SUBFAMILY CHRYSOMYINAE 165 
- but one discal bristle on each side; more commonly, two bristles 
occur on one side and only one on the other. The observed varia- 
tion per 100 specimens collected in nature is: Two on each side, 
52 percent; two on one side and only one on the other, 36 per- 
cent; one on each side, 12 percent. This variation, again, agrees 
with that found in Dr. Miller’s inbred strain. Invariably the 
weaker lateral discal bristle is the one that is absent. The varia- 
tion in these two characters does not appear to be correlated with 
sexual differences or with each other. Only one specimen in 
nearly 500 has been found that had at the same time only two 
sternopleural bristles and only one discal scutellar bristle. 
Distribution. Holaretic: Commonly found during the spring 
and fall throughout the United States, and occurring as far 
south as Mexico City, Mexico, at high altitudes. It is abundant 
during the spring months in the southern states. Australian: 
Oahu, Hawaiian Islands, at 1000 or more feet elevation. 
Aldrich found in the Paris Museum in 1929 a specimen of 
. regina labeled Chrysomya philadelphica Macquart. He indicated 
in his notes that this specimen might be Meigen’s type of regina. 
There are two species in the cotype series of Somomyia rufigena 
Bigot. Hough synonymized the name with Phorma regina 
(Meigen), but did not examine the type series. Brauer pointed 
out that one species should be referred to a new genus near Myio- 
trica. Aldrich, in 1929, found one species to be Myiophasia 
metallica Townsend, the other Phormia regina. I select the male 
specimen of Phormia regina from the Rocky Mountains as the 
lectotype of Somomyia rufigena Bigot. 
Biology, habits and immature stages. Eggs 1.5 mm. long, 
elongate, elliptic, tapering slightly toward one extremity; macro- 
type, large whitish (resembling those of Callitroga americana in 
coloration); usually deposited in agglutinated masses of vary- 
ing number among hair or in wool. The egg masses are some- 
times found in or near edges of wounds in animals and, in such 
instances, they resemble the egg masses of americana. 
Melvin (1934) found that, at a constant temperature of 59° 
F’., it required nearly 52 hours for eggs of this species to hatch, 
while at 104° F., only 8.7 hours were required. He also found 
that none of the eggs hatched at 109° F. The optimum tempera- 
ture for the incubation of eggs appears to be approximately 99° 
F’., at which temperature 8.13 hours are required to complete 
incubation. 
The embryology of the eges of Phormia regina has been studied 
by Miss Mary Auten (1934, pp. 481-506). 
