black diabrotica

not listed

NatureServe

NNR - Unranked

not listed

Black diabrotica is a small cucumber beetle. It occurs in the United States in the northeast from Massachusetts to Maryland, west to North Dakota and Colorado, and south in the Great Plains to Texas. It also occurs in southern Canada from Ontario to Manitoba, and in Mexico.

Black diabroticas are generalist feeders. The larvae feed on the roots of many plants, including big bluestem and other grasses, corn, radish, cucumber, lima bean, and plants in the aster (Asteraceae) family. Adults are found from May to September. They feed on the flowers, leaves, stems, and fruit of many plants, including bluestem, brome, panic grass, bristle grass, and goldenrod.

The body is elongated oval, ⅛″ to 3⁄16″ (4.1 to 4.7 mm) long, and 1⁄16″ (1.7 to 2.2 mm) wide. When viewed from above, the head and most of the legs are clearly visible.

The head is black. It is not pitted (punctate). The antennae are brownish-black, thread-like, and long, about half as long as the body. They have 11 segments. The third segment is short, no more than 1.5 times as long as the second segment. The antennae are close together at the base, about level with the middle of the eyes. They are flexible and can project in various directions. The eyes are not notched. The finger-like process attached to each under jaw (maxillary palp) is black or brownish-black.

The exoskeletal plate covering the thorax (pronotum) is squarish, wider than the head, and narrower than the base of the hardened wing covers (elytra). It is usually entirely black, sometimes partly or mostly brownish-orange, rarely entirely orange. The surface is shiny, and smooth, not granular. The sides are shallowly S-shaped. The lateral margins are distinctly flattened. There are two large, deep depressions near the middle. The plate between the wing bases (scutellum) is small, triangular, and black or brownish-black.

The elytra are entirely black or brownish-black, hairless, and finely punctate. They are widest at the rear and have a distinct, narrowly flattened margin. Each elytron has a long, deep, sinuous groove. The inner angles of the elytron tips (sutural angles) are rounded.

The legs are black or chestnut brown. The last part of each leg (tarsus), corresponding to the foot, has five segments. However, the fourth segment is minute and is concealed within the heart-shaped lobes at the end of the third segment, making it appear that there are only four segments. The last segment has a pair of claws.

Total length: ⅛″ to 2⁄16″ (4.1 to 4.7 mm)

May to September

Roots of many plants, including big bluestem and other grasses, corn, radish, cucumber, lima bean, and plants in the aster (Asteraceae) family

Flowers, leaves, stems, and fruit of many plants, including bluestem, brome, panic grass, bristle grass, and goldenrod

Sources

29, 30, 82, 83.

Diabrotica cristata cucumber beetle

Diabrotica cristata, small (abt. 5 mm) brown cucumber beetle on smooth aster.

Location: Barnes Prairie, Racine Co., WI

Diabrotica cristata, small (abt. 5 mm) brown cucumber beetle on smooth aster.