gnat ogre

(Holcocephala abdominalis)

Conservation Status
gnat ogre (Holcocephala abdominalis)
Photo by Alfredo Colon
  IUCN Red List

not listed

     
  NatureServe

not listed

     
  Minnesota

not listed

     
           
           
           
           
           
           
           
 
Description
 
 

Holcocephala is a genus of small flies called gnat ogres. Holcocephala abdominalis is a small gnat ogre. It occurs in North America from Quebec to Florida west to Minnesota and eastern Texas. It has not previously been recorded in Minnesota but it has been in seen in Wisconsin and Iowa. Adults are found from early July to early September in damp, grassy, open areas near woodlands.

Adults are light brownish-yellow and 316 to ¼ (4.5 to 7.0 mm) in length.

The head is black, much broader than the thorax, and is strongly compressed from back to front. There are two large compound eyes on the side of the head and three small simple eyes (ocelli) in a triangle on top of the head. The top of the head is depressed (“hollowed out”) between the compound eyes. The compound eyes are relatively large and very widely spread apart. This feature distinguishes the genus Holcocephala from all other fly genera in the United States. Each compound eye is composed of numerous visual elements (ommatidia) with a hexagonal outer face (facet). The facets on the front of the eye are very large but gradually decrease in size approaching the upper, outer, and lower margins. The facets are black but have bright bronze reflections. The antennae are short, slender, and black. They have three segments. The first two segments are very short and rounded. The first segment is spindle-shaped, distinctly broader in the middle. The third segment is two times as long as the first two segments together. At the tip of the third segment there is a long extension (style). The style is well developed, nearly as wide as the third segment at the base and tapering to a sharp point at the tip.

The thorax is stout, brownish-yellow, and strongly arched. It is densely covered with short, velvety hairs that completely hide the underlying color. It has no bristles. There are three segments. Each segment has four principal exoskeletal plates, one above, one below, and one on each side. The upper (dorsal) plates, from front to rear, are the prescutum, scutum, and scutellum. The prescutum and scutum have scattered, longer, rearward-curved, bristle-like hairs, but no long stiff bristles. There is a broad, brown, longitudinal stripe in the middle and another stripe on each side. The lateral stripes are interrupted at the groove (suture) between the prescutum and scutum, broader and dark on the prescutum, more diffuse and sometimes much lighter on the scutum. The scutellum is unmarked.

The abdomen is broad at the base and tapered toward the tip. It is reddish-yellow with brown markings above, pale tan below. It has no bristles.

The wings are longer than the abdomen. They are blackish, mostly dark, pale on the outer third. They are held over the body when at rest. Every cell near the wing tip is broadly open.

The legs are reddish and are sparsely covered with fine hairs and numerous, weak bristles. The third segment (femur) is sometimes black above, and the bristles are confined to the underside. The fourth segment (tibia) is more or less black at the tip. On the front leg there is no claw-like spur at the tip. On the hind leg it is swollen at the tip, about 35% wider than the femur. The last part of the leg (tarsus), corresponding to the foot, has five segments. The tip of each segment is more or less black. The first segment is at least twice as long as the second segment. The last segment has a pair of black claws at the tip. On the male, the first tarsal segment on the hind leg is much enlarged.

 
     
 

Size

 
 

Total Length: 316 to ¼ (4.5 to 7.0 mm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

Damp, grassy, open areas near woodlands.

 
     
 
Biology
 
 

Season

 
 

Early July to early September

 
     
 

Behavior

 
 

Adults perch at the tip or on the stalk of a grass blade when hunting.

 
     
 

Life Cycle

 
 

 

 
     
 

Larval Food

 
 

 

 
     
 

Adult Food

 
 

Gnats and other small flying insects

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 27, 29, 30, 82.

 
  1/27/2021      
         
 

Occurrence

 
 

It has not previously been recorded in Minnesota but it has been in seen in Wisconsin and Iowa.

 
         
 
Taxonomy
 
 

Order

Diptera (gnats, mosquitoes, true flies)  
 

Suborder

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

Infraorder

Muscomorpha  
 

Superfamily

Asiloidea  
 

Family

Asilidae (robber flies)  
 

Subfamily

Trigonomiminae  
 

Tribe

Damalini  
 

Genus

Holcocephala (gnat ogres)  
       
 

 

 
       
 

Synonyms

 
 

Dasyopogon abdominalis

Dasypogon aeta

Dasypogon laticeps

Discocephala rufiventris

 
       
 

Common Names

 
 

This species has no common name. The common name for the genus Holcocephala is gnat ogres, and is applied here for convenience.

 
       

 

 

 

 

 

 

 

Glossary

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.

 

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.

 

Scutum

The forward (anterior) portion of the middle segment of the thorax (mesonotum) in insects and some arachnids.

 

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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Alfredo Colon
       
  gnat ogre (Holcocephala abdominalis)   gnat ogre (Holcocephala abdominalis)
       
  gnat ogre (Holcocephala abdominalis)    
       
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Other Videos
 
  Robber fly eating insects & grooming | Holcocephala
GoTrails
 
   
 
About

Aug 27, 2020

Robber fly eating insects & grooming | flying, feeding, hunting / catching prey, attack | Holcocephala fusca / abdominalis, gnat ogre | assassin, Asilidae | cleaning itself | close up | Facts, Information, Documentary, Identification, Habitat, Behavior, Habits | Diet: wasp, bee, spider, dragonfly | bite | eyes, mouthparts, mystax, stout proboscis, sharp sucking hypopharynx | HD video | Animal, Wildlife, Nature | #gotrails, #robberfly, #arthropod, #insect, #insects

   
       
  Robber Fly (Holcocephala) with prey
Henry Jurenka
 
   
 
About

May 8, 2020

This mosquito-sized robber fly catches a tiny fly

   
       

 

Camcorder

         
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Alfredo Colon
8/13/2019

Location: Woodbury, MN

gnat ogre (Holcocephala abdominalis)


     
     
 
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Created: 1/29/2021

Last Updated:

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