18 SOME INSECTS INJURIOUS TO TRUCK CROPS. 
The pupa. — The pupa is illustrated by figure 5, d, which will 
answer better than a verbal description. The color is yellow, and the 
length is slightly less than that of the adult. 
The distribution of this species is probably moderately wide and 
additional study must be given this subject. At present we know of 
its occurrence in the District of Columbia, in Massachusetts, and 
probably in West Virginia. 
LITERATURE. 
Brief mention of the occurrence of this leaf-beetle as an enemy of 
water cress in Pennsylvania in 1903 was made by the writer, but 
Mr. Frederick Knab, of this office, mentioning the same species as 
Plagiodera viridis, has recorded h its occurrence in great abundance 
upon water cress near Springfield, Mass., in 1902. The identity of 
the species in question has been verified by the comparison of speci- 
mens, and Mr. Knab's record was evidently made on the assumption 
of Crotch c that aeruginosa was merely a variety of viridis. 
HABITS OF THIS AND A RELATED SPECIES. 
W T e can not at the present writing give an approximate statement 
of the life- history of Phcedon aeruginosa, and hence must depend on 
what is known of the related Ph. armoracice, which is common to both 
continents.^ This latter has evidently been introduced into this 
country, but its habits have apparently not been studied here. It is 
known in England as the blue beetle and mustard beetle/ and is of 
considerable importance locally, in some seasons ravaging entire 
fields of mustard, cress, cabbage, and kohlrabi. It passes the winter 
as adult, reappearing in spring on cruciferous plants. Fryer stated 
that in the three years prior to 1881 the Isle of Ely, England, suffered 
from the ravages of this species, entire fields being injured. Mustard 
was attacked at about the time of the formation of the seed pod and 
after the stalks were stripped nearly to the cuticle the beetles trans- 
ferred their attention to kohlrabi, which they completely consumed, 
at first attacking the leaves and afterwards the bulbs, leaving nothing 
but bare stalks. 
The water-cress leaf -beetle is doubtless no exception to the general 
rule among most Chrysomelidse and other species of Phsedon, in 
laying its eggs on the under side of the leaves. Both larvae and 
aYbk. U. S. Dept. Agric. f. 1903 (1904), p. 564; 6 Entomological News, March, 
1903, p. 89 ; c Crotch, Proc. Acad. Phila., 1873, pp. 54, 55 ; * Phcedon armoraciw 
L. syn. : Plagiodera cochleariw Panz., Gyll. ; Phcedon oetulw Kust. It is not 
the same as cochleariw Fab. «Fryer and others have given accounts of this 
species in The Entomologist (Vol. XIV, pp. 44, 187, etc.). 
