These papers consist of correspondence to Westwood from entomologists including Alexander Henry Haliday, Sidney Smith Saunders, and George Henry Kendrick Thwaites on fig insects; and Thomas Whitmarsh on isosoma and gall flies; correspondence between Thwaites and Stanford Green concerning fig insects in Ceylon, 1877, collected by Westwood; letters and notes collected by Westwood as part of his collection of autographs of his entomological contemporaries, 1816-1837, including Jean Baptiste Armand Louis Leonce Elie Beaumont, Jean Baptiste Alphonse Boisduval, Leon Dufour, Etienne Laurant Joseph Hippolyte de Fonscolombe, Leonhard Gyllenhal, Thomas Say, and others; and an autograph collection consisting of signatures only.
The manuscript collection, 1840-1890, consists of handwritten notes and drawings, some in color, mostly by Westwood (most were published); proof plates with notations by Westwood; correspondence concerning the disposition of Haliday's entomological collection after Haliday's death, 1882, and notes on the Haliday collection by Westwood; correspondence and drawings from Charles Robert Osten-Sacken and notes by Westwood concerning Diptera; and correspondence concerning corrections on manuscripts and proof plates to be sent for publication; handwritten manuscripts of a catalog of British insects by James Francis Stephens; entomological notes by Walter Elliot; and reprints. In addition, there are photographs of insects seen through the microscope.
The John Obadiah Westwood Papers were donated to Oxford University in May 1982. The Smithsonian Institution Archives retains a microfilm copy of the papers, and color transparencies of the color drawings.