Pennsylvania dingy ground beetle

Pennsylvania dingy ground beetle is a common, native, medium-sized, omnivorous beetle. It occurs throughout the United States and southern Canada.

Adults are active from July through September. They are found in various open habitats, including woodland edges and openings, and croplands. They are most common around the edges of cultivated fields. They hide during the day under rocks, logs, or plant debris. They emerge at night to feed on insects, pollen, and seeds. They are considered beneficial because they show a distinct preference for small weed seeds.

Adults are ½″ to ⅝″ (13.0 to 15.5 mm) in length. The body is oblong, robust, and nearly parallel sided. It is uniformly black and moderately shiny above. The underside is dark reddish brown to brownish black. Recently emerged (teneral) adults are soft and entirely reddish yellow. As they mature, the exoskeleton gradually hardens and blackens.

The head is black and moderate sized. It is not narrowed at the rear into a neck. The jaws (mandibles) are stout and sharply angled at the tip. The antennae are slender and reddish yellow, and they have 11 segments. Only the first two segments are hairless.

The plate covering the first segment of the thorax (pronotum) is broader than long. The sides are gradually curved. The lateral margins are flattened (margined). The rear of the pronotum is as wide as the wing covers (elytra). The area behind the rear angles is strongly depressed and densely pitted (punctate). The plate between the wing bases (scutellum) is very small, but it is visible.

The elytra are distinctly grooved. The grooves are moderately deep, and the spaces between the grooves (intervals) are convex. The fifth through eighth intervals on the female have numerous small pits (punctures). On the male, these intervals have very sparse punctures.

The legs are reddish yellow. The last part of each leg (tarsus), corresponding to the foot, has 5 segments. There is a pair of equal-sized claws at the tip of the last segment. On the male, the first four tarsal segments on the front legs are dilated and they have two rows of small scales below. On the hind legs of both sexes, the first tarsal segment is no longer than the next two segments combined.

Total length: ½″ to ⅝″ (13.0 to 15.5 mm)

Adults are active at night and will come to light.

Insects, pollen, and seeds

Sources

24, 29, 30, 82, 83.

Common

Beetle was found in damp sandy soil. I would say I found at least dozen or so in two 100 foot rows of turned soil as I was pickup the potatoes.

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Bill Reynolds
9/5/2024

Location: Pennington Co. MN

Beetle was found in damp sandy soil. I would say I found at least dozen or so in two 100 foot rows of turned soil as I was pickup the potatoes.