Elementary Zoology Part 29

=Wallace, A. R.= Island Life. 1881, Harper & Bros. $4.00.

APPENDIX III

REARING ANIMALS AND MAKING COLLECTIONS

Much good work in observing the behavior and life-history of some kinds of animals can be done by keeping them alive in the schoolroom under conditions simulating those to which they are exposed in nature.

The growth and development of frogs and toads from egg to adult, as well as their feeding habits and general behavior, can all be observed in the schoolroom as explained in Chapter XII. Harmless snakes are easily kept in gla.s.s-covered boxes; snails and slugs are contented dwellers indoors; certain fish live well in small aquaria, and many other familiar forms can be kept alive under observation for a longer or shorter time. But from the ease with which they are obtained and cared for, the inexpensiveness of their live-cages, and the interesting character of their life-history and general habits, insects are, of all animals, the ones which specially commend themselves for the schoolroom menagerie. In the technical notes in the chapter (XXI) devoted to insects are numerous suggestions regarding the obtaining and care of certain kinds of insects which may be reared and studied to advantage in the schoolroom. In the following paragraphs are given directions for making the necessary live-cages and aquaria for these insects.

=Live-cages and aquaria.=--Prof. J. H. Comstock has so well described the making of simple and inexpensive cages and aquaria in his book, "Insect Life," that, with his permission, his account is quoted here.

_Live-cages._--"A good home-made cage can be built by fitting a pane of gla.s.s into one side of an empty soap-box. A board, three or four inches wide, should be fastened below the gla.s.s so as to admit of a layer of soil being placed in the lower part of the cage, and the gla.s.s can be made to slide, so as to serve as a door (fig. 166). The gla.s.s should fit closely when shut, to prevent the escape of the insects.

[Ill.u.s.tration: FIG. 166.--Soap-box breeding-cage for insects. (From Jenkins and Kellogg.)]

"In rearing caterpillars and other leaf-eating larvae, branches of the food-plant should be stuck into bottles or cans which are filled with sand saturated with water. By keeping the sand wet the plants can be kept fresh longer than in water alone, and the danger of the larvae being drowned is avoided by the use of sand.

"Many larvae when full-grown enter the ground to pa.s.s the pupal state; on this account a layer of loose soil should be kept in the bottom of a breeding-cage. This soil should not be allowed to become dry, neither should it be soaked with water. If the soil is too dry the pupae will not mature, or if they do so the wings will not expand fully; if the soil is too damp the pupae are liable to be drowned or to be killed by mold.

"It is often necessary to keep pupae over winter, for a large proportion of insects pa.s.s the winter in the pupal state. Hibernating pupae may be left in the breeding-cages or removed and packed in moss in small boxes. Great care should be taken to keep moist the soil in the breeding-cages, or the moss if that be used. The cages or boxes containing the pupae should be stored in a cool cellar, or in an unheated room, or in a large box placed out of doors where the sun cannot strike it. Low temperature is not so much to be feared as great and frequent changes of temperature.

"Hibernating pupae can be kept in a warm room if care be taken to keep them moist, but under such treatment the mature insects are apt to emerge in midwinter.

[Ill.u.s.tration: FIG. 167.--Lamp-chimney and flower-pot breeding-cage for insects. (From Jenkins and Kellogg.)]

"An excellent breeding-cage is represented by fig. 167. It is made by combining a flower-pot and a lantern-globe. When practicable, the food-plant of the insects to be bred is planted in the flower-pot; in other cases a bottle or tin can filled with wet sand is sunk into the soil in the flower-pot, and the stems of the plant are stuck into this wet sand. The top of the lantern-globe is covered with Swiss muslin.

These breeding-cages are inexpensive, and especially so when the pots and globes are bought in considerable quant.i.ties. A modification of this style of breeding-cage that is used by the writer differs only in that large gla.s.s cylinders take the place of the lantern-globes. These cylinders were made especially for us by a manufacturer of gla.s.s, and cost from six to eight dollars per dozen, according to size, when made in lots of fifty.

"When the transformation of small insects or of a small number of larger ones are to be studied, a convenient cage can be made by combining a large lamp-chimney with a small flower-pot.

"_The root-cage._--For the study of insects that infest the roots of plants, the writer has devised a special form of breeding-cage known as the root-cage. In its simplest form this cage consists of a frame holding two plates of gla.s.s in a vertical position and only a short distance apart. The s.p.a.ce between the plates of gla.s.s is filled with soil in which seeds are planted or small plants set. The width of the s.p.a.ce between the plates of gla.s.s depends on the width of two strips of wood placed between them, one at each end, and should be only wide enough to allow the insects under observation to move freely through the soil. If it is too wide the insects will be able to conceal themselves.

