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.)
[a]Fig. 89.]—Net-head for Removable Frame. (After Riley.) The frame is made of elastic brass ribbon, and may be put inside of the hat when not in use, and the handle used as a cane.
[a]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, illustrating 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 glass 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 mass 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.
[a]Fig. 91.]—Collecting Jar. Cy., Cyanide of potash wedged into place with soft paper; P, perforated paper disc.
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.
