Directions for Collecting and Preserving Insects Part 7

[Ill.u.s.tration: FIG. 91.--The Cyanide bottle with paper strips to give support to the insects.]

A piece of heavy blotting paper or heavy cloth soaked with chloroform or ether or benzine and placed at the bottom of a jar or bottle makes an excellent killing bottle for large-sized insects. For smaller specimens the collecting vial should be half filled loosely with narrow strips of soft paper, upon which a few drops of the liquid are poured, not so much, however, as to wet the paper. While collecting, the vial must be kept closed as much as possible. Some collectors prefer chloroform, others ether. If this method of killing is practiced with the necessary care, there is no objection whatever to it; the specimens are not wetted as they are in alcohol, and remain cleaner than those killed by any other method. The drawback is that the substances mentioned evaporate very rapidly and have to be renewed even on short excursions. On account of this great volatility, one can never be certain that all the specimens in the collecting bottle are dead after a given time and there is always some danger that one or the other of the hardier insects may regain activity. What mischief such revived specimens are capable of doing, many collectors have experienced to their sorrow. Another disadvantage of these volatile substances is that if used in too large quant.i.ties they will, in delicate specimens, especially beetles, cause an extension of the soft ligaments between the head and prothorax or between the latter and the mesothorax, and thus bring the specimen into an unnatural position, or cause the head, or head and thorax to drop off.

_Cyanide of Pota.s.sium._--The method of killing which, of late years, has found most favor with collectors, is the use of cyanide of pota.s.sium.

For killing large sized specimens they are simply put in what is now universally known as the "cyanide bottle." This may be constructed as follows:

Take a 2-ounce quinine bottle, or still better a shorter bottle with a wide mouth; break up a quant.i.ty of cyanide of pota.s.sium into pieces of convenient size (about a cubic centimeter); put these pieces in the bottle so that they form an even layer at the bottom; mix in a convenient vessel a quant.i.ty of plaster of Paris with water just sufficient to make the mixture semifluid and then pour it over the cyanide so as to cover this last to a depth of about 5 millimeters. The bottle is then left open for an hour or two until the plaster is thoroughly dry. The walls of the bottle are then cleansed from particles of the plaster which may have splashed on them, and the bottle is ready for use. If not used too frequently, especially in warm weather, it will last for an entire year or longer. Bottles or vials of different sizes can be prepared in the same way, and a very small cyanide vial which can be carried in the vest pocket will be found most convenient for use on all occasions. Fig. 92 represents a medium-sized chemist's test tube, converted into a very convenient cyanide bottle, in which, however, a cotton wad has been used to keep the poison in place. When the collected specimens have been removed from the bottle the latter should be carefully wiped clean with a piece of cloth or paper. The surface of the plaster soon becomes dirty and, on account of the hygroscopic property of the cyanide, more or less moist, especially during warm weather. The cyanide bottle is, therefore, not well adapted for the killing and temporary preservation of small and delicate specimens. This difficulty can be altogether obviated by placing a circular piece of blotting paper, cut to neatly fit the interior of the bottle, on the surface of the plaster. This can be renewed once a week or so, or oftener if it becomes necessary. It will frequently be advisable, also, especially in the collection of Diptera, Hymenoptera, and other delicate insects, to put a strip of blotting paper partially round the inner side of the bottle. This will absorb any moisture which may gather on the inside of the bottle and which would otherwise wet and injure the specimens. The accompanying figure (Fig. 93) ill.u.s.trates a bottle arranged as described above. A similar result is attained by some collectors by partially filling the bottle with narrow strips of bibulous paper to support and separate the insects as shown at Fig. 91.

[Ill.u.s.tration: FIG. 92.--Pocket cyanide bottle.]

For delicate specimens, also, the collecting bottle may consist of a test-tube of about the size of Fig. 92. This is half filled with loose, thin strips of soft white paper. A piece of cyanide about the size of a pea is then wrapped carefully in paper and so placed in the middle of the strips that it can not come in contact with the sides of the gla.s.s. Some prefer to pin the paper containing the cyanide to the lower surface of the cork. The latter should be rather short and tapering toward its lower end. It is longitudinally perforated through its center by a round hole just large enough to insert a goose-quill, which is cut straight at the lower end and obliquely at its upper end.

