Harley Hudson was driven to become a crime-fighter since he was a young boy. He studied a wide variety of disciplines, eventually becoming an entomologist and chemist. He discovered that insects such as ants have super strength because they are able to coordinate their muscles. After teaching himself the same trick, Harley finds himself able to do astounding things and becomes the hero known as Firefly. His love interest was newspaper reporter Joan Burton. His enemies included Dr. Dread, Sneaky and the Mummy.

While he had no true superpowers, Firefly could optimize his physical strength and energy, which allowed him to become strong enough to uproot a tree and break through chains, leap across large distances like an insect, chuck bricks and stones and remain under water for long periods of time. He had been a champion pole vaulter at NYU, and he was skilled with a lasso. He had an airplane-glider called the Fireflier, which could seat him and one passenger.