tachinid fly

(Thelaira americana)

Conservation Status
tachinid fly (Thelaira americana)
Photo by Alfredo Colon
  IUCN Red List

not listed

     
  NatureServe

not listed

     
  Minnesota

not listed

     
           
           
           
           
 
Description
 
 

Thelaira americana is medium-sized tachinid fly. It occurs throughout the United States, in southern Canada, and in Mexico. It is uncommon in Minnesota. Larvae parasitize caterpillars of Virginia tiger moth and salt marsh moth.

Adults are 516 to (8 to 10 mm) in length.

There are two large compound eyes at the side of the head and three small simple eyes (ocelli) in a triangle at the top of the head. The compound eyes are brown and bare, not covered with hairs. They do not meet at the top of the head in either sex. The antennae have three segments. The second segment has a longitudinal groove (suture) on top. The third segment has a long, forward-pointing bristle (arista) on the upper side. The arista is feather-like (plumose). The upper face (frons), corresponding to the forehead, is black. The area between the frons and the compound eye (frontorbital plate) is white. On each side of the face below the antenna there is a sunken area (parafacial) defined by the inner margin of the compound eye on the outside and an inverted V-shaped groove (ptilinal suture) on the inside. The parafacial is bare, at least on the lower half. There are long sensory organs (palps) attached to the mouth. The protruding mouthpart (proboscis) is short and fleshy.

The thorax 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. The prescutum and scutum are shiny and black, with broad, powdery white (pruinose), lateral margins, and sometimes a narrow pruinose rear margin. There is a distinct groove (transverse suture) across the thorax separating the prescutum and scutum. The scutellum is black, shiny, and has three pairs of marginal bristles. On the underside, the plate on the second thoracic segment (katepisternum) has two or more bristles.

The abdomen has at least one pair of long bristles on each segment. On the male, the first and second segment and the front half of the third segment are orange with a broad black stripe on the upper side and a narrow black stripe on the underside. Segment three also has some white on the upper side bordering part of the orange area. The rear half of the third segment and the entire fourth segment are black. The abdomen on the female is entirely black.

The wings are mostly clear but with dark veins and a light, smoky-brown tint near the base. At the base of each wing there are two large rounded lobes (calypters) that cover the balancing organs (halteres). The first posterior cell (R5) is narrowed but open at the wing tip.

The legs are long and black.

 
     
 

Size

 
 

Total Length: 516 to (8 to 10 mm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

Grasslands

 
     
 
Biology
 
 

Season

 
 

June to August

 
     
 

Behavior

 
 

The wings are held out at an angle when at rest, not almost parallel to the body.

 
     
 

Life Cycle

 
 

 

 
     
 

Larva Food

 
 

Caterpillars of Virginia tiger moth and salt marsh moth

 
     
 

Adult Food

 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 27, 29, 30, 82.

 
  1/3/2021      
         
 

Occurrence

 
 

Uncommon 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  
  No Rank Schizophora  
  No Rank Calyptratae  
 

Superfamily

Oestroidea  
 

Family

Tachinidae (tachinid flies)  
 

Subfamily

Dexiinae  
 

Tribe

Voriini  
 

Genus

Thelaira  
       
 

The genus Thelaira was formerly placed in the tribe Thelairini in the subfamily Larvaevorinae. In 1960 Thelaira and three other genera were moved to the new tribe Voriini in the new subfamily Dexiinae. Some sources retain the older name for the tribe but accept the placement in the new family.

 
       
 

Synonyms

 
 

 

 
       
 

Common Names

 
 

This species has no common name. The common name for the family Tachinidae is tachinid flies, and is applied here for convenience.

 
       

 

 

 

 

 

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.

 

Frons

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

 

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.

 

Palp

Short for pedipalp. A segmented, finger-like process of an arthropod; one is attached to each maxilla and two are attached to the labium. They function as sense organs in spiders and insects, and as weapons in scorpions. Plural: palpi or palps.

 

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.

 

 

 

 

 

       
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Alfredo Colon
       
  tachinid fly (Thelaira americana)    
       
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Alfredo Colon
8/8/2019

Location: Woodbury, MN

tachinid fly (Thelaira americana)


     
     
 
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Created: 1/3/2021

Last Updated:

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