SETTING AND PRESERVING OF INSECTS.
COLLECTORS are generally satisfied, if they can obtain the In∣sect in its last, or fly state, but as a few instructions for the preser∣vation of the Egg, Caterpillar, and Chrysalis, may induce some future Naturalists to enrich their cabinets with such specimens, in addition to the Insect itself, we have selected a few particulars for their purpose.
The eggs of most Insects retain their form and colour well, if preserved in the cabinet, but those which do not promise fairly, may be prepared after the method practised by Swammerdam; he used to pierce the eggs with a very sine needle, and press all the contained juices through the aperture; then inflated them until they regained their proper form by means of a small glass tube, and lastly filled them with oil of spike, in which some resin had been dissolved.
The preservation of Insects in this state, is not only one of the most curious, but useful discoveries that have been made in this de∣partment of science. They may be preserved by being plunged into phials filled with well rectified spirits of wine: this method should ever be preferred by those who collect in a distant country, if their subjects are not likely to be injured by such a process, the most delicate Caterpillars will retain their exact size, but the spirits will generally extract the colour, and from those especially which have very tender skins.
But the manner in which Swammerdam preserved his Caterpillars, completely obviates this defect, and if carefully managed, it not only preserves the exact size, but generally retains the colours as per∣fectly as in the living creature.
He used to make a small incision or puncture in the tail, and having very gently and with much patience pressed out all the con∣tained humours, injected wax into them, so as to give them all the appearance of healthy living Insects. In this manner he has preserved many very small specimens.
There is another method which is more generally known to col∣lectors; it consists in taking out all the inside of the Caterpillar, and inflating the skin by means of a glass tube.
The entrails, with whatever of the sleshy substance can conve∣niently, is drawn through the anus by means of sine wire curved at the end; when the inside is emptied, the glass tube is inserted Page 38into the opening, through which the operator continues to blow while he turns the skin at the end slowly round over a charcoal fire; this hardens the skin equally, and dries up all the moisture within; a pin is then put through it to fix it in a standing position: if the skin is tender it may be filled with white paper or cotton.
But this is a most cruel operation on the little victim, and such as must shock the feelings of the human soul; if therefore any other method can be introduced which will effect the purpose in a short time, the practice should be exploded as wanton barbarity.
Various attempts have been made, and among these some have tried to drown the Caterpillar, but you will never be able to ac∣complish its death in this manner, unless it remains for a considerable time under water, and though it may appear dead, the principle of life will not be destroyed. Mr. Bonnet, making experiments on the respiration of Insects, had one Caterpillar which lived eight days with only two of its anterior spiracula in the air.
The method we wish to recommend is to observe when the Cater∣pillar is on the point of casting its last skin; drop it by the threads into scalding water, and quickly withdraw it; the creature will be killed instantly; then put it into some distilled vinegar mixed with spirit of wine, which will give a proper firmness to all the parts and ac∣celerate the separation of the skin from the body; the flesh may be carefully extracted, and the exuvia or skin be blown up by means of a glass tube while suspended over a charcoal fire, as before de∣scribed.
Anoint it with oil of spike in which some resin has been dis∣solved, unless it is a hairy Caterpillar.
THE PUPA OR CHRYSALIS.
When Insects have quitted the pupa state, the case will require only to be put into the drawers or boxes with some camphire, but those which have the Insects within, must be either dropped into scalding water, or inclosed in a small chip box, and exposed to the heat of a fire, which will shortly kill the Insect within.
I have found that if those chrysalides which have the appearance of gold, are put into spirit of wine they will always retain that co∣lour, but if the Insect within is killed first, or if the fly has quitted it, such appearance is entirely lost.