LIKE A MOTH flittering in a night light, the story of the first computer "bug" at Dahlgren just can't keep still. Every time it's told, it sounds a little different.

The tale of an errant moth causing a computational error in an early-stage computer, thereby giving birth to the term "computer bug," came up again at a community forum I moderated this month on behalf of the Dahlgren Heritage Foundation, of which I am president. In an effort to get at the truth, I've gone to the most reliable source I know--a genial, well-respected retiree from the Navy base at Dahlgren named Ray Hughey.

It's a fascinating tale, one of those odd happenings in scientific history that's born in truth and then is gradually embellished with myth.

The 1940s story of the first computer "bug" involves an unlikely scenario of players: Harvard University and a remote Navy base in King George County named Dahlgren; an esteemed faculty member at Harvard working with a technician who was careful to note his findings, even when they involved a moth; and a resourceful woman who joined the Harvard faculty as a research associate and ended up becoming a rear admiral in the Navy.

According to Hughey, the stage was set for Dahlgren's involvement with the first computer "bug" 2 decades before the 1947 discovery of a moth that was caught in a computer relay. In the early 1920s, the chief physicist of the new Navy base at Dahlgren, Dr. L.T.E. Thompson, "began the march to an ever-increasing computational need at Dahlgren," writes Hughey, who lives in King George and whose 35-year career at Dahlgren as a senior scientist and division head ended in 1994.

By the late 1940s, with the end of World War II, Dahlgren's need for computational support ballooned. As Hughey notes, the base was "being tasked with responsibility for all of the Navy's guns, unguided rockets and bombs. The computational capability requirements became staggering for the technology available at the time."

To help fill the need, a large number of Navy WAVES (Women Accepted for Volunteer Emergency Service) were assigned to Dahlgren to tackle the mammoth task with hand calculators. But the Navy soon realized that digital computing machines, which were just beginning to be developed, would be the real solution to Dahlgren's needs.