Eggs may be preserved by plunging them in boiling water or piercing them with a very fine needle, or they may have their contents squeezed out and be refilled by means of a fine blowpipe, with some coagulable tinted fluid; but the shells themselves, after the escape of the larvæ, form, when mounted, beautiful objects for the microscope.
The three most successful plans of obtaining caterpillars are searching, beating, and sweeping. The first requires good eyesight and a certain amount of preparatory knowledge; the others are a sort of happy-go-lucky way of collecting, useful enough and profitable in their way, but affording a very limited scope for the exercise of the wits. In searching for larvæ, the chief thing is to observe the indications of their presence. A mutilated leaf, a roughened bark, a tumid twig, a sickly plant, an unexpanded bud, an abortive flower, or a windfall fruit, should at once set us thinking as to the cause; or, again, the webs, the silken threads, the burrowings and trails, or the cast-off skins of larvæ, may first call our attention to their proximity. Of course, larvæ may be found on almost all plants, as well as in the bark, stems, or wood of many; but the collector should fortify himself with a knowledge of what each plant is likely to produce, and hunt accordingly; for though indiscriminate collecting may sometimes be successful, it does not tend to improve the intellectual powers.
Beating is the more applicable method of working trees and bushes. It is carried out by jarring the larvæ from their positions by the aid of a stick or pole, in such a manner that they will fall into an inverted umbrella, or net; or a sheet may be spread beneath for their reception. Sweeping with a strong net, passed from side to side with a mower-like movement, is better adapted for working low ground-herbage. The umbrella net, shown in [Fig. 11], is, perhaps, the best for the purpose. It is constructed by hinging two lengths of jack-spring on two pieces of brass, and adapting them to the stick of the net, the upper piece of brass being fixed, the lower movable.
Fig. 11. Umbrella Net.
When captured, larvæ should be transferred to chip boxes, or else to finely and freely perforated tins, the latter better preserving the food. A very handy box for the purpose is formed by fitting a second lid on to the bottom of a chip box, and then cutting from the second lid and bottom a hole, as shown in [Fig. 12 (2)]; larvæ may then be inserted through the hole; but when the lid is shifted round, and the holes are not opposite, of course there will be no opening, as in [Fig. 12 (1)], and the contents are secured from escape.
Fig. 12. Collecting Box for Larvæ.