Frequently asked questions

1. Species epithets ending in i/ii

In his monumental work “Bibliographia araneorum” (1945-1961), Bonnet analyzed this case carefully and replaced all “-ii” endings of species epithets dedicated to persons by “-i” (except in original names of persons ending with “i”, e.g. Pavesi, Kulczyński, Canestrini etc.). He also gave an exhaustive grammatical / linguistic explanation (Bonnet 1945: 114ff). The vast majority of arachnologists took over his nomenclature that can now be considered as “common usage”. In 2014/15, when the World Spider Catalog was started in his current web-based format, a discussion came up again whether these endings should be altered to the original spelling, according to ICZN article 33.4. This led to intensive discussions with colleagues from all over the world, unequivocally showing to us that practically nobody wants to alter the names commonly used since Bonnet. Therefore, also for the sake of nomenclatural stability, we decided to leave the names as they are used since 1959 at latest (when vol. 2 of “Bibliographia araneorum” was finalized) by the vast majority of authorities in arachnology. The only exception is Heliophanus kochii because this is covered by a decision of ICZN (1990a: Opinion 1611).

2. Why does the WSC not include new faunistic records?

The World Spider Catalog gives a very brief description of the geographic range of a species. This shall provide a general guide and no attempt has been made to ensure that these records are comprehensive. Therefore, references of new faunistic records will usually not be included, but the distribution information maybe corrected. Also, the WSC is not a catalogue or checklist for each country. The taxonomic references are listed, but one cannot find country-wise references in the WSC.

3. Early view status of a publication, DOI links and upcoming papers

For the most recent publications, DOI links are added to the references. In older papers (before 2014) the DOI links are added only cursorial [you may send such additions to].

Pre-publication versions of articles, early view publications and related forms of not yet finally published manuscripts (but already peer reviewed) may be listed among the upcoming articles (, but are not yet considered by the WSC. Only publications with their final pagination will be included into the WSC and are available as PDF for WSCA members..

The year of publication of an article is the year in which the final version becomes available, not the year of a preliminary or of an early view version (see also International Code of Zoological Nomenclature Article 21.8.3 and Krell, 2015).

4. Why are subfamilies, tribes, subgenera etc. not considered in the WSC?

Admittedly, there are several reasons why the inclusion of subgenera, tribes and subfamilies into the World Spider Catalog would be desirable. However, the World Spider Catalog team only has limited financial resources and these are more or less sufficient to cover the present running costs. Including and adapting names of the family- and genus-group other than genus and family names is beyond our current capability. In addition, the World Spider Catalog is a tool for taxonomy, not for phylogenetics of spiders, and in the Introduction chapter of the World Spider Catalog, it is clearly stated that the usage of the World Spider Catalog does not unburden researchers from consulting the classical literature, including the volumes of Bonnet and Roewer, that can be easily accessed through the World Spider Catalog. Finally, we feel that creating too many new superspecific names in the age of highly dynamic phylogenies brings more confusion than stability into spider taxonomy. In the present situation it is more desirable to use terms with no nomenclatural relevance, like species groups instead of new subgenera (e.g. “Pardosa lugubris species group”) and vernacular names for clades (e.g. “spiny leg clade”), and we highly recommend such a usage.

5. Why no colon to distinguish primary and secondary citations?

Article 51.2.1 of the International Code of Zoological Nomenclature recommends that “The name of a subsequent user, if cited, is to be separated from the name of the taxon in some distinctive and explicit manner”. While the citation of the article where the taxon has first been described (primary citation) has to be added without colon or other characters, all other citations (secondary citations) should be separated by a colon or comparable characters. The World Spider Catalog does not follow this article because (1) it is only a recommendation and it may be discussed how meaningful this is; (2) the Code applies only to taxonomic publications, whereas the World Spider Catalog is an internet-based database; (3) neither Roewer, Brignoli nor Platnick followed this recommendation; (4) adding a colon for secondary citations would require too much handwork because this process cannot easily be automatized; (5) however, we believe that the user can easily distinguish between primary and secondary citation.

6. Why are some “grammatically incorrect“ species epithets corrected and some not?

It may be difficult to distinguish if a species epithet is a noun (not declined) or an adjective (declined according to the gender of the genus name). Also the gender of the genus name may be difficult to know if not given by the genus author (see ICZN Article 30, especially It should be kept in mind that the “original spelling” is protected in many cases (ICZN Article 32.3), thus supporting nomenclatorial stability. Further, it is stated that incorrect transliteration or Latinization is no reason to correct a name and the code explicitly allows different writings or formations of the stem of a word (ICZN Article 31.1.). Cases, in which corrections are allowed, are listed in ICZN Articles 32.5 and 34.2. If endings of specific epithets dedicated to persons and built in genitiv are wrong in respect to the gender of the persons, this is interpreted as a 'lapsus calami' (ICZN Article 32.5.1.) and corrected. Other corrections are only accepted by the World Spider Catalog when they are proposed with convincing argumentation in a publication.

