Insecta Britannica Diptera is a seminal work of entomology by Francis Walker. The work spans three volumes; a fourth volume was never published. Parts of the work were credited by Walker to Alexander Henry Haliday, including the characters and synoptic tables of the Empididae, Syrphidae, and Dolichopodidae and addenda and corrigenda intended for volume 4.
The precise dates of early entomological publications are frequently hard to establish.
A digitized version of the work can be found at the Internet Archive: