The Info List - International Code Of Zoological Nomenclature

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The INTERNATIONAL CODE OF ZOOLOGICAL NOMENCLATURE (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals . It is also informally known as the ICZN CODE, for its publisher, the International Commission on Zoological Nomenclature (which shares the acronym "ICZN"). The rules principally regulate:

* How names are correctly established in the frame of binominal nomenclature * Which name must be used in case of name conflicts * How scientific literature must cite names

Zoological nomenclature is independent of other systems of nomenclature, for example botanical nomenclature . This implies that animals can have the same generic names as plants.

The rules and recommendations have one fundamental aim: to provide the maximum universality and continuity in the naming of all animals, except where taxonomic judgment dictates otherwise. The Code is meant to guide only the nomenclature of animals, while leaving zoologists freedom in classifying new taxa .

In other words, whether a species itself is or is not a recognized entity is a subjective decision, but what name should be applied to it is not. The Code applies only to the latter, not to the former. A new animal name published without adherence to the Code may be deemed simply "unavailable" if it fails to meet certain criteria, or fall entirely out of the province of science (e.g., the "scientific name" for the Loch Ness Monster
Loch Ness Monster

The rules in the Code determine what names are valid for any taxon in the family group, genus group, and species group. It has additional (but more limited) provisions on names in higher ranks . The Code recognizes no case law . Any dispute is decided first by applying the Code directly, and not by reference to precedent.

The Code is also retroactive or retrospective , which means that previous editions of the Code, or previous other rules and conventions have no force any more today, and the nomenclatural acts published 'back in the old times' must be evaluated only under the present edition of the Code. In cases of disputes concerning the interpretation, the usual procedure is to consult the French Code, lastly a case can be brought to the Commission who has the right to publish a final decision.


* 1 Principles

* 1.1 Principle of binominal nomenclature * 1.2 Principle of Priority * 1.3 Principle of Coordination * 1.4 Principle of the First Reviser * 1.5 Principle of Homonymy * 1.6 Principle of Typification

* 2 Structure

* 2.1 Gender agreement

* 3 History * 4 Commission * 5 Local usage and name changes * 6 Citation * 7 Versions * 8 See also * 9 References * 10 External links


In regulating the names of animals it holds by six central principles, which were first set out (as Principles) in the third edition of the Code (1985):


This is the principle that the scientific name of a species, and not of a taxon at any other rank, is a combination of two names; the use of a trinomen for the name of a subspecies and of uninominal names for taxa above the species group is in accord with this principle.

This means that in the system of nomenclature for animals, the name of a species is composed of a combination of a generic name and a specific name ; together they make a "binomen ". No other rank can have a name composed of two names. Examples: Species
_Giraffa camelopardalis _

* Subspecies
have a name composed of three names, a "trinomen": generic name , specific name , subspecific name :

_ Giraffa camelopardalis
Giraffa camelopardalis
rothschildi _

* Taxa at a rank above species have a name composed of one name, a "uninominal name".

_ Giraffa
_, family Giraffidae

In botanical nomenclature, the equivalent for "binominal nomenclature" is "binary nomenclature" (or sometimes "binomial nomenclature ").


Main article: Principle of Priority

This is the principle that the correct formal scientific name for an animal taxon , the _valid name _, correct to use, is the oldest available name that applies to it. It is the most important principle—the fundamental guiding precept that preserves zoological nomenclature stability. It was first formulated in 1842 by a committee appointed by the British Association to consider the rules of zoological nomenclature. Hugh Edwin Strickland wrote the committee's report.

Example: Nunneley 1837 established _ Limax maculatus _ (Gastropoda), Wiktor 2001 classified it as a junior synonym of _ Limax maximus _ Linnæus 1758 from S and W Europe. _ Limax
maximus_ was established first, so if Wiktor's 2001 classification is accepted, _ Limax
maximus_ takes precedence over _ Limax
maculatus_ and must be used for the species.

There are approximately 2-3 million cases of this kind for which this Principle is applied in zoology.


The _principle of coordination_ is that within the family group, genus group and species group, a name established for a taxon at any rank in the group is simultaneously established with the same author and date for taxa based on the same name-bearing type at other ranks in the corresponding group. In other words, publishing a new zoological name automatically and simultaneously establishes all corresponding names in the relevant other ranks with the same type.

