pigweed flea beetle

not listed

NNR - Unranked

not listed

Pigweed flea beetle is a small beetle, a moderate-sized leaf beetle, and a relatively large flea beetle. It occurs in North, Central, and South America. In the United States it occurs from Massachusetts to Florida, west to Kansas and eastern Texas, with a disjunct population in southern Arizona, and just a handful of records scattered across the rest of the country. It is uncommon in Minnesota.

Adults are somewhat shiny, slender, oblong, 3⁄16″ to ¼″ (5.4 to 6.5 mm) in length, and ⅛″ (2.8 to 3.4 mm) wide.

The head is yellow and black. Behind the eyes it is covered by the pronotum. The eyes are not notched. The space between the eyes is more than half the width of the head. The antennae have 11 segments. They are black and relatively long but less than half as long as the body. The basal segments are pale. The third segment is shorter than the fourth or fifth.

The exoskeletal plate covering the thorax (pronotum) is about twice as wide as long and widest at the base, nearly as wide as the hardened forewings (elytra). On each side the rear corner is distinctly cut off at an oblique angle, which puts the corner at a distance from the elytron. The lateral margin is bowed outward, narrowly flattened, and sharp. There is a slight depression in the middle of the pronotum near the base. The pronotum is red and shiny with a whitish margin. There is a small, distinct, elongated, black spot in the middle and sometimes a smaller, less distinct, round spot on each side.

The elytra are oblong with parallel sides, rounded in the shoulder (humeral) region, and broadly rounded at the tip. They have a narrow, flattened margin that does not extend all the way to the tip. The surface is smooth, shiny, and hairless. It is distinctly and densely covered with pits that are not in rows. On the female there is no trace or only a faint trace of longitudinal ridges. Each elytron is yellow or dingy white (pale) with a broad black stripe in the middle that does not quite reach the tip, a black stripe on the inner margin (sutural) that does extend to the tip, and a narrow black outer margin that also reaches the tip. The flattened part of the outer margin is also black. The plate between the wing bases (scutellum) is triangular and black.

The legs are slender, relatively short, and variable in color. They are usually mostly pale, either red or yellow, but the amount of black varies. The tips of the third segment (femur) and fourth segment (tibia) are black, and the femur near the outer (distal) end is black on the upper surface. Sometimes the legs are mostly or even entirely black. The tibia on the front leg does not have a spur at the tip. The femur on the hind leg is enlarged and modified for jumping. The tibia on the hind leg is shallowly grooved and has a short spur at the tip. 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. The last segment is not swollen. On the hind leg the first tarsal segment is less than half as long as the tibia. There is a pair of widely diverging claws at the tip of the tarsus. Each claw has a short wide tooth at the base (appendiculate).

Length: 3⁄16″ to ¼″ (5.4 to 6.5 mm)

Width: ⅛″ (2.8 to 3.4 mm)

May to September

Pigweed (Amaranthus spp.)

Sources

24, 29, 30, 82, 83.

Location: Tucson, Arizona