thick-headed fly

(Myopa clausa)

Conservation Status
thick-headed fly (Myopa clausa)
Photo by Greg Watson
  IUCN Red List

not listed

     
  NatureServe

not listed

     
  Minnesota

not listed

     
           
           
           
 
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 (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 (7 to 9 mm)

 
     
 

Similar Species

 
     
     
 
Habitat and Hosts
 
 

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

 
     
 
Biology
 
 

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

 
 

 

 
     
 

Adult Food

 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 29, 30.

 
  5/25/2021      
         
 

Occurrence

 
 

Uncommon

 
         
 
Taxonomy
 
 

Order

Diptera (flies)  
 

Suborder

Brachycera (circular-seamed flies, muscoid flies, short-horned flies)  
 

Infraorder

Muscomorpha  
  No Rank Eremoneura  
  No Rank Cyclorrhapha (circular-seamed flies)  
  Zoosection Schizophora (schizophora flies)  
  Zoosubsection Acalyptratae (acalyptrate flies)  
 

Superfamily

Conopoidea  
 

Family

Conopidae (thick-headed flies)  
 

Subfamily

Myopinae  
 

Tribe

Myopini  
 

Genus

Myopa  
       
 

Synonyms

 
 

 

 
       
 

Common Names

 
 

This species has no common name. The common name of the family Conopidae is thick-headed flies abnd is used here for convenience.

 
       

 

 

 

 

 

Glossary

Arista

A large bristle on the upper side of the third segment of the antenna of a fly.

 

Femur

On insects and arachnids, the third, largest, most robust segment of the leg, coming immediately before the tibia. On humans, the thigh bone.

 

Ocellus

Simple eye; an eye with a single lens. Plural: ocelli.

 

Proboscis

The protruding, tubular mouthpart of a sucking insect.

 

 

 

 

 

 
 
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Greg Watson

 
 

I was hiking in Eagles Bluff City Park in La Crescent, MN and I spotted these flies mating. The best I can determine while searching the Internet is that they are “red and white big headed fly”. I found just one mention of them at Bugguide.net.

I’m interested in finding out more about them and thought that maybe you would like to include them in your list.

  thick-headed fly (Myopa clausa)  
           
  I was hiking in Vetsch Park, here in La Crescent, and came across another pair of them.   thick-headed fly (Myopa clausa)  
           
 
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  Greg Watson
5/24/2021

Location: Vetsch Park, La Crescent MN

I was hiking in Vetsch Park, here in La Crescent, and came across another pair of them.

thick-headed fly (Myopa clausa)

 
  Greg Watson
5/17/2021

Location: Eagles Bluff City Park, La Crescent, MN

I was hiking in Eagles Bluff City Park in La Crescent, MN and I spotted these flies mating. The best I can determine while searching the Internet is that they are “red and white big headed fly”. I found just one mention of them at Bugguide.net.

I’m interested in finding out more about them and thought that maybe you would like to include them in your list.

thick-headed fly (Myopa clausa)

 
           
 
MinnesotaSeasons.com Sightings
 
 

 

 

 

 

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Created: 5/25/2021

Last Updated:

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