The spider was developed by the WIADF from studying crashed examples of the 'Conveyor' bombers of the KAA. Early marks of Spider were inferior to the conveyor in many ways, with insufficient defences and low top speeds. They required a fighter escort in order to operate effectively. Continued development of the spider eventually produced a fine aircraft, which still serves today in the auxiliary bomber force of the WIADF, occasionally attacking targets on Snowstone.

The Mk.1b was the 3rd mark of Spider. A new propellor design and increased engine power were the main improvements and this gave the aircraft an increased ability to evade enemy fighters. Unfortunately the defensive armament remained fixed and so fighter cover was still necessary. All Mk1b aircraft were refitted into later Marks of Spider.