bean leaf beetle

not listed

NR - Unranked

not listed

Bean leaf beetle is a small skeletonizing leaf beetle. It is common in North America east of the Great Plains. It is found in most soybean fields every year.

Adults are ⅛″ to ¼″ long. The body is longer than wide and slightly convex. When viewed from above, the head and most of the legs are clearly visible.

The head is always black. The mouthparts project from the front of the head. The antennae are thread-like. The bases of the antennae are close together.

The upper thoracic shield (pronotum) and hardened wing covers (elytra) are usually yellow but may be red or any color in between. The pronotum is broad but slightly narrower that the base of the elytra. It has a distinct lateral margin and no black markings.

Each elytron has a black spot on the front (anterior) inner margin that joins with an identical spot on the opposite elytron forming a backward-pointing triangle. There are usually two large spots in the middle (mid-dorsal), one small spot near the tip (apex), and one stripe on the outer margin. The spots and stripes may be absent, but the triangle is always present.

The last part of each leg (tarsus), corresponding to the foot, has five segments but the fourth segment is minute, making it appear that there are only four segments.

Total length: ⅛″ to ¼″

One generation: Mid-May to late September

Adults overwinter in the soil. They become active in the spring when the plant seedlings first emerge and feed on the leaves that were preformed in the seed (cotyledon leaves). They remain active until the first new (neoformed) leaf unfurls. At that time the female lays small groups of orange eggs on the soil near the stems of host plants. The eggs hatch in about 11 days and the larvae begin feeding on host plant roots. In the next 35 to 55 days the larvae pass through three stages, pupate in the soil, and emerge as adults. These progeny of overwintered adults appear in the summer. They feed on mature leaves and on the green tissue of the pod wall, only occasionally eating through the wall to the bean. They do not occur in numbers large enough to cause serious crop damage.

Roots of legumes

Leaves of legumes

Sources

24, 27, 29, 30.

Common

Location: Woodbury, MN