Ray in 1649. Willughby graduated B.A. in 1655–6, and proceeded M.A. in 1659.
In 1660 Willughby spent a short time at Oxford in order to consult some rare works in the libraries there; and in the preface to his ‘Catalogus Plantarum circa Cantabrigiam,’ published in that year, Ray alludes to help received from Willughby and to his success in the study of insects. In a letter to him, dated 1659, Ray asks for his help, for Warwickshire and Nottinghamshire, towards a catalogue of British plants (Correspondence of John Ray, Ray Soc., p. 1). In 1661 Willughby did not accompany Ray on the second botanical journey described in ‘Mr. Ray's Itineraries,’ published in his ‘Remains’ in 1760, though in the notes and in Derham's ‘Life of Ray’ he is stated to have done so, the naturalist's companion being Philip Skippon (op. cit. p. 3), but in May and June 1662 he did accompany Ray on his third journey from Cambridge through the northern midland counties and Wales. He appears to have parted company from him in Gloucestershire, to have chanced upon a find of Roman coins near Dursley, and to have fallen ill at Malvern (op. cit. p. 5). Willughby was at this time much interested in mathematical questions, as appears from two letters of his, dated March 1662 and October 1665, to Barrow, published by Derham in the ‘Philosophical Letters’ (1718). Barrow dedicated to him and others his edition of ‘Euclid,’ and is recorded in Cole's manuscripts to have said ‘that he never knew a gentleman of such ardor after real learning and knowledge, and of such capacities and fitness for any kinde of learning.’
It must have been at this time that, as Ray afterwards told Derham (Memorials of Ray, p. 33), he and Willughby ‘finding the “History of Nature” very imperfect … agreed between themselves, before their travels beyond sea, to reduce the several tribes of things to a method, and to give accurate descriptions of the several species from a strict view of them. And forasmuch as Mr. Willughby's genius lay chiefly to animals, therefore he undertook the birds, beasts, fishes, and insects, as Mr. Ray did the vegetables.’ Ray, having been deprived of his fellowship in August 1662 by the operation of the Act of Uniformity, he and Willughby determined to go abroad, and left Dover for Calais on 18 April 1663, accompanied by Philip (afterwards Sir Philip) Skippon and Nathaniel Bacon, two of Ray's pupils. On 22 May Willughby was included in the original list of fellows of the Royal Society, which had been incorporated on 22 April. War with France compelled the travellers to turn aside into Flanders, after which they traversed Germany, Switzerland, Italy, Sicily, and Malta. In August 1664 Willughby parted from the others at Montpelier, and accompanied a merchant into Spain. His journey is summarised in a letter to Ray, written from Paris in December (Corresp. of Ray, p. 7). Many of the travellers' papers were lost on their return journey; but Ray published their ‘Observations. … Whereunto is added a brief Account of Francis Willughby, esq., his Voyage through a great part of Spain,’ in 1673, and many of Willughby's specimens of birds, fishes, fossils, dried plants, and coins are still at Wollaton Hall.
Recalled to England by the death of his father in December 1665, Willughby was kept at Middleton Hall during much of 1666; but on 22 July, in company with Robert Hooke and others, he observed the eclipse of the sun through Boyle's 60-foot telescope in London (Phil. Trans. 9 Sept. 1666). In October of that year Dr. John Wilkins [q. v.] wrote asking his assistance in drawing up tables of animals for his ‘Essay towards a Real Character,’ which was published in 1668; and Ray spent the greater part of the following winter at Middleton, as he says in a letter to Martin Lister, ‘reviewing, and helping to put in order, Mr. Willughby's collections … in giving what assistance I could to Dr. Wilkins in framing his tables of plants, quadrupeds, birds, fishes, &c., for the use of the universall character’ (Memorials of Ray, p. 17); in the dedication of his work, however, Wilkins acknowledges his indebtedness to Willughby in respect of animals, and to Ray only in respect of plants. From June to September 1667 Willughby and Ray made a tour into the south-west of England (ib. p. 21); but Willughby's marriage in 1668 temporarily suspended their collaboration. Ray was, however, re-established at Middleton Hall in September 1668, and in the following spring the two friends carried out some important experiments on the rise of sap in trees (Phil. Trans. iv. 963). In the autumn of 1669 Willughby sent letters to the Royal Society on the ‘cartrages’ of rose leaves made by leaf-cutting bees. In 1671 he wrote on the same subject and on ichneumon wasps, and from a letter from Ray to Lister in 1670 he seems to have added considerably to the latter's list of English spiders (Corresp. of Ray, p. 60). At the close of 1671 Willughby meditated a journey to America to ‘perfect his history of animals;’ but his health, never robust, failed him. He was taken seriously ill in
