milkweed stem weevil

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 3⁄16″ 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 form 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.

Total length: 3⁄16″ to ¼″ (5.5 to 6.5 mm)

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

May to August

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.

Stems of milkweeds

Leaves, stems, and pods of milkweeds.

Sources

24, 27, 29, 30, 82, 83.

Milkweed Stem Weevil (Curculionidae: Rhyssomatus lineaticollis)
Carl Barrentine

Alfredo Colon
6/12/2024

Location: Albany, NY

Location: Saint Louis Park, MN

Location: Albany, NY

Location: Woodbury, MN