Some insects are carnivorous as larvae, and deposit their eggs upon dead animal matter, or even, as the ichneumon-flies and other parasitic forms, upon the tissues of living animals. Some lay their eggs upon decaying wood, or upon the ordure of animals. Some deposit their eggs in water. The female of some of the myriapoda deposits her eggs in a ma.s.s under the bark of decaying trees, and, coiling up about them, apparently guards them with maternal instinct until they are hatched. The sp.a.w.n of many of the crustacea is carried about by the female, attached in ma.s.ses to the lower surface of the body. The eggs of some insects, as the c.o.c.kroach and the mantis, are deposited in ma.s.ses concealed within cases, and so united as to appear to form composite or multiple eggs. These are conspicuous objects. A similar arrangement is found in the case of the ova of Hydrophilus and allied aquatic Coleoptera. The eggs of the mosquito are deposited upon the surface of the water in small, boat-shaped ma.s.ses, composed of from fifty to one hundred ova. The eggs of the Lepidoptera, which are generally deposited upon the leaves and blossoms of trees and plants, are not difficult to find, and have been more carefully observed and described than those of other orders. By confining impregnated females of many species of b.u.t.terflies and moths in nets of gauze drawn over the branches of the food-plant, it is often possible to obtain their eggs in considerable numbers. The insects thus confined should be supplied with food and drink.
This may be done by sprinkling upon the leaves water sweetened with sugar, or preferably honey. The females of many of the bombycid moths and hawk-moths will lay freely, if enclosed in a dark box, without the presence of the food-plant. When eggs are found and their parentage is unknown, a few should be preserved as hereafter described, and the remainder should be retained and kept until they have been hatched and the perfect insect has been reared therefrom. Insect eggs may often be obtained by dissecting the gravid female, but it is always preferable to obtain them, if possible, after oviposition has taken place, since in many cases the color of the egg in the oviduct is somewhat different from what it is after having been laid.
The eggs of insects may be deprived of their vitality by immersion in alcohol or by exposure to heat. The alb.u.men of ova coagulates at 160 F., and the temperature of the egg should not be raised above 175. They are best killed by being placed in the stove used for drying the skins of larvae, which is described on page 315. It is better to kill by means of a gentle heat than by immersion in alcohol, as by the latter process a change in color is sometimes produced. After they have been deprived of their vitality they may be preserved in small phials in dilute glycerine, or, if this cannot be had, in a solution of common salt. The phials should be kept tightly corked, and should be numbered by a label, written in lead pencil and placed within the bottle, to correspond with the note made in the collector"s note-book giving an account of the place of discovery, the food-plant, the date when found, and the name of the insect which deposited them, if known. In the latter case it is best to put the name of the insect in the phial with the number. Unless insect eggs are preserved in a fluid they are apt in many cases to shrivel with the lapse of time and become distorted, through the drying up of their contents, which, on account of their small size, it is impossible to void. The sh.e.l.l of some eggs is often very neatly voided by the escape of the larva, but there is generally a large orifice left, the color is frequently materially altered, and great vigilance in securing the sh.e.l.l must be exercised, as the young larvae of many species have the curious habit of whetting their appet.i.tes for future meals by turning about, as soon as they have been hatched, and eating the sh.e.l.l which they have just left.
The eggs of insects are best mounted in the form of microscopic slides in glycerine jelly contained in cells of appropriate depth and diameter. It is well to mount several upon the same slide, exhibiting the lateral as well as the terminal aspect of the eggs. At the upper end of all insect eggs there are one or more curious structures, known as micropyles (little doors), through which the spermatozoa of the male find ingress and they are fertilized. The peculiar, and often very beautiful, features of this part of the egg are, in a well-mounted specimen, exposed to view. In some cases it is advisable to slice off the end of the egg with the micropyle and mount it microscopically. The best display of this curious structure is thus often obtained.
