This also makes a cheap substitute for the breeding cage for larvae, if a little earth only is put in the flower pot in which a bottle of water is placed containing the food plant. Wire gauze cylinders are handy as affording plenty of air to delicate larvae. Bandboxes with a square piece cut out from the top lid, the hole thus made covered with muslin, will do very well for breeding a quantity of a hardy common sort.
Fig. 57 — Insect breeding cage
The usual wooden breeding cage is shown at Fig. 57. This requires hardly any explanation: A is a glass door, B B B are sides and top of perforated zinc, C is a tray fitting inside, where dotted lines are shown, to hold the earth in which the bottle of water holding food is placed, or where the larvae bury themselves to change to pupae. Properly, the inner tray of box C should be constructed of zinc perforated with a few holes at the bottom, in order that it may be lifted out to allow the pupae to be well damped when "forcing." [Footnote: For those larvae of butterflies and moths which do not require earth, it will be sufficient to have a zinc pan, with covered top perforated with holes, in which the stalks of the food plants be inserted in the water which fills the pan, whose covering prevents the insects from drowning themselves therein.]
"Forcing" is a method adopted to cause any moth to emerge at the collector's will, and several months before its proper time, it having been proved that certain moths more than others die in the chrysalis or pupa state if left to go their full time, notably the "Death's Head," the "Spurge," and other hawks. The best time for forcing is about Christmas, and the conditions are simply heat and moisture, the pupae being placed over a spirit lamp, in a hothouse, on the kitchen mantelpiece, or by the fire grate even, kept for a week or so at a temperature of 85 deg. or thereabout, and constantly damped with moss wrung out in warm water. Bear in mind that heat without moisture will not do by any means.
The breeding cage itself need not be used, but only the tray, provided that gauze is stretched over in such a manner as to allow room for the moth to dry its wings on emergence. But if the whole of the breeding cage were made of framed zinc (such as aquaria are made of), and the glass and perforated zinc fixed in, the cost, though greater at first, would be more than counterbalanced by its greater strength, with lightness and capability of resisting wear and tear, added to which is the advantage of being used as a whole during the operation of "forcing," wood not standing, of course, the heat and moisture necessary. Breeding cages should not be painted.
Fresh food, and plenty of it, should, if possible, be supplied to the larvae. Dry food is, as a rule, the best, though the larvae of one or two of the foreign Saturnidae require their food to be sprinkled with water, and sometimes even with the addition of salt, to make them thrive. Moths on emergence should not be killed at once, as they are then too flaccid, and have not sufficiently purged themselves. Yet they should not be left too long or over night, as they often fly at that time, and knock themselves about in the cage, to the detriment of their beauty; destroying, in fact, the whole aim and end of breeding, which is of course, instituted to procure specimens for the cabinet as fine as it is possible to get them.
In collecting insects it is always as well to bear in mind that a "worn" female, though not of the slightest use to the entomologist, unless she can be induced to lay in confinement, may become the progenitor of many, and may thus afford you during the next season great pleasure in collecting. This being so, I should like to impress upon my readers (the young especially) the propriety of giving all insects, not actually noxious, heir liberty, if on examination they prove to be useless as specimens. These remarks apply also to the case of hybernated females. Many female insects, though unwilling to lay in confinement, may be watched at large, and the flowers and plants on which they have from time to time rested, searched for their eggs.
In concluding this chapter, I feel that I might have said much more upon nearly every section — have explained many new "dodges," and so forth, were it not that the limit of space has been reached. One thing, however, may be noted as an omission, and that is the recommendation as to what books should be procured by the young entomologist. This is so difficult a matter — depending entirely upon the aim of the individual — that I prefer to leave it an open question, merely making the general statement that nearly all our advanced systems are founded upon the labours of German and French entomologists. [Footnote: Mr. Wm. Wesley. Essex Street Strand, London, publishes monthly a "Natural History Book Circular," which he will send to naturalists if asked.]