Part 38

Such is the apparatus to be provided by the entomological Nimrod: it is not often, however, that it will be necessary, except in distant excursions, to encumber and disfigure yourself with the whole. Even in this pursuit more may be effected by a judicious division of labour, than by grasping at every thing at once; and your acquisitions will in the end be more numerous, and your acquaintance with them more intimate, if at one time you devote yourself to the woods and hedges, another to the plains and meadows, a third to any heaths in your vicinity, and a fourth to the collection of aquatic insects whether from stagnant or running waters:--having thus chosen the scene of action, you may equip yourself accordingly. You will of course, though in pursuit of a particular description of game, not neglect to seize any other insects that fall in your way; but for this purpose it is unnecessary to be always provided with a certain instrument. Dr. Franklin used to say that a man would never make a Natural Philosopher, who, in performing his experiments, could not saw with a gimblet or bore with a saw; and so we may say, he will never make an expert collector of insects, who on occasion cannot fish with his hand or forceps, use his hat or an old letter to beat his game into, or, in the absence of boxes or bottles, contrive to secure his captures in small pieces of paper twisted up. Sparrman, when at the Cape, was wont,--to the no small amazement of the wondering natives, who took him for a conjurer,--to stick his impaled insects round the outside of his hat[1563]: and though I should not recommend such an exhibition in a civilized region, it has often struck me that the cavity of a modern hat, if lined with cork, might be made a very useful receptacle for these animals in a long excursion. Indeed, an active Entomologist is never at a loss for an apparatus, but often makes his most valuable captures when unprovided with other instruments than his hands and eyes. A careful survey of the trunk and branches of trees and shrubs, particularly of the underside of their leaves, seldom fails to detect many a lurking moth or beetle, which may be transfixed or otherwise captured with little trouble by an expert hand. In this way an ingenious collector, who scarcely knew what a net of any kind was, told me he had made his whole collection, which was rather extensive. It is, in fact, only by thus detecting them when reposing, and adroitly shutting them up along with the leaf on which they sit, in a box, that minute moths (whose beauty and freshness the slightest handling destroys) can ordinarily be taken without being injured. The boxes containing them should afterwards be exposed to the action of heat, a low degree of which will destroy them.

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Enough has been said upon the best modes of _catching_ insects:--I shall next attempt to give you some further instructions as to the most effectual one of _destroying_ them when caught, and to point out how you are to proceed with them after they are dead. As I sufficiently rebutted the charge of cruelty in a former letter[1564], it will not be necessary to enter here into that subject.

I have before recommended to you the use of _spirits of wine_, and shall here repeat my recommendation; for after several years trial, I am of Böhm's opinion, who had tried it nine years[1565], that it is superior to any other method; particularly, because it not only effectually kills the insects, and they may be put together into it while you are collecting, if you have no reason for keeping them separate, of all sorts and sizes, in a wide-mouthed phial, without danger of their devouring each other: but when you come home wearied with a long day's hunt, you may let your insects remain in it without injury till the next morning. In collecting beetles abroad, when there is a want of store-boxes the readiest way is to put them into a wide-mouthed bottle or jar filled with any spirit, and send them home in it: some few may lose their colours, or become greasy; but in general they will receive little injury. This method saves room, and avoids the risk of breakage. The derangement which some hairy species sustain from this method may be readily repaired by brushing them with a dry camel's-hair pencil.

When you wish to take the insects you have immersed in spirits out of the phial, you must strain its contents through a piece of muslin, return the spirit into it for future use, and spread the insects _separately_ upon blotting-paper, to absorb the moisture remaining about them. With regard to such as you have in boxes or phials without spirit, these must be immersed in a basin of _boiling_ water. First empty into it the contents of your boxes, and next, those of your phials; giving each, before you take out the cork, a smart rap, that the insects adhering to the latter may drop to the bottom: or you may immerse the phial itself, with the cork in, which soon destroys them, and is the safest plan. This done, with a camel's-hair pencil or feather take them out of the water, lay them upon blotting-paper to dry, and put them by for a few hours till you have leisure to impale and set them.

