The U.S. Navy officer Grace Hopper found a moth between the relays on the Harvard Mark II computer when she was working on the computer on September 9, 1945. In those days computers fill the (large) rooms and the warmth of the internal components attracts moths, flies, and other flying creatures. Those creatures then shorten the circuits and cause the computer to malfunction. She wrote in her diary “first actual case of bug being found” which became popular and still we are using it.