The way to prevent such intrusions is to make the atmosphere of the compartments so obnoxious (to them) that they dare not enter; and, further, to so spice up your specimens that they are no longer safely edible to the invaders.

The first object can be attained by always keeping camphor or naphthaline (albo-carbon) in each division. A lump of either substance may be secured by pins or a little perforated cell in the corner of each drawer or box, or the bottom of each may be dusted with finely powdered naphthaline; but as both these solids are volatile, care must be taken to renew the supply as occasion requires.

Then, with regard to the second precaution, perhaps nothing is more effectual than corrosive sublimate. A little of this may be dissolved in a small bottle of alcohol (spirits of wine), labelled with the name and the word POISON, and kept ready for use. All the skins of stuffed specimens should be painted with this solution, and the stuffing itself may be moistened with it before insertion.

There is yet another circ.u.mstance that renders a watchful care of your cabinet specimens necessary, if you happen to possess many that were captured 'at sugar.' Some of these will have so gorged themselves with syrup that they are literally full of it, and this will sometimes find its way to the outside, often dropping on the surface beneath. In such cases the sugar should be removed as completely as possible, and the bodies stuffed, before they are quite dry; but if the specimens have been in the cabinet so long that they are stiff and hard, the under sides of the abdomens may be completely cut out with a very sharp knife and thrown away, and then the sugar cleaned out from the upper sh.e.l.l as neatly as possible.

CHAPTER X

_PRESERVING OVA, LARVae AND PUPae_

Many young entomologists give their attention almost solely to the perfect forms of insects, often collecting and studying a very large number of species without regard to their earlier stages and metamorphoses. This is decidedly a very great mistake. Although the lifeless form pinned in a cabinet may be a most beautiful object in itself, yet a study of this alone is uninteresting compared with that of the wonderful changes it has undergone since the time it was a very young larva.

The different stages of the insects should be known as far as possible, and these, as well as the perfect forms, should be included in the collection for future study and reference. A good cabinet, according to my own opinion, is one that possesses, among other good features, a number of complete sets ill.u.s.trative of the life history of at least the more typical forms; and as it is not a difficult matter to preserve the earlier stages, there is really no excuse for their omission from the collection.

The empty sh.e.l.ls of ova are in themselves sometimes interesting objects, especially when they ill.u.s.trate some peculiar instinct on the part of the parent. Sterile eggs, also, often fall into the hands of breeders and rearers, and these, though in other respects unprofitable, are useful in the cabinet.

If fertile eggs are to be prepared for a collection, they must be killed. This is easily done by thrusting into each one the point of a very fine needle, or by immersing them for a moment in boiling water, or by shutting them up in a bottle with camphor. In drying they often contract more or less, and frequently change their colour; still these are useful, providing notes have been taken of the characters thus lost.

The larger eggs are capable of special treatment where the owner has the necessary time and patience, and where the highest results are desired.

By means of a surgeon's injector of small size the contents of the eggs can be removed; and then, by the same instrument, a warm solution of gelatine, coloured in such a way as to restore the natural tint, may be forced into the empty sh.e.l.l. As the gelatine cools and hardens, it prevents any shrinking of the sh.e.l.l, and thus both form and colour are well preserved.

For the preservation of larvae you will require one or two simple appliances.

The first of these is a suitable gla.s.s blowpipe, one form of which is here ill.u.s.trated. It consists of a gla.s.s tube, one end of which has been drawn out very fine; a piece of watch spring tied to it in such a manner that it will hold the skin of a larva at the small end, and a piece of india-rubber tubing at the other end, pressed by means of a bra.s.s spring clip.

[Ill.u.s.tration: FIG. 64.--A BLOWPIPE FOR LARVae.]

A little drying oven is also very useful, but not absolutely necessary.

If you decide to have one, any square box of sheet iron (not soldered tinned iron) may be readily converted into one. It must be provided with a hinged door in the front with a ventilator at the bottom, a hole for the escape of hot air at the top, and a tripod wire stand inside on which to rest the specimens while drying. The whole should be supported on a wire stand, so that heat may be applied below.