The slides should be kept in a cabinet arranged in shallow trays. They should be accurately named, and have references to a book into which, from time to time, should be carefully transcribed from the field-book the observations of the collector, or his a.s.sistants and correspondents. Such a collection of insect ova is not only valuable but intensely interesting.
THE LARVA.--By reference to the table of the cla.s.sification of the Arthropoda, given in Chapter XL., it will be observed that the Insecta are broadly divisible into two groups, the Heterometabola and the Metabola. The animals cla.s.sified in the first group do not undergo metamorphosis in the development from the egg to the perfect insect to the same extent and in the same manner as the Metabola. In this respect the Peripatidea, the Myriapoda, and the various cla.s.ses included under the Acerata agree with them. The young myriapod and the young spider are found immediately after they have emerged from the egg to present most of the features of the mature insect, and so also the immature gra.s.shopper and squash-bug resemble the perfect insect in nearly everything but size and the absence of fully developed wings. In preparing a suite of specimens of these insects, designed to ill.u.s.trate their life-history, the directions which are given for the preparation of the imago apply equally well to the larva. It is simply necessary, for instance, in preparing a series of specimens of the Rocky Mountain Locust, to make sure that a specimen representing the creature after each successive moult has been secured, and these are mounted upon pins, and treated exactly as specimens of the adult insect are treated. Be careful not to pin, however, too soon after the moult.
In the case of many of the Coleoptera, and of all the Metabola the work of the collector is rendered far more laborious, for these pa.s.s from the egg into vermiform larvae, which undergo in some cases many moults, are then transformed into pupae, which are either naked or contained in a protecting envelope known as the coc.o.o.n, and then finally, after a longer or shorter period in the pupal state, are transformed into the perfect insect.
The student and collector, if intending to benefit science by their efforts, dare not neglect these rudimentary forms.
The larvae of most insects which undergo a complete metamorphosis are very small when first emerging from the egg, and before they make the first moult are, for the most part, best preserved as microscopic objects in cells filled with glycerine. In the case of the larvae of the great bombycid moths, which at the time of hatching are dark in color, it is possible to make a fairly good specimen by piercing the a.n.a.l extremity of the caterpillar, and spitting it upon the extremity of a thick, black bristle, or a fine copper wire wrapped with black silk. Specimens so mounted will not shrivel greatly, and may be attached to pins and placed in the cabinet after the slide containing the egg, as the first in the series of slowly maturing forms. After each successive moult the larvae increase rapidly in size. The method of preparing the larger forms which is now preferred by good collectors is that of inflation.
In inflating larvae the first step is to carefully remove the contents of the larval skin. This is best effected by making an incision with a stout pin or needle at the a.n.u.s, and then, between the folds of a soft towel, gently pressing out the contents of the abdominal cavity. The pressure should be first applied near the point where the pellicle has been punctured, and then be carried forward until the region of the head is reached. Great care must be exercised not to apply such a degree of pressure as will expel those tissues lying nearest to the epidermis, in which the pigments are located, and in the case of hairy larvae not to rob them of their hair. Practice can alone make perfect in this regard. The contents of the larva having been removed, the next step is to inflate and dry the empty skin. Some persons, as preliminary to this step, recommend that the empty skin be soaked for a period of a few hours in pure alcohol.
By this process undoubtedly a certain portion of the watery matter contained in the pellicle is removed, and the process of desiccation is facilitated, but it is objectionable in the case of all larvae having light colors, because these are more or less effaced by the action of the alcohol.
The simplest method of inflating the skins of larvae after the contents have been withdrawn is to insert a straw or gra.s.s stem of appropriate thickness into the opening through which the contents have been removed, and then by the breath to inflate, while holding over the chimney of an Argand lamp, the flame of which must be regulated so as not to scorch or singe the specimen. Care must be taken in the act of inflating not to unduly extend the larval skin, thus producing a distortion, and also to dry it thoroughly. Unless the latter precaution is observed a subsequent shrinking and disfigurement will take place. The process of inflating in the manner just described is somewhat laborious, and while some of the finest specimens, which the writer has ever seen, were prepared in this primitive manner, various expedients for lessening the labor involved have been devised, some of which are to be highly commended.
