black firefly

LC - Least Concern

NNR - Unranked

SNR - Unranked

not listed

Black firefly is a medium-sized typical firefly. It occurs in the United States and southern Canada east of the Great Plains. It is common in Minnesota. Larvae live in decaying wood, in leaf litter, under stones, and in other moist areas. They prey on soft-bodied invertebrates, including snails and slugs. Adults are found from late May to July in shady open woodlands.

Adults are soft-bodied, flattened, and 5 ⁄16″ to ½″ (7.5 to 13.0 mm) long.

The head is covered by the exoskeletal plate over the thorax (pronotum). On both sexes the eyes are small and well separated. The mouthparts are directed downward. The antennae are black, have 11 segments, and gradually narrow toward the tip. The segments are thick, broadly triangular, strongly flattened, and straight across at the tip, not saw-toothed. They are never branched. The first segment is longer than the third. The second segment is very short, much wider than long.

The pronotum is flat, not saddle-shaped, and broad, nearly as wide at the base as the forewings (elytra). It is black in the middle, orange or pink on the sides, with broad pale margins. The front of the pronotum is rounded, extended forward, and completely covers the head, though the head may be extended beyond it.

The elytra are leathery and entirely black, without pale margins. The upper surface is finely granular and there is a weak raised ridge mostly near the base. The lateral margins are flattened. On the underside of the abdomen of the female there is a pair of small yellowish light organs on the last abdominal segment. On the male they are on the last two segments.

The legs are black. The last part of each leg (tarsus), corresponding to the foot, has five segments, but the fourth segment is minute and is concealed within the lobes of the heart-shaped third segment, making it appear that there are only four segments. There is a pair of claws at the end of the last segment. The claws are not toothed or split.

5 ⁄16″ to ½″ (7.5 to 13.0 mm)

Shady open woodlands

Late May to July

Adults are active during the day.

Males do not flash except sometimes for one or two days after emerging. They fly in shady areas and rest on low vegetation and tree trunks.

When threatened, they exude a milky juice from their abdomen and their legs.

Adults emerge beginning in late May.

Having lost bioluminescence through evolution, black firefly uses pheromones to find a mate.

Soft-bodied invertebrates

Sources

7, 24, 27, 29, 30, 82.

Lucidota atra black firefly

Lucidota atra Barnes Prairie Racine Co. WI June 25, 2020

Lucidota atra black firefly on Cornus racemosa, gray dogwood flowers June 7, 2021

Lucidota atra black firefly Barnes Prairie near hedgerow July 15, 2022

Location: Magelssen Bluff Park

Location: Barnes Prairie, Racine Co., WI

near hedgerow

Location: Great River Bluffs State Park

Location: Barnes Prairie, Racine Co., WI

on Cornus racemosa, gray dogwood flowers

Location: Barnes Prairie, Racine Co., WI