PLATE I. 
ABBREVIATIONS. 
B. Back surface covered with wings. _O. Orifice for admission of light. 
F. Front surface covered with wings. 8S. Spectroscope. 
Arrow indicates directions of rays of light. 
Fig. 1. Perspective view of spectroscopic apparatus used in determining the 
composition of the colors of Lepidoptera. 
Fig. 2. Horizontal section of same. See p. 175. 
Fig. 3. Pendulum used in determination of the frictional resistance between 
the air and the wings of Lepidoptera. See p. 193. 
Figs. 4,5. Diagrams to illustrate Keeler’s method of projection, as applied to 
Lepidoptera. See p. 207. 
