164 THE BLOWFLIES OF NortH AMERICA 
Female. Head length at vibrissa and at antenna 6.5; head 
width 14.0; eve height 8.25; head height 11.0; frontale 0.30 
frontal width, with numerous interfrontal bristles; bucca 0.33 
eye height; front at vertex 0.31 head width, slightly wider near 
middle and 0.41 at lunule; outer vertical bristles two-thirds as 
long as inner; frontoorbital bristles two, moderate in size, pro- 
elinate. Otherwise similar to male except for normal sexual 
differences. 
Length. 6-11 mm. 
There is considerable variation in certain characters of 
Phormia regina, even in series of reared specimens. Specimens 
from the southern limits of the known distribution have smaller 
eyes than specimens from the northern limits, which results, of 
course, in a variation in the buccal and eye height proportion: 
Southern specimens have the buccal height 0.16 to 0.20 the eye 
height. Some specimens, particularly females, have the length 
of the head at the vibrissa slightly greater than the ena on 
the head at the antennal base. 
Viable puparia of an inbred strain of this species were kindly 
forwarded to me by Dr. David F. Miller, Department of Zoology 
and Entomology, Ohio State University, Columbus, Ohio, who 
has continued the strain through more than 200 generations in 
10 years. The original parent stock consisted of one male and 
one female collected during 1930 in Washington, D. C. 
Variation in head proportions has been reduced by inbreeding 
in this strain, but variation in several bristle series has persisted 
and is identical with such variation in specimens found in 
nature. 
In nature, adults of regina usually have three sternopleural 
bristles on each side; there is one large bristle posteriorly and one 
large and one small bristle anteriorly, the latter of these two 
being situated slightly below and caudad to the former. Oc- | 
easionally, specimens are collected which have three sterno- 
pleural bristles on one side and two on the other or have only 
two sternopleural bristles on each side. The observed variation 
per 100 specimens collected in nature is: Three on each side, 47 
percent; three one one side and two on the other, 37 percent; 
two on each side, 16 percent. This variation agrees with that 
found in the inbred strain. Invariably, the missing bristle is the 
small anteroventral one. The usual number of discal scutellar 
bristles in field-collected specimens of regina is two on each 
side; one occurs almost anterior to the strong apical marginal 
bristle and the other, a weaker bristle, is usually situated an- 
terolaterally. Sometimes specimens collected in nature have 
