1. Two strips of pine or other soft wood 18 inches long, 11/2 inches wide and 1/2 inch thick.
2. One strip of wood 18 inches long, 31/4 inches wide and 1/2 inch thick.
3. Two cleats 31/4 inches wide, 3/4 inch high and 1/2 inch thick; and two cleats 1 inch wide and as high and thick as the others.
4. A strip of cork or linoleum 17 inches long and a little less than an inch wide.
To construct the spreading-board, take the two narrow strips of wood, place them one-fourth inch apart and on the under side fasten them across the ends of the longer cleats. Then on the same side as the cleats tack the piece of cork or linoleum over the space between the strips of board, and as the cleats are one-half inch wide the linoleum should cover all the space left. Then midway the boards fasten the two smaller cleats. [Fig. 135] shows a cross-section of the spreading-board just in front of these two middle cleats. Now it is ready for the bottom board which will fit exactly if directions are followed, and this completes it. The space between the two upper boards is wide enough to take in the body of the moth or butterfly. The cork or linoleum below the space will hold firmly the pin on which the butterfly is impaled. The cleats hold the top and bottom boards apart and so protect the points of the pins. Spreading-boards may be made much smaller or much larger to suit moths of different sizes; the space between the top boards must always be large enough to admit the body of the insect.
Fig. 135. A cross-section of spreading-board in front of the cleat "d" in [Fig. 134].
To use the spreading-board: Insert the pin with the butterfly on it into the linoleum just far enough so that the body of the insect will be in the space between the boards up to the wings, [Fig. 135]. Place the wings out flat on the board and fasten them there with narrow strips of paper pinned across them, [Fig. 134], a. While held down by these strips of paper arrange them so that the hind margins of the front wings shall cover the front margins of the hind wings and shall be in a line at right angles to the body; then pin larger pieces of paper over the rest of the wings, [Fig. 134], b. Sometimes isinglass is used instead of paper to hold the wings down, [Fig. 134], c. The insects should be left on the spreading-board at least three days; and when the board has insects on it, it should be kept in a box where the museum pests and mice cannot get at it.
Sometimes when the moths are not spread soon after being killed, they become so stiff that the wings cannot be moved without breaking them. In such cases the insects should be put on paper in a jar which has some wet sand in the bottom and which can be covered tightly. The air in such a can is so moist that in two or three days the insect will become limber and may be spread with ease.