Genus Pieris 



the veins of the fore wing black, contrasting sharply with the 

 white ground-color. All the spots are smaller and more reg- 

 ular, especially those on the outer margin of the fore wing, giving 

 the edge an evenly checkered appearance. On the under side the 

 hind wings have the veins somewhat widely bordered with gray, 

 interrupted about the middle of the wing by the divergence of 

 the lines on either side of the veins in such a way as to produce 

 the effect of a series of arrow-points with their barbs directed 

 toward the base. The female is like the male, with the markings 

 a little heavier. A yellow varietal form is sometimes found. 



Early Stages. — The life-history is given and illustrated by Ed- 

 wards in his second volume. The caterpillar, which is green, 

 banded with black, feeds upon the Cnicifera\ 



(6) Pieris napi, Esper, Plate II, Figs. 8, 9, larva; Plate V, 

 Figs. 57, 6}, 64, chrysalis (The Mustard White). 



Butterfly. — This is a Protean species, of which there exist 

 many forms, the result of climatic and local influences. Even the 

 larva and chrysalis show in different regions slight microscopic 

 differences, for the influences which affect the imago are opera- 

 tive also in the early stages of development. The typical form 

 which is found in Europe is rarely found in North America, though 

 1 have specimens from the northern parts of the Pacific coast re- 

 gion which are absolutely indistinguishable from European speci- 

 mens in color and markings. I give a few of the well-marked forms 

 or varieties found in North America to which names have been given. 



{a) Winterformoleracea-hiemalis, Harris, Plate XXXI V, Fig. 

 16, 6 (see also p. 5, Fig. 9, and p. 13, Fig. 27). The wings are white 

 above in both sexes. Below the fore wings are tipped with pale 

 yellow, and the entire hind wing is yellow. The veins at the apex 

 of the fore wings and on thQ hind wings are margined with dusky. 



{]}) Aberrant form virginiensis, Edwards, Plate XXXIV, Fig. 

 14, 5. The wings are white above, slightly tipped at the apex 

 of the fore wings with blackish. Below the wings are white, 

 faintly, but broadly, margined with pale dusky. 



{c) Form pallida, Scudder, Plate XXXIV, Fig. 15, ?. In this 

 form the wings are white above and below, with a small black 

 spot on the fore wing of the female above, and hardly any trace 

 of dark shading along the veins on the under side. 



(i/) Alpine or arctic form bryoniae, Ochsenheimer, Plate 

 XXXIV, Fig. 17, ?. In this form, which is found in Alaska, 



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