In the species-group, publishing a species name (the binomen ) _ Giraffa
camelopardalis_ Linnaeus, 1758 also establishes the subspecies name (the trinomen ) _ Giraffa
camelopardalis camelopardalis_ Linnaeus, 1758. The same applies to the name of a subspecies; this establishes the corresponding species name.

In the genus-group, similarly, publishing the name of a genus also establishes the corresponding name of a subgenus (or vice versa): genus _Giraffa_ Linnaeus, 1758 and subgenus _ Giraffa
(Giraffa)_ Linnaeus, 1758.

In the family-group, publication of the name of a family, subfamily, superfamily (or any other such rank) also establishes the names in all the other ranks in the family group (family Giraffidae, superfamily Giraffoidea, subfamily Giraffinae).

Author citations for such names (for example a subgenus) are the same as for the name actually published (for example a genus). It is immaterial if there is an actual taxon to which the automatically established name applies; if ever such a taxon is recognised, there is a name available for it.


This is the principle that in cases of conflicts between simultaneously published divergent acts, the first subsequent author can decide which has precedence. It supplements the _principle of priority _, which states that the first published name takes precedence. The Principle of the First Reviser deals with situations that cannot be resolved by priority. These items may be two or more different names for the same taxon , two or more names with the same spelling used for different taxa, two or more different spellings of a particular name, etc. In such cases, the first subsequent author who deals with the matter and chooses and publishes the decision in the required manner is the First Reviser, and is to be followed.


Linnæus 1758 established _Strix scandiaca_ and _Strix noctua_ (Aves), for which he gave different descriptions and referred to different types, but both taxa later turned out to refer to the same species, the snowy owl . The two names are subjective synonyms. Lönnberg 1931 acted as First Reviser, cited both names and selected _Strix scandiaca_ to have precedence.

A problem is that sometimes the First Reviser is unknown. For the sperm whale Linnæus 1758 established three subjective synonyms, _Physeter macrocephalus_, _Physeter catodon_, and _Physeter microps_. The First Reviser remains unknown; both _Ph. macrocephalus_ and _Ph. catodon_ are used.


This is the principle that the name of each taxon must be unique. Consequently, a name that is a junior homonym of another name must not be used as a valid name.

It means that any one animal name, in one particular spelling, may be used only once (within its group). This is usually the first-published name; any later name with the same spelling (a homonym ) is barred from being used. The Principles of Priority and the First Reviser apply here. For family-group names the termination (which is rank-bound) is not taken into account.

Genera are homonyms only if exactly the same — a one-letter difference is enough to distinguish them.

Examples: _Argus_ Bohadsch, 1761 (Gastropoda) (was made available for homonymy by ICZN in Opinion 429, Bohadsch 1761 was non-binominal - this had the effect that no other one of the various following names _Argus_ can be used for a taxon) _Argus_ Scopoli, 1763 (Lepidoptera: Lycaenidae: Polyommatinae) _Argus_ Scopoli, 1777 (Lepidoptera: Nymphalidae: Satyrinae) _Argus_ Poli, 1791 (Bivalvia) _Argus_ Temminck, 1807 (Aves) _Argus_ Lamarck, 1817 (Lepidoptera: Hesperiidae) _Argus_ Walckenaer, 1836 (Araneae) _Argus_ Gerhard, 1850 (Lepidoptera: Lycaenidae: Theclinae) Homonyms of _Argus_ are not: _ Argua _ Walker, 1863 (Lepidoptera), _Argusa _ Kelham, 1888 (Aves), _Argusina _ Hebard, 1927 (Dermaptera), _Arcus _ Hong, 1983 (Diptera), _ Argas _ Latreille, 1795 (Araneae), _ Argulus
_ Müller, 1785 (Crustacea). Homonyms are not: _Isomya _ Cutler & Cutler, 1985 (Sipunculida), _Isomyia _ Walker, 1859 (Diptera). Homonyms are not: _Adelomya _ Mulsant white-space:nowrap;"> is only a temporary state, it is only effective in this classification. If another classification is applied, the secondary homonymy may not be produced, and the involved name can be used again (Art. 59.1). A name does not become unavailable or unusable if it was once in the course of history placed in such a genus where it produced a secondary homonymy with another name. This is one of the rare cases where a zoological species does not have a stable specific name and a unique species-author-year combination, it can have two names at the same time.

