bee-mimic robber fly

not listed

not listed

not listed

Laphria index is a small to medium-sized bee-mimic robber fly. It occurs in the United States from the northeast to the Midwest, south to Virginia and Missouri, and in adjacent Canadian provinces. It is uncommon in Minnesota.

Adults are dark, slender, and ½″ to 11 ⁄16″ (13 to 18 mm) long.

There are two large compound eyes and three small simple eyes (ocelli). The compound eyes extend above the level of the top of the head (vertex), making the head appear hollowed out between the eyes when viewed from the front. The ocelli are arranged in a triangle on a prominent rounded projection (tubercle) in the middle of the head between the compound eyes. There is a dense mustache of long, stiff, black bristles (mystax) on the immediately above the mouth. The antennae have 3 segments. The third segment is elongated.

The thorax is black with a narrow triangle of pale to reddish-gold hairs on the upper (dorsal) surface. The triangle is widest at the rear, about as wide as the triangular plate between the thorax and abdomen (scutellum). It narrows rapidly to at least the middle of the thorax, and fades at the tip. The hairs are iridescent and the color varies with the angle of the light. The rest of the thorax is covered with longer whitish hairs and shorter black hairs. The scutellum is covered with paler hairs and has a white bristles on the margin. The small, knob-like structures on each side of the thorax (halteres) are yellow.

The abdomen is long, slender, and black, and has six segments. The first two segments are black with white hairs on the side. The remaining segments are densely covered with orangish-gold hairs. At the rear margin of segment six there are two black, well-defined projections. The genital bulb at the tip of the abdomen is black and very large.

The wings are clear. They are dark smoky brown at the tip, becoming paler at the base. The first and second radius veins (R₁ and R₂₊₃) join before the end of R₁ creating a closed cell that does not reach the margin.

The legs are stout and black. They are covered with long gray and black hairs. The last part of the leg (tarsus), corresponding to the foot, has five segments. The last segment has 2 pads.

Total Length: ½″ to 11 ⁄16″

bee-mimic robber fly (Laphria ithypyga) is very similar in appearance. On the male, the genital bulb is “substantially smaller”. At the tip of the abdomen there is just a single small projection. Neither of these characteristics is visible on most photos. The female “appears to be more robust”, and the golden triangle on her thorax “more conspicuous” (BugGuide.net). Based on the recorded sightings, this species is much less common. It has not been recorded in Minnesota, though CCESR does have it on their state insect checklist as Choerades ithypygus.

Woodland edges and openings

June through mid-August

Sources

7, 24, 27, 29, 30, 82.

Few of the North American Laphria species have a common name. One common name for the genus is bee-mimic robber fly, and it is applied here for convenience.

An Awesome Robberfly

Location: Woodbury, Minnesota

An Awesome Robberfly