Those insects that are caught by the _forceps_ would for the most part escape you, were you to attempt to get them out before you had transfixed them. You must therefore do this while the leaves of the instrument are closed; and then opening them, and taking the pin by the point, the head will readily pass through the catgut; and thus you may safely take, and more effectually kill your specimen by pressing it as before directed. With respect to _Lepidoptera_, it is necessary to disable them while yet in the fly-net, immediately after their capture. To effect this, while one hand holds both the rods of the closed net, with the other stretch the gauze so as to confine your insect within a narrow space; bring its wings into an erect position, and prevent its fluttering: which being done, with your finger and thumb give its breast a strong pinch below the wings; and then unfolding your net, and taking it up by one of its antennæ, place it between the finger and thumb of your left hand, stick a pin through it, and deposit it in your pocket-box.

But though nipping the breast will kill many small _Lepidoptera_, the larger ones will live long after it; as will likewise many _Neuroptera_, _Hymenoptera_, and _Diptera_: and besides this, in some _Bombycidæ_ the thorax presents a very conspicuous and interesting character, which renders it desirable, in order to avoid the damage or derangement occasioned by pressure, to transfix them without it. To dispatch these effectually, you will find the following apparatus very convenient. Fix in a small tin saucepan[1566] filled with boiling water, a tin tube consisting of two pieces[1567] that fit into each other; cover the mouth of the lower one[1568] with a piece of gauze or canvass, and place your insects upon it; then fix the upper one[1569] over it, and cover also the mouth of this with gauze, &c.; and the steam from the boiling water will effectually kill your insects without injuring their plumage. There is another more simple mode of doing this, the apparatus for which may be met with every where. Fix a piece or two of elder, willow, or any soft wood, with the bark on, across the bottom of a mug, and on this stick your impaled insects; invert the mug in a deep basin, into which pour boiling water till it is covered, holding it down with a knife, &c., that the expansion of the included air may not overturn it. In two minutes, or less, all the insects will be found quite dead, and not at all wetted. If the sticks do not exactly fit, they may be wedged in with a piece of cork. Professor Peck, who used to put minute insects into the hollow of a quill stopped with a piece of wood made to fit, killed them instantaneously by holding it over the flame of a candle.

Having killed your insects, your next object should be to prepare them for your cabinet. First, place by you a pincushion well stored with lace-pins of various magnitudes and lengths: for most insects those nearly an inch in length, for large ones, those that are thicker and longer, but for _Lepidoptera_, a stouter kind, as _short whites_, are best. Next, take the _Coleoptera_ and _Hemiptera_ that, as before directed, you have laid by on blotting-paper after immersion, and begin your operations, selecting the largest first. The pin should be stuck through the middle of the right-hand elytrum[1570], and about _one third_ of its whole length should emerge above the insect. Some _foreign_ collectors, probably having in view its more convenient examination with a microscope under the glass of a drawer, bring it nearer the head of the pin: while the _English_ ones, on the contrary, studying the most ornamental position of their specimens, leave only enough of the point free to fix them safely in their drawers[1571]. Both these methods are open to objection. When the insect is too near the head of the pin, it is difficult to fix it in your cabinet without bending the wire; and there is danger, without great care, of injuring the specimen when you put it in or take it out. Again: When the legs of your insect rest on the surface they collect the dust and dirt, are very liable to be broken, and the length of the pin above it is inconvenient when you have occasion to examine any one under a lens. _Lepidoptera_, however, which are never thus examined, may always be transfixed in this way, which sets them off to the greatest advantage.

Some insects, especially of the beetle tribe, are so extremely minute that it is next to an impossibility to get a pin through them without injuring, and often destroying them. By using fine needles, or very slender pins manufactured on purpose, this difficulty might perhaps be surmounted; but the needles will be subject to rust, and the pins, I know by experience, cannot be fixed in cork without difficulty. For such minute insects, therefore, by far the best mode is to _gum_ them on small pieces of card, which may be stuck upon a pin. Talc, which admits the underside of an insect to be seen through it, has been used for this purpose; and where you have only a single specimen, a thin small lamina of it would answer well; but ordinarily I should recommend the former mode. Your pieces of card, which must be small, may be either oblong and cut at the corners for neatness, with a couple of specimens gummed upon each, one on its belly and the other on its back; or you may cut little narrow card wedges, about four lines long and terminating in a point, upon which you may so gum your insects as to show the principal part of the under side, as well as the upper side of its body. Common gum-water made rather thin, with a very little glue mixed with it, will answer your purpose very well: it should be thinly spread on the card with a camel's-hair pencil, and then the insect placed upon it. With the same implement, if it has not been killed too long, before the gum is dry you may expand its antennæ, palpi, legs, and wings, &c. If you want to remove a specimen gummed on a card for any purpose, it is easily effected by plunging it into hot water.

