black-margined loosestrife beetle

not listed

NNA - Not applicable

not listed

Black-margined loosestrife beetle is an exotic, small leaf beetle. It is native to Europe, Asia, northwest Africa, and Australia. It was intentionally released, along with the closely related golden loosestrife beetle (Neogalerucella pusilla), into 27 states in the United States and 6 provinces in Canada to control the spread of invasive purple loosestrife. In the U.S., it now occurs from Maine to Maryland, west to Minnesota and Illinois, and in Washington and northern Oregon. It is now common and widespread in Minnesota.

Black-margined loosestrife beetle is a food specialist. In North America, it feeds only on purple loosestrife. Prior to its introduction, fifty other plant species were tested in Europe for susceptibility to this beetle. Only winged loosestrife was found susceptible, but it is not attacked when purple loosestrife is available.

Adults are ⅛″ to ¼″ (3.6 to 5.6 mm) long and about half that wide. The body is elongate, parallel sided, coarsely pitted (punctate), and densely covered with short fine hairs. It is light brownish-yellow, brownish orange, or brownish red (pale) with dark brown to black (dark) markings.

The head is inserted into the first segment of the thorax and is visible from above. It is mostly pale, but the top of the head (vertex) is dark. The antennae have 11 segments and are less than half as long as the body. The third antennal segment is longer than the fourth. The antennae bases are close together. The eyes are not notched. The mouthparts are directed downwards.

The plate covering the first segment of the thorax (pronotum) is two times wider than it is long. It is pale with a dark triangle or longitudinal stripe in the middle. The plate between the wing bases (scutellum) is black.

The hardened wing covers (elytra) are rounded in the shoulder (humeral) area, nearly parallel along the sides, and broadly rounded at the tip. Each elytron has a single broad, dark, ill-defined, longitudinal stripe. The stripe extends from the base to about two-thirds of the way to the tip.

The legs are mostly pale. The third segment (femur) on each leg is mostly dark. 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: ⅛″ to ¼″ (3.6 to 5.6 mm)

Golden loosestrife beetle (Neogalerucella pusilla)

One generation per year: April to August

Adults overwinter in leaf litter near a host plant. They emerge the following year in early spring. The female lays 2 to 10 eggs on the stem or in a leaf axil of a host plant. She can lay 300 to 400 eggs in her lifetime. Mature larvae drop to the ground and pupate in leaf litter below the host plant.

Purple loosestrife

Purple loosestrife

The first stage (instar) larvae feed within leaf buds and flower buds. Later instars feed exposed on buds, leaves, and stem tissue. They feed on the photosynthetic tissue of the leaves, leaving the upper epidermis intact. This creates a distinctive “windowpane” effect. A heavy infestation can completely defoliate a plant. A lighter infestation will leave some leaf tissue, but it will cause reduced vigor, and the plant will not produce seeds.

Adults chew holes in young leaves, causing a characteristic “shothole” effect.

Sources

29, 30, 82, 83.

Common

This species was originally described as Chrysomela calmariensis by Carl Linnaeus in 1767. In 1833, it was placed in the genus Galerucella by Jean-Baptiste Boisduval. In 1962, Makoto Chûjô proposed a new genus, Neogalerucella, for several species including calmariensis, but the placement was not widely recognized. The Catalog of the Leaf Beetles of America North of Mexico, published by The Coleopterists Society in 2003, recognized Neogalerucella calmariensis. The Catalog of Palearctic Coleoptera, edited by I. Löbl and A. Smetana and published by Apollo Books in 2010, demoted Neogalerucella to a subgenus of Galerucella, and once again recognized this species as Galerucella calmariensis.

Currently, most taxonomic sources classify this species as Neogalerucella calmariensis. These include ITIS, GBIF, NatureServe, and BugGuide.net. Many sources still prefer the older classification Galerucella calmariensis due to historical precedent and morphological similarities. These include iNaturalist, EDDMaps, and Invasive.org. Some sources, including NCBI and Discover Life, avoid the controversy and list both species names as valid.

Location: Albany, NY