oak besma

(Besma quercivoraria)

               
Hodges #

6885

oak besma

 

Conservation Status

IUCN Red List

not listed

NatureServe

NNR - Unranked

SNR - Unranked

Minnesota

not listed

Occurrence

Common in Minnesota

Flight/Season

Two generations per year. Early May to late August.

Habitat

Deciduous and mixed woodlands and forests

Size

Wingspan: 1116 to 1 (27 to 41 mm)

         
          Photo by Alfredo Colon
 
Identification

Oak besma is a medium-sized to large typical geometer moth. It occurs throughout the United States except for California, and across southern Canada. It is most common east of the Great Plains. It is common in Minnesota. Adults are found from early May to late August in deciduous and mixed woodlands. Larvae feed on oak, birch, elm, poplar, willow, and white spruce.

Adults have slender bodies and relatively large wings, with a wingspan of 1116 to 1 (27 to 41 mm).

The antennae on the female are slender and thread-like. On the male the antennae are branched, feather-like, on both sides (bipectinate).

The wings are large and thin. Each wing has a projection on the outer margin, giving the moth a scalloped appearance. The background color is variable; yellow, pale tan, or light reddish-brown on the male, paler on the female. All wings are have dark veins and dark lines, and are peppered with dark scales. On the forewings there is a curved antemedial (AM) line and a scalloped subterminal (ST) line. The AM line extends to the forward (costal) margin but often ends before the inner margin. It is always dark and distinct. The ST line extends to the (costal margin but always ends well before the inner margin. It is usually faint. On all wings there is a distinct postmedial (PM) line that always extends from the costal to the inner margin. It forms a continuous, straight or slightly scalloped line across all four wings. There is usually a small black spot (discal spot) on the inner half of all wings. The discal spots are “almost always present” on the forewing and hindwing. On the female there is sometimes a dark smudge on the outer half of the forewing near the inner margin. On the male there is often dark shading beyond the PM line and along the AM line. On both sexes the scales at the base of the fringe are dark, creating a fine dark line on the outer margin.

The caterpillar, called a looper, is twig-like and up to 1916 (4 cm) long. The ground color is “exceedingly variable.” Early stages (instars) are green and do not have any wart-like bumps. Middle instars usually have some brown. The second segment of the thorax (T2) has a pair of dark, wart-like bumps on top (subdorsal). On the third abdominal segment (A3) there are similar subdorsal warts and a wart on each side. There are smaller warts on the side and near the underside (subventral) of A2. There is also a pair of small subdorsal warts on A1, A5, A6, and A8, and these may be well or poorly developed. The warts are usually reddish or blackish. Late instars may be brown, tan, or gray, or a combination of these, and the bumps are larger. There are 3 pairs of legs on the thorax, one on each segment, and just 2 pairs of leg-like structures (prolegs) on the abdomen, one pair on A6 and one pair on A10. The head is brown and black. Mature caterpillars are active from June onward.

 
Similar
Species

Straw besma (Besma endropiaria) is paler overall and has lighter markings. There is no discal spot. The fringe scales are the same color as the wing background.

 
Larval Food

Oak, birch, elm, poplar, willow, and white spruce

 
Adult Food

 

 
Life Cycle

The pupa overwinters.

 
Behavior

Adults rest with their wings spread flat. They are active at night and will come to light.

 
Distribution Distribution Map  

Sources: 21, 24, 27, 29, 30, 71, 72, 75, 82.

 
Comments

 

 
Taxonomy

Order:

Lepidoptera (butterflies and moths)

 

Suborder:

Glossata

 

Infraorder:

Neolepidoptera

 

Parvorder:

Heteroneura

 

No Rank:

Ditrysia

 

No Rank:

Obtectomera

 

Superfamily:

Geometroidea (inchworm moths)

 

Family:

Geometridae (geometer moths)

 

Subfamily:

Ennominae (typical geometers)

 

Tribe:

Ourapterygini

 

Genus:

Besma

 
Synonyms

Meatnema aeliaria

 
Common
Names

oak besma

 

 

 

 

 

 

 

Glossary

Costal margin

The leading edge of the forewing of insects.

 

Instar

The developmental stage of arthropods between each molt; in insects, the developmental stage of the larvae or nymph.

 

Proleg

A fleshy structure on the abdomen of some insect larvae that functions as a leg, but lacks the five segments of a true insect leg.

 

 

 

 

 

       
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Alfredo Colon
       
  oak besma    
       
MinnesotaSeasons.com Photos
   
       
       
       

 

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Slideshows
   
  Oak Besma - Hodges#6885 (Besma quercivoraria)
Andree Reno Sanborn
 
  Oak Besma - Hodges#6885 (Besma quercivoraria)  
     

 

slideshow

       
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  besma quercivoraria larvae
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About

Mar 8, 2016

besma quercivoraria larvae on basil

   
       

 

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Alfredo Colon
8/9/2019

Location: Woodbury, MN

oak besma


 
         
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Created: 12/12/2020

Last Updated:

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