By means of this goose-quill the specimens may be introduced into the bottle without taking off the cork. This form of cyanide bottle lasts for only one day's collecting, except in cold weather, and in very warm weather it is advisable to take two prepared bottles along, so that the first used can be stowed away as soon as the cyanide begins to moisten the paper strips. Most insects are quickly killed in such a bottle, but some Coleoptera must be left in for five or six hours, while others resist death for a still longer time. This is especially true of the Coleopterous families Curculionidae, Trogositidae, and Tenebrionidae.

Submersion in alcohol will prove a satisfactory method of killing these or other beetles with similar vitality.

[Ill.u.s.tration: FIG. 93.--The cyanide bottle with blotting-paper lining (original).]

_Other Agents._--Prof. E. W. Claypole has found the use of benzine or gasoline very cheap and satisfactory for killing Lepidoptera, as the largest are at once killed thereby without injury to their scales.

(_Can. Ent._, XIX, p. 136.) He squirts it onto the specimen within the net or in the open air by means of a druggist's dropping tube. Hot water kills rapidly and leaves the specimens in good flexible condition for mounting. The heads of large insects may be held for a few moments in the water, while smaller specimens should first be thrown into a corked bottle and the bottle submitted to heat. Where the laurel grows its bruised leaves may be used in place of cyanide; they kill less quickly.

The leaves of the Laurel-cherry (_Prunus laurocerasus_), a plant commonly grown in England for screens and hedges, are also used for this purpose.

Some collectors, with indifferent olfactory sense, moisten the cork of their boxes with creosote. Its killing power lasts for several days. A few whiffs from a cigar, when nothing else is at hand, will also kill many of the more tender insects.

SPECIAL DIRECTIONS FOR DIFFERENT ORDERS.--A few brief directions for the special treatment of different orders may be given. Certain Coleoptera, notably those of the Curculionid genus Lixus, are covered with a yellowish pruinosity resembling pollen, which is of an evanescent nature, so that if the specimens are collected and killed by the ordinary methods, the pruinosity is completely lost. To preserve the natural beauty of such species it is necessary to put each specimen alive in a small vial and to kill it at once by means of a lighted match held under the vial for a few seconds. In pinning or otherwise mounting the specimen it should not be handled between the fingers.

Many Hymenoptera and Lepidoptera, especially species with yellow markings, if kept for any length of time in a cyanide bottle, will become discolored, the yellow changing to reddish, and hence such insects should not be left longer than necessary in the bottle. If care is exercised in this respect, no danger of discoloration need ordinarily be feared. The chloroform collecting bottle may be used with these insects if discoloration is antic.i.p.ated. All the more delicate insects, including Hymenoptera, Diptera, the smaller Lepidoptera, and the Neuroptera, require special care in killing. Large numbers should not be thrown into a killing bottle together, and plenty of bibulous paper should be kept in the bottle to prevent moisture from acc.u.mulating and wetting and ruining the specimens. It is frequently advisable to pin Diptera, especially the hairy forms (as the Bee-flies), in the net and transfer them at once to a cigar box containing a sponge moistened with chloroform. When the collecting shears are used, the insects are always thus pinned at once, which is, in fact, the only method of securing them. This is also necessary in the case of many Lepidoptera. Delicate Neuroptera may be killed by the use of the cyanide bottle, or, preferably, placed at once in a vial of alcohol, as these insects, in many instances, cannot be kept securely if pinned or mounted. Large Lepidoptera, as the Bombycids, may be killed by pouring benzine, naphtha, or chloroform over the thorax and abdomen. These substances evaporate rapidly and do not appreciably injure the vest.i.ture of the insects. Some collectors, in the case of b.u.t.terflies, seize them dexterously between the thumb and finger, and give a sharp pinch on the sides of the thorax. This will prevent the fluttering of the insect when transferred to the cyanide bottle, and, if carefully done, the scales need not be rubbed off. It is objectionable, however, because the thorax is distorted and subsequent anatomical study interfered with, and, in the case of moths, should never be practiced, as the thorax affords important characters used in cla.s.sification. Orthoptera may be killed by the use of the cyanide bottle but should be transferred at once to the vials of alcohol. If placed in a cyanide bottle, especially in the case of Locusts (_Acrididae_), they are apt to exude colored juices from the mouth, so that the specimens become soiled. Hence the use of vials of alcohol is preferable, and these insects should never be thrown into vials containing delicate insects of other orders. Plant-lice, together with the plant which they infest, should be placed at once in vials of alcohol, and specimens of the Aphides, representing all the forms present, should be mounted on slides for microscopic examination. The fixed forms of Coccids, comprising the majority of the species, require no special treatment, and the leaves, twigs, or bark on which they occur may be pinned at once and placed in the collection. The free forms are treated as in the case of plant-lice.

