Aleochara bilineata as an adult is predaceous, but its larvae are parasitic. Appearance A. bilineata adults are glossy black with short coarse hairs and are about 5-6 mm long. They have very small, reddish-brown, inconspicuous forewings beneath which the membranous hindwings are elaborately folded. The forewings look like pads on the upper abdomen. The long abdomen is held aloft like a scorpion if the beetles are disturbed.
Adults are active, strong fliers.
Eggs are oval, about 0.5 mm long and 0.4 mm wide, and are covered with a gelatin-like material which is pale green at first and turns darker after a few days. First instar larvae are pale brown, about 1.5 mm long, slender, segmented, and tapered toward the anterior. They have large heads. The parasitic second and third instar larvae are white, have rudimentary legs, and are found within the host puparium. Pests Attacked Root maggot eggs, larvae, and pupae, especially the cabbage and onion maggot.