Palpus reddish orange; larger species, wing length 
in male over 4 mm 1>. betulivora Spencer 
Synopsis. Frons broad, twice width of eye, con- 
spicuously projecting above eye in profile (fig. 
472); 5 or 6 long, slender orbital bristles, only 
upper ors reclinate, others incurved; gena broad, 
0.25 height of eye; oral margin with conspicuous 
epistoma (fig. 473); 3d antennal segment quadrate; 
arista with small but distinct swelling at base; 
frons predominantly reddish orange, including or- 
bit; upper orbit and area adjoining ocellar tri- 
angle blackish gray; lunule, gena, parafacial, and 
all antennal segments reddish orange; legs black- 
ish brown, all knees paler, more orange; squama 
pale gray, margin and fringe black; last section 
of vein M 3+4 at least 1.5 times length of pen- 
ultimate, inner crossvein beyond center of discal 
cell; male genitalia with aedeagus having long, 
paired distal tubules (fig. 474). 
Host/Early Stages. Betula nigra . Larva mining in 
cambium of twig and trunk down to root, mine can 
be as long as 40 ft; pupation takes place ex- 
ternally, larva leaving tree at or below ground 
level; puparium reddish brown, 4-5 mm in length, 
posterior spiracles each with 3 bulbs (fig. 475). 
Distribution. District of Columbia, Illinois, New 
York; new record: Kansas, Douglas Co., Natural 
History Reserve, Lawrence, 1 m., 28.V.56 (J. G. 
Chillcott, CNC) ; Canada. 
References. Greene, 1914: 471 (biology, as Agro- 
myza pruinosa ); Spencer, 1969a: 103. 
11 (9). 2 crossveins approximate, outer crossvein less 
than own length from inner (fig. 476) 
P . waltoni (Mai loch) 
Synopsis. Large species, wing length 4 mm, last 
section of M 3+4 slightly longer than penultimate; 
frons broad, twice width of eye, only slightly 
projecting above eye in area of ori; 2 ors, 3 ori; 
gena 0.17 height of eye; epistoma lacking; frons 
and all antennal segments entirely black, lunule 
slightly paler; mesonotum blackish gray, side of 
thorax entirely black; squama brownish gray, mar- 
gin and fringe black; male genitalia with aedeagus 
membranous, as in figures 477, 478. 
Host/Early Stages. Unknown. 
Distribution. Iowa, New York; new records: North 
Carolina, South Carolina; Canada. 
References. Malloch, 1913a: 303; Frick, 1959: 377; 
Spencer, 1969a: 109; part 2, p. 272. 
Outer crossvein more than own length from inner 12 
12 (11). 3d antennal segment and frons black 13 
3d antennal segment brownish, frons normally at 
least faintly reddish adjoining lunule 15 
13 (12). Mesonotum matt, grayish black 14 
Mesonotum deeper black P . californica Spencer 
Synopsis. Frons 1.5 times width of eye, not pro- 
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