Part 29 (1/2)
=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_.