STUDIES OF VARIATION IN INSECTS 295 



tective value, no wide range of variation among adult individuals 

 (that is, those exposed to the rigor of selection) obtains. 



Variation in the Eye-spots on wings of Parnassius smintheus 

 and Ccenonympha galactinus (Butterflies). Butterflies have a 

 complete metamorphosis, the wing-pattern appearing in its 

 definitive condition at the time of the first activity (free flight) 

 of the adult insect (imago). The colors and pattern are pro- 

 duced by scales, the color depending on pigment contained in 

 the scales (reds, browns, etc.,) or on their structure, consisting 

 of superposed transparent lamellae, and parallel, microscopically 

 adjacent, ridges or striae (metallic blues, greens, purples, etc.). 

 The scales are dead structures when the wings are once fully 

 expanded and dried, so that the color-pattern is congenital, i. ., 

 not acquired by reaction during the life-time of the adult to 

 environmental chromatic conditions. 



In a lot of 60 adult individuals of Ccenonytn^ha galactinus 



FIG. 59. The Parnassian butterfly, Parnassius smintheus, showing eye-spots 

 on wings. 



collected at various times and places near Stanford University, 

 the small ocelli or eye-spots which occur on the under sides of 

 the fore and hind wings were found to vary as follows : In 

 males, from no spot to two distinct spots on fore wings, and 

 from one incomplete spot to one incomplete and three complete 

 spots on the hind wings. In females, from no spot to one com- 

 plete and one incomplete spot on fore wings, and from one in- 

 complete spot to one incomplete and two complete spots on hind 

 wings. 



In a lot of 1 6 males and 6 females of Parnassins smintheus 

 collected in one summer in Estes Park, Colorado, the following 

 conditions of the wing ocelli (fig. 59) were found : 



