Cocklebur weevil

Cocklebur weevil is a medium-sized true weevil. It is widespread in the eastern half of the United States. The body is 3 ⁄16″ to 5 ⁄16″ long, elongated, and oval, more-or-less football-shaped.

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 slightly wider than long and is rounded at the sides. The pronotum is reddish-orange with five black spots: a single, oval, median spot; and two smaller spots on each side.

There are two pairs of wings, a membranous inner pair and a hardened outer pair (elytra). The elytra are attached to the second thoracic segment (mesothorax). They cover almost but not quite all of the abdomen. They are wider than the pronotum, oblong egg-shaped, rounded at the tips, moderately convex, longitudinally grooved, and pitted. They are reddish-orange and each has five black spots. The median line where the elytra meet (elytral suture) is black. A large spot at the tip coalesces with one on the opposite elytra forming a single large spot. A smaller spot halfway between the base and the tip usually coalesces with one on the opposite elytra. A single lateral spot near the tip sometimes coalesces with the one at the tip. Two smaller lateral spots near the base are always separated. Rarely, almost the entire elytra will be black.

The head is greatly elongated between the eyes and the mouth parts form a conspicuous snout. The snout is narrow, enlarged toward the tip, and very long, about as long as the prothorax. It is projected forward and bent downward. The antennae are short, slender, and elbowed. They have eleven segments. The last 3 segments are expanded and form a club. The antennae are inserted near the eyes.

The legs are black. The last part of each leg (tarsus), corresponding to the foot, has five segments. The fourth segment is very short and is concealed within the broadened tip of the third segment, making the tarsus appear to have only four segments.

Total length: 3 ⁄16″ to 5 ⁄16″

Ironweed curculio (Rhodobaenus tredecimpunctatus) is larger, up to 7 ⁄16″ long. The median line where the elytra meet (elytral suture) is red. The black spots on the elytra are always separated. They do not coalesce to form patches.

Larvae bore into the stems or roots of cocklebur and ragweed.

Stalks of all of the adult’s host plants

Stalks and leaves of cocklebur (Xanthium), ragweed (Ambrosia), thistle (Carduum), ironweed (Vernonia), Joe Pye weed (Eutrochium), sunflower (Helianthus), marsh elder (Iva), and rosinweed (Silphium).

Sources

24, 29, 30, 82, 83.

Widespread in eastern the United States

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