May, 1911,] Two Species of Syrphidae. 343 



ADULT. 



Length, cf 9 10-12.5 mm. 



Description, slightlv modified after Osten Sacken. Proc. 

 Bost. Soc. N. H., XVIII, 139 (1S75). 



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 nan-owly brownish. Front and vertex shining black with 

 black pile; the front on both sides along the eyes with a broad 

 border of ^-ellowish 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 form.ing 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 obHque tubercle, receding below (Fig. 

 16). 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 flrst posterior cell acute. Entire sub- 

 costal cell brown; root of wings as far as humeral cross-vein and 

 the costal cell sHghtly 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 



