imported long-horned weevil

not listed

NNA - Not applicable

not listed

Imported long-horned weevil is a small, exotic, flightless, broad-nosed weevil. It is native to Japan. It was first reported in the United States in Yonkers, NY in 1929. Thousands of the weevils were seen in a localized area, indicating that it had been present for a few years. Since then, it has spread rapidly. It now occurs in the United States from Maine to North Carolina, west to Minnesota and Oklahoma, and in southern Quebec and Ontario Canada.

The larvae feed on the roots of alfalfa, aster, clover, goldenrod, and several species of grasses. Adults have been reported feeding on at least 100 species of forbs, shrubs, trees, and grasses. They often occur in explosive populations and can completely defoliate plants. They are a minor pest of soybean crops. However, even when they occur in very large numbers, they do not cause economic injury.

Adults are ⅛″ to 3⁄16″ (3.6 to 4.7 mm) in length. The body is oval, robust, and dark reddish brown to black, but is densely covered with grayish white scales and erect bristles. The head, the plate on the first segment of the thorax (pronotum), and the hardened wing covers (elytra), often have some brown scales, giving the individual a darker appearance.

The head and snout (rostrum) together are longer than the front part of the body (prothorax). The rostrum is short and broad, and expanded at the tip. The tip of the rostrum has two grooves and a V-shaped ridge. The antennae are reddish-brown or brown and bent (elbowed). They have 11 segments. The first segment (scape) is slightly curved and long, extending to the front margin of the prothorax. The last three segments are slightly expanded, forming a weak club. The club is elongated and is pointed at the end. The section beyond the bend and supporting the club (funicle) is as long as the scape.

The pronotum is wider than long, slightly wider in front than behind, and slightly rounded on the sides. The front margin is extended (lobed) on each side behind the eyes. The surface is coarsely pitted (punctate). The plate between the wing bases (scutellum) is not visible,

The elytra are egg-shaped when viewed from above, convex when viewed from the side. Each elytron has 10 narrow longitudinal grooves. The intervals between the grooves are convex, those on the sides slightly convex, those in the middle more strongly convex. They are pitted (punctured) and there is a stiff bristle emerging from each puncture.

The legs are reddish brown or brown and are covered with fine, reclining hairs (setae). The third segment (femur) of each leg are more or less club shaped, narrow at the base and broadest about the two-thirds point. At the widest point there is a very small, sharp tooth on the underside.

Total length: ⅛″ to 3⁄16″ (3.6 to 4.7 mm)

One generation per year: late June to the first week of August

Adults feed in groups on the upper parts of low growing plants.

Females lay unfertilized eggs that produce only female offspring (parthenogenesis). In late fall the larvae burrow into the soil up to eleven inches, deep enough to avoid the freezing temperatures of winter. Adults emerge in late June and are most abundant in July and early August.

Small roots of alfalfa, aster, clover, goldenrod, and several species of grasses

Foliage and blooms of at least 100 species of forbs, shrubs, trees, and grasses

Sources

24, 29, 30, 82, 83.

Common and increasing

I find them on our patio door screen all the time. Not a good picture since my camera focused on the screen instead of the bug no matter what I tried.

Location: West St. Paul, Dakota County

I find them on our patio door screen all the time. Not a good picture since my camera focused on the screen instead of the bug no matter what I tried.