Morse has given in the "American Naturalist" (Vol. i, p. 156) a plan which is very neat and useful for lining boxes in a large museum, which are designed to be placed in horizontal show-cases (Fig. 120). "A box is made of the required depth, and a light frame is fitted to its interior.

Upon the upper and under surfaces of this frame a sheet of white paper (drawing or log paper answers the purpose) is securely glued. The paper, having been previously damped, in drying contracts and tightens like a drumhead. The frame is then secured about one-fourth of an inch from the bottom of the box, and the pin is forced down through the thicknesses of paper, and if the bottom of the box be of soft pine, the point of the pin may be slightly forced into it. It is thus firmly held at two or three different points, and all lateral movements are prevented. Other advantages are secured by this arrangement besides firmness: when the box needs cleaning or fumigation, the entire collection may be removed by taking out the frame; or camphor, tobacco, or other material can be placed on the bottom of the box, and concealed from sight. The annexed figure represents a transverse section of a portion of the side and bottom of the box with the frame. A A, box; B, frame; P P, upper and under sheets of paper; C, s.p.a.ce between lower sheets of paper and bottom of box."

[Ill.u.s.tration: FIG. 120.--Paper lining for insect box. (After Morse.)]

Other subst.i.tutes are the pith of various plants, especially of corn.

Palm wood and "inodorous felt" are also used, being cut to fit the bottom of the box.

Pita wood or the light porous wood of the Agave or Century plant when cut into proper strips also makes a very light and satisfactory lining, while good close bog-peat cut into proper thicknesses is not infrequently used in France and Germany. Druce & Co., 68 Baker street, London, W., England, have lately been manufacturing what is known as cork carpet, which seems to be a combination of ground cork and rubber.

It comes in various colors and of the proper thickness, and makes a very smooth and desirable lining, holding the pins very firmly. It cost 90 cents per square yard in England, and I have had one cabinet lined with it as an experiment, as there is a probability that the pins may corrode in contact with the rubber.

ARRANGEMENT OF INSECTS IN THE CABINET.

_Systematic and biologic Collections._--The permanent arrangement of specimens in boxes and drawers will vary somewhat with the nature of the insects. The almost universal custom of collectors, however, is to arrange the insects in vertical columns. In the case of the smaller forms, as Coleoptera, Hymenoptera, Diptera, 2 to 3 inches in width is allowed for the columns; and for the larger insects, as Lepidoptera, Orthoptera, for which larger drawers are recommended, a greater width of column is needed and 4 to 5 inches will be found necessary. With alcoholic material, a similar arrangement in columns may be followed.

In s.p.a.cing or dividing insect boxes into columns for the arrangement of specimens, I have followed the plan of pinning narrow strips of colored paper in the boxes at regular distances to divide the columns of insects. A fine line made with a medium pencil will answer the same purpose and will not materially disfigure the box.

The appearance of the collection will largely depend on the care used in the alignment of the specimens, both vertically and horizontally. It is advisable to have at least four specimens of a species, which, entomologically speaking, const.i.tute a set. The collector, however, should not limit the number of his specimens to four, as it is frequently necessary to have a larger number to represent, firstly, the s.e.xes; secondly, varieties; and thirdly, geographical distribution.

In the systematic collection the species should be arranged serially in accordance with the latest catalogue or monograph, and if the collector intends making a complete study of the group, s.p.a.ce should be left for the subsequent insertion of species not at present in his possession and also for new species. This will avoid the rearrangement of the entire collection at brief intervals.

_Economic Displays._--In the case of economic displays, which will include pinned specimens, alcoholic material, early states and specimens ill.u.s.trating the work of the insect--also the parasitic and predaceous enemies--the horizontal arrangement can be followed, and I have found it advisable, in making such displays, to arrange them in this manner, so that any needed width for the display of particular species may be had.

