Thick-headed fly

Description

Myopa is a genus of parasitic thick-headed flies (family Conopidae). They parasitize western honey bees, miner bees (Andrena spp.), and digger bees (Anthophora spp.). There are at least 31 currently recognized species of Myopa worldwide, at least 4 in Minnesota. Four species make up what is called the “curticornis complex”. Morphological features of these four intergrade, making identification to species level difficult. However, Myopa clausa is the only one of the four that occurs east of the Rocky Mountains.

Myopa clausa is a reddish, brightly colored, medium-sized, thick-headed fly. The adult is ¼″ to ⅜″ (7 to 9 mm) in length.

The head is thick. There is a large compound eye on each side of the head and three small simple eyes (ocelli) in a triangle on the top of the head. The compound eyes do not meet at the top of the head on eithe sex. The cheeks are as wide as the compound eye is high. The protruding mouthpart (proboscis) is usually long but may be quite short. It is bent at a sharp angle in the middle. The second segment is often nearly as long as the third segment (femur) of the hind leg. The antennae have three segments. The first segment is very short. The second segment is disctinctly longer than the third. The third segment is lighter than the first two and has a forward-pointing bristle (arista) in the middle. The arista is bare, not feather-like (plumose).

The abdomen is narrowed at the base. It is long and spherical, especially on the male. It is reddish, shiny, and sparsely covered with short black hairs. There is a pale, semi-circular spot on each side of segments 2 and 3, and pale, powdery (pollinose) markings on segments 4 and 5. The pollinose markings are distinct on the female, less distinct on the male, especially on the fifth segment.

The wing is clear or lightly tinged with brown but is otherwise unmarked. The radial-media (r-m) cross vein is not thickened. There is no spurious vein between the radius (R) and media (M) veins. The first posterior cell is closed. The anal cell (Cu) is much longer than the second basal cell (M).

Size

Total length: ¼″ to ⅜″ (7 to 9 mm)

Similar Species

Habitat

Ecology

Season

One generation per year:

Behavior

Adults perch on the lowest twigs of shrubs, on grass stems, and on flowers, usually no more than 16″ above the ground. They are active in sunny conditions, inactive when cloudy or overcast.

Males aggregate on hilltops and wait for a female to fly there and copulate with them.

Life Cycle

The female pounces on a host bee while in flight. She inserts her ovipositor between two abdominal segments, inserts a single egg, and flies away. The entire process takes a very short time. The larva feeds within the abdominal cavity, eventually killing the host. The adult fly emerges from the abdomen of the dead host.

Larva Food/Hosts

Western honey bee (Apis mellifera), miner bees (Andrena spp.), and digger bees (Anthophora spp.)

Adult Food