Thick-headed fly

Physoconops is a genus of thick-headed flies (family Conopidae). There are 13 currently recognized species of Physoconops in North America north of Mexico. At least five are found in Minnesota or surrounding states.

At 5 ⁄16″ to ⅜″ (8 to 10 mm) in length, Physoconops obscuripennis is a small to medium-sized thick-headed fly. With a thread-waisted body and yellow and black coloration, it strongly resembles a wasp.

The head is broad, a little wider than the thorax. There are two large compound eyes and no simple eyes (ocelli). The compound eyes are situated at the sides of the head and do not meet in the middle on either sex. The face and cheeks are yellow and prominently grooved. The grooves are not darkened. The top of the head (vertex) and the area above the face, corresponding to the forehead (frons) are entirely black. The frons is longer than wide, and has a coppery sheen when viewed at an angle. On the back of the head, next to each compound eye, there is a shiny yellow line extending to the vertex, and in the middle a small but prominent triangular or V-shaped mark. The protruding mouthpart (proboscis) projects forward needle-like. It is long, straight (not elbowed), nearly black, and conspicuously swollen at the base. The antennae have three segments. They are straight, black, and long, longer than the head, and are project forward and up. The first and third segments are reddish below and are each about half as long as the second segment. The third segment is cone-shaped and has a slender, elongated process (style) at the tip.

The thorax is black. The front angles are narrow, black, and raised like shoulder pads. On each side there is a yellow spot just behind the shoulder (humeral) area, a smaller, less distinct spot near the wing base, and a large pale spot in front of the base of the haltere. The halteres are knob-like and bright yellow. The exoskeletal plate between the wing bases (scutellum) is dark brown or black.

The abdomen is black and has six segments. Segment 2 and part of segment 3 are very constricted (petiolate). The tip of segment 2 and the beginning of segment 3 are yellow, and there is a narrow yellow hind border on segments 3, 4, and 5. Segment 6 has a yellowish dusting at the end.

The legs are slender and mostly dark brown or black. The first segment (coxa), the tips of the third segment (femur), and the basal half of the fourth segment (tibia) are yellow. The last part of the leg (tarsus), corresponding to a foot, has five segments.

The forward (anterior) half of each wing is dark smoky brown to the submarginal cell but pales near the end. The remainder is translucent but tinted smoky brown. There is no distinct outline between the dark and translucent smoky areas. There is a small cross-vein near the middle of the discal cell.

Total length: 5 ⁄16″ to ⅜″ (8 to 10 mm)

Solitary bees, wasps

Adults are active during the day and are usually found on flowers.

The female grasps a bumble bee in flight and forces an egg between the bee’s abdominal segments.

Solitary bees and sometimes wasps