[Ill.u.s.tration: FIG. 82.--Apparatus for Inflating Larvae. B, Foot-bellows; K, rubber tube; C, flask; D, anhydrous sulphuric acid; E, overflow flask; F, rubber tube from flask; G, standard with c.o.c.k to regulate flow of air; H, gla.s.s tube with larva upon it; I, copper drying-plate; J, spirit-lamp.]
A comparatively inexpensive arrangement for inflating larvae is a modification of that described in the "Entomologische Nachrichten," 1879, vol. v., p. 7, devised by Mr. Fritz A. Wachtel. It consists of a foot-bellows such as is used by chemists in the laboratory, or, better still, of a small cylinder such as is used for holding gas in operating the oxy-hydrogen lamp of a sciopticon. In the latter case the compressed air should not have a pressure exceeding fifty pounds to the square inch, and the c.o.c.k regulating the flow from the cylinder should be capable of very fine adjustment. By means of a rubber tube the air is conveyed from the cylinder to a couple of flasks, one of which contains concentrated sulphuric acid and the other is intended for the reception of any overflow of the hydrated sulphuric acid which may occur. The object of pa.s.sing the air through sulphuric acid is to rob it, so far as possible, of its moisture. It is then conveyed into a flask, which is heated upon a sand-bath, and thence by a piece of flexible tubing to a tip mounted on a joint allowing vertical and horizontal motion and secured by a standard to the working-table. The flow of air through the tip is regulated by a c.o.c.k.
Upon the tip is fastened a small rubber tube, into the free extremity of which is inserted a fine-pointed gla.s.s tube. This is provided with an armature consisting of two steel springs fastened upon opposite sides, and their ends bent at right angles in such a way as to hold the larval skin firmly to the extremity of the tube. The skin having been adjusted upon the fine point of the tube, the bellows is put into operation and the skin is inflated. A drying apparatus is provided in several ways. A copper plate mounted upon four legs, and heated by an alcohol lamp placed below, has been advocated by some. A better arrangement, used by the writer, consists of a small oven heated by the flame of an alcohol lamp, or by jets of natural gas, and provided with circular openings of various sizes, into which the larval skin is introduced. (See Fig. 83.) A modification of the oven is given in Fig. 84.
[Ill.u.s.tration: FIG. 83.--Drying Oven. A, Lamp; B, pin to hold door open; C, door open; D, gla.s.s cover.]
[Ill.u.s.tration: FIG. 84.--Oven for Drying Larva-skin, made of tin joined without solder and with top made of gla.s.s. (After Riley.)]
A less commendable method of preserving larvae is to place them in alcohol.
The larvae should be tied up in sacks of light gauze netting, and a label of tough paper with the date and locality of capture, and the name, if known, written with a lead pencil, should be attached to each such little sack.
Do not use ink on labels to be immersed, but a hard lead pencil. Alcoholic specimens are liable to become shrivelled and discolored, and are not nearly as valuable as well-inflated and dried skins.
When the skins have been inflated they may be mounted readily by being placed upon wires wrapped with green silk, or upon annealed aluminium wire.
The wires are bent and twisted together for a short distance and then made to diverge as in Fig. 85. The diverging ends are pressed together, a little sh.e.l.lac is placed upon their tips, and they are then inserted into the opening at the a.n.a.l extremity of the larval skin. Upon the release of pressure they spread apart, and after the sh.e.l.lac has dried the skin is firmly held by them. They may then be attached to pins by simply twisting the free end of the wire about the pin, or they may be placed upon artificial imitations of the leaves and twigs of their appropriate food-plants. This method of preparation is applicable to the larvae of Coleoptera and Diptera as well as to those of the Lepidoptera.
