Milbert’s proctacanthus

(Proctacanthus milbertii)

Conservation Status
Milbert’s proctacanthus
Photo by Carrie Murch
  IUCN Red List

not listed

 
  NatureServe

NNR - Unranked

 
  Minnesota

not listed

 
           
           
           
           
           
           
           
 
Description
 
 

Milbert’s proctacanthus is a common, large, robust, late summer, robber fly. It occurs across the United States and southern Canada. Adults are active from July to early September.

Adults are 1 to 1916 (28 to 40 mm) in length, the females a little larger than the males.

The lower three-fourths of the face is swollen. The patch of hairs above the mouth (mystax) is yellow and the beard is pale yellow. The antennae have 3 segments. The third segment is elongated and has a long bristle (arista) at the end. The arista is bare, not feather-like (plumose).

The thorax is arched and stout. It is often covered with a loose, gray, powdery substance (pollinose). There is a dark longitudinal stripe in the middle, but it is not sharply delineated. The plate between the abdomen and thorax (scutellum) is covered with black bristles and usually a few pale hairs.

The abdomen is half cylindrical, rounded on top, flat below, widest at the base, and tapering to the tip. It is much longer than the wings. It is gray or sometimes brownish pollinose. The first abdominal segment is not elongated, no more than four times as long as wide. The sides of the first and second segments are sparsely covered with short hair. On the female the ovipositor is cylinder-shaped, and usually black, occasionally red. It has a circle of spines at the tip.

The wings are uniformly light brown. 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. R5 reaches the wing margin in front of the wing tip.

The legs are brown and stout. The third leg segment (femur) is dark. On the front legs the fourth segment (tibia) has no spur at the tip and all of the spines at the tip are straight, not curved. The last part of each leg (tarsus), corresponding to the foot, has five segments. The last segment has 2 pads. The tibia and tarsus are the same color and lighter than the femur.

 
     
 

Size

 
 

1 to 1916 (28 to 40 mm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

 

 
     
 
Biology
 
 

Season

 
 

July to early September (CCESR)

 
     
 

Behavior

 
 

 

 
     
 

Life Cycle

 
 

 

 
     
 

Larva Food

 
 

 

 
     
 

Adult Food

 
 

Bees and yellowjackets, moths, an other flying insects.

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 27, 29, 30, 82, 83.

 
  9/24/2022      
         
 

Occurrence

 
 

Common

 
         
 
Taxonomy
 
 

Order

Diptera (flies)  
 

Suborder

Brachycera  
 

Infraorder

Asilomorpha (Orthorrhapha)  
 

Superfamily

Asiloidea  
 

Family

Asilidae (robber flies)  
 

Subfamily

Asilinae  
 

Tribe

Asilini  
 

Genus

Proctacanthus  
       
 

Synonyms

 
 

Asilus agrion

Asilus missouriensis

 
       
 

Common Names

 
 

Milbert’s proctacanthus

 

 

 

 

 

 

 

 

 

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.

 

Mystax

On flies, especially in the family Asilidae, a patch of bristles or hairs (mustache) immediately above the mouth.

 

Ovipositor

A tube-like organ near the end of the abdomen of many female insects, used to prepare a place for an egg and to place the egg.

 

Scutellum

The exoskeletal plate covering the rearward (posterior) part of the middle segment of the thorax in some insects. In Coleoptera, Hemiptera, and Homoptera, the dorsal, often triangular plate behind the pronotum and between the bases of the front wings. In Diptera, the exoskeletal plate between the abdomen and the thorax.

 

Tarsus

On insects, the last two to five subdivisions of the leg, attached to the tibia; the foot. On spiders, the last segment of the leg. Plural: tarsi.

 

Tibia

The fourth segment of an insect leg, after the femur and before the tarsus (foot). The fifth segment of a spider leg or palp.

 

 

 

 

 
 
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Carrie Murch

 
 

Was saddened to see the robber fly had caught a honey bee

 
    Milbert’s proctacanthus   Milbert’s proctacanthus  
           
 
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Other Videos
 
  Proctacanthus milbertii with prey
Stoil Ivanov
 
   
 
About

Aug 15, 2016

Proctacanthus milbertii with Common buckeye 8-14-2016 Illinois Beach State Park, Lake County, Illinois, USA

 
  Proctacanthus milbertii with bumblebee ROBBER FLY 3023047
Rob Curtis
 
   
 
About

Mar 12, 2021

Proctacanthus milbertii ROBBER FLY feeding on bumblebee. Illinois Beach SP. 3023047

 
  Robber Fly with Grasshopper
Stoil Ivanov
 
   
 
About

Aug 16, 2020

Robber fly ( Proctacanthus milbertii ) with grasshopper. Common sight if anyone walk and actually look . Hundreds of those huge flies on the sandy trails killing mostly grasshoppers scared by the people walking.People think of flies as annoying but as can see they are awesome predators! video taken on 8-16-2020 at Illinois Beach State Park, Illinois.

 

 

Camcorder

 
 
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  Carrie Murch
9/5/2022

Location: Browerville, MN Todd County

Was saddened to see the robber fly had caught a honey bee

Milbert’s proctacanthus  
           
 
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Created: 9/24/2022

Last Updated:

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