The heat is derived from the flame of a spirit or petroleum lamp. Above this is placed a piece of sheet-tin, and over this the roasting proceeds. A bulging lamp cylinder, laid horizontally, serves as a roasting oven. In this the insect to be dried, when prepared as directed, and stuck on a piece of pith, is to be held over the flame; or the cylinder may be closed at the lower end with a cork, which should extend far inwards, and on this the insect should be fastened; the latter mode being preferable because the heat is more concentrated, and one hand is left free. The mode of procedure varies according to the nature of the objects to be treated. For the class of larger objects, such as Hemiptera, Cicadina, and Orthoptera, in their young stages of existence, the heat must not be slight, but a little practice shows the proper temperature required. If the heat be insufficient, a drying up instead of a natural distention ensues. The insect to be roasted is to be pierced by a piece of silver wire on the under side of the thorax, but it is not to be inserted so far as to damage the upper side, and the wire should then be carried through a disk of pith, placed beneath the insect, on which the legs should be set out in the desired position. But with some objects, such, for instance, as a young _Strachia_, the drying proceeds very quickly, so that if distention be not observed then the heat is too great, for the expansion of the air inside will force off the head with a loud report; also, with softer, thicker Pentatomidae care must be taken to begin with a heat only so strong that the internal juices do not boil, for in such case the preparation would be spoiled. It is of advantage to remove the cylinder from time to time, and test, by means of a lens, if a contraction of the skin has taken place on any part; if so, the roasting is to be continued. The desired hardness may be tested with a bristle or wire. For _Aphides_ the _living Aphis_ is to be put on a piece of white paper, and at the moment when it is in the desired position it is to be held over the flame, and in an instant it will be dead and will retain the attitude. Then put it, still on the paper, into the oven; or, still better, hold it over the heated tin, carefully watching the drying and moving the paper about in order to prevent it getting singed. The roasting is quickly accomplished in either way, but somewhat slower out of the oven especially in the larger kinds, such as Lachnus. If the paper turn brown it is a sure sign that caution is requisite. To pierce these brittle preparations for preservation is hazardous, and it is a better way to mount them with gum on card, placing some examples on their back.