The old saying, 'Prevention is better than cure,' applies well in the present case; but as there are times when a knowledge of the 'cure' is the only means of saving a valuable specimen from destruction, we will study both.
To deal with the two in the order of the well-worn proverb, we will consider the prevention first. Always carefully clean out and stuff the abdomens of large-bodied insects; and as a rule, treat them with some substance that will either absorb or dissolve out all oily matter. I think the best plan is to remove the abdomen, clean it out if its size permits of such an operation, and then, after labelling it to prevent its future application to the wrong body, either let it
remain in a bottle of magnesia for several weeks, or soak it in benzole or ether for a few hours or longer.
If magnesia has been employed as an absorbent, you have simply to blow or lightly brush off the loose powder that clings to the body, and then fix it in its place with coaguline. A body dipped in ether or benzole will look as if completely spoilt at first, for the furry coat that clothes it will lie matted and almost entirely robbed of its beautiful colours, reminding one forcibly of the proverbial 'drowned rat.' But take no notice of this change. Let the body have at least a few hours in the liquid, extending the time to a day or two in the case of very large ones and those which experience has proved to be particularly liable to 'grease;' and, immediately on withdrawing it, fix it with a pin in a good strong draught, such as you may obtain by opening a window about an inch, or, if a breezy day, in the open air.
These liquids are so volatile (and for that reason should never be left exposed in an open vessel) that they rapidly evaporate, leaving the dry hair to be loosened by the breeze, thus bringing back the natural appearance almost perfectly.
It is probable that many of the smaller insects that were not considered to require the stuffing or grease-removing operations will sooner or later exhibit a greasy tendency in the cabinet. At first the abdomen is affected, and the oily matter then gradually creeps over the rest of the body, finally spreading over the wings, and giving the insect a most deplorable aspect. But these are not irreparably lost, and the following cure will often bring them back to their former beauty.
If the abdomen only shows signs of grease, cut it off and soak it in one of the above-named liquids for a day or so, replacing it as above after the drying operation. If, however, the oily matter has spread to the thorax and the bases of the wings, the whole specimen must be soaked, using a basin or jar of suitable size, covered with a plate of glass. A good draught during the drying operation will do much to prevent the hair from sticking in matted tufts close against the surface of the body and wings, and a gentle brushing with a very soft camel-hair brush will loosen and reset the fur.
The other danger to which we have referred is the invasion of certain 'mites' and other museum pests that pay periodical visits to our cabinet drawers and store boxes, often committing such havoc as to severely try the patience of an interested naturalist.
The way to prevent such intrusions is to make the atmosphere of the compartments so obnoxious (to them) that they dare not enter; and, further, to so spice up your specimens that they are no longer safely edible to the invaders.