[4] P. macdermotti is a medium-sized beetle, with adults that measure about 10 mm (0.4 in) long.

The head shield, or pronotum, is pale yellow with a black, rectangular central mark bounded by red or pink.

[3] Beetles such as P. macdermotti go through four life stages: egg, larva, pupa, and adult.

[1][3] Adult male P. macdermotti fireflies fly 0.3–1.2 m (1–4 ft) off the ground and flash to attract the attention of females.

[3] P. macdermotti is found in the eastern United States from Oklahoma to the west, Florida to the south, and New England to the north.