trefoil sawfly

(Atomacera debilis)

Conservation Status
trefoil sawfly
Photo by Alfredo Colon
  IUCN Red List

not listed

     
  NatureServe

not listed

     
  Minnesota

not listed

     
           
           
           
 
Description
 
 

Trefoil sawfly is a small argid sawfly. It occurs in the eastern United States and in Ontario, Canada. It is uncommon in Minnesota.

Adults are stout-bodied and mostly black. The female averages (4.0 mm) in length, the male (3.8 mm) in length.

The head is black. There is a raised crest on the upper part of the head. The mouthparts are optimized for chewing. The upper part of the mouth (labrum), which corresponds to the upper lip, the area above the labrum (clypeus), and the area above the clypeus and between the antennae bases (supraclypeal area) are all brownish. The antennae are black and have just 3 segments. The third segment is slender and very long. On the male it has numerous erect hairs. On both sexes it is not forked or U-shaped.

On the female, the upper side of the thorax, including the area just behind the head (prescutum), is reddish. On the male the thorax is entirely black. The small plate between the wing bases (scutellum) is reddish, and sometimes has a small or large black spot in the middle.

The abdomen is black. The wings are smoky, almost opaque at the base to almost clear at the tip. On the forewing, there are 3 marginal cells. There is an additional vein, the intercostal vein (ic), between the costal (c) and the subcostal (sc) veins. The basal anal cell in the forewing is missing. There is no anal cell in the hindwing.

The legs are black. The second segment (trochanter) has 2 segments. The fourth segment (tarsus) on the middle and hind legs does not have a spine just before the tip (preapical spine). The last part of the leg (tarsus), corresponding to the foot, has 5 segments. At the end of each tarsus there is a pair of claws. The claws are simple, not forked, and are sharply bent at over the tip.

 
     
 

Size

 
 

Male: average (3.8 mm)

Female: average (4.0 mm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

 

 
     
 
Biology
 
 

Season

 
 

 

 
     
 

Behavior

 
 

 

 
     
 

Life Cycle

 
 

 

 
     
 

Larva Food

 
 

Leaves of tick-trefoil (Desmodium spp.)

 
     
 

Adult Food

 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 29, 30, 82

Key to genera of Nearctic Argidae (Hymenoptera) with revisions of the genera Atomacera Say and Sterictiphora Billberg. Smith D.R. 1969. Trans. Am. Ent. Soc. 95: 439-457.

 
  11/22/2020      
         
 

Occurrence

 
 

Uncommon in Minnesota

 
         
 
Taxonomy
 
 

Order

Hymenoptera (ants, bees, wasps, and sawflies)  
 

Suborder

Symphyta (horntails, sawflies)  
 

Superfamily

Tenthredinoidea (sawflies)  
 

Family

Argidae (argid sawflies)  
 

Subfamily

Atomacerinae  
 

Genus

Atomacera  
       
 

Synonyms

 
 

 

 
       
 

Common Names

 
 

trefoil sawfly

 
       

 

 

 

 

 

Glossary

Clypeus

On insects, a hardened plate on the face above the upper lip (labrum).

 

Labrum

The upper part of the mouth, sometimes considered the lower part of the face, corresponding to the upper lip, on an insect or crustacean.

 

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

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
       
  trefoil sawfly   trefoil sawfly
       
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Alfredo Colon
8/9/2019

Location: Woodbury, MN

trefoil sawfly


Alfredo Colon
8/8/2019

Location: Woodbury, MN

trefoil sawfly


     
     
 
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Created: 11/22/2020

Last Updated:

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