soldier fly

(Stratiomys adelpha or discalis)

               
Conservation Status

IUCN Red List

not listed

soldier fly (Stratiomys adelpha or discalis)

 

NatureServe

not listed

Minnesota

not listed

Occurrence

Common

Flight/Season

 

Habitat

Rivers and other wet places

Size

Total Length: 9 16 (14 mm)

          Photo by Alfredo Colon

Identification

Stratiomys adelpha and Stratiomys discalis are very similar in appearance. They are distinguished by the colored markings on the abdomen, but those vary between individuals and overlap between the two species. Some authors consider them to be the same species, Stratiomys adelpha, and list Stratiomys discalis as a synonym.

Stratiomys discalis is a large, bee-like, soldier fly. It occurs in northern United States and southern Canada. It is common in Minnesota. Adults are black with yellow marking and 9 16 (14 mm) long.

The head is more or less hemispherical and is not wider than the thorax. There are two large compound eyes on the side of the head and three small but prominent simple eyes (ocelli) in a triangle at the top of the head. On the male they meet at the top of the head. On the female they are widely separated. On both sexes the compound eyes are bare. The face is rounded and covered with thick, long, yellow hairs. Below the antennae the face recedes (is not projected forward). On the female, the head is mostly black with a small yellow spot below the ocelli and yellow around the compound eyes. On the male the head and face are entirely black. The antennae are black, long (for a fly), and are inserted just above the middle of the face. They have three segments. The first segment is three or four times as long as the second. The third segment is as long as the first two segments together, and is divided into five ring-like segments (annulated). It does not have a bristle-like appendage (arista).

The thorax is black and trapezoidal, straight in front and back, tapered toward the front. It is densely covered with long, yellowish, woolly hairs. The hairs on the sides of the thorax are entirely pale. The exoskeletal plate between the wing bases (scutellum) is prominent. On the female it is black except for a narrow yellow band at the rear margin. On the male it is entirely black. On both sexes it is covered with long hairs and has a single, strong, yellow spine at each rear corner.

The abdomen is broader than the thorax and as long as the head and thorax together. It is egg-shaped and has five visible segments when viewed from above, thick and very convex when viewed from the side. It is black, shiny, and has conspicuous yellow markings on the lateral margins. The hairs and yellow markings on the male are different from those on the female. On the male, the hairs on the first, second, and fifth segments are yellow, those on the third and fourth segments are black. On the female, the hairs on all segments are very short and whitish. Both sexes have a small spot at the rear corners of the first segment. On segment 2 the male has a large squarish spot, the female has an even larger sub-triangular spot. On segment 3, the male has a spot similar in shape and slightly smaller than the one on segment 2, the female has a triangular spot on the forward margin that is much smaller than the one on segment 2. The male has a very broad marginal stripe on segment 4 and a narrow stripe on segment 5. The female has a very narrow marginal stripe on segments 4 and 5. Both sexes have a yellow longitudinal line in the middle of segment 5.

The legs are moderately long. On the male, basal half of the third leg segment (femur) on the hind legs is yellow, the remainder black. On the female, only the basal third is yellow. On both sexes, the femurs on the front and middle legs are mostly black, yellowish just at the tip. The basal half of the fourth segment (tibia) is yellow, the outer half black. The tibia have no spurs. The last part of the leg (tarsus), corresponding to the foot, is yellow and has three pads. On the male, the basal half is yellowish, the outer half is brownish, the tip is black. On the female it is mostly yellowish, black just at the tip.

The wings are clear and tinted brownish. There are five distinct cells at the outer part of the wing. The radial vein (R) has two branches, and they are crowded in the front of the wing. The posterior branch (Rs) has three branches. The posterior branch of Rs (R5) ends at the margin before the wing tip. The anal cell is longer than the second basal cell and is closed near the wing tip. The knob-like balancing structures (halteres) are pale green on the male, yellow on the female.

 
Similar
Species

 


Larval Food

Decaying vegetation and aquatic microorganisms

 
Adult Food

 

 
Life Cycle

 

 
Behavior

Adults are found on the leaves and flowers of umbelliferous plants. Larvae live in water.


Distribution Distribution Map  

Sources: 24, 27, 29, 30.


Comments

No Common Name
None of the 90 described species in the genus Stratiomys has a common name. The common name for the family Stratiomyidae is soldier flies, and is applied here for the sake of convenience.


Taxonomy

Order:

Diptera (gnats, mosquitoes, true flies)

 

Suborder:

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

 

No Rank:

Orthorrhapha

 

Family:

Stratiomyidae (soldier flies)

 

Subfamily:

Stratiomyinae

 

Tribe:

Stratiomyini

 
Subordinate Taxa

 

 
Synonyms

Stratiomyia discalis

Stratiomys media

 
Common
Names

no common name


 

 

 

 

 

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.

 

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.

 

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

The last two to five subdivisions of an insect’s leg, attached to the tibia; the foot. Plural: tarsi.

 

Tibia

The fourth segment of an insect leg, after the femur and before the tarsus (foot).

 

 

 

 

 

       

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Alfredo Colon


  soldier fly (Stratiomys adelpha or discalis)   soldier fly (Stratiomys adelpha or discalis)

       
       
       

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Alfredo Colon
7/23/2018

Location: Woodbury, MN

soldier fly (Stratiomys adelpha or discalis)


     
     
 

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