[Ill.u.s.tration: FIG. 85.--Wire Bent into Shape for Mounting Larva. (After Riley.)]
An account of the manner of preserving larvae would not be complete without an account of the manner of rearing them. In rearing the larvae of Coleoptera, Diptera, and Hymenoptera, the student must be left in a large degree to his own devices. A few large gla.s.s jars capable of being closed with a gauze top are necessary, though in the case of the Hymenoptera reliance must be mainly placed upon finding the larvae in their nests. Bees and wasps construct various larval edifices, and these must be explored as found in nature for a knowledge of the immature insect. Breeding them in captivity is attended by difficulties which are rarely overcome by the most expert, except in a few isolated cases. This is also true, but to a less extent of the larvae of the Coleoptera. The larvae of many beetles which are carnivorous may be reared in gla.s.s jars, or boxes, covered with fine wire gauze, at the bottom of which earth or sand has been placed, and in which a supply of appropriate food can be put, such as the soft larvae of beetles, maggots, and bits of meat. It is best to previously scald the earth and sand placed at the bottom of the breeding cages in order to destroy the eggs and small larvae of other species which might be introduced. The cages should have a sufficient supply of moisture, and, so far as possible, the circ.u.mstances should be made to approximate those under which the larvae were found. The larvae of wood-boring beetles may be bred in portions of the wood which they frequent. A tight barrel with a cover made of wire gauze fitting closely over the top is a good device. In the fall of the year it may be filled with fallen twigs and pieces of branches from the forest, on which beetles have oviposited, and in the spring there will be generally found a large number of beautiful specimens of species, some of which are otherwise very difficult to secure. The barrels should be placed in a covered spot in the open air, and the twigs and wood occasionally lightly moistened with water. The larvae of leaf-eating beetles may be bred as the larvae of lepidoptera. The larvae of neuropterous insects, such as Myrmeleon, may be easily reared in boxes at the bottom of which sand to the depth of six inches has been placed. They may be fed with house-flies which have been deprived of their wings, and soft bodies of coleopterous larvae, and the larvae of ants. The larvae of the Odonata and aquatic beetles must be reared in aquaria in which there is a muddy bottom provided, and in which there are a few pieces of rotting wood, with loose bark upon it, so that they protrude some inches above the surface of the water, and in which aquatic plants are kept growing. Many aquatic insects pupate under the bark of trees growing at the edge of the water.
[Ill.u.s.tration: FIG. 86.--Breeding Cage. (After Riley.) _a_, Bottom board; _g g_, battens to prevent warping; _f f_, zinc pan four inches deep; _d_, zinc tube soldered to bottom of pan and intended to hold jar of water for food-plants; _e_, earth in pan; _b_, box with gla.s.s sides and hinged door; _c_, removable cap of box covered with wire gauze.]
[Ill.u.s.tration: FIG. 87.--Breeding Cage. B, Jar with food-plant; E, box with soil; G, gauze lid.]
