Vipers were developed by accident, when lab had a malfunction and partly exploded in the factory, dropping specimens of moths, human arms, and cockroach legs into a genetic hybrid T-virus "stew." The first Viper emerged, looking like a bipedal mouth with three roach arms with human fingers, and large moth wings. Its head was that of a moth, and Albert Wesker loved these creatures. Coining them "Vipers", he ordered them mass-produced and about twenty were created in a few days. Wesker unleashed them into the "wild" during the Maine Outbreak, where they made their main nesting grounds near the lighted village where they were released.
Vipers are not immediatly hostile, but territorial and will buzz angrily when an unfamiliar creature enters their area, eventually attack this newcomer in swarms if they do not leave. Vipers are strong, and having slashing arms and legs, and are quite fast. They can easily lift a full grown man into the air, and proceeded to tear him apart. However, they are not overly durable, and die within ten days, much like moths.