ENTOMOTAXY.

Under this term may be considered the preparation of insects for the cabinet.

CARE OF PINNED AND MOUNTED SPECIMENS.

_Insect Pins._--In mounting insects for the cabinet, expressly made entomological pins should be used. These come from three different sources: Klager pins, made by Hermann Klager, Berlin, Germany; Karlsbad pins, made by one or several firms in Karlsbad, Bohemia, Austria; and Vienna pins, made by Miller, Vienna, Austria.[4] These three kinds of pins have each their own slight advantages and disadvantages, so that it is difficult to say which is the best. All have the disadvantage that the pinned specimens are liable to be ruined by verdigris, and to obviate this j.a.panned ("black") insect pins are made by Klager and Miller. These black pins are, however, much softer than the "white"

pins, and therefore more difficult to handle. A pin of 35 millimeters in length will be found most convenient for pinning all insects excepting the larger Lepidoptera and other heavy-bodied insects, for which a longer pin may advantageously be used. According to the different degrees of fineness, the pins are numbered from No. 00 (the finest in the trade) to No. 7 or 8, but the numbers used by the different manufacturers do not correspond with each other. In experience, pins of Nos. 1, 2, 3, and 4 (Klager numbers) are more often needed than the others. The long pins of the finer numbers (Nos. 0 and 00) are difficult to handle in the collection and, for this reason, not to be recommended.

[4] In North America, Klager pins and Karlsbad pins can be obtained through Mr. John Ackhurst, 78 Ashland Place, Brooklyn, N. Y., and possibly also through Messrs. Blake & Co., 55 North Seventh street, Philadelphia, Pa. The Vienna pins and the Minutien-Nadeln have to be ordered direct through the manufacturer, Mr. Miller.

For many small insects, especially Microlepidoptera and Microdiptera, which _must_ be pinned, even the finest ordinary insect-pins are too large, and two special makes of pins are in use for this purpose. The "elbow pin" (formerly made and sold by Dr. Kuenow, of Konigsberg, Prussia, Germany) consists of a piece of fine silver wire, pointed at one end, and with a coil loop at the other end, into which a longer pin (No. 3 or No. 4) is thrust. This pin is ill.u.s.trated in Fig. 94. Still more satisfactory are the "Minutien-Nadeln" (pins for minute insects) manufactured by Mr. Miller, of Vienna, Austria, and which consist of a straight piece (about 14 mm. long) of extremely fine steel wire which is pointed at one end, and which is used in connection with a piece of pith or cork. The mode of using this pin is shown in Fig. 101. These fine and elbow pins may be obtained either "white" or j.a.panned.

[Ill.u.s.tration: FIG. 94.--Insect mounted on "elbow-pin."]

"Many English entomologists use short pins, very much like those of ordinary make, and my late friend Walsh never gave up the custom, and most vehemently opposed the use of what he ridiculed as 'long German skewers.' But the only advantage that can possibly be claimed for the short pins is that they are less apt to bend, consequently more easily stuck into the bottoms of boxes, and require less room; while, compared with the long pins, they have numerous disadvantages. Long pins admit of the very important advantage of attaching notes and labels to the specimen; render it more secure from injury when handled, and from museum pests in the cabinet; and on them several rows of carded duplicates may be fastened, one under the other, so as to economize room."

I have seen few old collections in better condition than that of the late E. Mulsant, of Lyons, France; and he used iron wire, cut slantingly, of the requisite length--a common custom in France. These wires bend so easily and have such dull points that they require much more careful manipulation than the pins, and the claim made for them that they do not verdigris would, perhaps, be offset by their rusting in moist climates or near the sea. Silver wire or silver-plated wire is also used.

_Preparation of Specimens._--Upon the return from an excursion the specimens should be prepared for the collection as soon as practicable.

If they have been collected in the forenoon they should be mounted the same evening, and those collected during an afternoon or evening excursion should be mounted the following morning, or, at any rate, before they get dry and brittle. Even specimens collected in alcohol should be attended to as soon as possible.

Specimens are taken from the collecting bottle, spread out on a sheet of white blotting paper and cleaned from adhering impurities either with a soft dry brush, or, in the case of species with hard covering, by was.h.i.+ng them with chloroform or ether or benzine where necessary.