The breeding of the larvae of lepidopterous insects has received far greater attention than that of other insects, and many modifications of devices for this purpose have been suggested. The simplest devices are often the best, and in the early stages of the smaller forms the best plan is to pot a specimen of the appropriate food-plant, when it is low and herbaceous and capable of being thus treated, and then put it under a cover of tarletan or under a bell gla.s.s. When the larva undergoes its transformations in the ground a bed of earth several inches in depth, upon which some dead leaves and litter are placed, should be provided. A convenient form of a breeding-cage is represented in Fig. 86. Mr. W.H. Edwards, who has done more than any other person to elucidate the life-history of North American b.u.t.terflies, often uses a breeding-cage made of a nail keg, the top of which has been knocked out, and over which gauze netting is tied. The writer has successfully employed, for breeding moths upon a large scale, common store boxes, with about eight inches in depth of good soil at the bottom, covered with a close-fitting frame lid over which mosquito-netting is tacked. Branches of the food-plant are set into the box in jars of water, in which they remain fresh for several days (see Fig. 87). If possible, and if operations are to be prosecuted upon a large scale, it is well to appropriate to breeding purposes a small room from which all the furniture and carpets have been removed. The windows should be closed with gauze netting tacked over them, and the doors should also be made tight so as to prevent the escape of the insects. When the caterpillars descend from the food-plants which are placed in the apartment in jars of water, or in pots, and thus indicate their readiness to undergo transformation, they should be secured and placed in smaller boxes fitted up as before described, and, in case the insect pupates in the soil, provided with a sufficient depth of earth. In case it is desired to go to still greater expense, a small house, arranged after the manner of a greenhouse, and with suitable cages and compartments, may be provided. Such an insect-house exists at Cornell University, and is under the care of that admirable investigator, Professor Comstock, who no doubt would be glad to furnish students with a knowledge of the details of its construction. The larvae of many lepidopterous insects emerge from the egg in the fall of the year, and after feeding for a time and undergoing one or two moults, hibernate, and upon the return of the springtime begin feeding again, and finally pupate.
It is best in the case of such to leave the larvae in the fall in a cold place, as an icehouse, and to suffer them to remain there until an abundant supply of the proper food-plant can be obtained.
In the breeding of larvae experience must be the great instructor, and practice can alone make perfect. No department of entomological study is, however, quite so fascinating as this, even though its prosecution may be somewhat laborious.
CHAPTER XLII.
COLLECTING IMAGOES.
[Ill.u.s.tration: FIG. 88.--Net Frame. (After Riley.) _a_, Wire ring with ends bent to insert in ferule _b_; _c_, point where plug and net-handle meet.]
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 bra.s.s 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 bra.s.s 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 st.i.tched 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 b.u.t.terflies are "highfliers." Nets made of stout muslin are useful for sweeping the tops of gra.s.s and low herbage, and in this way mult.i.tudes 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.
[Ill.u.s.tration: PLATE XXII. FIG. 1.--BEATING THE BUSH. FIG. 2.--A SUCCESSFUL STROKE.]
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.)
[Ill.u.s.tration: FIG. 89.--Net-head for Removable Frame. (After Riley.) The frame is made of elastic bra.s.s ribbon, and may be put inside of the hat when not in use, and the handle used as a cane.]
[Ill.u.s.tration: FIG. 90.--Folding Net. (After Riley.) _a_, Net-ring open; _b_, enlarged view of joint and check; _c_, ring folded and detached from ferule; _d_, nut sunk into end of ferule; _e_, screw to hold ring in place; _f_, ill.u.s.trating manner of putting ring and rod together.]
Collecting-jars are of various sizes. For Lepidoptera the one-pound jars used by Schering for hydrate of chloral, which have nicely ground gla.s.s 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 ma.s.s 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.
[Ill.u.s.tration: FIG. 91.--Collecting Jar. Cy., Cyanide of potash wedged into place with soft paper; P, perforated paper disc.]
[Ill.u.s.tration: FIG. 92.--Perforated Disc of Paper for Holding Cyanide in Place at Bottom of Jar.]
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 gla.s.s 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 a.s.sistant to carry some of his "traps" and a.s.sist 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 b.u.t.terfly 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 b.u.t.terflies 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 Tortricidae and Phycitidae and Tineidae should be "boxed" in the pillboxes provided for this purpose. The Lycaenidae, Hesperidae, 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, b.u.t.terflies 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.
[Ill.u.s.tration: FIG. 93.--Method of Pinching a b.u.t.terfly.]
The labors of the collector should not be confined to the day. Mult.i.tudes 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 s.e.x. 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 mult.i.tudes 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 mola.s.ses 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 Erebidae 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.
[Ill.u.s.tration: PLATE XXIII. FIG. 1.--BOTTLING A SKIPPER. FIG. 2.--j.a.pANESE PORTER WITH COLLECTING BOXES.]
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 Felidae, 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 b.u.t.terflies, 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.