Example: Nunneley (1837) established _ Limax maculatus _ (Gastropoda), Wiktor (2001) classified it as a junior synonym of _ Limax
(Limax) maximus _ Linnæus, 1758 from S and W Europe. Kaleniczenko, 1851 established _ Krynickillus maculatus _ for a different species from Ukraine. Wiktor, 2001 classified both _Limax maximus_ Linnæus, 1758 and _Krynickillus maculatus_ Kaleniczenko, 1851 in the genus _ Limax
_. This meant that _L. maculatus_ Nunneley, 1837 and _K. maculatus_ Kaleniczenko, 1851 were classified in the same genus, so both names were secondary homonyms in the genus Limax
, and the younger name (from 1851) could not be used for the Ukrainian species. This made it necessary to look for the next younger available name that could be used for the Ukrainian species. This was _Limax ecarinatus _ Boettger, 1881, a junior synonym of _K. maculatus_ Kaleniczenko, 1851. For Wiktor (2001) and those authors who follow Wiktor's system the name of the Ukrainian species must be _Limax ecarinatus _ Boettger, 1881. For the others who classify _ Limacus _ as a separate genus, the name of the Ukrainian species must be _Limacus maculatus _ (Kaleniczenko, 1851). So the Ukrainian species can have two names, depending from its generic classification. _Limax ecarinatus _, _ Limacus maculatus _, the same species.

Art. 59.3 states that in exceptional cases, junior secondary homonyms replaced before 1961 by substitute names can become invalid, "...unless the substitute name is not in use," an exception of the exception. However, the ICZN Code does not give an example for such a case. It seems that this passage in the ICZN Code is widely ignored. It also does not define what the expression "is not in use" should mean.

Example: _Glischrus caelata _ Studer, 1820 (Gastropoda) was once classified in the genus _Helix _, and became a junior secondary homonym of _Helix caelata _ , 1801. Locard (1880) established a replacement name _Helix glypta _, which has very rarely been used. The species is now known as _ Trochulus caelatus _ (Studer, 1820), and Art. 59.3 is commonly ignored.

DOUBLE HOMONYMY (genus and species) is no homonymy: if the genera are homonyms and belong to different animal groups, the same specific names can be used in both groups.

Examples: The name _Noctua _ Linnæus, 1758 was established for a lepidopteran subgenus. In 1764 he established a genus _Noctua_ Linné ,1764 for birds, ignoring that he had already used this name a few years ago in Lepidoptera. _Noctua_ Linné, 1764 (Aves) is a junior homonym of _Noctua_ Linnæus, 1758 (Lepidoptera). Garsault (1764) used _Noctua_ for a bird and established a name _ Noctua caprimulgus _ Garsault, 1764 (Aves). Fabricius (1775) established a name _Noctua caprimulgus _ Fabricius, 1775 (Lepidoptera), thus creating a double homonym. Double homonymy is no homonymy, both names are available. The same happened with _ Noctua variegata _ Jung, 1792 (Lepidoptera) and _ Noctua variegata _ Quoy & Gaimard, 1830 (Aves).

For DISAMBIGUATING one genus-group name from its homonym, it is important to cite author and year. Citing the author alone is often not sufficient.

Examples: _ Echidna _ Forster, 1777 (Actinopterygii), not _ Echidna _ Cuvier, 1797 (Mammalia) _Ansa _ Walker, 1858 (Lepidoptera), not _Ansa_ Walker, 1868 (Hemiptera) _Helix balcanica _ Kobelt, 1876, not _Helix balcanica _ Kobelt, 1903 (both Gastropoda) _Conus catenatus _ Sowerby, 1850, not _Conus catenatus _ Sowerby, 1875 (both Gastropoda)

The name _Ansa_ can only be used for a lepidopteran taxon. If that name cannot be used (for example because an older name established prior to 1858 takes precedence), this does not mean that the 1868 name can be used for a hemipteran genus. The only option to use the 1868 name for the hemipteran taxon is to get the 1858 name officially suppressed by the Commission .

