It is shown that the correct year of publication of the 2^nd edition of Linnaeus’ “Fauna Svecica” is 1761, not [1760].

Taxonomists may have noticed that the date of publication of the second edition of Linnaeus’ “Fauna Svecica”, a work traditionally dated as 1761 in agreement with the date printed on its front cover (Linnaeus 1761a), is increasingly being recorded as “[1760]” (e.g., Evenhuis 1997; Bousquet 2016; Wiemers et al. 2018). Rationale for this interpretation has been summarised by Evenhuis (1997) with the following evidence:

1. Presence in the British Museum library of a copy purchased on 22^nd December 1769 with a fly-leaf bearing the annotation “Ex libris M. Maty. 1759. Presented Novr. 14, 1760”, as recalled by Soulsby (1933: 91).

2. Mention of the publication in Gronovius’ (1760: 169) compendium of natural history publications.

Evenhuis thus concluded that copies of the second edition were already circulating in 1760 and that the final dating as 1761 can be explained if the title page and preface have been printed subsequently and then bound with the main text.

The first piece of evidence is highly suspicious, as the date of the annotation would imply that Matthew Maty, who became principal librarian of the British Museum in 1772, would have already had that copy in hand in 1759. The second one is instead clearly erroneous, indeed as Gronovius listed “Fauna Svecica” on page 169 of his bibliographic compendium, but referred only to the first edition of Linnaeus’ work: “Fauna Suecica sistens Animalia Sueciae regni. – * Lugduni Batavorum 1746. in 8°. cum tabulis aeneis”. It may be noted that Gronovius recorded the pirated version issued in Leiden of the first edition of “Fauna Svecica” (Linnaeus 1746a) as being issued one year in advance of the Stockholm one (Linnaeus 1746b) as being issued one year in advance of the Stockholm one (Linnaeus 1746b), but he made no mention of the second edition.

It may be noted that in the main text of the second edition, Linnaeus (1761a: 4, 250) mentions an article issued in 1760 (Gmelin 1760) and adds a biological observation dated 1760. However, in order to clarify the issue, which has bearing on the dating of numerous taxa described in this work it is fair to assume that there is no more reliable source of information than Linnaeus himself, who can posthumously be ‘queried’ after his massive correspondence and manuscripts he left over to posterity.

In a letter dated 24 October 1760 to Carl Christoffer Gjörwell, the Swedish naturalist mentioned that his “Fauna Svecica”, i.e. the first edition (Linnaeus 1746b), was out of print and needed to be re-published, but he did not know which among his plethora of projects to prioritise (Linnaeus 1760). If, on 24^th October 1760, Linnaeus did not know how to cope with a re-edition of the book, it seems impossible that just 20 days later (on 14^th November 1760), such a work could already have been in circulation. Clearly also, Matthew Maty could not have annotated his copy in 1759.

Further to this, in the letter dated 2 March 1761 to Abraham Bäck, Linnaeus (1761b) told his friend that what was left of his time besides other commitments was taken up by the new edition of the Fauna [Svecica], which now imposed on him a huge investment in effort. Importantly, in a letter of 3 April 1761 to the same correspondent, Linnaeus (1761c) said that on “martis et veneris” (Tuesdays and Fridays) he worked three hours each afternoon to correct the Fauna, stressing that such time was barely sufficient to write the additions.

In the letter of 2 July 1761 to Johannes Burman, Linnaeus (1761d) said he had eventually brought to completion “Fauna Svecica” altera editio, which exhausted him, and in a letter on 5 August 1761 to Nicolaas Laurens Burman, he reported that the work had then been published (Linnaeus 1761e). The very same information was also expressed in another letter dated 10 September 1761 that was addressed to the Italian botanist Carlo Allioni (Linnaeus 1761f).

All this first-hand information by Linnaeus is evidently compatible only with an actual printing date of the book between 3^rd April 1761 and 5^th August 1761. This interval may further be restricted as starting from 2^nd July 1761, if by ‘completion’, written literally as “now I have brought to end” (“jam ad finem perduxi”), he meant conclusion of the manuscript and not its printing. In either case, these time spans are perfectly consistent with the date of 28 July 1761 that is stated in the dedication of the book.

It is also worthy to recall an undated curriculum vitae (“Memorial”) by Linnaeus, deposited at what was then the Königlichen Bibliothek in Berlin, in which the Swedish naturalist listed his publications and attributed the date of 1761 to the second edition of “Fauna Svecica” (Fries 1907: 37).

It is therefore recommended to reinstate ‘1761’ as the correct year of publication of the second edition of “Fauna Svecica”, adopting [5^th August] 1761 as the best fit for the precise date of publication. Meanwhile, the annotation on the copy mentioned by Soulsby (1933) must be regarded as a clerical error by Matthew Maty that was likely introduced while recording subsequently lots being itemised from his library.