Each larva to be preserved should be dealt with in this way. First kill it by means of any one of the killing bottles or boxes already described, or by immersion in spirit of wine. When quite dead, enlarge the a.n.a.l orifice by thrusting a needle into it, and then lay it on a piece of blotting paper with its head toward you. Now take a round ruler, previously covered with blotting paper, and roll the larva gently from head to tail till all the contents of the skin have been expelled.

Next fix the skin on the fine end of the blowpipe, by thrusting the point of the latter into the opening, and allowing the spring to press gently on its edge. Gently blow into the skin till it is inflated just to a _little below_ natural size, then either hold it near a fire or rest it in the drying oven till it is quite dry and rigid.

If you have done your work neatly, the skin and blowpipe will both be quite air-tight when the clip is closed; and the air, finding no outlet, will still further inflate the skin when it expands on exposure to heat.

This is the reason why you are directed to blow it out to something short of the natural dimensions. If you find that this expansion causes the skin to stretch beyond its normal size, a little of the air must be allowed to escape while it is yet soft and flexible.

The front of the larva is generally the last portion to become dry, and when this is quite rigid the skin may be removed from the blowpipe. This is a matter that requires the greatest care; for the skin is so very thin and brittle that a little rough handling will break it to pieces.

As a rule it may be easily pushed off the pipe by a slight pressure behind, or a gentle twisting motion will loosen its hold; but this latter method can hardly be applied to hairy larvae without breaking off the hairs, now rendered very brittle by the heat.

If you find the slightest difficulty in detaching the skin of a valuable specimen, it is far better to damage the blowpipe than to risk spoiling the skin. Supposing your blowpipe is a gla.s.s one, you can easily break off the end of it after making a cut with a very small triangular file, and the portion thus removed may be left attached to the skin. Then, after softening the gla.s.s blowpipe in a gas flame or the flame of a spirit lamp, it can be drawn out thin again for future work. Those who can manipulate gla.s.s tubing in this way will find it far better to lay in a stock of suitable material, drawing it out when required, than to purchase blowpipes ready made at the naturalist's shop.

Very fine hollow stems, such as those of the bamboo cane, may be used instead of gla.s.s; and these possess the advantage of being easily cut with a sharp knife when there is any difficulty in removing the skin.

Again, whether gla.s.s or fine stems are used, a little grease of any kind placed previously on the end will allow the dried skin to be slid off with less difficulty.

Preserved larvae should preferably be mounted on small twigs or artificial imitations of the leaves of the proper food plants. A little coaguline applied to the claspers will fix them very firmly on these twigs or leaves, which are then secured in the cabinet by means of one or two small pins.

It is much to be regretted that the natural colours of many caterpillars cannot be preserved in the blown skins. Some are rendered much lighter in colour on account of the withdrawal of the contents, while others turn dark during the drying. In the smooth-skinned species the natural tints may be restored by painting or by staining with suitable aniline dyes, but these artificial imitations of the natural colours are always far less beautiful than the hues of the living larvae.

Very few words need be said on the preservation of pupae. Many of them do not alter much in form and colour, and therefore they require no special preparation.

If a pupa has to be killed for the purpose of adding to the value of the collection, simply plunge it into boiling water, and it is ready to be fixed in the cabinet as soon as it is quite dry.

The empty pupa cases, too, from which the perfect insects have emerged, are often worth preserving, especially if the damage done by the imago on forcing its way out is repaired with the aid of a little coaguline.

Let all larvae and pupae be preserved in their characteristic att.i.tudes and positions as far as possible, so that each one tells some interesting feature of the life history of the living being it represents. Further, enrich your collection by numerous specimens of the various kinds of coc.o.o.ns constructed by the larvae, pinning each one beside its proper species; and never refuse a place to any object that relates something of the life history of the creatures you are studying.

CHAPTER XI

_THE CABINET_--_ARRANGEMENT OF SPECIMENS_

The selection of a cabinet or other storehouse for the rapidly increasing specimens of insect forms is often a matter of no small difficulty to a youthful entomologist. Indeed, there are very many points of considerable importance to be considered before any final decision is made. Freedom from dust, the exclusion of pests, the convenience of the collector, the depth of his pocket, and the general appearance of the storehouse must be considered, and it is impossible, therefore, to describe a form that is equally suitable to all.

