170 BULLETIN 15 7, U. S. NATIONAL MUSEUM 



less broad and are lighter and more yellowish in color. In the males 

 the hind wings below show- only faint traces of the markings of the 

 early-spring form, consisting of a row of obscure chevron-shaped 

 spots of dusky parallel to the outer border of the wing and about 

 4 mm. from it, a broad dusky band across the end of the cell, and a 

 scarcely perceptible dusting of olive-gray scales in wide bands along 

 the veins. 



Fourteen males taken on May 30 and 31, 1931, have the fore wing 

 from 23 mm. to 25 mm. (averaging 24 mm.) in length, and eight 

 females taken on the same days have the fore wing from 23 mm. 

 to 27 mm. (averaging 25 mm.) in length. 



Two summer females from Cabin John at hand have the fore 

 wings 26 mm. long. 



Mr. Scudder gives the average length of the fore wing in the male 

 as 23.5 mm., and in the female as 25.5 mm. 



PIERIS RAPAE (Linnaeus) 



Cabbage Buttekfly 

 Plate 28, Figures 1 to 3; Plate 29, Figures 9, 10 



Occurrence. — Common throughout the District, and in summer 

 abundant in the vicinity of cabbage fields. 



In spring this butterfly is rather local and infrequent, being found 

 chiefly near the borders of woods, especially where there is an 

 abundance of cruciferous plants. In summer it wanders more widely 

 over open fields. 



Within this area the cabbage butterfly is very unequally distrib- 

 uted. Broadly speaking, it is by no means so common as would be 

 expected — indeed in many areas it is quite uncommon. Thus in the 

 meadows at Cabin John, Md., one will not see more than half a 

 dozen in the course of an entire day, even during the height of the 

 season. In this area the only place where they are at all frequent is 

 a small patch of about half an acre near a bridge crossing the canal. 

 The butterfly is even less common in the open country at Silver 

 Spring. But within a radius of a quarter of a mile or more about 

 large cabbage patches it is very numerous, though by no means so 

 abundant as farther north. On the cabbages themselves the cater- 

 pillars are not especially frequent and are greatly outnumbered by 

 the caterpillars of the cabbage moth {AutograpJia hrassicae) . The 

 cabbage butterfly is frequently seen throughout the gardens, parks, 

 and even streets of the city. Many of these individuals come from 

 pupae formed by caterpillars that have crawled from cabbages ex- 

 posed for sale. Others were raised on various cruciferous plants, 

 native, introduced, and cultivated, in gardens and in unkept yards 