Immediately outside of each gla.s.s there is a piece of blackened zinc which slips into grooves in the ends of the cage, and which can be easily removed when it is desired to observe the insects in the soil.

"_Aquaria._--For the breeding of aquatic insects aquaria are needed.

As the ordinary rectangular aquaria are expensive and are liable to leak we use gla.s.s vessels instead.

"Small aquaria can be made of jelly-tumblers, gla.s.s finger-bowls, and gla.s.s fruit-cans, and larger aquaria can be obtained of dealers. A good subst.i.tute for these is what is known as a battery-jar (fig.

168). There are several sizes of these, which can be obtained of most dealers in scientific apparatus.

"To prepare an aquarium, place in the jar a layer of sand; plant some water-plants in this sand, cover the sand with a layer of gravel or small stones, and then add the required amount of water carefully, so as not to disturb the plants or to roil the water unduly. The growing plants will keep the water in good condition for aquatic animal life, and render changing of the water unnecessary, if the animals in it live naturally in quiet water. Among the more available plants for use in aquaria are the following:

"Waterweed, _Elodea canadensis_.

"Bladderwort, _Utricularia_ (several species).

"Water-starwort, _Callitriche_ (several species).

"Watercress, _Nasturtium officinale_.

"Stoneworts, _Chara and Nitella_ (several species of each).

"Frog-spittle or water-silk, _Spirogyra_.

"A small quant.i.ty of duckweed, _Lemna_, placed on the surface of the water adds to the beauty of an aquarium.

[Ill.u.s.tration: FIG. 168.--Battery-jar aquarium. (From Jenkins and Kellogg.)]

"When it is necessary to add water to an aquarium on account of loss by evaporation, rain water should be used to prevent an undue acc.u.mulation of the mineral-water held in solution in other water."

=Making collections.=--Much is to be learned about animals by "collecting" them. But the collecting should be done chiefly with the idea of learning about the animals rather than with the notion of getting as many specimens as possible. To collect, it is necessary to find the animals alive; one learns thus their haunts, their local distribution, and something of their habits, while by continued work one comes to know how many and what different kinds or species of each group being collected occur in the region collected over. Collecting requires the sacrifice of life, however, and this will always be kept well in mind by the humane teacher and pupil. Where one set of specimens will do, no more should be collected. The author believes that high-school work in this line should be almost exclusively limited to the building up of a common school collection. Let a single set of specimens be brought together by the combined efforts of all the members of the cla.s.s, and let it be well housed and cared for permanently. Each succeeding cla.s.s will add to it; it may come in time to be a really representative exhibition of the local fauna.

The high-school collection should include not only adult specimens of the various kinds of animals, forming a systematic collection, as it is called, but also all kinds of specimens which ill.u.s.trate the structure and habits of the animals in question and which will const.i.tute a so-called biological collection. Specimens of the eggs and all immature stages; dissections preserved in alcohol or formalin showing the external and internal anatomy; nests, coc.o.o.ns, and all specimens showing the work and industries of the various animals; in short, any specimen of the animal itself in embryonic or postembryonic condition, or any parts of the animal, or anything ill.u.s.trating what the animal does or how it lives, all these should be collected as a.s.siduously as the adult individuals. Each specimen in the collection should be labelled with the name of the animal, the date, and locality, and the name of the collector, with any particular information which will make it more instructive. If such special data are too voluminous for a label, they should be written in a general note-book called "Notes on Collections" (kept in the schoolroom with the collection), the specimen and corresponding data being given a common number so that their a.s.sociation may be recognized. In the following paragraphs are given brief directions for catching, pinning up, and caring for insects, for making skins of birds and mammals, and for the alcoholic preservation of other kinds of animals.

_Insects._--For catching insects there are needed a net, a killing-bottle, a few small vials of alcohol, and a few small boxes to carry home live specimens, coc.o.o.ns, galls, etc. For preparing and preserving the insects there are needed insect-pins, cork- or pith-lined drawers or boxes, and small wide-mouthed bottles of alcohol.

[Ill.u.s.tration: FIG. 169.--Insect killing-bottle; cyanide of pota.s.sium at bottom, covered with plaster of Paris. (From Jenkins and Kellogg.)]

The net, about 2 feet deep, tapering and rounded at its lower end, is made of cheesecloth or bobinet (not mosquito-netting, which is too frail), attached to a ring, one foot in diameter, of No. 3 galvanized iron wire, which in turn is fitted into a light wooden or cane handle about three and a half feet long.