In some cases, the same genus-group or species-group name was published in the same year by the same author. In these cases it would be useful to cite the page where the name was established. _Amydona _ Walker, 1855 (Lepidoptera: Limacodidae) (p. 1110), not _Amydona _ Walker, 1855 (Lepidoptera: Lasiocampidae) (p. 1413) _ Betousa _ Walker, 1865 (Lepidoptera: Thyridae) (p. 1111), not _ Betousa _ Walker, 1865 (Lepidoptera: Noctuidae) (p. 1208). _Cicada variegata _ Fabricius, 1775 (p. 684), not _Cicada variegata _ Fabricius, 1775 (p. 686) (both Auchenorrhyncha). _ Noctua marginata _ Fabricius, 1775 (p. 597), not _ Noctua marginata _ Fabricius, 1775 (p. 610) (both Lepidoptera: Noctuidae). _Clausilia (Albinaria) oertzeni_ Boettger, 1889 (p. 42), not _Clausilia (Albinaria) schuchi_ var. _oertzeni_ Boettger, 1889 (p. 52) (both Gastropoda: Clausiliidae).

There are cases where two homonyms were established by the same author in the same year on the same page: _Zonites verticillus_ var. _graeca_ Kobelt, 1876 (Gastropoda) (p. 48), not _Zonites albanicus_ var. _graeca_ Kobelt, 1876 (p. 48).

Animal, plant, and fungi nomenclature are entirely independent from each other. The most evident shortcoming of this situation (for their use in biodiversity informatics ) is that the same generic name can be used simultaneously for animals and plants. For this kind of homonyms the expression "hemihomonyms" is sometimes used. Far more than 1000 such names are known.

Examples: The generic name _Dryas _ L. (1753) represents a genus of magnoliophytan plants (family Rosaceae), and at the same time _Dryas _ Hübner, 1807 is also a lepidopteran insect genus (family Nymphalidae). The genus _Tandonia_ was established in animals (Gastropoda: _ Tandonia _), in plants (Euphorbiaceae) and in Fungi (Ascomycetes). Other examples for sometimes well known plant names with zoological equivalents are _Aotus_ (Fabaceae and Mammalia), _Arenaria_ (Caryophyllaeceae and Aves), _Betula_(Betulaceae and Hymenoptera), _Chloris_ (Cactaceae and Aves), _Dugesia_ (Asteraceae and Plathelminthes), _Erica_ (Ericaceae and Araneae), _Hystrix_ (Poaceae and Mammalia), _Iris_ (Asparagales and Orthoptera), _Liparis_ (Orchidaceae and Actinopterygii), _Phalaenopsis_ (Asparagales and Aves), _Pinus_ (Pinaceae and Mollusca), _Prunella_ (Lamiaceae and Aves), _Ricinus_ (Fabaceae and Acari), _Taxus_ (Taxaceae and Mammalia), _Typha_ (Typhaceae and Porifera), _Ulva_ (Ulvophyceae and Lepidoptera), _Viola_ (Violaceae and Lepidoptera).

For names above the family level, the Principle of Homonymy does not apply.

Examples: PULMONATA is usually used for a very prominent group in Gastropoda , but the name is also (rarely) used for a group in Arachnida . RETICULATA is used as an order in Foraminifera
, and as an undefined higher group in Ephemeroptera .

Homonyms occur relatively rarely in families (only if generic names are identical or very similar and adding an ending "-idae" produces identical results). Discovering such a homonymy usually produces the same problems as if there were no rules: conflicts between entirely independent and unconnected groups of taxonomists working in different animal groups. Very often the Commission must be asked to take a decision.

Examples: _Bulimina _ (Foraminifera) and _ Buliminus _ (Gastropoda) give both BULIMINIDAE, and both families were used since the 1880s. When the homonymy was discovered 110 years later in the 1990s, the younger (gastropod) taxon had to receive a new family name, and the Commission needed was asked for a solution (Opinion 2018). _ Claria _ (Rotifera) and _ Clarias _ (Actinopterygii) give both CLARIIDAE, but only the actinopterygian fish name was used since 1845. Shortly after Clariidae had been proposed in Rotifera in 1990, the homonymy was discovered and the Commission had to decide that the Rotiferan family had to be amended to Clariaidae (Opinion 2032).