If it is absolutely necessary that the cabinet (or its subst.i.tute) be of a very inexpensive character, and if, at the same time, the collector has not the mechanical skill necessary for its construction, then perhaps the best thing he can do is to procure a number of shallow (about an inch and a half deep) cardboard, gla.s.s-topped boxes, such as are to be obtained at drapers' shops. For the sake of uniformity and convenience in packing, have them all of one size. Glue in small slices of cork just where the insects are to be pinned, and see that each box is supplied with either camphor or naphthaline. All the boxes may be packed in a cupboard or in a case made specially to contain them; and a label on the front of each will enable you to select any one when required without disturbing the others.

It may be mentioned here that gla.s.s is not necessary, though it is certainly convenient at times, especially when you are exhibiting your specimens to admiring non-entomological friends, who have almost always a most alarming way of bringing the tip of the first finger dangerously near as they are pointing out their favourite colours. 'Isn't _that_ one a beauty?' is a common remark, and therewith off snaps a wing of one of your choicest insects. When gla.s.s is used, however, see that the specimens are excluded from light, or the colours will soon lose their natural brilliancy.

Anyone who has a set of carpenter's tools and the ability to use them well will be able to construct for himself either a set of store boxes or a cabinet of many drawers in which to keep his natural treasures. In this case a few considerations are necessary before deciding on the form which the storehouse is to take.

A cabinet, if nicely made, forms a very sightly article of furniture; and, if s.p.a.ce can be found for it, is the best and most convenient receptacle. One of about twelve to twenty drawers will be quite sufficient for a time; and the few following hints and suggestions may be useful.

The wood used should be well seasoned, and free from resin. The drawers should fit well, and slide without the least danger of shaking. Each one should be lined with sheet cork, about one-eighth of an inch thick, glued to the bottom, nicely levelled with sand paper, and then covered with thin, pure white paper, laid on with thin paste. It is also advisable to cover each with gla.s.s, inclosed in a light wood frame that fits so closely as to prevent the intrusion of mites.

The drawers may be arranged in a single vertical tier if the cabinet is to stand on the floor, or in two tiers if it is to be shorter for placing on the top of another piece of furniture; and gla.s.s doors, fastened by a lock and key, may be made to cover the front if such are desired as a matter of fancy, or as a precaution against the meddlesome habits of juvenile fingers.

Store boxes are sometimes chosen in preference to cabinets because they are more portable, and because they can be arranged on shelves--an important consideration when floor s.p.a.ce is not available.

These boxes should be cork-lined and glazed like the cabinet drawers; and if they are made in two equal portions, lined with cork on both sides, and closing up like a book, they may be arranged on shelves like books, in which position they will collect but little dust.

Both store boxes and cabinets are always kept in stock by the dealers, the former ranging from a few shillings each, and the latter from fifteen shillings to a guinea per drawer. Knowing this, you can decide for yourself between the two alternatives--making and purchasing.

We have now to consider the manner in which our specimens should be arranged and labelled.

The table forming Appendix I contains the names of _all_ the British b.u.t.terflies and larger moths, and shows their division into _Sections_, _Tribes_, _Families_, and _Genera_. This table is the result of most careful study on the part of leading entomologists, and shows how, in their opinion, the insects can best be arranged to show their relation to one another; and you cannot do better than adopt the same order in your collection.

RHOPALOCERA PAPILIONIDae _Euchloe_ NYMPHALIDae _Papilio_ O O O _Argynnis_ O O O O O O O O O O O O O O O Machaon Rapae Cardamines Edusa O Selene PIERIDae O _Leucophasia_ O _Aporia_ O O O O O O O v. Helice O O O Sinapis O Crataegi Napi _Gonopteryx_ O _Colias_ O Euphrosyne _Pieris_ O O O O O O O O O Daplidice O O Latona O O Rhamni O Hyale Bra.s.sicae

Complete label lists can be purchased, printed on one side of the paper only. These, when cut up, supply you with neat labels for your specimens.

If you intend to study the British _Lepidoptera_ as completely as possible, you may as well start at once with a sufficiently extensive cabinet, and arrange all the labels of your list before you introduce the insects. You will thus have a place provided ready for each specimen as you acquire it, and the introduction of species obtained later on will not compel you to be continually moving and rearranging the drawers.