broad-headed marsh fly

(Helophilus latifrons)

Conservation Status
broad-headed marsh fly
 
  IUCN Red List

not listed

 
  NatureServe

NNR - Unranked

SNR - Unranked

 
  Minnesota

not listed

 
           
           
 
Description
 
 

Broad-headed marsh fly is a medium-sized, brightly colored, flower fly. It occurs in the western, north-central, and northeastern United States, in southern Canada, and in the mountainous regions of Mexico. It is mostly absent from the southeast and south-central United States. It was once very common, but its numbers have declined significantly, as much as 80% to 90%. However, it is still widespread and relatively common. It is the most common Helophilus species in Minnesota. The larvae, known as rat-tailed maggots, are aquatic and feed on decaying vegetation. Adults have been recorded from May 7 to September 10 in Minnesota. They feed on flower nectar.

Adults are robust and 716 to (10.6 to 16.6 mm) in length.

The head is hemispherical, not flattened. There are two large compound eyes on the sides of the head and three small simple eyes (ocelli) in a triangle on top of the head. The compound eyes are bare, with no erect hairs, and are narrowed abruptly at the top of the face. They do not meet at the top of the head in either sex. On the male they abruptly converge slightly at the top, but the top of the head (vertex) is wider than the base of the antennal pits. The face is entirely covered with hairs except for a bare, shiny, yellow or reddish-yellow vertical line in the middle. The upper part of the face (frons) is covered with entirely yellow hairs. Both sexes have black hairs on the vertex and only on the vertex. On the female the space between the ocelli and the antennae bases is covered with yellow hairs. The antennae are short and have three segments, the scape at the base, the pedicel, and the flagellum. The scape and pedicel are black. At the base of the flagellum there is a long, forward-pointing bristle (arista) on the upper side.

The thorax is covered with erect yellow hairs. The large front portion (scutum) is brownish-black and has four bold longitudinal stripes. The two middle stripes may be white or yellow. The small rear part of the thorax (scutellum) is yellowish and more or less translucent. There are no bristles on the scutum or scutellum. The small plate in the shoulder area just behind the head (postpronotum) is bare, with no hairs or bristles. Unfortunately, this is not visible without first removing the fly’s head.

The abdomen on the male has four visible segments. It is black with a yellow or white band on each segment. The first segment is very narrow. The band on the second segment is broad, yellow, and incomplete, interrupted in the middle. The band on the third segment is broad, yellow, and is usually connected in the middle by a narrow pale yellow or white extension. The band on the fourth segment is pale yellow or white, is arced on each side, and is complete, meeting in the middle. On the female the abdomen has five visible segments. The bands are similar but variable.

The wings are mostly clear. The pigmented region (stigma) near the leading edge of the wing is a diffuse smoky brown patch more than twice as long as wide. It does not resemble a cross vein. The marginal cell R1 is closed, R3 is open. The anal is cell closed before the border of the wing.

 
     
 

Size

 
 

Total length: 716 to (10.6 to 16.6 mm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

 

 
     
 
Biology
 
 

Season

 
 

May 7 to September 10

 
     
 

Behavior

 
 

 

 
     
 

Life Cycle

 
 

 

 
     
 

Larva Food

 
 

Rotting vegetation

 
     
 

Adult Food

 
 

Flower nectar

 
     
 
Distribution
 
 

Distribution Map

 

Sources

7, 24, 27, 29, 30, 82, 83.

Telford, Horace S.. (1939). The Syrphidae of Minnesota. University of Minnesota. Minnesota Agricultural Experiment Station.

 
  9/4/2022      
         
 

Occurrence

 
 

 

 
         
 
Taxonomy
 
 

Order

Diptera (flies)  
 

Suborder

Brachycera  
 

Infraorder

Muscomorpha (=Cyclorrhapha)  
  Zoosection Aschiza  
 

Superfamily

Syrphoidea  
 

Family

Syrphidae (hover flies)  
 

Subfamily

Eristalinae (drone flies and allies)  
 

Tribe

Eristalini (rat-tail maggot flies)  
  Subtribe Helophiliina  
 

Genus

Helophilus (marsh flies)  
  Subgenus Helophilus  
       
 

Synonyms

 
 

Elophilus latifrons

 
       
 

Common Names

 
 

broad-headed marsh fly

 

 

 

 

 

 

 

Glossary

Arista

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

 

Frons

The upper part of an insect’s face, roughly corresponding to the forehead.

 

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.

 

Stigma

In plants, the portion of the female part of the flower that is receptive to pollen. In Lepidoptera, an area of specialized scent scales on the forewing of some skippers, hairstreaks, and moths. In other insects, a thickened, dark, or opaque cell on the leading edge of the wing.

 

Vertex

The upper surface of an insect’s head.

 

 

 

 

 
 
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Greg Watson

 
 

I was riding my bike along the Wagon Wheel Trail in La Crescent this morning and I was able to get these two pictures of a [Broad-headed] Marsh Fly. A first time for me on seeing one. It is on a Blue Vervain, Verbena hastata.

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  Greg Watson
7/3/2022

Location: La Crescent, MN

I was riding my bike along the Wagon Wheel Trail in La Crescent this morning and I was able to get these two pictures of a [Broad-headed] Marsh Fly. A first time for me on seeing one. It is on a Blue Vervain, Verbena hastata.

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Created: 9/4/2022

Last Updated:

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