Chapter XLII: Collecting Imagoes

The name _imago_ is applied by naturalists to the perfect form of insects, which is revealed at the conclusion of the round of metamorphoses. In the collection and the preservation of these the most necessary implement at the outset is the _net_. A simple way of making a serviceable and strong net is to take a piece of brass or galvanized iron wire about three feet and six inches in length, and about three-sixteenths of an inch in diameter, and having bent it into the form of a hoop, with the two ends forming shanks, to insert these into the end of a brass ferule such as is used on fishing-rods, and fix them there by pouring in melted lead or solder in such a way that the handle can be inserted into the other end of the ferule. This can be easily accomplished by plugging the handle end of the ferule with a piece of soft wood or with clay. The handle should be light, and not more than four or five feet in length for ordinary use. To the ring of the net a sack made of green tarletan, or less preferably mosquito-netting, about two and a half times as deep as the diameter of the ring, should be sewn. A piece of green muslin should be then stitched on as a binding over the ring. Green is to be always preferred to any other color as less likely to alarm the insects. Nets with folding rings and jointed bamboo handles are to be had of most dealers, and are to be highly recommended for convenience, if well made. In collecting about electric lights which hang high, and along the woodland walks of tropical forests, it is well to be able to add to the length of the handle by inserting more joints of bamboo. Some butterflies are "highfliers." Nets made of stout muslin are useful for sweeping the tops of grass and low herbage, and in this way multitudes of small insects of various orders may be taken. Such nets should be larger than the ordinary net. Nets made of stout lace cloth are used for capturing aquatic insects in pools and ditches. For this purpose a scoop made of wire gauze may also be advantageously employed.

In the capture of insects the umbrella plays, in the hands of a skilful collector, a very important part. It is used as a receptacle for insects which are beaten from the overhanging branches, under which it is held in an inverted position while the operation of beating is going on. As the insects fall they must be caught and placed in the collecting-jars. (See Plate XXII., Fig. 1.)

Collecting-jars are of various sizes. For Lepidoptera the one-pound jars used by Schering for hydrate of chloral, which have nicely ground glass stoppers, are admirable. In preparing the jars the following directions should be closely attended to: Place at the bottom of the jar some lumps of cyanide of potash, over these place a few pieces of paper loosely crumpled and rammed down so as to hold the lumps of the cyanide in position. Pour in two or three drops of water. Take a piece of stout and clean writing-paper and describe upon it a circle of the same size as the inside of the bottle, and around this another circle three-quarters of an inch greater in diameter. Cut out a circular disc of paper, following with the scissors the line of the outer circle. At intervals of a quarter of an inch cut slits all around the disc of paper extending them inwardly only as far as the first circle drawn upon the paper. Fold back the outer edge of the disc upon the side of the paper which is to come uppermost in the bottle. With a pin, or a small punch, pierce a number of holes through the middle of the paper. Apply some gum to the edge of the disc which has been folded back, and fix it securely on the top of the mass of cyanide and paper at the bottom of the jar, by pressing the gummed edge against the sides of the bottle. This method is infinitely preferable to the old way of fixing the cyanide in the bottom of the jar by pouring in a cement of plaster of Paris. Instead of lumps of cyanide of potash, lumps of carbonate of ammonia may be used to charge the poisoning-jar, but a jar so charged must never be used to kill insects which are green in color, as the fumes of the ammonia often serve to bleach these and make them white or brown.

In the case of large insects, or insects which struggle violently, a few drops of chloroform may be poured into the collecting-jar, to prevent them from injuring themselves. Chloroform is not, however, to be commended as a killing agent, inasmuch as it induces thoracic spasms, which make the specimen difficult to set after death. In the case of the larger moths and beetles death may be instantaneously induced by injecting a solution of cyanide of potash with a hypodermic syringe. The use of oxalic acid in solution, administered by making an incision into the thorax of the insect with the point of a crow-quill pen dipped into the solution, is not to be highly commended, as the acid changes the color of the specimen, and, after it has been pinned, corrodes the pin. Likewise when specimens have been kept too long in a jar charged with ammonia, and are pinned immediately after they have been taken out, the pins are liable to be corroded and eaten through.

The collector having provided himself with nets and killing-jars, will not be thoroughly equipped for field work until he have added to his outfit the necessary conveniences for carrying his captures with him uninjured. The writer, after long experience as a collector in many lands, is inclined to think that the best appliance is a tin box lined with cork, and provided with a compartment in which a cyanide cake[11] may be placed before going to the field, and in which, after the return, when the cyanide cake has been withdrawn, a sponge may be put, which should be saturated with a weak solution of carbolic acid for the double purpose of keeping the specimens from drying out too rapidly and from moulding. The box should not be more than 10 × 8 × 3-1/2 inches inside measurement, and should be divided into two equal parts, hinged at the side which is carried uppermost, and hung over the shoulder by a strap. A pincushion filled with pins may be attached to the belt. A belt arranged like a cartridge-belt, with pockets to carry pillboxes about one and one-half inch square and three-quarters of an inch deep should also be provided. These boxes should have glass bottoms. They are to be used in "boxing" the smaller lepidoptera and other delicate insects which, if killed and pinned on the field, would be too dry upon return from the chase to make good cabinet specimens. Boxed specimens may be kept for a day or two, and killed and mounted at leisure. A bag containing several small boxes may also be carried. These boxes should have in them a supply of paper envelopes, for papering specimens in the way hereafter to be described. A loose sack-coat, with an abundance of capacious pockets inside and out, is indispensable. A small poisoning-jar for beetles should be carried in the right-hand pocket of the pantaloons, a similar jar in the left-hand pocket for hymenoptera and diptera. In the right-hand pocket of the sack-coat should be carried the large jar for killing lepidoptera, and in the left-hand pocket a smaller jar for neuroptera and orthoptera. Thus arrayed the collector is completely furnished for the chase. It will, however, be well for him, if he can, to secure the attendance of an assistant to carry some of his "traps" and assist him. We will now go out with him into the field and give him a few practical instructions as to the best mode of procedure.