Species epithets ending in -icola or -igena can be interpreted, in accordance with classical Latin usage:
(1) either as nouns in apposition and are, therefore, not declined with respect to the gender of the genus name (noun). According to ICZN Article 32.2 they stay unchanged, even though the ending is formed wrongly with -us or -um.
(2) or as adjectives of common gender, with identical forms for masculine, feminine and neuter (all ending with -a). According to ICZN Article 34.2 a wrong adjectival ending (in this case -us or -um) is to be corrected. When a specific epithet clearly reflects an attribute of a species, it is interpreted as adjective.
The second possibility is the regular interpretation in the World Spider Catalog.

7. Why is COI barcoding not useful on genus level?

In many cases COI (cytochrome oxidase one) barcoding is an excellent tool to separate species but it is generally advised, to add other characters, either further molecular markers or morphological pattern. On genus or higher taxonomic level, COI barcoding alone is meanwhile considered as not useful for several reasons:

  • Due to its maternal inheritance as a mitochondrial gene, strong differences between resulting gene tree and real phylogeny have been found (e.g., Edwards & Bensch (2009) Molecular Ecology 18: 2930-2933, doi: 10.1111/j.1365-294X.2009.04270.x)
  • Widely spread endosymbionts such as Wolbachia lead to introgression of mtDNA from other species and falsify the results (e.g., Klopfstein et al. (2016) Zoological Journal of the Linnean Society 177: 541-557, doi: 10.1111/zoj.12380).
  • COI on genus level is usually strongly saturated, making phylogenetic trees unreliable (long branch attraction). Intensive sampling and adding as many taxa as possible may help to counter this a bit (e.g., Quicke et al. (2012) Molecular Ecology Resources 12: 676-685, doi: 10.1111/j.1755-0998.2012.03143.x).
  • Databases such as BOLD or the NCBI databases contain also species that are not correctly identified. Relying exclusively on such databases and/or including low numbers of specimen may result in error-prone and misleading phylogenies.
  • A further good argumentation can be found here:

In conclusion, COI barcoding should be imbedded into a set of other markers and/or morphological data. Intensive sampling, high taxa density and a selection of reasonable outgroups are important. The isolated usage of COI barcoding does not qualify for good laboratory practice, it is therefore rejected by experts in this field, and the WSC will normally not take over such results.

8. Are references listed as a, b, c in chronological order?

If an author produces several publications per year, the WSC lists them as a, b, c. This system goes back to Roewer’s catalogue (1942, 1955a) and is not necessarily in chronological order. With more recent publications, we try to keep the chronological order, but this is not always possible. There are several reasons for this: In former times, Roewer did not follow a strict order or the information on the exact publication date was not available. If it turned out (just to give an example) that a publication was not published in December (e.g., as 1963c) but only in January 1964 it had to be moved to 1964 and received the next available letter, thus it could become 1964f. We want to avoid confusion and do not “correct” the sequence within the a-b-c system, once a publication is listed in the WSC. This means that within the a-b-c numeration, you should only conclude that b was published before c, when the publication date on the PDF or other information supports this. Also references from the same year, as listed in the taxonomic reference section of the species pages, may not be listed in chronological order. 