This is the principle that each nominal taxon in the family group, genus group, or species group has—actually or potentially—a name-bearing type fixed that provides the objective standard of reference that determines what the name applies to.

This means that any named taxon has a name-bearing type , which allows the objective application of that name. Any family-group name must have a type genus, any genus-group name must have a type species, and any species-group name can (not must) have one or more type specimens (holotype, lectotype, neotype, syntypes, or others), usually deposited in a museum collection. The type genus for a FAMILY-GROUP NAME is simply the genus that provided the stem to which was added the ending "-idae" (for families). Example: The family name Spheniscidae has as its type genus the genus _ Spheniscus _ Brisson, 1760.

The type species for a GENUS-GROUP NAME is more complicated and follows exactly defined provisions in Art. 67-69. Type species are very important, and no general zoological database has recorded the type species for all genera. Except in fishes and some minor groups, type species are rarely reliably recorded in online animal databases. In 60% of the cases the type species can be determined in the original publication. The type species is always the original name of the taxon (and not the currently used combination).

Example: The correctly cited type species of _Locusta_ Linnæus, 1758 (Caelifera) is _Gryllus migratorius _ Linnæus, 1758, not _ Locusta migratoria _ (Linnæus, 1758).

Designation and fixation have different meanings. A designation is the proposal of the type species. It is not necessary to have spelled the name of the genus or species correctly with correct authors (Art. 67.2.1, 67.6, 67.7), type species are always the correctly spelled name. If the designation is valid, the type species is fixed.

A designation can also be invalid and ineffective—for example—if the genus had already a previously fixed type species, or if a type species was proposed that was not originally included, or contradicted the description or figure for a genus for which no species had originally been included.

There are various possible modes of type species designation. This is their order of legal importance, with approximate proportions of occurrence and examples:

* Superior type fixation:

Designation by ICZN under the plenary powers (3 %) Example: _ Galba _ Schrank, 1803 (Gastropoda) was established with one species included, _ Galba pusilla _ Schrank, 1803. This would be the type species by monotypy. In Opinion 1896 (published in 1998) this type fixation was set aside and _Buccinum truncatulum _ Müller, 1774 was fixed as type species under the plenary power(s) (now _Galba truncatula _). Designation under Art. 70.3 (misidentified type species) (1 %) Examples: _Bollingeria _ Forcart, 1940 (Gastropoda) was established with its type species _Chondrus pupoides _ Krynicki, 1833 proposed by original designation. But Forcart 1940 misidentified the type species and meant _Bulimus lamelliferus _ Rossmässler, 1858. It would be convenient to designate _Bulimus lamelliferus _ as type species under Art. 70.3. _ Helisoma _ Swainson, 1840 (Gastropoda) was established with one species included, cited by Swainson as "_H. bicarinata _ Sow. Gen. f. 4". This suggested that the type species was misidentified, and that _Planorbis campanulatus _ Say, 1821 and not _Planorbis bicarinatus _ Say, 1819 was meant. But since the incorrect type species _Planorbis bicarinatus _ has been regarded as type, it would be convenient to fix this as type under Art. 70.3.

* Type fixation in the original work:

