The Butterflies of the British Isles

by Richard South

In connection with nets it may be well to advise the wielder to remember that carrying a threaded needle is a useful practice. Tears and rents are apt to occur, and it is well to have the means of repair handy.

Killing.

Some collectors seem to be expert at killing butterflies by pressing the sides of the thorax together. The method is not, however, as satisfactory as one could wish, and so no more need be said about it. For the happy despatch of insects, the cyanide bottle is frequently used. All that has to be done is to clap the open bottle over the captive while still in the net, then draw the gauze or what-not over the mouth of the bottle until the bung can be inserted, and the whole affair withdrawn from the net.

Cyanide of potassium is a deadly poison, and no inexperienced person should attempt to charge a cyanide bottle himself. In fact, chemists are not permitted to supply the poison to unknown customers. Under certain conditions, however, a chemist might consent to make up a killing bottle, and the following instructions may help him in doing this. A fairly strong, clear glass bottle, holding about 4 to 6 ounces; the mouth must be pretty wide, and closed with a well-fitting bung that has been dipped in melted wax; if the bung is of fine grained cork, the wax will not be needed. At the bottom of the bottle place a thick layer of the cyanide, and over this pour plaster of Paris which has been mixed with water and converted into a cream-like paste: one-third of the depth of the bottle to be occupied by the poison and plaster, but only a thin layer of the latter should cover the former.

Dealers who supply cyanide bottles (uncharged) also have in stock a brass bottle for chloroform, which some people prefer as a killing agent because it does not change the colour of insects as cyanide is occasionally apt to do. In using this, the insect should be boxed, then a drop of the chloroform may be allowed to run from the bottle over the perforated lid or bottom of the box, and a finger put over the hole or holes for a short time.

The majority of butterflies, if transferred to pill boxes from the net, settle down quietly. In this way they may be taken to one's home and there placed, boxes and all, into the ammonia jar, a simple but very effective contrivance. To start one of these lethal chambers, procure a good sized pickle jar, one of the brown earthenware kind, holding about 2 gallons. At the bottom put in several layers of stout blotting-paper, and have ready a covering for the mouth of the jar. This covering may be of skin, waterproof-apron material, or even thick brown paper. Before turning the boxes into the jar, lift up the blotting-paper, drop in about half a teaspoonful of strong liquid ammonia (⋅880) and replace blotting-paper. Directly the boxes are in the jar, put on cover and tie it down securely. If brown paper is used, a piece of pasteboard should be put over it and a weight on top of that. Suffocation takes place directly the gas reaches the insect, but it often happens that one or more of the boxes exclude the gas longer than others. At the end of half an hour all may be removed, but the insects will not hurt in any way if left in all night.

The best kind of boxes for field work are those known as "glass bottomed," as in these the captives can be examined and, if not wanted, may be set free. It is always better to retain only those specimens that we know are really useful, rather than to incur the necessity of throwing away insects after we have deprived them of life.

Pinning.

If butterflies are pinned on the spot, a collecting box will be required, and the most useful and convenient is one of an oval shape. This should be made of zinc, and lined with cork that is held in place by zinc clips. The cork should be kept damp when in use, and the water used for damping should have a few drops of carbolic acid mixed with it so as to prevent the formation of mould. Insects may remain in such a box for several days without injury. This box will also be useful for relaxing specimens that have been badly set, or have been simply pinned during the busy season.

In the matter of pins, it is not altogether easy to make suggestions. There are, perhaps, only two makers in this country of entomological pins, and each of these supplies a large number of sizes. The selection of suitable pins will largely depend on the method of setting adopted. Black pins are, however, the best for butterflies, and are now used almost exclusively.