9. Valid taxa, nomina dubia, species inquirenda, incertae sedis?

The common unit of taxonomy are species and this is what the WSC lists and counts. The International Code of Zoological Nomenclature (ICZN) does not define a species concept, but describes in its Art. 5 what a species name is.
It happens occasionally, that a described species cannot be identified anymore because the initial description is insufficient, does not contain suitable illustrations, or because the species relied on juvenile or not identifiable types. Also loss of the type material can be a reason why the initial species name cannot be traced back to real animals. If a taxonomist meets such a case, it is possible to argue in a publication that a given species should no longer be treated as a valid species. This argumentation shall contain reasons, it must be convincing and the name of a questionable species has to be declared a nomen dubium. Nomina dubia and the respective references are listed in the WSC in a special list on genus level respectively on family level, but they are no longer counted as valid species or genera. If another taxonomist has good reasons to doubt an earlier declaration as nomen dubium (seemingly lost type material might have re-appeared or other good arguments may have come up), it is possible to “resurrect” the old species name in a publication. The WSC will then list this species or genus as valid again. Nomina dubia are defined in the glossary of the ICZN code ("a name of unknown or doubtful application") but not regulated.
If a taxonomist has doubts on the identity of a species but cannot investigate this point further, for whatever reasons, it is possible to tag this species in a publication as species inquirenda. This does not change its status as a valid species and the WSC adds this information with the corresponding reference as comment or additional information to the respective species page. The term of species inquirenda is defined in the glossary of the ICZN code as “A Latin term meaning a species of doubtful identity needing further investigation.”, but the usage of this term is not regulated.
Since the WSC is electronically available, mainly those species/taxa have been classified as nomina dubia, which have been explicitely named as such in a publication. In the past such a classification has been interpreted in many cases from texts in publications. All those nomina dubia are maintained in the current WSC and will only be turned back after a respective publication.
Taxa, evaluated as "incertae sedis" (= of uncertain taxonomic position), are not listed separately but maintained in their current genus and family, if they have not been transferred explicitly to another taxon. A comment refers to the uncertain position of this taxon.

10. Clerck 1757 or 1758?

Article 3 of the International Code of Zoological Nomenclature (ICZN 1999) sets 1 January 1758 as starting point of the zoological nomenclature because Linnaeus' Systema Naturae, 10th Edition, was published in that year. Carl Clerck, influenced by a lecture of Linnaeus, he attended in 1739, wrote “Aranei Svecici/Svenska Spindlar” in 1757. As a friend of Linnaeus, he applied the binominal nomenclature to 66 spider species, he described in detail. Thus, spiders received as first animal group binominal names, still valid today. Linnaeus included some of Clerck’s 1757 names in his 1758 edition, and cited Clerck.
The arachnological community primarily refers to Clerck’s 1757 oeuvre, a publication date that never was doubted, and consequently, this was also accepted by the spider catalog of Roewer (1942, 1955) and the first volume of Bonnet (1945). Nevertheless, there was much confusion due to Article 3 of the code. To solve this problem, Pierre Bonnet submitted a petition in 1947 that was supported by 48 of 52 spider taxonomists, he included into his action (see Breitling, 2022b). After several meetings and long discussions, the ICZN Commission came to two conclusions (ICZN 1959): (1) they re-dated Clerck as having been published on 1 January 1758, and (2) it was accepted that Clerck’s “1758” names, they created artificially by the earlier decision, had priority over the Linnean names (see also ICZN 1999: Article 3.1). This led to the absurd situation that the objectively wrong publication year of 1758 was proclaimed as correct and that a spider now officially described as of 1758 was published in a book that in reality appeared in 1757 (the date of publication was 18 April 1757, see Breitling, 2022b: 10). So the catalogs by Brignoli (1983), Platnick (1989, 1993, 1998, 2001-2014) and the recent World Spider Catalog, as well as the wide majority of the spider literature, used and still use the correct publication year of Clerck’s Aranei Svecici, 1757.
In a mail correspondence in 2010, Norman Platnick stated the following: "The catalog uses actual dates of publication. That the Code, for nomenclatorial purposes, considers Clerck to have been published on January 1, 1758, does not change history – indeed, the ICZN does not have that power.” In general the ICZN is very accurate concerning the correct year of publication (see ICZN 1999: Articles 21 and 22).
Today, the World Spider Catalog continues a long tradition and, therefore, keeps the correct Clerck, 1757 combination. Clerck described only spiders, so our usage affects no other animal group. Nevertheless, old regulations should be revised from time to time and analysed whether they are still up to date. We recommend to the ICZN Commission to reconsider this old case and to follow our argumentation. We all need an authoritative taxonomy and ICZN Commission that enjoys acceptance by a broad community.

11. Are supplements of electronic articles a valid publication?

Initially, electronic supplements aimed at containing additional information (such as methods or supporting data), sometimes useful to understand the main article. Such supplementary material, however, is usually not handled with the same care as the main article with respect to peer-reviewing, maintenance and archiving. Following Krell (2015) electronic supplements should be considered unavailable for the purposes of zoological nomenclature, however, this case is not yet covered by the International Code of Zoological Nomenclature. It should be kept in mind, that Article of the Code defines an electronic publication as “widely accessible electronic copies with fixed content and layout". A “fixed content and layout” is not given with Word files and comparable files. Therefore, we urgently recommend, to avoid forthcoming problems with the validity of electronic supplements, to restrict nomenclaturally relevant information to the main body of an article.