Directions for Collecting and Preserving Insects

by Charles V. Riley

Fig. 107.—Spreading-case (original).

Fig. 108.—Spreading apparatus for Microlepidoptera
(original).

[A new Apparatus for Spreading Microlepidoptera.]—For the spreading of Microlepidoptera my assistant, Mr. Theo. Pergande, has devised an apparatus, represented in the accompanying illustration, which he finds very convenient. It consists of a small spreading-block represented at B and the support with attachment shown at A. The former is made in a long strip of the shape shown in the illustration, having a square groove, c, cut in the top. Over this is glued a thin strip of wood, b, say ⅛ inch thick, and a narrow slit is sawed in the center of this above, cutting through into the groove c. This is then sawed up into pieces of uniform length, say 1½ to 2 inches, and the block is completed by the insertion of a rectangular strip of pith or cork into the groove. The Micro is pinned on a short black pin, and the pin is thrust down into the narrow opening made by the saw and is held firmly by the pith or cork. This block is then slid into the groove in the setting-board A, which narrows slightly from e, and pushed along until firmly secured (d). The operator can then rest his hands and arms on either side of the support, and, if necessary, bring a large hand lens over the object by means of a support with ball-and-socket joint shown at e. The wings may thus be easily and accurately arranged and fixed in position with pins or strips of paper, as in the ordinary mounting of such insects. Two or three specimens may be mounted on each of these blocks. The construction of the support is indicated in the annexed drawing. One side is attached by clamps, shown enlarged at f, which afford means of adjusting the width of the slit in which the small sawed blocks slide and correct the shrinking or swelling which may take place in moist or dry seasons. The advantage of the apparatus is that the operator has the setting block firmly fixed before him and has both hands free to manipulate the wings of the insect in addition to having the lens in a convenient position, the use of which is necessary in the preparation of the very minute forms.

[Spreading Microlepidoptera.]—The mounting of Microlepidoptera is about the most delicate work in entomotaxy, and I can not do better than quote the explicit directions given by Lord Walsingham on the subject.

Returning to camp I put a few drops of liquid ammonia on a small piece of sponge and place it in a tin canister with such of the boxes as do not contain the smallest species, and put these and the remainder away until morning in a cool place. In the morning I prepare for work by getting out a pair of scissors, a pair of forceps, my drying-box containing setting-boards, a sheet of white paper, and some pins.

First, I cut two or three narrow pieces of paper from 3 to 6 lines wide, or rather wider, according to the size of the largest and smallest specimens I have to set. I then double each of these strips and cut it up into braces by a number of oblique cuts. Now I turn out the contents of the canister and damp the sponge with a few drops of fresh ammonia, refilling with boxes containing live insects. Those which have been taken out will be found to be all dead and in a beautifully relaxed condition for setting. Had the smallest specimens been placed in the canister over night there would have been some fear of their drying up, owing to the small amount of moisture in their bodies.

If the weather is very hot there is some danger of killed insects becoming stiff while others are being set, in which case it is better to pin at once into a damp cork box all that have been taken out of the canister, but under ordinary circumstances I prefer to pin them one by one as I set them.

