wedge-shaped beetle

(Macrosiagon limbata)

Conservation Status
wedge-shaped beetle (Macrosiagon limbata)
Photo by Alfredo Colon
  IUCN Red List

not listed

     
  NatureServe

NNR - Unranked

     
  Minnesota

not listed

     
           
           
           
 
Description
 
 

Macrosiagon limbata is a common and widely distributed, parasitic, wedge-shaped beetle. It occurs in eastern North America west to Arkansas and in Central and South America. The body is black and orange, slender, and 3 16 to ½ long.

The head is elongated, directed downward, and mostly orange. It is strongly constricted behind the eyes. The neck is inserted in the first thoracic segment (prothorax). The upper surface (vertex) is black, hairless, rounded, and is distinctly elevated above the front (anterior) margin of the upper thoracic plate (pronotum). The upper part of the face (frons) is smooth. The upper part of the mouth (labrum), corresponding to the upper lip, is elongated and rounded at the tip. The pair of chewing structures of the mouth (mandibles) are moderately curved. They are mostly black but orange at the base. There are two small, black, oval, prominent, compound eyes and no simple eyes (ocelli). The antennae are black except for the first two segments, which are orange. The base of each antenna is near the middle of the inner margin of the eye. On the female they are deeply sawtoothed. On the male they are shorter than the pronotum and are comb-like, with a long projection on both sides of each antenna segment (biflabellate).

The pronotum is longer than the base is wide, and slightly tapers toward the front. It is orange and has a black spot that is variable in size. It does not have a sharp lateral ridge or a distinct suture. The base has sharp, prolonged, acutely angled corners and a large triangular lobe in the middle that covers the plate over the wing bases (scutellum).

The hardened forewings (elytra) are long, slightly tapered toward the end, and entirely dark brown to black. They extend well beyond the end of the abdomen. For most of their length they do not touch each other but are separated like an inverted V, exposing the brown hindwings.

The legs are long and slender. The third segment of each leg (femur) is orange with a black tip. On the front legs the femur is indented at the tip. On the hind legs the femur is distinctly compressed. The fourth segment (tibia) on the front legs is entirely black. On the middle and hind legs it is usually orange on the basal half, black on the apical half, sometimes entirely black. On the front and middle legs, the last part of the leg (tarsus), corresponding to the foot, is black and has five segments. On the hind leg it has only four segments. The inner surface is smooth and hairless. The second tarsal segment on the hind leg is flat, shiny above, and about half as long as the third segment. There is a pair of claws at the end of each tarsus. Each claw is split in two.

 
     
 

Size

 
 

Total Length: 3 16 to ½

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

 

 
     
 
Biology
 
 

Season

 
 

June to August

 
     
 

Behavior

 
 

 

 
     
 

Life Cycle

 
 

The female lays eggs on flowers. When an egg hatches, the first stage larva (triungulin) attaches itself to the underside of a solitary bee or wasp. After it is carried back to the host’s nest, the triungulin invades the cell of a host larva and enters into the body of the larva. It then delays further development while the host matures. When the host larva is completely developed, the triungulin exits the larva’s body and consumes it and its stored food.

 
     
 

Larva Food

 
 

Larvae of wasps and bees

 
     
 

Adult Food

 
 

Flower nectar

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 29, 30.

 
  12/11/2018      
         
 

Occurrence

 
 

Common and widely distributed

 
         
 
Taxonomy
 
 

Order

Coleoptera (beetles)  
 

Suborder

Polyphaga (water, rove, scarab, longhorn, leaf and snout beetles)  
 

Infraorder

Cucujiformia  
 

Superfamily

Tenebrionoidea (Fungus, Bark, Darkling and Blister Beetles)  
 

Family

Ripiphoridae (Wedge-shaped Beetles)  
 

Subfamily

Ripiphorinae  
 

Genus

Macrosiagon  
       
 

Synonyms

 
 

Macrosiagon limbatum

 
       
 

Common Names

 
 

No species in this genus has a common name, nor does the genus itself. The common name for the family Ripiphoridae is wedge-shaped beetles, and is applied here for convenience.

 
       

 

 

 

 

 

Glossary

Elytra

The hardened or leathery forewings on an insect used to protect the fragile hindwings, which are used for flying, in beetles and true bugs. Singular: elytron.

 

Femur

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

 

Frons

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

 

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.

 

Ocellus

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

 

Pronotum

The saddle-shaped, exoskeletal plate on the upper side of the first segment of the thorax of an insect.

 

Prothorax

The first (forward) segment of the thorax on an insect, bearing the first pair of legs but not wings.

 

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).

 

Vertex

The upper surface of an insect’s head.

 

 

 

 

 

       
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Alfredo Colon
       
  wedge-shaped beetle (Macrosiagon limbata)   wedge-shaped beetle (Macrosiagon limbata)
       
  wedge-shaped beetle (Macrosiagon limbata)   wedge-shaped beetle (Macrosiagon limbata)
       
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  wedge-shaped beetle (Macrosiagon limbata)
Bill Keim
 
  wedge-shaped beetle (Macrosiagon limbata)  

 

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Other Videos
 
  Wedged shaped beetle forages on hoary mountain mint
Robert Klips
 
   
 
About

Published on Jul 22, 2012

A wedged-shaped beetle, Macrosiagon limbata (Coleopytera; Ripiphoridae) forages for nectar on hoary mountain-mint, Pychnanthemum incanum (Lamiaceae) July 22, 2012 in Hocking County, Ohio, USA.

   
       

 

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Alfredo Colon
6/22/2018

Location: Woodbury, Minnesota

wedge-shaped beetle (Macrosiagon limbata)


     
     
 
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Created: 12/12/2018

Last Updated:

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