SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 5 
Environment —Its Effect on Butterfly Forms 
By J. R. Haskin. 
The study of Butterflies at first glance seems to the un- 
thinking majority to be a very trivial pursuit. As a science, 
however, it presents many points of interest which increase 
rapidly as one goes more and more deeply into the subject. 
To the beginner, the raw amateur, it sometimes seems as if 
distinctions were too finely drawn, and certain forms were 
differentiated into far too many species. But as one progresses 
in the study, one soon realizes that he is face to face with 
Darwin’s theory of the evolution of species and that the 
changes, great and small, which he gradually becomes able to 
distinguish, are due to environment. 
The genus Colias illustrates very nicely these changes which 
the influence of climate and food produce in the size and color- 
ation of butterflies. A well-known authority specifies eleven 
spiecies that are fairly well defined, but he, also, states that 
there are a number of other named species as well as numerous 
varieties from the Central and Western States. These numer- 
ous species differ very slightly from each other in many eases, 
but if a sufficient number of specimens from each locality be 
grouped and compared with each other, the difference can 
readily be seen. 
Generally speaking a warm equable temperature and abun- 
dant food produces the richest coloring and largest specimens, 
Colias Eurytheme illustrates this particularly well on account 
of its being a triple-brooded southern and western species. 
Those specimens taken late in the Fall and early in the Spring, 
(Form Ariadne) show the effects of a meagre diet and expo- 
sure to the nipping cold night temperatures by their small size 
and the absence of the rich coloring of the Summer form, 
shown in the accompanying illustration. It seems, in fact, 
hardly believable that these widely different forms are of 
identically the same species. Ariadne is small and insignifi- 
cent looking, pale yellow in coloring, with only an occasional 
touch of orange. The typical Summer form, on the contrary, 