Taking the lid off a box, and taking the box between the finger and thumb of the right hand, I roll out the insect on the top of the left thumb, supporting it with the top of the forefinger and so manipulating it as to bring the head pointing toward my right hand and the thorax uppermost. Now I take a pin in the right hand and resting the first joint of the middle finger of the right against the projecting point of the middle finger of the left hand to avoid unsteadiness, I pin the insect obliquely through the thickest part of the thorax, so that the head of the pin leans very slightly forward over the head of the insect. After passing the pin far enough through to bring about one-fourth of an inch out below,[6] I pin the insect into the middle of the groove of a setting board so that the edge of the groove will just support the under sides of the wings close up to the body when they are raised upon it. The board should be chosen of such a size as will permit of the extension of the wings nearly to its outer edge. The position of the pin should still be slanting a little forward. The wings should now be raised into the position in which they are intended to rest, with especial care in doing so not to remove any scales from the surface or cilia of the wings. Each wing should be fastened with a brace long enough to extend across both, the braces being pinned at the thick end, so that the head of the pin slopes away from the point of the brace; this causes the braces to press more firmly down on the wing when fixed. The insect should be braced thus: The two braces next the body should have the points upwards, the two outer ones pointing downwards and slightly inwards towards the body, and covering the main portion of the wings beyond the middle. Antennæ should be carefully laid back above the wings, and braces should lie flat, exercising an even pressure at all points of their surface. The fore wings should slope slightly forwards so that a line drawn from the point of one to the point of the other will just miss the head and palpi. The hind wings should be close up, leaving no intervening space, but just showing the upper angle of the wing evenly on each side. I can give no more precise directions as to how this desirable result may most simply and speedily be attained; no two people set alike. Speed is an object; for I have often had to set twelve dozen insects before breakfast. A simple process is essential, for a man who is always pinning and moving pins, and rearranging wings and legs, is sure to remove a certain number of scales and spoil the appearance of the insect, besides utterly destroying its value. I raise each of the fore wings with a pin, and fix the pin against the inner margin so as to keep them in position while I apply the braces. Half the battle is really in the pinning. When an insect is pinned through the exact center of the thorax, with the pin properly sloped forward, the body appears to fall naturally into its position on the setting board, and the muscles of the wings being left free are easily directed and secured; but if the pin is not put exactly in the middle it interferes with the play of the wings. Legs must be placed close against the body or they will project and interfere with the set of the wings. Practice, care, and a steady hand will succeed. When all the insects that have been killed are set the contents of the canister will be found again ready, twenty minutes being amply sufficient to expose to the fumes of ammonia. Very bright green or pale pink insects should be killed by some other process, say chloroform, as ammonia will affect their colors.

Insects should be left on the setting boards a full week to dry; then the braces may be carefully removed and they may be transferred to the store box.

In my own experience I have found that a touch or two of the chloroform brush on the pill-box containing small moths is sufficient to either kill or so asphyxiate them that they can easily be mounted. I have also found that strips of corn pith or even of soft cork, with grooves cut into them, are very handy for the pinning and spreading, and that by means of a small, broad-tipped, and pliable forceps the smallest specimens can be deftly arranged in the groove and kept in place until pinned. In fact, for all persons who have not very great experience and dexterity this method is perhaps more to be recommended than that of holding them between the thumb and fingers. Where chloroform is used either to kill or deaden specimens, it is important that after they are once spread and in the drying box they should be subjected to an additional asphyxiation, as the larger species may revive and are apt to pull away from the holding strips, and thus rub off their scales.

Microlepidoptera, together with Microhymenoptera and Diptera may be conveniently pinned on fine, short pins, and these thrust into an oblong bit of cork or pith. This form of mounting has already been described and is represented in figure 102. The neatest mounting of Microlepidoptera which I have seen is the work of my assistant, Mr. Albert Koebele, who mounts these insects on an oblong strip of pith. This is very light and presents no difficulty in pinning. The strips may be made of considerable length and both sexes may be pinned on the same block (see [Fig. 103]). Most Lepidoptera present on the under surface an entirely different aspect from that on the upper surface, and, in such cases, it is a good plan to mount a number of specimens obversely.

[Relaxing.]—It will frequently be desirable to re-spread insects which have been incorrectly mounted, or to spread specimens which have been collected and stored in papers, or pinned and allowed to dry without being prepared for the cabinet. Such specimens may be relaxed by placing them in a tight tin vessel half filled with moist sand to which a little carbolic acid has been added to prevent molding. Small specimens will be sufficiently relaxed to spread in twenty-four hours. Larger specimens require from two to three days. More rapid relaxing may be caused by the use of steam, and a flat piece of cork with the specimens laid or pinned thereon and floated on the top of hot water in a closed vessel constitutes an excellent relaxing arrangement.