27 
well marked, the head, as is usual with related maggots, being minute, 
while the posterior extremity is truncate. The general appearance is 
shown at 5, the spiracles at 6', and the anal segment at cl. The length 
of the mature larva is a little less than three-tenths of an inch (7 mm ). 
The puparium (e) is of about the same color as the larva, and the 
anterior portion is obliquely truncate, recalling the appearance of 
the anal segment of the Scolytida? or bark-beetles. The length is 
nearly one-fifth of an inch (4.5 mm ). 
Fig. G. — Psila rosse: $, male fly; 9» female fly, lateral view; a, antenna of male; b, full-grown larva, 
lateral view; c, spiracles of same; d, anal extremity from the end; e, puparium; /, young larva; 
g, anal segment from side— flies, young and mature larva, and puparium, eight times natural size; 
other portions more enlarged (original). 
According to Curtis, when the imago issues from the puparium an 
oval lid on this portion lifts up, permitting the fly to crawl out. The 
posterior extremity ends in two minute and not prominent dark 
tubercles. 
DISTRIBUTION. 
The carrot rust fly is a pest in England and Germany and probably 
elsewhere on the continent of Europe. It was originally described 
from Kilia, in Bessarabia. Just when it was first introduced in this 
country does not appear to be known, but ravages were not apparent 
until 1885, and until the present year the species seems to have been 
confined to Canada, although we have in the National Museum a single 
specimen received from Mrs. A. T. Slosson, labelled Franconia, N. H. 
New York is apparently, therefore, an unrecorded locality and celery 
a new food plant. It frequently happens that a species introduced 
from one country into another, particularly from the Old World into 
America, assumes new habits and acquires new tastes as regards food. 
The localities in which the species has been observed in Canada will be 
mentioned further on. 
From the known distribution of the carrot rust fly it would seem 
probable that this species will not be troublesome far southward, its 