Theoretically the best way of mounting would be to pin all specimens, since the under side with its important characters then remains free for examination. Pins adapted for pinning even the smallest insects have been described above, but this pinning is such a delicate operation and requires so much time that considering the large number of small specimens that may be collected on a single short excursion it is next to impossible to carry out this method, and therefore only the larger specimens need be pinned and the smaller may be glued onto the paper points described later. If the work is done with proper care all insects can be prepared for the cabinet so that both the upper and under surface of the specimen may be examined without further manipulation.

_Pinning._--"Insects should be pinned through the middle of the thorax, when, as is more generally the case, this portion (the mesothorax) is largely developed. Beetles (_Coleoptera_) and Bugs (_Hemiptera_), should, however, be pinned, the former through the right elytron or wing-cover (Fig. 95), and the latter through the scutel or triangular piece behind the thorax, the pin issuing between the middle and hind legs (Fig. 96). The specimens look very pretty with all the legs neatly spread out, but for practical purposes it is better to let them dry in the natural, partly bent position. It is a saving of time and s.p.a.ce, and the limbs are not so apt to break. The legs must also not reach too far downward or they will interfere with the proper labeling and the secure pinning of the specimen in the cabinet. Moreover, the antennae and legs must be brought into such position that they will not obstruct the view of any important part of the undersurface. The pin should always project about half an inch above the insect to facilitate handling, and uniformity in this regard will have much to do with the neat appearance of the collection. In pinning very large and heavy insects on a No. 4 or No. 5 pin, it is a good plan to first flatten the pin by a few blows of a hammer, in order to prevent the specimen from subsequently turning round on the pin."

[Ill.u.s.tration: FIG. 95.--Method of pinning and labeling Coleoptera (original).]

In pinning specimens which have a flat or nearly flat undersurface and short legs (as in many Coleoptera and Hemiptera and some Hymenoptera, _e. g._ the Saw-flies) the specimens are laid on a piece of cork and held in place there with the fingers or with a forceps. The pin is then pushed through the insect at the proper point, care being taken not to strike one of the legs or c.o.xae, and that the pin pa.s.ses through the specimen in a vertical direction.

[Ill.u.s.tration: FIG. 96.--Method of pinning Hemiptera (original).]

After the pin has been pushed through the specimen it is taken out of the cork and the specimen is pushed up to its proper height. This can be done either by holding the specimen between the fingers or by placing it on the upper edge of a thick book. A piece of cardboard provided with a small hole may also be used for this purpose. The perforations in ordinary sheet-cork, or the lapel of one's coat, will answer the same purpose. In pinning Lepidoptera or Hymenoptera the specimen should lie lightly in the angle formed by the thumb and first two fingers of the left hand and the pin be carefully thrust through at the proper angle.

In pinning all insects the pin should be so inserted that the insect is nearly at right angles with the pin, the posterior end being slightly depressed.

_Mounting on Points._--Most insects which are too small to be pinned on a No. 2 pin may be fastened to cardboard by means of gum tragacanth, gum sh.e.l.lac, or any good glue. It is not always easy to determine whether to pin a medium specimen or to glue it to a triangle. Pinned specimens are more secure, and not so apt to fall or be knocked off, but they are liable to become corroded by verdigris and ultimately lost, especially in families the larvae of which are endophytous or internal feeders. It is better to glue wherever there is doubt. A drop of corrosive sublimate added to the water in which the gum tragacanth is dissolved will indefinitely prevent its souring, but should not be used where the gum is to come in contact with the pin, as it inclines the latter to verdigris. In such cases a little spirits of camphor mixed with the gum tragacanth is best. Sh.e.l.lac should be dissolved in alcohol and this requires some time. This glue is not affected by moisture, and if it is desired to remove the specimens, they must be immersed in alcohol until the sh.e.l.lac is again dissolved.

