They are very abundant in Spain and in the South of France, especially in June, when they assemble in swarms. This is the time for gathering them, and the hour of sunset or sunrise is chosen for the purpose, as they are then in a somewhat torpid state. They are found upon ash-trees, honey-suckles, lilacs, rose-trees, poplars, elms, &c., the leaves of which they devour, and when this food fails they attack corn and grass, and do much damage. The swarms are preceded by a fœtid odour resembling that of _mice_. They are gathered in various ways; the most simple is to spread cloths under the tree upon which a swarm has settled, and then to shake them down; they are afterwards collected upon a hair sieve, and held over the vapour of boiling vinegar, which kills them; or the cloth in which they are collected may be folded loosely up and dipped in vinegar, which has the same effect. Another method is to boil a quantity of vinegar under the tree where they are collected, and the ascending vapour kills them. The particles emitted by these insects are so very corrosive that persons are liable to be violently affected who attempt to gather them with bare hands during the heat of the day. It is also dangerous to be under a tree where a swarm has gathered. Persons who collect them should always wear a mask and gloves. After the insects are killed they must be dried; this is done in the sun or in a heated room, upon tiles covered with cloth or paper. They are moved about from time to time with a stick, or with the hands furnished with gloves. When properly dry they are so light that fifty weigh scarcely a drachm. They are packed in boxes or barrels lined with paper and perfectly dry. If damp gets to them they contract a detestable odour, and are unfit for use. A portion of our supply of cantharides is from Astracan and Sicily: but the greatest quantity is from St. Petersburgh, the Russian insects being superior to those of Sicily and France. In using cantharides they are reduced to powder, mixed with some fatty substance, and applied in the form of a plaster to the surface of the body: it begins to act immediately, and separates the outer skin from the dermis with great rapidity. A singular employment of insects in the composition of _soap_ is made in some parts of Africa. Geoffrey the younger relates, that being at the village of Postudal, some leagues from Senegal, in search of insects, one of the negroes whom he had employed in the same pursuit brought him a vessel containing an immense quantity of a small species of carabus, and informed him that this insect entered into the composition of the soap used in that country; at the same time he exhibited a ball of a dark-coloured soap, the properties of which are similar to the soap used in Europe. It appears that the insect abounds in alkali, which makes it useful for the purpose in question.