Original designation (31 %) Examples: Montfort 1810 established the genus _ Theodoxus _ (Gastropoda) and designated _Theodoxus lutetianus _ Montfort 1810 as type species (now _ Theodoxus fluviatilis _). Vest 1867 established the subgenus _Clausilia (Isabellaria) _ (Gastropoda) and designated _Clausilia isabellina _ Pfeiffer, 1842 as type species (now _Isabellaria isabellina _). Riedel 1987 established the genus _Turcozonites _ (Gastropoda) and designated _Zonites wandae _ Riedel, 1982 as type species (now _Turcozonites wandae _). Monotypy (28 %) Examples: _ Anodonta _ Lamarck, 1799 (Bivalvia) was originally established with one included nominal species, _Mytilus cygneus _ Linnæus, 1758. This is the type species fixed by monotypy (now _ Anodonta cygnea _). _ Microcondylaea _ Vest 1866 (Bivalvia) was originally established with two included nominal species, _Unio bonellii _ Férussac, 1827 and with doubts _ Anodonta lata _ Rafinesque, 1820. Doubtfully included species do not count, type species is _Unio bonellii _ fixed by monotypy (now _Microcondylaea bonellii _). Absolute tautonymy (2 %) Examples: Kobelt 1871 established the gastropod genus-group name _ Candidula _ and included 23 species. Among these was _Glischrus candidula _ Studer 1820. _Glischrus candidula _ is type species fixed by absolute tautonymy (now _ Candidula unifasciata _). Draparnaud 1801 established the gastropd genus _ Succinea
_ and included two species, _Succinea amphibia _ Draparnaud 1801 and _ Succinea
oblonga _ Draparnaud 1801. Among the synonyms of _S. amphibia _, Draparnaud listed a name _Helix succinea _ Müller 1774. Synonyms do count here, so _Helix succinea _ is type species by absolute tautonymy (now _ Succinea
putris _). Kobelt 1904 established the gastropod subgenus _Iberus (Balearica) _ and included 10 species. Among these was _Helix balearica _ Rossmässler 1838, which Kobelt cited as _Iberus (Balearica) balearicus _. The ending -us is irrelevant here, _Helix balearica _ is type species by absolute tautonymy (currently _Iberellus balearicus _ or _Iberellus hispanicus _). _Euxinolauria _ Lindholm, 1924 (Gastropoda: Lauriidae) was established as a new replacement name for _Caucasica _ Caziot & Margier, 1909 (not _Caucasica _ Boettger, 1877 (Gastropoda: Clausiliidae)). _Caucasica _ Caziot & Margier, 1909 contained originally four species, among which was _Pupa caucasica _ Pfeiffer, 1857. This is the type species for _Caucasica _ Caziot there is no restriction to the number of ranks and the use of names is not restricted by priority.

The names in the family, genus, and species groups are fully regulated by the provisions in the Code. There is no limitation to the number of ranks allowed in the family group. The genus group has only two ranks: _genus _ and _subgenus _. The species group has only two ranks: _species _ and _subspecies _.


In the species group GENDER AGREEMENT applies. The name of a species, in two parts, a binomen , say, _ Loxodonta africana _, and of a subspecies, in three parts, a trinomen , say _ Canis lupus albus _, is in the form of a Latin phrase, and must be grammatically correct Latin. If the second part, the specific name (or the third part, the subspecific name ) is adjectival in nature, its ending must agree in gender with the name of the genus. If it is a noun, or an arbitrary combination of letters, this does not apply.

* For instance, the generic name _Equus _ is masculine; in the name _ Equus africanus _ the specific name _africanus_ is an adjective, and its ending follows the gender of the generic name. * In _ Equus zebra _ the specific name _zebra_ is a noun, it may not be "corrected" to "Equus zebrus". * In _ Equus quagga burchellii
Equus quagga burchellii
_ the subspecific name _burchellii_ is a noun in the genitive case ("of Burchell").

If a species is moved, therefore, the spelling of an ending may need to change. If _Gryllus migratorius_ is moved to the genus _ Locusta
_, it becomes _ Locusta migratoria _. Confusion over Latin grammar has led to many incorrectly formed names appearing in print. An automated search may fail to find all the variant spellings of a given name (e.g., the spellings _atra_ and _ater_ may refer to the same species).

