Francis Willughby (sometimes spelt Willoughby, Latin: Franciscus Willughbeius)[a] FRS (22 November 1635 – 3 July 1672) was an English ornithologist, ichthyologist and mathematician, and an early student of linguistics and games.

Willughby, Ray, and others such as John Wilkins were advocates of a new way of studying science, relying on observation and classification, rather than the received authority of Aristotle and the Bible.

To this end, Willughby, Ray and their friends undertook a number of journeys to gather information and specimens, initially in England and Wales, but culminating in an extensive tour of continental Europe, visiting museums, libraries and private collections as well as studying local animals and plants.

[8] He appears to have read widely, his library at his death containing an estimated 2,000 books,[9] including literary, historical and heraldic works as well as natural science volumes.

[20] In the late sixteenth and early seventeenth centuries, Francis Bacon had advocated the advancement of knowledge through observation and experiment, rather than relying on the authority of Aristotle and the church.

[21][f] The Royal Society and its members such as Ray, Wilkins and Willughby sought to put the empirical method into practice,[19] including travelling to collect specimens and information.

[23][g] Willughby helped Ray in collecting plants for his botanical work Catalogus Plantarum circa Cantabrigiam Nascentium (the Cambridge Catalogue), which was published anonymously in February 1660.

[33] In August 1662 Ray resigned his Fellowship at Cambridge, being unwilling to subscribe to the requirements of the Act of Uniformity imposed on Church of England clerics.

Unemployed and without a source of income, his position might have been difficult, but Willughby offered him accommodation and work at Middleton, writing "I am likely to spend much of my life afterwards in wandring or else in Private Studiing at Oxford.

[37] The party continued north through Haarlem, Amsterdam and Utrecht before heading to Strasbourg,[38] where Willughby made a diversion to buy a handwritten book from its author, Leonard Baldner.

[38] Ray claimed in his preface to the Ornithology: "For my part, I must needs acknowledge that I have received much light and information from the Work of this poor man, and have been thereby inabled to clear many difficulties, and rectifie some mistakes in Gesner.

[44][k] The journey through the Alps was arduous, with poor mountain tracks, bad weather and little food except bread, and it was 6 October before they reached their destination, where Skippon listed 60 species of fish and 28 kinds of birds he had noted in the Venetian markets.

Their first child, Francis, died at the age of nineteen, while their daughter Cassandra Willoughby married the Duke of Chandos, who was a patron of the English naturalist Mark Catesby.

[59] Willughby and Ray continued their researches, now mainly on birds, with the help of Francis Jessop, another Trinity alumnus, who sent them specimens from the Peak District, including twite and red grouse.

[61][62] Willughby had suffered several periods of illness, including violent fevers, between 1668 and 1671, described by Ray as "tertian ague" (malaria), and the additional physical and financial demands occasioned by having to defend a bitterly disputed inheritance put him under more strain.

[69] The authors also largely avoided the practice of previous writers, such as Conrad Gessner, by not including extraneous material relating to the species, such as proverbs, references in history and literature, or use as an emblem.

[76] The next book, on fish, was many years in the making; Willughby's widow had remarried, and her new husband, Josiah Child, had barred Ray from accessing his friend's papers.

[77][78] The Historia Piscium was finally published in Latin in 1686 with a dedication to Samuel Pepys, President of the Royal Society, who had made a generous financial contribution to the project.

[77][79][80] In the seventeenth century, the term "insect" had a much wider meaning than it does today, so the third major book, Historia Insectorum, included many other invertebrates, such as worms, spiders and millipedes.

[81] The second section contained the main species descriptions, followed by Ray's observations of butterflies and moths and their caterpillars, and an appendix by Martin Lister on British beetles.

Many illustrations were taken from previous publications by other writers,[94] and some were based on Francis Barlow's oil-paintings of birds in Charles II's aviary in St James's Park.

[74] In addition to these authors, sources used for the text included works by Carolus Clusius, Adriaen Collaert, Gervase Markham, Juan Eusebio Nieremberg and Ole Worm.

[97][98] Olina's Ucelliera, at least, seems to have been revisited between the Latin and English editions of the Ornithology, since the later version contains a description of territorial behaviour by the nightingale absent from the earlier work.

[99] Much of Willughby's written work has been lost, along with his scientific equipment and most of his collections of items of natural history interest;[100][101] what remains is largely owned by the family and housed in the University of Nottingham Middleton archive.

Georges Cuvier commented on the influence of the Historia Piscium, and Carl Linnaeus from 1735 onwards relied heavily on Willughby and Ray's books in his Systema Naturae, the basis of binomial nomenclature.

[103][104] The lack of physical evidence, together with Willughby's early death and the publication of his books by Ray, means that the relative contributions of the two men has subsequently been disputed.

[108] Raven was unaware of the Willughby family archive at the University of Nottingham when he wrote his book,[109][110] and access to that and other new material have led to modern appraisals giving a more balanced picture, with the two men seen to have made significant individual contributions, each demonstrating his own strengths.

[114] The names of the Windermere charr (Salvelinus willughbii),[115] Willughby's leaf-cutter bee (Megachile willughbiella) and the tropical plant genus Willughbeia all commemorate the younger man.