178 THE BLOWFLIES OF NortH AMERICA 
Second instar: Cephaloskeleton more heavily sclerotized, and 
the dorsal and ventral cornua closer together than in Phormia, 
with two labial sclerites. Anterior spiracles each with 10 to 12 
branches. Posterior spiracles each with two ovate apertures, the 
plates broader transversely than longitudinally, closer together 
than in Phormia. Six tubercles on upper and four on lower 
portions. Segments 2-11 with complete anterior spinose bands; 
posterior bands on segments 10 and 11; posterior bands ventrally 
on segments 6-9. Lateral fusiform areas on segments 5-8. Spines 
almost all wedge-shaped, with two or three points, and arranged 
in short rows. 
Third instar: As in second and third instars of Phormia regina 
except as noted. Posterior spiracles (pl. 37, F) as illustrated. 
Puparium. With external characters of mature larva. 
This saprophagous species is seemingly the northern counter- 
part of Phormia regina, which is not abundant north of the 
Canadian Border. It is an early spring species in the United 
States, although occasional specimens may be collected in the 
summer months. I have collected terrae-novae in considerable 
numbers on flowers of wild parsnip during early July in northern 
Michigan, but never in southern Ohio. It occurs in Utah from 
March 27 to June 29 at altitudes of 4,000 to 6,000 feet, being 
most abundant there during the last week in May; but specimens 
may be collected in high altitudes as far south as southern 
California during June, and it is not uncommon in Colorado 
above 7,000 feet during July and August. During July terrae- 
novae is a very abundant species in the subarctic region especially 
in southern Alaska, Greenland, and in the vicinity of Hudson 
Bay, Canada. ; 
Economic wmportance. In Alaska terrae-novae is the common 
blowfly during the summer season; it acts much the same as 
Phormia regina in Texas. In western North America, where it 
sometimes attacks soiled wool of sheep, it is the ‘‘black blowfly’’ 
of various authors. In Alaska, Hadwen and Palmer (1922) stated 
that larvae attack living reindeer and often kill the animal. In 
the northern Middlewest it is often found to be the cause of © 
myiasis in dehorned cattle and in docked lambs during early 
spring months. In Scotland it is found in the role of a ‘‘primary’’ 
blowfly in cases of myiasis in sheep during the early part of the 
season; it sometimes occurs along with Phaenicia sericata accord- 
ing to MacLeod (1937). Larvae of terrae-novae have been re- 
ported as parasites of nestling birds in Europe by Séguy (1929), 
but not in North America. 
