Check your sources

During the finalization of a long-delayed article on snails and spiders, I checked again the sources that I used for the first draft. One of these was a review paper by Nyffelder & Symondson (2001). According to this paper, “one of the earliest published reports on malacophagy involving a spider was by Johnson (1863). He reported that the large wolf spider Isohogna [= Lycosa] maderiana (Walkenaer), found in Madeira, fed on snails.”. 

When I looked up this paper, I found indeed a note on “Lycosa tarentuloides maderiana Walkenaer”, but this was on the colouration of a female specimen. The only reference in this paper to snails, was this text under the remarks of a newly described Lycosa species:


A possible clue to the source of this error may be found in the methodology section of Nyffelder & Symondson’s paper. “Several hundred reports on the feeding habits of spiders and harvestmen published in scientific journals, books, and in unpublished theses were searched for information on malacophagy. This search was based largely on the Liste des Travaux Arachnologiques (1968-1999), published by the International Society of Arachnology (formerly C.I.D.A.), Paris. An inquiry among fellow arachnologists was carried out via specialist Internet discussion groups”. 
It seems plausible that Nyffelder and Symondson have copied the statement on Johnson’s paper from the replies among their fellow arachnologists. Besides apparently not having checked their source, they also quote the reference to Johnson’s paper incorrectly and incomplete. Not only the authors have to be blamed for that, but also the editors of Ecological Entomology (an ISI ranked journal, current impact factor 1.697).

If Johnson’s paper is not the first recorded case of malacophagy by spiders, who has then to be given the credits? Based on Nyffelder & Symondson’s list it should be Carl W. Verhoeff. His 1900 paper mentions that he had observed in the field the co-occurrence of the harvestmen Ichrysopsalis helwigii with the snail Vitrina pellucida. When he placed them together in the lab, he found the next morning only a clean shell.  
Credit where credit is due.

But overall the lesson is: check your sources!


Johnson, J.Y., 1863. Description of a new species of Lycosa living in the island of Madeira; with some remarks on Lycosa tarentuloides maderiana Walkenaer. Annals and Magazine of Natural History (3) 12: 152-155.

Nyffeler, M. & W.O.C. Symondson, 2001. Spiders and harvestmen as gastropod predators. Ecological Entomology 26: 617-628.

Verhoeff, C.W., 1900. Zur Biologie von Ischryropsalis. Zoologischer Anzeiger 23: 106-107.


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