128 THE BLOWFUIES oF NortH AMERICA _ 
(Coquillett). Callitroga americana is not known to occur in 
these areas. 
It was pointed out a good many years ago that several species 
of blowflies were confused in studies upon screwworm infesta- 
tions in the Americas. Lahille (1915) correctly diagnosed the 
situation and showed that two species were involved in the con- 
fusion, one being clearly saprophagous, the other a species of 
identical superficial appearance, the one responsible for myiasis 
of man and animals. He showed how these species might be 
separated by the use of characters which he found in the male 
genitalia. 
This species differs most obviously from macellaria in having 
the anterior portion of the parafrontale clothed with black hair 
instead of pale yellowish hair. It is also deeper blue and less: 
greenish in color, it is generally larger and more heavily built, 
and. the male genital structures are distinctly different. 
Male. Head length at antenna 7.1 and at vibrissa 8.0, this 
difference being largely due to the posterior production of the 
metacephalon; head height 13.8; width 16.0; eye height 9.8; 
bueea 0.37 of eye height and bright shining orange with but a 
trace of golden pollen and with abundant golden-orange hair; 
frontale narrow just anterior to- foremost ocellus but plainly 
discernible and widening to about one-half the width of the 
front at the lunule, orange brown anteriorly, black posteriorly; 
front at vertex 0.11 of head width, 0.06 at narrowest (just an- 
terior to foremost ocellus) and 0.31 at lunule, with heavy golden 
pollen, and with abundant scattered short black hair outside 
the frontal row of bristles which extends almost to the base of 
the antenna where the short hairs of the parafaciale are golden; 
frontal row of bristles following the margin of the frontale, ex- — 
tending anteriorly to about the middle of the second antennal 
segment, and consisting of about 12 or 14 bristles; postvertical 
bristles weak, decussate; facial carina less apparent than in 
macellaria, practically vestigial, separating the antennal bases 
by a distinct but narrow space; parafaciale 1.6 in width op- 
posite lunule, not so markedly narrowed above, with heavy gold- 
en pollen over bright orange ground color, and with numerous 
oolden-orange hairs of medium length which are most abundant 
near eye; faciale with several rows of short black setae which 
ascend about three-fourths the distance to the antennal base; 
vibrissae separated by 2.2; antenna with third segment 3.2 times 
as long as second; back of head with abundant golden-orange 
hairs of medium length which become longer below. 
Thorax much as in macellaria but considerably stouter, es- 