Other insects may be transfixed through the thorax or upper side of the trunk; as also those _Coleoptera_, _Orthoptera_, and _Hemiptera_, whose wings you are desirous of expanding; only you should be careful that your pin passes through them _behind_ the _prothorax_.

Having impaled your insects, the next thing to be done is to _set_ them. The best time for doing this is not till they have begun to stiffen, but before they are become quite stiff. If attempted soon after they are killed, the parts, unless you keep them in the intended position by means of pins or braces, will not retain it; and if after they are become too stiff, they are liable to be broken. Not only should the antennæ and palpi be extended so as to be readily seen; but the legs, and often the wings, ought to be placed in their natural position; all of which tends much to the beauty of your specimens, and adapts them for more ready examination. But as this operation requires time, and beauty and regularity may be purchased too dear if at the price of hours called for by science, you may be left to your own discretion in this business, only you should always with a pin expand the antennæ and palpi if possible. You might, however, both save your time and have your insects neatly set, if you would take the trouble to instruct some acute and handy youth in your neighbourhood in the _modus operandi_, and devolve this department upon him: and as none are quicker and more expert in capturing insects than boys, he might also assist you in your hunting expeditions.

I do not mean, however, to leave you at liberty with regard to the setting of _Lepidopterous_ insects, which not only have a much worse appearance than those of other Orders if their wings be not regularly and uniformly expanded, but require it for the proper display of their characters. The necessary apparatus consists of a piece of cork about nine inches long, four broad, and half an inch thick, which should be made perfectly smooth, with a piece of white paper pasted over it; and of several narrow slips of card or braces, tapering gradually to a point, of different lengths, from half an inch to two inches or more, with a pin fixed in each at the broadest end. Thus provided, you may proceed to action. But you must first decide whether, like the continental Entomologists, you will set your _Lepidoptera_ horizontally; or, like the British, with their wings declining obliquely from the body. If you prefer the former method, the body must be let into a groove, and the wings expanded as flatly as possible, the anterior margin of the primary pair being brought forward so as to project beyond the head. But as this usually gives the insect an unnatural and formal appearance, I apprehend a man of your taste will prefer the mode adopted by your compatriots, the collectors of Britain, who in setting make the wings form an angle, varying according to the size and characters of the insect, with the body, and do not bring the anterior wings so forward. The wings of butterflies however, in order to appear at all natural, should be set more horizontally. Which fashion soever you prefer, the mode of operating is nearly the same; only that the English plan, except in the case of some large-bodied moths or hawk-moths, requires no groove in the setting-board. After you have stuck the insect upon the cork so as to bring its body close to its surface, stretch the anterior wing with a needle fixed in a handle, or a camel's-hair pencil, applied to the joint at the base, sufficiently forward, and then confine it by means of one of your card braces:--next, do the same by the opposite wing. Afterwards expand the posterior wings, which must not be separated from the anterior so as to leave any interval between them, and fix them with braces. When you are become expert, you will find, if the fly is not large, that a single brace will be sufficient for each pair of wings[1572]: but sometimes, if the card be not sufficiently stiff, you may confine it by a pin near the point. You must be careful in expanding the wings that each is brought equally forward. Lastly, give the antennæ their proper position, and if necessary confine them with braces; and leave your specimen in an airy situation to dry and stiffen. In a few days the braces may be removed, and the specimen transferred to the cabinet. When you put them away to become stiff, you must be careful to place them and your other insects at _night_ where earwigs cannot come at them; for in sultry weather these animals will often then attack and spoil them.

