136 
PSYCHE 
[Dece'iiber 
THE PATTERN VARIATION IN THE PUPA OF MELITAEA CHALCE- 
DON.— PLATE VHI. 
BY LILIAN' RAMSAY, .STANFORD UNIVERSITY, CAL. 
Variation in color pattern Is familiar among adult insects. If color pattern is 
of advantage in the way of aiding insects, by protective resemblance, mimicry, warn- 
ing, recognition, etc., in the struggle for e.xistence, variations in the pattern are the 
material seized on by natural selection upon which new types of pattern and ulti- 
mately new species are built. That is, this is true if the natural selection theory 
of specie.s-forming is true. 
But in.sects have a .struggle for existence in their immature stages as well as in 
adult condition and these young stages must be protected as well as the imaginal 
life. Are variations as numerous and as marked in immature characters as in adult 
ones? The assumption is, of course, that they are, but as a matter of fact there 
seem to be few specific proofs of this recorded in the large and rapidly growing litera- 
ture of variation. As a simple contribution of definite data of variation in an imma- 
ture character, I present the following brief statement and plate showing the variation 
in the pattern (black markings on a gray-green ground) of the antero-ventral half 
of the naked pupa of the checker spot butterfly, Melitaea Chalcedon. 
The series examined included 127 pupae (chrysalids) obtained from as many 
nearly full-grown larvae collected at one time in one place on the University campus 
and reared to pupation in the laboratory. All the larvae were enclosed in a single 
breeding cage and hence all pupated under identical environment. The variations 
may be looked on therefore as blastogenic in character. 
No two of the chrysalids have exactly the same markings. The pattern variation 
is typically continuous or gradatory, any two types being perfectly connected by 
gradatory inter-types. Hence no statistical tabulation of the variation can be made. 
The twenty-four types figured re])resent the range of variation and to some one of 
them can be referred ajiproximately any chrysalid examined. But actually each 
figure represents accurately the jiattern of only one ]iarticular specimen. The modal 
pattern is plainly of the type with numerous large strong blotches, like figs. S, 16, 6 
and the like, rather than of the le.ss strongly marked type, as exemplified by figs. 23, 
10, 13 and the like. 
As these pupae are naked and wholly exposed to discovery by roving enemies 
they mu.st depend largely for protection on a dissimulating color pattern. The 
variation in this color pattern must belong therefore distinctly to the class of slight, 
continuous variations that offer themselves as ‘handles’ for natural selection: that 
is, they mu.st if any such class really exists. 
