bee-mimic robber fly

not listed

NNR - Unranked

not listed

Laphria posticata is a small to medium-sized, robust, robber fly. The thorax and abdomen are partially covered with long yellow hairs making it resemble a bumble bee. It is thought to be a mimic of golden northern bumble bee (Bombus fervidus). Adults are ½″ to 11 ⁄16″ long

The thorax is stout, black, and evenly covered with long yellow hairs. There is a tuft of black hairs in front of the wings and a tuft of mostly yellow hairs with a few black hairs in front of the balancing organs (halteres). The hairs on exoskeletal plate between the abdomen and the thorax (scutellum) are black.

On the male, abdominal segment (tergite) 1 is entirely covered with black hairs; tergite 2 has a patch of yellow hairs on the trailing edge (posterior) at each side of the upper surface (dorsolateral); tergite 3 has a similar but larger patch; tergite 4 is completely covered with yellow hairs; tergite 5 is covered by yellow hairs except for the forward (anterior) middle part, which has black hairs; tergites 6 and 7 are entirely covered with black hairs. The female is similar except tergites 1 and 2 are entirely black, and only tergite 3 has yellow dorsolateral patches.

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. The upper face has long, yellow, erect hairs. There is a cluster of forward-directed bristles (a “beard”) on the lower part of the face. The beard on males is entirely yellow. On females there are yellow hairs at the upper margin of the beard, black hairs below. The hairs below the sucking mouth part (proboscis) are yellow on the male, black on the female. The antennae have 3 segments. The third segment is elongated.

The legs are stout and spiny. On the male, the third segment (femur) of the hind leg has a weak line of yellow hairs above (dorsally) and below (ventrally). On the female these are all black. The fourth segment (tibia) of the front and middle legs are covered with long hairs. On the female, these are all black. On the male, the hairs on the front (anterior) side are black, those on the back (posterior) side are yellow. On the female they are all black. The hind tibia of both sexes have all black hairs.

The last segment of the foot (tarsus) has 2 pads.

The above description refers to the nominate subspecies L. p. posticata. The other subspecies that may be found in Minnesota is L. p. scutellaris. It has yellow or golden-yellow hairs on the margin of the scutellum and on the upper surface of the hind tibia. Tergite 6 is covered with yellow hairs.

Total length: ½″ to 11 ⁄16″

Woodlands and woodland edges

June through August

Flying insects, including bees, wasps, beetles, and other robber flies

Sources

24, 27, 29, 30.

Few of the North American Laphria species have a common name. The common name for the genus is bee-mimic robber fly, and will be used here for convenience.

Robber Fly having a meal

Location: Cass County

Robber Fly having a meal