milkweed stem weevil

(Rhyssomatus lineaticollis)

Conservation Status
milkweed stem weevil
Photo by Alfredo Colon
  IUCN Red List

not listed

     
  NatureServe

NNR - Unranked

     
  Minnesota

not listed

     
           
           
           
 
Description
 
 

Milkweed stem weevil is a small snout beetle. It occurs in the United States from Maine and Florida west to Utah and Arizona, and in Canada in Quebec and Ontario. Adults feed on the leaves, stems, and pods of mostly common milkweed but also on other milkweed species. Larvae feed on the stems of the same plants.

Adults are black, hard bodied, robust, oval, and 316 to ¼ (5.5 to 6.5 mm) long. They are convex when viewed from the side. They are almost completely free of hairs and scales.

The head is greatly elongated between the eyes and the mouth parts forming a conspicuous snout (rostrum). The rostrum is almost cylinder-shaped, projected forward, and slightly bent downward. It is shorter than the head and thorax combined. The antennae are short. slender, elbowed, and reddish. They have 11 segments. The last 3 segments are expanded and form a club.

The thorax is composed of three segments. The first segment (prothorax) is large and prominent and appears to be the entire thorax. It is covered by a saddle-shaped plate (pronotum). The pronotum is wider than long, strongly arched at the sides, and narrower than the hardened wing covers (elytra). It is covered with deep, longitudinal grooves. The grooves are parallel to the midline, not oblique.

The elytra completely cover the abdomen. They are grooved and have narrow ridges between the grooves. Within the grooves there are two rows of deep pits (punctures).

The legs are mostly black except for the last part of the leg (tarsus), corresponding to the foot, which is reddish. The tarsus has 5 segments, but the fourth segment is very small and is concealed within the lobes at the end of the third segment, making it appear to have just 4 segments.

 
     
 

Size

 
 

Total Length: 316 to ¼ (5.5 to 6.5 mm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

Fields, prairies, and pastures. Mostly common milkweed but also other milkweeds.

 
     
 
Biology
 
 

Season

 
 

May to August

 
     
 

Behavior

 
 

 

 
     
 

Life Cycle

 
 

The female chews several holes in a line near the base of the stem of a host plant. She lays a single egg in each hole.

 
     
 

Larva Food

 
 

Stems of milkweeds

 
     
 

Adult Food

 
 

Leaves, stems, and pods of milkweeds.

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 27, 29, 30, 82.

 
  11/19/2020      
         
 

Occurrence

 
 

 

 
         
 
Taxonomy
 
 

Order

Coleoptera (beetles)  
 

Suborder

Polyphaga (water, rove, scarab, long-horned, leaf and snout beetles)  
 

Infraorder

Cucujiformia  
 

Superfamily

Curculionoidea (snout and bark beetles)  
 

Family

Curculionidae (snout beetles, weevils)  
 

Subfamily

Molytinae  
 

Tribe

Cleogonini  
 

Genus

Rhyssomatus  
       
 

Synonyms

 
 

Rhynchaenus linealicolis

 
       
 

Common Names

 
 

common milkweed stem weevil

milkweed curculio

milkweed stem weevil

 
       

 

 

 

 

 

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.

 

Pronotum

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

 

Rostrum

The stiff, beak-like projection of the carapace or prolongation of the head of an insect, crustacean, or cetacean.

 

 

 

 

 

       
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Alfredo Colon
       
  milkweed stem weevil   milkweed stem weevil
       
       
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Other Videos
 
  Milkweed Stem Weevil (Curculionidae: Rhyssomatus lineaticollis)
Carl Barrentine
 
   
 
About

Jun 26, 2010

Photographed at the Rydell NWR, Minnesota (25 June 2010).

   
       

 

Camcorder

         
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Alfredo Colon
8/8/2019

Location: Woodbury, MN

milkweed stem weevil


     
     
 
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Created: 11/19/2020

Last Updated:

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