wood. Small cells must be made in the inside of the fronts for camphor.
=Corking of Drawers.= The simplest way to get the cork is to purchase it of a cork-cutter, ready prepared, but it will be much cheaper for the entomologist to prepare it himself. In this case, it should be cut into strips of about three inches wide, with a cork-cutter’s knife, to smooth the surface and to divide it. The strips should be fixed in a vice, and cut to the thickness required with a fine saw; but grease must not be used in the operation, as it will not only prevent the cork from adhering to the bottom of the drawer, but will also grease the paper which should be pasted on its surface. The black surface of the cork should be rasped down to a smooth surface. After having reduced the slips to about three quarters of an inch in thickness, the darkest, or worst side of the slip should be glued down to a sheet of brown, or cartridge paper; this should be laid on a deal board, about three feet in length, and the width required for a drawer or box; a few fine nails, or brads, must be driven through each piece of cork to keep it firm and in its place until the glue is dried; by this means, sheets of cork may be formed the size of the drawer. All the irregularities are filed or rasped down quite to a level surface, and then polished smooth with pumice-stone. The sheet, thus formed and finished, is glued into the drawers. To prevent its warping, some weights must be equally distributed over the cork, that it may adhere firmly to the bottom of the drawer. When quite dry, the weights are removed, and the cork covered with fine white paper, but not very thick. The paper is allowed to be quite damp with the paste before it is placed on the cork, and when dry it will become perfectly tight.
Insect cabinets should be kept in a very dry situation, otherwise the antennæ, legs, etc., will become quite mouldy. The same evil will ensue if the insect is not perfectly dry before it is placed in the cabinet.—Should an insect be covered with mold it can be washed off with a camel’s hair pencil, dipped in camphorated spirits of wine; in which case, the insect must be dried in a warm airy situation, before being placed in the cabinet.
There should always be plenty of camphor kept in the drawers, otherwise there is great danger to be apprehended from mites; where these exist, they are easily discovered by the dust which is under the insects by which they are infested. In which case, they must be immediately taken out, and rubbed clean with a fine camel’s hair pencil, and well imbued with the solution of corrosive sublimate, and then placed near a fire, taking care, however, that too great a heat is not applied, as it will utterly destroy the specimen. The butterfly, sphinx and moth tribes are extremely liable to the attack of mites, and should, therefore, be frequently examined.
SHELL FISH, TO PRESERVE—AND THE ART OF POLISHING SHELLS.
Cuttle fish, and all other molluscous animals, can only be preserved in spirits. The same observation applies to the animals which inhabit that numerous tribe called Testaceous Shells. They must be detached from the shells, and put into spirits, while the shells themselves must be preserved, independent of the animal.
Shells naturally arrange themselves under three distinct heads: Marine, Land, and Fluviatile, or Fresh Water.
Marine shells are only to be expected perfect, when procured in a living state. The way to extract the animal is to pour some warm water on it; but, if too hot, it is liable to crack the shells. When the animals are dead, they can easily be pulled out with any hooked instrument, or fork, or if the animal is small, by a common pin. This applies to all marine shells; whether univalve, bivalve or tubular. It is of great consequence to preserve the ligament of bivalve shells entire, so that the valves may not be separated. The animals of land and fresh water shells are killed by the same means, only that the water requires to be very hot.