A number of different kinds of glue are used by entomologists. The requirements of a good glue are that it be colorless, and, what is of greater importance, that the specimens adhere firmly to the paper points so that there is little or no danger of their being jarred off. Those glues which are readily soluble in cold or lukewarm water are perhaps more convenient than those which require alcohol or chloroform for dissolving. Gum arabic and gum tragacanth have the disadvantage that they are more liable to attract mites and are more brittle, so that they do not hold specimens as well as some of the liquid glues that are on the market. Spalding's glue answers a very good purpose, as also the preparation known to European entomologists as Leprieur's gum. White bleached sh.e.l.lac, while requiring alcohol to dissolve it, has the advantage that a very minute quant.i.ty suffices. In olden times the method employed was simply to glue the specimen by the ventral side to the middle of a quadrangular piece of cardboard, which was then pinned on a No. 3 or No. 4 insect pin. This method is still in vogue with English entomologists, but can not be recommended except for mounting duplicates. Much better are the small isosceles triangles which, before mounting the specimen, are pinned through near the base on a No. 2 or No. 3 insect pin. Only the best and finest cardboard should be used for this purpose, since that of poor quality is liable to be broken while pa.s.sing the pin through it and will yellow with age. "Reynolds's Superfine Board," which may be ordered through any dealer in artist's supplies of Devoe & Co., Fulton street, New York City, is perhaps the best for this purpose. Some of the neatest mounting which I have had done by any of my agents or a.s.sistants is by Mr. Albert Koebele, who has used mica or gelatine instead of cardboard, the object being not only to show the whole of the under side of the specimen, but to obscure less of the light from the labels and to render the triangles less conspicuous in the cabinet. These have been in use in the museum collection only for the last two or three years, and whether they will eventually tend to corrode the pins is not yet settled. Mica and isingla.s.s are also used for the same purpose. The points used in mounting may easily be cut by hand to a convenient size, say one-fourth of an inch (6-8 mm) long by one-sixteenth or less at the base, and tapering to a point. The point may be narrower or wider to accommodate insects of different sizes.

For cutting these triangles or points, various forms of punches similar to the appended figure (Fig. 97) known to the trade as conductor's punches may be used, and points thus cut are to be preferred to those made by other means, on account of the greater uniformity secured.

An experienced hand, however, will cut these points very rapidly and accurately with a pair of shears, and most collectors use no special instrument for this purpose.

The punches mentioned may be obtained of the manufacturers[5] of such instruments at from $2 to $3. Care should be observed in ordering to state explicitly the length, width at base and point, or, what is better, to inclose sample of the size of point it is desired to cut; but above all, to state that the block of paper to be cut out is the result desired, and that the instrument should cut clean and even, with no ragged edges.

[5] Montgomery & Co., 105 Fulton street, New York City.

[Ill.u.s.tration: FIG. 97.--Insect punch for cutting triangles or points (original).]

For mounting different forms and sizes the fastidious collector uses four or five sizes of points, but for all practical purposes one to cut a card point not less than 1.3 mm at the base and prolonged as nearly as possible to a point, and another a trifle wider at the base, say 1 or 1 2/3 mm and with a point about 1 mm in width will suffice.

[Ill.u.s.tration: FIG. 98.--Points for mounting insects (original).]

For mounting most long-bodied insects, _e. g._, Staphylinidae and Elateridae, an oblong card say 1 mm in width is desirable. With a little care these may be cut with sufficient uniformity with scissors. Seven and one-half millimeters may be taken as a standard of length, as this is about the size used by the majority of our best collectors. Shorter points, say 6 mm or one-quarter inch long, are sometimes preferred, where economy of s.p.a.ce is a desideratum.

A series of four points of different sizes for mounting insects is shown in the accompanying ill.u.s.tration. The sharp-pointed one, _a_, is designed for the minutest forms and the larger points for large insects.

The largest should be mounted on points of a nearly rectangular shape, shown at _d_. The dimensions of these points as adopted by most entomologists, are as follows:--

+------+---------+----------+--------+ Length. Breadth. Point. +------+---------+----------+--------+ _a_ 7.5mm. 1.5mm. .0mm. _b_ 7.5 1.5 .4 _c_ 7.5 1.5 .6 _d_ 7.5 1.6 1.6 +------+---------+----------+--------+

The point or triangle should be mounted on the pin and directed to the left, the height from the top of the pin varying somewhat with the specimen, but averaging about one-half an inch. The insect is then glued to the point with the head pointed forward. In the case of Coleoptera and Hymenoptera, and in fact of most insects, the specimen is mounted with the back uppermost, but in the case of the smaller Hymenoptera it is advisable to mount some of the specimens, at least, on the left side (see Fig. 99). This directs the legs toward the pin, as a matter of safety, prevents their being broken in handling, and also gives opportunity for subsequent examination of the back, side, and venter of the specimen. Coleopterists always mount specimens on the venter, and in the case of a correctly mounted specimen the whole underside of the body should be available for examination except the right half of the metasternum, as shown in figure 100.

[Ill.u.s.tration: FIG. 99.--Insect mounted on cardboard triangle.]

[Ill.u.s.tration: FIG. 100.--Method of gluing beetle on paper point (original).]