First of all, it is proper to observe that it is advisable not to be in a hurry and not to rush over the ground. The representations in comic newspapers of the entomologist, wildly tearing about the fields and in mad haste chasing a butterfly over hills and meadows, are not drawn from a study of the methods of experts. "All things come to him who waits." Slyness, coolness, a keen eye, and adroit quickness in the use of the net are the qualities which yield the largest returns to the collector. In the use of the net the habits of insects must be noted. Those which alight upon the ground or low herbage may be caught by clapping the net over them. Most butterflies and moths have the habit, when caught, of flying upward in the net. Therefore so soon as the insect, if a lepidopteron, is enclosed in the net, hold up the closed end of the sack, and, introducing the poison jar, from which the stopper has been removed, take the insect. A little practice will soon enable the collector to do this without allowing the fly to beat and injure its wings, and without touching them in the least with the fingers. (Plate XXIII., Fig. 1.) A convenient way of securing small insects in the net is by a rapid motion hither and thither, with the mouth open to the wind, to drive them back into the bottom of the sack, and then to place this in the bottle and leave it there a few seconds until the insects are stunned, when they may be shaken into the jar. When the insect alights within reach upon the ends of branches or the tops of flowering plants, it may be swept into the net by a dexterous movement and thus secured. A similar stroke will often, when well-aimed, secure specimens flying past the station of the collector. (Plate XXIII., Fig. 2.) Beetles and insects of other orders than the lepidoptera may be placed in the jars appropriated to them and left there until the return from the fields. With the Lepidoptera it is necessary to exercise greater care. The smaller specimens, such as the Tortricidæ and Phycitidæ and Tineidæ should be "boxed" in the pillboxes provided for this purpose. The Lycænidæ, Hesperidæ, and most of the moths, should be caught in the large jar in the manner just described, and when stunned, pinned and placed in the cork-lined box, where the process of completely depriving them of life will be completed. The larger, and even some of the smaller, butterflies may be killed while in the net by gently pinching them through its folds, between the first finger and the thumb at the point where the wings are attached to the thorax (see Fig. 93). The pressure should be applied when the wings are folded back to back, as the insect sits when in repose. If applied in any other way the specimen is likely to be seriously damaged, and moths should never be thus killed. In pinning specimens in the tin box used for transportation while upon the hunt, the storage power of the box will be increased by pinning a number of specimens upon one pin, thrusting the pin through the insect horizontally and not perpendicularly through the upper surface of the thorax.

The labors of the collector should not be confined to the day. Multitudes of the rarest and most desirable species are nocturnal in their habits. Some of them are readily attracted to light, though, strangely enough, the individuals among the lepidoptera thus attracted are mainly of the male sex. By placing a lamp at an open window many moths may be secured. Electric lights are good points for the collector, if they are within reach. The burnt and ragged refuse which the cleaner finds in the globes in the morning, half-buried in the dust of the disintegrated carbons, is of little or no value. Various traps lighted with lanterns have been suggested, but so far few of them have equalled the simple device of a friend of mine, who, living in a tropical country, has set apart a small room for this purpose, and having cleared it of all furniture, and whitewashed the walls, keeps a powerful lamp burning in it every night opposite a large window facing the forest. His captures vary from a dozen to a hundred specimens of lepidoptera every night of the year, and multitudes of insects of other orders. In the temperate zones a favorite method of collecting lepidoptera is by "sugaring." For this a mixture of sugar and stale beer, or molasses and water, flavored with rum, and of about the consistency of thin maple syrup, should be used. It is best applied to the trunks of trees upon the edge of clearings, and on moonlight nights on the side of the wood toward the moon. Apply the mixture to from forty to eighty trees, stumps, or stakes, with a whitewash brush, and then go over the "beat" with a dark lantern and capture the moths in the wide-mouthed cyanide jar. In this way the writer has taken as many as three or four hundred moths in a single evening. The same trees should be sugared and visited night after night, and the best results are often only obtained after a beat has been in operation for some time and the insects have learned to know it. The best catch is generally to be had in the two hours immediately following sunset. In tropical countries, aside from the Erebidæ and allied moths, few species appear to be attracted to sugar, and in warm climates plenty of rum should be added to the mixture. To keep ants off from trees which have been sugared, the writer finds it good to tie a band of dark cloth which has been treated with a saturated solution of corrosive sublimate about the trunk near the ground. This only is to be done where a regular route has been selected for nightly visitation, and it has the disadvantage of keeping away from the baits many beetles which are attracted to sugar. Trees which have been sugared and visited at night should be revisited in the daytime, and many day-flying species will be found feasting upon what has been left by the revellers who attended the banquet of the night before.

Some insects have quite revolting tastes, and may be captured by pandering to them. The ordure of wild animals has a charm for many, and by placing the dung of dogs, or civet-cats, or any of the Felidæ, in the woodland paths of tropical forests many great rarities may be secured. Carrion and dead fish in particular are attractive baits.

It has been recently claimed by a writer that painted decoys representing butterflies, placed upon flowers, or kept in motion at the tip of a switch, may be effectively used in securing rare and wild species. The writer has no personal knowledge of the merit of the plan. It might be worth trying, however, in the case of monstrous rarities.

FOOTNOTE:

[11] The cyanide cake is made by pouring plaster of Paris into a mould of proper size and imbedding in it before setting a number of lumps of cyanide of potash.