wedge-shaped beetle

(Macrosiagon flavipennis)

Conservation Status
wedge-shaped beetle (Macrosiagon flavipennis)
Photo by Mike Poeppe
  IUCN Red List

not listed

     
  NatureServe

not listed

     
  Minnesota

not listed

     
           
           
           
           
 
Description
 
 

Macrosiagon flavipennis is a parasitic, wedge-shaped beetle. It occurs in the United States east of the Great Plains and in California, in southern Ontario Canada, and in Mexico.

Adults are robust, ¼ to 716 (7 to 11 mm) in length, and mostly dull black.

The head and thorax are entirely black. The head is elongated, directed downward, and strongly constricted behind the eyes, creating a “neck”. The upper surface (vertex) is hairless, rounded, and distinctly elevated above the front margin of the upper thoracic plate (pronotum). The upper part of the face (frons), corresponding to the forehead, is smooth and has a distinct concavity or dimple. The upper part of the mouth (labrum), corresponding to the upper lip, is elongated, rounded at the tip, and hairy. The pair of chewing structures on the mouth (mandibles) are very little curved. There are two oval, small but prominent compound eyes and no simple eyes (ocelli). The antennae have 11 segments. The base of each antenna is near the middle of the inner margin of the eye. On the female the antennae are black except for the first two segments, which are orange, and they have a single, short, forward-pointing projection on each segment (pectinate). On the male they are entirely orange and comb-like, with dense, thick, long projections on both sides of each antennal segment (biflabellate). The projections on both sides are usually pointed forward, making the antennae appear one-sided (flabellate). On both sexes there are no projections on the first two segments.

The pronotum is bell-shaped, longer than the base is wide and narrowest behind the head. The rear corners are acutely angled and a large triangular lobe in the middle covers the plate between the wing bases (scutellum). It does not have a sharp lateral ridge on each side. At the base there is a distinct, raised, fin-like projection (tubercle).

The abdomen on the male is entirely black. On the female the abdomen is mostly orange, black on the last one-and-a-half segments. The hardened forewings (elytra) are strongly pointed and long, as long as the abdomen but not as long as the hindwings. For most of their length they do not touch each other but are separated like an inverted V, exposing the hindwings. On the female they are yellow on the basal half, black on the rear half. The line separating the black from the yellow is semicircular. On the male they are entirely yellow. The hindwings are yellowish-brown.

The legs are long and slender. On the front legs the third segment (femur) is indented at the tip. On the hind legs the femur is distinctly compressed. On the front and middle legs, the last part of the leg (tarsus), corresponding to the foot, 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 not flat above, and is 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: ¼ to 716 (7 to 11 mm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

 

 
     
 
Biology
 
 

Season

 
 

June and July

 
     
 

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.

 
  8/8/2021      
         
 

Occurrence

 
 

 

 
         
 
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 flavipenne

 
       
 

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.

 

Tarsus

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

 

Tubercle

On plants and animals: a small, rounded, raised projection on the surface. On slugs: raised areas of skin between grooves covering the body

 

Vertex

The upper surface of an insect’s head.

 

 

 

 

 

 
 
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Mike Poeppe

 
    wedge-shaped beetle (Macrosiagon flavipennis)      
           
 

I found these after the rain today just west of Houston.

 
    wedge-shaped beetle (Macrosiagon flavipennis)   wedge-shaped beetle (Macrosiagon flavipennis)  
           
 
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Camera

     
 
Slideshows
 
Ontario Wedge-Shaped Beetles (Ripiphoridae)
David Beadle
  Ontario Wedge-Shaped Beetles (Ripiphoridae)  
     

 

slideshow

       
 
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  Mike Poeppe
7/10/2021

Location: Houston County, MN

wedge-shaped beetle (Macrosiagon flavipennis)

 
  Mike Poeppe
7/7/2021

Location: west of Houston, MN

I found these after the rain today just west of Houston.

wedge-shaped beetle (Macrosiagon flavipennis)

 
           
 
MinnesotaSeasons.com Sightings
 
 

 

 

 

 

Binoculars


Created: 8/8/2021

Last Updated:

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