A good idea of the system of arrangement adopted for an economic exhibit may be obtained from the accompanying ill.u.s.tration (Pl. I). Every insect will require a somewhat different treatment, owing to its different habit, but the plan indicated in the ill.u.s.tration should, in the main, be followed. Prof. J. H. Comstock uses and recommends a sort of block system, which consists in pinning the insects and specimens showing their work, and alcoholic material, to blocks of soft wood. These are then arranged in the display cases. The advantage claimed for the system is facility in transferring and rearranging the exhibits. This method is somewhat c.u.mbersome, and in making and handling economic exhibits I have found pinning specimens directly to the cork lining of the box, as already described, to be entirely satisfactory. A biologic exhibit should be carefully planned beforehand, and when once completed is permanent and does not require rearrangement, as is frequently necessary in a systematic collection, owing to the constant changes in cla.s.sification. The only alteration necessary is a renewal of specimens which have become injured, or faded by exposure to light.

_Labeling Collections._--I have already fully discussed the subject of labeling insects before placing them in their final resting place in the collection. In the collection certain additional labels are required, viz, labels for the order, family, subfamily, genus, species, and sometimes variety. The label for the order should be placed above the first species in the collection, and should be in large type, as should also be the name of the family, which is to be placed above the first species in the family. The genus label should be in prominent type, somewhat smaller than the family label, and should be placed at the head of the genus. Custom varies as to placing the label of the species. In my practice I have adopted the plan of placing the label below the series of specimens representing the species. Some entomologists reverse this plan and place the label above the series of specimens. Others recommend pinning the label to the first and best-determined specimen of the series. This has the advantage of always keeping the label with the species and preventing the danger of mistake or confusion of the latter.

In the case of large insects, however, this plan has the disadvantage that the label can not be seen except by taking out the specimen, and, on the whole, the plan which I have adopted of placing the label below the series of specimens is preferable, but may be supplemented by the other, as in addition to the independent label, one of the specimens should have a label pinned with it. The labels should be neatly written on blanks printed for the purpose; but a better plan, perhaps, and one which I have followed, where possible, in labeling the national collection, is to cut the names neatly from a catalogue of the insects, which will furnish all the labels from order to species, and fasten them with short, inconspicuous pins in their proper places in the collection.

Where it is not desired to keep the collection as compact as possible, or where one has limited s.p.a.ce, I would advise labeling the species, not only with the recognized name, but also with the synonyms. This requires some s.p.a.ce, and will hardly be followed except in public collections. It is also desirable to arrange together, and label as such, the varieties of any given species. The appearance of the collection will depend largely on the uniformity of the labeling, and too much care can not be exercised in this respect.

MUSEUM PESTS, MOLD, ETC.

Unfortunately for the well-being of collections, dried insects are liable to the attacks of various museum pests, the most troublesome of which are themselves insects, but altogether out of their proper place and role in the general collection. Unless constant precautions are taken, the collector will discover after a few months that instead of the rare specimens with the preparations of which he has taken no little pains there remains only a series of fragmentary specimens, which a few years' neglect will reduce to little more than a ma.s.s of dust or powder.

The price, then, of a good collection is eternal vigilance. Most insects, when exposed for any length of time to strong light, fade or lose color, and the only way to prevent such achromatism is to exclude the light.

Insect pests affecting collections include Psocidae, Mites, Tineidae, Coleoptera of the families Ptinidae and Dermestidae, these last being the most injurious.

[Ill.u.s.tration: FIG. 121.--_Tineola biselliella_: _a_, adult; _b_, larva; _c_, coc.o.o.n and empty pupa--skin enlarged.]

The Psocidae--degraded wingless insects already referred to in the cla.s.sification (p. 24)--will find their way into the tightest boxes, but ordinarily do little if any damage, except in the case of delicate insects, such as Ephemerids, Microlepidoptera, and Microdiptera. The common forms found in collections are _Atropos divinatorius_ and _Clothilla pulsatoria_. Mites or Acari are rarely troublesome in collections, though Dr. H. A. Hagen reports having found a species (probably of Tyroglyphus) with imported insects, and considers them as liable to become dangerous enemies. Tineid larvae are rarely found in collections, and only affect the larger moths. They are not easily discovered, since they make no dust, as do most other pests. Some persons have been considerably annoyed by one of the common clothes moths, _Tineola biselliella_ (Fig. 121). Dr. Hagen found that it attacked freshly collected or newly spread insects, where the spreading-boards were left uncovered, but Mr. F. M. Webster has found it injurious to the general collections at Columbus, Ohio.

