Microdon tristis

Microdon tristis is a species of syrphid fly in the family Syrphidae.

Description
For terminology Speight key to genera and glossary external link gbif external image

Head

 * Face and frons
 * Bronze black, unusually flat and broadened below, not convex above, but convex-retreating below.
 * Facial depressions are narrow and gray pollinose.
 * The pile is pale brassy yellow.
 * There is a nearly triangular polished area above antennae that shines steel blue.
 * The transverse depression is deep and narrow.
 * Frons is moderately constricted below.
 * The posterior ocelli distant.
 * The ocellar triangle is long, extends nearly to transverse depression and is connected with the vertical bump.
 * Vertical bump is usually rather large and transversely covered with tiny, granular bumps and ridges, with a greenish reflection
 * The occiput is greenish black, with pale pile that is more concentrated along the eyes.
 * The antennae are black.
 * The first segment, the scape, is more or less reddish basally.
 * third segment, the flagellum, is longer than the first, widest at basal third, beyond which it curves slightly upwards and narrows to a moderately narrow blunt tip.
 * Female face.
 * Face about equal in width throughout.
 * Frons a little narrowed.
 * Facial side depressions wider and joined to broader, more triangular.
 * Very densely punctured depressions on either side of lower half of frons.
 * Polished area above antennae of females larger than males.
 * Vertical bump of female is a little larger.

The thorax

 * bronzed or purplish.
 * Scutum.
 * four to six longitudinal greenish stripes present, sometimes indistinct.
 * The pile is brassy yellowish
 * Scutellum
 * Purplish bronzed, somewhat concave, with a stout, bare spur on either side of the concavity.
 * female.
 * Pile of the thorax and scutellum is more yellow-brassy.

Abdomen

 * The color and texture of the abdomen
 * Dull black with glossy brownish black, reddish or luteous sides and apex
 * Densely and coarsely punctured, except along margin and apex


 * The segments size and color
 * Second segment has greenish reflection with shallow depression inside anterior angles
 * Third segment almost 1.75 times longer than second, slightly depressed basally and inside posterior angles
 * Fourth segment longer than first three combined, with lateral depressions and less densely punctured laterally and apically.
 * V-shaped depression of the fourth segment is usually indistinct or entirely wanting.
 * The pile
 * Brassy yellow on first two segments
 * Light-colored pile on lateral and posterior margin of third segment and on posterior two-thirds of fourth segment
 * Shorter and black pile elsewhere
 * Light-colored pile may sometimes extend entirely across posterior margin of fourth segment
 * Description of the female abdomen
 * Female pile on sides of abdomen golden brassy
 * Fourth and fifth segments are of about equal length
 * Black pilose areas on base of fourth segment, emitting a broad median and narrow lateral black pilose areas

Wings

 * The first posterior ceil (r4+5) has a stump of a vein from the third longitudinal vein ( R4+5).
 * This stump of vein is at or slightly beyond the middle of the first posterior cell in the male, but before the middle in the female.
 * The wings are lightly infuscated, and darker along the veins.
 * The apical crossvein (M1), is recurrent and joining the third longitudinal ( R4+5) vein before the tip of the second vein..
 * The squamae is tinged with yellow, the border and fringe of the same color.
 * Halteres pale yellow.

Legs

 * Mainly blackish.
 * Coxae, trochanters, and bases of femora are reddish.
 * The tibiae are usually reddish or sometimes just reddish basally and apically.
 * The tarsi are similar in color but highly variable.
 * Pile
 * Mostly whitish yellow.
 * More golden under the tarsi.
 * The inside of the front tibiae is golden dorsally.

key to adults and pupae north of Mexico. includes head drawing of M. tristis