May, 1911.] 
Two Species of Syrphidae. 
343 
ADULT. 
Length, cT 9 10-12.5 mm. 
Description, slightly modified after Osten Sacken. Proc. 
Bost. Soc. N. H., XVIII, 139 (1875). 
Female (Fig. 9) : Face and cheeks yellow with a very slight blu- 
ish reflection, covered with fine scattered yellow and black pile; a 
faint grayish spot on the cheeks under the eyes; oral margin in 
front narrowly brownish. Front and vertex shining black with 
black pile; the front on both sides along the eyes with a broad 
border of yellowish pollen sometimes meeting the similar border 
of the opposite side. This pollen continues in dilute form down 
the sides of the face crossing narrowly beneath the antennae. 
Eyes pubescent (in many specimens the pubescence is very 
much rubbed off and very difficult to perceive) posterior orbits 
covered with white pile and pollen. Antennae inserted beneath 
a double arched ledge of front. The dark color of the front 
begins immediately above their root forming a blackish brown 
arch with a projecting angle in the middle. Antennae dark 
brown; third antennal joint below and the bare arista sometimes 
more or less reddish. Face in profile perpendicular beneath the 
antennae produced but little below the eyes, slightly concave 
beneath the antennae to oblique tubercle, receding below (Fig. 
1G). Thorax dull greenish with but little lustre; in well preserved 
specimens with three faint dorsal longitudinal darker stripes, 
divergent posteriorly; scutellum dull yellowish with a slight 
bluish reflection. The black pile of scutellum and dorsum of 
thorax changes to yellow on the sides of the latter where it is also 
much thicker and longer. Wings large considerably longer than 
abdomen. Third longitudinal vein nearly straight; anterior 
cross- vein a third of the way from base to apex of the discal cell; 
anterior outer angle of first posterior cell acute. Entire sub- 
costal cell brown; root of wings as far as humeral cross-vein and 
the costal cell slightly tinged with brown. Legs slender; coxae 
and basal third of femora black ; on the hind pair the black reaches 
beyond the middle of the femora; hind tibiae often with a brown- 
ish ring; four anterior tarsi brown the root of the first joint often 
reddish ; hind tarsi dark brown. 
Abdomen oval slightly broader than thorax; about twice as 
long; with three prominent yellow cross bands, the first inter- 
rupted in the middle, all attaining the lateral margins. First 
segment entirely black; second segment with a yellow elliptical 
spot about the middle on each side prolonged usually as a narrow 
neck which reaches forward and touches the margin. Third and 
fourth segments each with a yellow cross-band on its anterior half, 
the hind margins of these bands very gently biconvex with a very 
shallow sinus at the middle; on each side the cross bands are 