Of beetles, the Ptinidae are sometimes found in collections but are not common. Two species are known to attack entomological specimens, namely, _Ptinus fur_, which is quite rare, in this country, but much more abundant in Europe, and _Tribolium ferrugineum_, a cosmopolitan species which, however, has several times been a.s.sociated in injurious numbers with large collections of insects imported from the East Indies.

But by far the most dangerous enemies of insect collections are the larvae of some half dozen or more species of Dermestidae belonging to the genera Anthrenus, Attagenus, TroG.o.derma, and Dermestes. Of these _Anthrenus varius_ is the more common pest, in museums, especially in the North and East. In the South and West _TroG.o.derma tarsale_ and _T.

ornatum_ (?) replace Anthrenus. The European species _Anthrenus musaeorum_, is, on the authority of Hagen, rare in this country, and probably occurs chiefly in collections of imported insects. It is the common injurious species of Europe. _Anthrenus scrophulariae_ (see Fig.

67) occurs also in collections, Dr. Hagen stating that he has found it nearly as common as _A. varius_, and certainly more dangerous. In my own experience it is rarely found in insect collections. Two species of Attagenus (_A. pellio_ and _A. megatoma_) have also been found in collections. _A. megatoma_ has been found by Dr. Hagen to do not a little damage to insect collections in Cambridge, as well as to equal if not exceed the Carpet Beetle in its disastrous attacks upon carpets and household furniture. The other species, _A. pellio_, is rarely found in this country, but is much more common and obnoxious in Europe than _A.

megatoma_. _Dermestes lardarius_ is sometimes found in collections, and is attracted by the presence of animal matter such as skins, etc. The two particularly destructive pests, as pointed out, are _Anthrenus varius_ and _TroG.o.derma tarsale_. These species, together with most of the others, have no definite breeding period, but, in the uniform temperature of the laboratory or museum, breed all the year round and present no definite broods. It is the experience at the Museum that the boxes on the lower tier of shelves are very much more subject to attack than those on the upper tiers, from which it would seem that the parent beetle deposits her eggs outside the boxes on the floor of the cases and that the young larvae work their way into the smallest crevices. The danger of infection by these pests is greater in warm climates like that of Washington than in regions further north, as the warm season begins earlier, lasts longer, and furnishes better conditions for breeding and multiplication.

[Ill.u.s.tration: Fig. 122.--A naphthaline cone.]

REMEDIES.--The following remedies and preventives will prove efficient in checking or preventing the work of these pests.

_Naphthaline._--Where tight boxes are employed little fear of the work of these destructive agents need arise, especially if the boxes are kept supplied with repellent naphthaline cones. These are hard cones of naphthaline, mounted on pins for convenient placing in the boxes (see Fig. 122), and may be obtained of dealers in entomological supplies.

Naphthaline cones act as repellents to these insects and also to some extent r.e.t.a.r.d the development of the larvae in all stages and particularly of the eggs.

Mr. Schwarz states (_Proc. Ent. Soc. of Washington_, Vol. I, page 63) that in place of these cones a form of naphthaline may be used which is known in commerce as "white carbon," and is put up in the form of small square rods for use in intensifying the flames of gaslight. The material is very cheap, costing only 8 cents per pound wholesale, and may be broken up into small pieces, wrapped in paper, and pinned. The use of naphthaline cones is not advisable in boxes containing delicate specimens, as it leaves a deposit which dulls the colors and encourages greasing. The deliquescence of the naphthaline cones produces a blackish, oily residuum which will soil the lining of the box, and it is always advisable either to pin a piece of blotting paper beneath the cone or to wrap this in paper.

Constant watchfulness is necessary to see that the eggs which have been deposited and checked in development by the application of this insecticide do not ultimately hatch and start a new generation in the insect box.

_Bisulphide of Carbon._--If the collection is found to be infested with insect pests, it may be renovated by pouring a little bisulphide of carbon into the boxes and closing them at once. This substance evaporates rapidly and will destroy all insect life, and does not injure specimens or pins nor stain the boxes. If infested specimens are received, these should be inclosed in a tight box and treated with bisulphide of carbon before being added to the general collection, and it is always well for those who are receiving pinned specimens by exchange or otherwise to keep a quarantine box of this kind on hand.

