milkweed stem weevil

(Rhyssomatus lineaticollis)

               
Conservation Status

IUCN Red List

not listed

milkweed stem weevil

NatureServe

NNR - Unranked

Minnesota

not listed

Occurrence

 

Flight/Season

May to August

Habitat

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

Size

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

Photo by Alfredo Colon
 
Identification

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. Ther 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.

 
Similar
Species

 

 
Larval Food

Stems of milkweeds

 
Adult Food

Leaves, stems, and pods of milkweeds.

 
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.

 
Behavior

 

 
Distribution Distribution Map  

Sources: 24, 27, 29, 30, 82.

 
Comments

 

 
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).

   
       

 

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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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