slender smoothtail

(Epistrophella emarginata)

Conservation Status
slender smoothtail
Photo by Alfredo Colon
  IUCN Red List

not listed

     
  NatureServe

NNR - Unranked

SNR - Unranked

     
  Minnesota

not listed

     
           
           
 
Description
 
 

Slender smoothtail is a small to medium-sized hoverfly. It occurs in North America from Quebec to Manitoba south to Florida and Texas. A disjunct (unconnected) population occurs in the Pacific Northwest. It is most common in Quebec and in the bordering U.S. states. It is not common in Minnesota. Adults are found from early May to October in hardwood forests, meadows, and fens, and near lake shores. They feed on flower nectar and pollen. Larvae prey on a wide variety of aphids.

Adults are 516 to ½ (7.8 to 11.7 mm) in length. They are black and shiny with bright yellow markings. As the common name suggests, they are slender-bodied.

The head is hemispherical and wider than the thorax. The back of the head is strongly concave and closely appressed to the thorax. There are two large compound eyes on the sides of the head and and three small simple eyes (ocelli) in a triangle on top of the head. The compound eyes are bare, with no hairs. On the male they meet at the top of the head. On the female they do not. The face is entirely yellow. The protruding mouthpart (proboscis) is short and fleshy. The antennae are short, shorter than the head, and have just three segments. The color is variable, from entirely black to orange with a black just on the upper margin. On the third segment there is a stiff, forward-pointing bristle (arista). The arista is bare, not feather-like (plumose).

The thorax is large and has 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. There is a broad, sharply defined, bright yellow, longitudinal stripe on each side of the scutum. On each side of the scutum, in the shoulder (humeral) area just behind the head, there is small plate (postpronotum). The postpronotum is bare, with no hairs or bristles. Unfortunately, this is not visible without first removing the fly’s head. The scutellum is large, rounded, and bright yellow. The lower front plate of the middle segment (katepisternum) has an upper and a lower patch of hairs. The two patches are distinctly separated.

The abdomen has five visible segments on both sexes. The first segment (A1) is short and black above. A2 through A4 each have a pair of bright yellow spots above. The size of the spots is variable. On A2 the spots are usually small, distinctly separated in the middle, and do not reach the lateral margin. Often they are large and and reach the lateral margin. Rarely they are small and and reach the lateral margin. On A3 there is sometimes a narrow yellow band on the front margin. The spots are large and usually narrowly separated in the middle, sometimes joined in the middle. They usually narrowly touch the lateral margin. Sometimes there is a narrow yellow band on the rear margin. On A4 the spots are large. They are rarely joined in the middle and usually broadly touch the lateral margin. The yellow band on the rear margin is narrow but broader than that on A3. A5 may be yellow at the front corners or yellow with a broad black inverted U or V.

The wings are clear. The small membranous lobe (calypter) at the base of the forewing that covers the balancing organ (haltere) is has two lobes. The lower lobe is hairless above. Beyond that, the hairiness of the wing is extremely variable. The vein on the leading edge of the wing (costa) ends before the wing tip. There is a false vein (spurious vein) between the radius (R) and media (M) veins. The anal cell is long and is closed near the wing margin. The marginal, R1, R5, and M2 cells are also closed.

The legs are variable in color. On some specimens they are almost entirely yellow, with just the first segment (coxa) and the fifth part (tarsus) on the hind leg dark. There is often a dark brown ring on the lower half of the third segment (femur) of the hind leg. The fourth segment of the hind leg is often brownish toward the tip.

The description above refers to the eastern population. Almost all specimens in the west have abdominal spots well separated, and extensively hairy wings. In the east, many specimens have abdominal spots connected, and wings extensively hairy. The color of legs and upper face is also variable. Some specimens have different combinations of these characters. DNA studies suggest that Epistrophella emarginata is a complex of two or more species.

 
     
 

Size

 
 

Total Length: 516 to ½ (7.8 to 11.7 mm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

Hardwood forests, meadows, and fens, and lake shores

 
     
 
Biology
 
 

Season

 
 

Probably one generation per year: Early May to October

 
     
 

Behavior

 
 

 

 
     
 

Life Cycle

 
 

 

 
     
 

Larval Food

 
 

Aphids

 
     
 

Adult Food

 
 

Flower nectar and pollen

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 29, 30, 82, 83.

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

Skevington, J. H., Locke, M. M., Moran, K., Marshall, S. A., Crins, W. J., Young, A. D. (2019). Field Guide to the Flower Flies of Northeastern North America. United States: Princeton University Press.

 
  1/15/2021    
         
 

Occurrence

 
 

Not common in Minnesota

 
         
 
Taxonomy
 
 

Order

Diptera (gnats, mosquitoes, true flies)  
 

Suborder

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

Infraorder

Muscomorpha  
  No Rank Eremoneura  
  No Rank Cyclorrhapha (circular-seamed flies)  
  Section Aschiza  
 

Superfamily

Syrphoidea  
 

Family

Syrphidae (hover flies)  
 

Subfamily

Syrphinae  
 

Tribe

Syrphini  
 

Genus

Epistrophella  
       
 

In 2008 the genus Epistrophella was formally split from the genus Epistrophe. The new genus contains just three species, only one of which occurs in North America.

 
       
 

Synonyms

 
 

Metasyrphus emarginatus

Scaeva emarginata

Syrphus disjectus

Syrphus disjunctus

Syrphus emarginatus

Syrphus infuscata

Syrphus infuscatus

Syrphus invigorus

Syrphus maculifrons

Syrphus weborgi

Xanthogramma aenea

Xanthogramma divisa

Xanthogramma emarginata

Xanthogramma felix

Xanthogramma fragila

 
       
 

Common Names

 
 

slender smoothtail

 
       

 

 

 

 

 

Glossary

Arista

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

 

Calypter

On flies: one of two small membranous lobes at the base of the forewing that covers the haltere. On mosses: A thin cap that covers and protects the capsule and operculum and drops off at maturity.

 

Costa

On ferns: The central axis of a pinna, to which pinnules are attached. On mosses: the central axis (midvein) of a leaf. On insects: The vein on the leading edge of the forewing.

 

Femur

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

 

Halteres

In flies: a pair of knob-like structures on the thorax representing hind wings that are used for balance.

 

Ocellus

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

 

Proboscis

The protruding mouthpart(s) of a sucking insect.

 

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
       
  slender smoothtail   slender smoothtail
       
  slender smoothtail    
       
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Alfredo Colon
8/26/2019

Location: Woodbury, MN

slender smoothtail


Alfredo Colon
8/21/2019

Location: Woodbury, MN

slender smoothtail


     
     
 
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Created: 1/16/2021

Last Updated:

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