_Mercury Pellets._--The use of mercury pellets is recommended to free boxes from Mites, Psoci, etc., and also to collect any particles of dust which may gain entrance. A few small pellets of mercury, placed free in the bottom of the horizontal box will, by the movement of the box, be caused to roll to and fro and accomplish the desired end.

_Carbolic Acid._--Mr. A. T. Marshall (_Entomologist's Monthly Magazine_, Dec., 1873, p. 176) records that he washes the paper of his boxes with the common disinfecting solution of carbolic acid in two-thirds water, which dries without staining and protects the specimens from Psoci.

_A Means of preserving Insects in dry hot Countries._--In the "_Horae Societatis Entomologicae Rossicae_," XXIV, pp. 233, 234 (1889), M. A.

Wilkins, writing from Tachkent in Turkestan, alludes to the inefficiency of ordinary preservatives in Central Asia, on account of their rapid volatilization through the hot dry air, so that if a collection be neglected for only two or three months _Anthreni_ are sure to be found in the boxes. He has. .h.i.t upon a plan which he finds effective, and at the same time very simple. He employs India-rubber bands about 1 inches in width and less than the length of the boxes to which they are to be applied. These bands are stretched over the opening line of the boxes, and effectually prevent the entrance of the most minute destroyers.

Possibly a similar plan might be adopted in other countries with a like climate. At any rate, the method has the merit of extreme simplicity.

(The _Ent. Mo. Mag._, Apr., 1891, p. 107.)

MOLD.

Collections kept in damp places or in a moist climate are very liable to mold, and under such conditions it is difficult to avoid this evil.

Carbolic acid is recommended, but Mr. Ashmead, who has kept a large collection in the moist climate of Florida, has found the use of naphthaline much more satisfactory. Mr. Herbert H. Smith who has had more extensive experience in the tropics prefers the carbolic acid.

Moldy specimens may be cleansed by washing with carbolic acid applied with a fine camel's hair brush.

VERDIGRISING AND GREASING.

The action of the acid juices in the bodies of certain specimens--as many of the Lepidoptera, Coleoptera, and Diptera--will cause the formation of verdigris about the pin, which in time acc.u.mulates and disfigures and distorts the specimen, and ultimately corrodes the pin, so that the slightest touch causes it to bend or break. There is no preventive yet known for this trouble other than the use of pins which have no bra.s.s to be corroded. j.a.panned pins are made for this purpose, and are, on the whole, satisfactory, but they bend easily and some caution is required in handling them. In place of these pins, which are somewhat more expensive than the steel pins, iron pins may be used.

These are very soft and bend too easily for satisfactory use. The steel pins may be rendered available for use by an immersion in a silver bath, which is comparatively inexpensive.

Insects the larvae of which live in wood are particularly subject to verdigris, as the Cerambycidae and Elateridae in Coleoptera, the Uroceridae in Hymenoptera and Sesiidae in Lepidoptera. In Hymenoptera the families Formicidae, Mutillidae, and the endophytous Tenthredinidae verdigris very rapidly, and most Diptera also. With all these insects j.a.panned or silvered pins should be used, or when not too large the insects should be mounted on triangles. This verdigrising is a.s.sociated with what is known as greasing, and this, as just indicated, is also a.s.sociated with endophytous larval life. The verdigris may be prevented by the methods indicated, and I would strongly advise, as a good general rule to be followed, the rejection of the ordinary pins for all species which, in the larva state, are internal feeders. But there is no way of preventing greasing or decomposition of the fats of the body, which may affect a specimen years after it has been in the cabinet. If the specimen is valuable the grease may be absorbed by immersion in ether or benzine, or by a longer treatment with powdered pipe-clay or plaster of Paris.

Insects collected on seabeaches, and saturated with salt water, also corrode the common steel pin very quickly and should be mounted on j.a.panned pins. It is also advisable to rinse such specimens thoroughly in fresh water before mounting.

The conviction has been forcing itself on my mind for some time that the naphthaline cones tend to promote greasing and verdigris, and carbolic acid in some small vessel secured to the cork, were, perhaps, preferable.

THE REARING OF INSECTS.