It is obvious that this process can only be performed while the joints and ligaments of the insect are still flexible; so that small species, in warm weather, will often be immoveably rigid before you can have an opportunity of setting them. On this account collectors usually set minute moths as soon as taken, which can be readily done on the lid of a cork-lined box. But fortunately both these, and specimens which have been dried for years, may be relaxed and rendered pliable by a very simple process. Fill a basin more than half full of sand, and saturate it with water; pour off the superfluous water, and cover the sand with blotting-paper: into this stick the insects you wish to relax, and covering the basin closely, leave them there for two or three days, according to their size; and the evaporation will render them sufficiently flexible for expansion or any other purpose. Beetles may be relaxed by plunging them for a short time in warm water or spirits of wine[1573].

Many moths of the tribe of _Tinea_ L. are so extremely minute, that it is almost impossible to set them without defacing their characters: indeed, the trunk of some is so small as not to admit being pierced by a pin. These, therefore, it is adviseable merely to gum upon card, expanding their wings (which the gum will easily retain in their proper situation) with a camel's-hair pencil. If you have two specimens, you may fix one in the natural position when at rest,--a method I should recommend with respect to other _Lepidoptera_, and indeed insects in general. Pezold advises that, by way of contrast, _white_ card should be used for _dark_-coloured species of these little moths, and _black_ for such as are _pale_. As the wings of different _Coleopterous_ groups, as well as those of _Hymenoptera_, _Diptera_, &c., vary in their neuration[1574], you should, whenever you can, set open the elytra and expand the wings of one specimen at least in each group, which will be very important to you in making out the characters of your genera.

When sufficiently dried, your insects should be transferred from the setting-boards, either to their place in your cabinet or to the store-box before described, till you have leisure to investigate them.

However tedious some of the foregoing manipulations may seem, they are in fact much less so than those required in several other branches of Natural History, where, in addition to the labour of catching, the nice and difficult task of clearing the skeleton of its muscular covering, and its internal cavity of its contents, and then of stuffing it and replacing its perished eyes by glass ones of the proper colour, is a necessary process with every individual. Happily the Entomologist, from the smallness of his game and the nature of their integument, is usually spared this labour. There are some few insects, however, in which a process in some degree analogous is requisite, if the beauty of the specimens be a consideration. Thus the abdomen of _dragon-flies_ is very apt to lose its colour, and that of the _Meloës_ to shrink up, if left in their natural state: these therefore should be eviscerated; which may be done by slitting the abdomen longitudinally on the _under_ side, then carefully removing its contents, and stuffing it with cotton. In the former, a small straw or stalk of hay may be used, which will prevent the fractures to which that part, when dry, is so liable. _Spiders_, and a few _apterous_ genera, as well as almost all _larvæ_, as they usually shrink up, in drying, into a shapeless mass, destitute of every character dependent on colour or form, require to be preserved in a different manner. They may all be very well kept in rectified spirits of wine mixed with water, in the proportion of three parts of the former to one of the latter. Each, suspended by a thread, should be put in a separate very small labelled phial. Larger spiders, such as _Mygale aviculare_, &c., when suffered to dry, though the abdomen shrinks, do not wholly lose their characters, and are often kept in cabinets: but if preserved in spirits, they may be put into larger wide-mouthed bottles, suspended at different heights, with a label on the outside opposite to each species. Mr. Abbott of Georgia had an excellent method of preserving _caterpillars_, so that his specimens retain their colours and other attributes, and look as if they were alive. I am not acquainted with his process, but the following will answer very well.--The animal must first be killed by immersion in spirits of wine; next you must eviscerate it, which is best effected by gradual pressure of the finger and thumb. You must begin at the head, and so proceed till all the fluid contents of the body have passed out at the anus, which you may enlarge with a fine pair of scissors, being careful not to injure the anal prolegs. When you have cleared the skin as much as possible, introduce a fine glass tube, or a piece of hay or slender straw into the anus, round which, as near to the extremity as may be, pass loosely a fine thread: then blowing through the tube, when the skin is fully inflated withdraw it, at the same time pulling the thread tight and securing it by a knot. The caterpillar will now exhibit its proper shape and colours; to retain which, all that is necessary is to hold it near the flame of a lamp until perfectly dry, which will be in a few minutes, when it may be placed in the cabinet along with the imago to which it belongs[1575].

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