MAYER: COLOR AND COLOR-PATTERNS. 173 
(5) Spectrum Analysis of Colors of Lepidoptera. 1 haye made 
some spectrum analyses of the light reflected from the wings 
of various butterflies, by means of a piece of apparatus most kindly 
suggested for the purpose by Prof. Ogden N. Rood of Columbia 
College. The arrangement is shown in Figs. 1, 2, Plate 1; Fig. 1 
being a perspective view, and Fig. 2 a horizontal section of the 
apparatus, which consists of a rectangular box, blackened upon the 
inside, and having a well-fitting cover. A rectangular slit (0) was 
cut through one of the long sides of the box, near one end, and the 
other end of the same side was perforated in order to allow the 
admission of the direct-vision spectroscope (S). Imagine that we 
wish to examine the yellow spots from a butterfly’s wing. All of 
the yellow spots from the wing are cut out, and pasted upon two 
pieces of cardboard so as to make two large unbroken patches of 
color. The pieces of cardboard are then blackened upon all those 
places where the colored wing was not pasted. One of the card- 
boards is then suitably mounted upon the back of the box at B; the 
other is placed upon a vertical support (IF), the plane of which is 
parallel to the back of the box. 
The working of the apparatus is as follows: the sunlight enters 
by the slit (O) and is reflected and diffused three or four times 
between the pieces of colored wing mounted upon the back (B) of 
the box, and the vertical support (I*). The manner of this reflec- 
tion and diffusion is shown by the dotted lines of Fig. 2. After 
undergoing several reflections, the light enters the direct-vision 
spectroscope (5). The slit of the spectroscope is wide open, and 
thus the light which enters it may readily be examined. It was 
found that it was necessary that the light be reflected more than 
once from the wing before it enters the spectroscope, for the first 
reflection shows so much white light that it is usually quite impossi- 
ble to analyze the true color of the wing, the predominant colors 
being obscured by a continuous spectrum. In general it was found 
that the colors of the wings are not simple, but compound ; that is 
to say, they are made up of a mixture of several different colors. 
For example, the spectrum of the rufous ground color of the 
upper surface of the wings of Danais plexippus consists of all of the 
red and yellow of the spectrum and about 75% of the green, 
The red spots upon the upper side of the fore wings of Heliconius 
melpomene also consist of the red and yellow and a very faint, 
hardly visible, trace of green. 