The killing-bottle (fig. 169) is prepared by putting a few small lumps (about a teaspoonful) of cyanide of pota.s.sium into the bottom of a wide-mouthed bottle holding about four ounces, and covering this cyanide with wet plaster of Paris. When the plaster sets it will hold the cyanide in place, and allow the fumes given off by its gradual volatilization to fill the bottle. Insects dropped into it will be killed in from two or three to ten minutes. Keep a little tissue paper in the bottle to soak up moisture and to prevent the specimens from rubbing. Also keep the bottle well corked. Label it "Poison," and do not breathe the fumes (hydrocyanic gas). Insects may be left in it over night without injury to them.

b.u.t.terflies or dragon-flies too large to drop into the killing-bottle may be killed by dropping a little chloroform or benzine on a piece of cotton, to be placed in a tight box with them. Larvae (caterpillars, grubs, etc.) and pupae (chrysalids) should be dropped into the vials of alcohol.

In collecting, visit flowers, sweep the net back and forth over the small flowers and gra.s.ses of meadows and pastures, look under stones, break up old logs and stumps, poke about decaying matter, jar and shake small trees and shrubs, and visit ponds and streams. Many insects can be collected in summer at night about electric lights, or a lamp by an open window.

When the insects are brought home or to the schoolroom they must be "pinned up." Buy insect-pins, long, slender, small-headed, sharp-pointed pins, of a dealer in naturalists' supplies (see p. 453). These pins cost ten cents a hundred. Order Klaeger pins, No. 3, or Carlsbaeder pins, No.

5. These are the most useful sizes. For larger pins order Klaeger No. 5 (Carlsbaeder No. 8); for smaller order Klaeger No. 1 (Carlsbaeder No.

2). Pin each insect straight down through the thorax (fig. 170) (except beetles, which pin through the right wing-cover near the middle of the body). On each pin below the insect place a small label with date and locality of capture. Insects too small to be pinned may be gummed on to small slips of cardboard, which should be then pinned up. Keep the insects in drawers or boxes lined on the bottom with a thin layer of cork, or pith of some kind. (Corn-pith can be used; also in the West, the pith of the flowering stalk of the century plant.) The cheapest insect-boxes and very good ones, too, are cigar-boxes. But unless well looked after they let in tiny live insects which feed on the dead specimens. For a permanent collection, therefore, it will be necessary to have made some tight boxes or drawers. Gla.s.s-topped ones are best, so that the specimens may be examined without opening them. A "moth-ball"

(naphthaline) fastened in one corner of the box will help keep out the marauding insects.

[Ill.u.s.tration: FIG. 170.--Insect properly "pinned up." (From Jenkins and Kellogg.)]

b.u.t.terflies, dragon-flies, and other larger and beautiful-winged insects should be "spread," that is, should be allowed to dry with wings expanded. To do this spreading- or setting-boards (figs. 171 and 172) are necessary. Such a board consists of two strips of wood fastened a short distance apart so as to leave between them a groove for the body of the insect, and upon which the wings are held in position until the insect is dry. A narrow strip of pith or cork should be fastened to the lower side of the two strips of wood, closing the groove below. Into this cork is thrust the pin on which the insect is mounted. Another strip of wood is fastened to the lower sides of the cleats to which the two strips are nailed. This serves as a bottom and protects the points of the pins which project through the piece of cork. The wings are held down, after having been outspread with the hinder margins of the fore wings about at right angles to the body, by strips of paper pinned down over them.

"Soft specimens" such as insect larvae, myriapods, and spiders should be preserved in bottles of alcohol (85 per cent). Nests, galls, stems, and leaves partly eaten by insects, and other dry specimens can be kept in small pasteboard boxes.

For a good and full account of insect-collecting and preserving, with directions for making insect-cases, etc., see Comstock's "Insect Life," pp. 284-314.

[Ill.u.s.tration: FIG. 171.--Setting-board with b.u.t.terflies properly "spread." (After Comstock.)]

_Birds._--In collecting birds, shooting is chiefly to be relied on. Use dust-shot (the smallest shot made) in small loads. For shooting small birds it is extremely desirable to have an auxiliary barrel of much smaller bore than the usual shotgun which can be fitted into one of the regular gun-barrels. In such an auxiliary barrel use 32-calibre sh.e.l.ls loaded with dust-shot instead of bullets. Plug up the throat and vent of shot birds with cotton, and thrust each bird head downward into a cornucopia of paper. This will keep the feathers unsoiled and smooth.

[Ill.u.s.tration: FIG. 172.--Setting-board in cross-section to show construction. (After Comstock.)]

Birds should be skinned soon after bringing home, after they have become relaxed, but before evidences of decomposition are manifest. The tools and materials necessary to make skins are scalpel, strong sharp-pointed scissors, bone-cutters, forceps, corn-meal, a mixture of two parts white a.r.s.enic and one part powdered alum, cotton, and metric-system measure.