Many laymen, and some scientists, object to continued adherence to this rule, especially those who work with butterflies and moths . This is for historical reasons. In 1758 , Linnæus placed all butterflies in the genus _ Papilio
_, which, after a few decades, contained thousands of species. From the beginning, the gender of _Papilio_ was unclear, undecided, and disputed. Some authors regarded it as masculine, others as feminine. Linnæus knew this problem and avoided any statement. All his 250 specific names in the genus _Papilio_ were either nouns, indeclinable adjectives, or adjectives ending in _-is_ (which can be masculine or feminine but not neuter). He did not use a single adjective ending in _-us_, _-a_, _-um_. P. Brown , Cramer , Fabricius , Fueßlin , Goeze , Poda and Schrank regarded _Papilio_ as masculine, Ménétriés , Pontoppidan and most modern authors as feminine. In ICZN Opinion 278 from 1954, it was regarded as masculine. In many cases lepidopterists would not change the ending of a name as used by the author who established a name. So we find for example _ Papilio
fuscus _ or _ Papilio
macilentus _, but also _ Papilio
osmana _ and _ Papilio
paradoxa _. Only in a few cases are both versions found in the Web (an example is _ Papilio
multicaudatus _ and _Papilio multicaudata _). This works also with other butterfly genera of which the gender is undisputed. _Graphium _ appears neuter, but only the inconsistent versions _ Graphium angolanus _ and _ Graphium mandarinus _ are used, while _ Graphium sandawanum _ can only be found with a neuter specific name. Likewise, pairs are more frequently found in genera of which the gender is not obvious: _Delias castaneus_ and _Delias gigantea_, _Belenois albumaculatus_ and _Belenois rubrosignata_, _Mylothris arabicus_ and _Mylothris ruandana_. Even in moths, such pairs occur: _ Xylophanes obscurus _ and _ Xylophanes turbata _, _ Manduca boliviana _ and _ Manduca caribbeus _, _ Sphinx caligineus _ and _ Sphinx formosana _, _ Macroglossum albolineata _ and _Macroglossum vicinum _. It may also occur that a lepidopteran subspecies can have a different gender from the name of the species , as for example in _ Papilio
multicaudata pusillus_ Austin only French was official). From then on, amendments and modifications were subsequently passed by various zoological congresses (Boston 1907, Graz 1910, Monaco 1913, Budapest 1927, Padua 1930, Paris 1948, Copenhagen 1953, and London 1958). These were only published in English, and can only be found in the reports of these congresses or other official publications.

The 1905 Rules became increasingly outdated. They soon sold out, and it became increasingly difficult to obtain to a complete set of the Rules with all amendments. In Copenhagen 1953 the French and English texts of the Rules were declared of equivalent official force, and a declaration was approved to prepare a new compilation of the rules. In 1958, an Editorial Committee in London elaborated a completely new version of the nomenclatural rules, which were finally published as the first edition of the _ICZN Code_ on 9 November 1961.

The 2nd edition of the Code (only weakly modified) came in 1963. The last zoological congress to deal with nomenclatural problems took place in Monte Carlo 1972, since by then the official zoological organs no longer derived power from zoological congresses. The 3rd edition of the Code came out in 1985. The present edition is the 4th edition, effective since 2000. These Code editions were elaborated by editorial committees appointed by the International Commission on Zoological Nomenclature . The ICZN Commission takes its power from a general biological congress (IUBS, International Union of Biological Sciences ). The Editorial Committee for the 4th edition was composed of seven persons. Such new editions of the ICZN Code are not democratically approved by those taxonomists who are forced to follow the Code's provisions, neither do taxonomists have the right to vote for the members of the Commission or the Editorial Committee.

As the Commission may alter the Code (by declarations and amendments) without issuing a new edition of the book, the current edition does not necessarily contain the actual provision that applies in a particular case. The Code consists of the original text of the 4th edition and Declaration 44. The Code is published in an English and a French version; both versions are official and equivalent in force, meaning, and authority. This means that if something in the English Code is unclear or its interpretation ambiguous, the French version is decisive, and if there is something unclear in the French Code, the English version is decisive.


The rules in the Code apply to all users of zoological names. However, its provisions can be interpreted, waived, or modified in their application to a particular case when strict adherence would cause confusion. Such exceptions are not made by an individual scientist, no matter how well-respected within the field, but only by the International Commission on Zoological Nomenclature , acting on behalf of all zoologists. The Commission takes such action in response to proposals submitted to it.

* Carl Linnaeus named the domestic cat _Felis catus_ in 1758; Johann Christian Daniel von Schreber named the wildcat _Felis silvestris_ in 1775. For taxonomists who consider these two kinds of cat a single species the Principle of Priority means that the species ought to be named _F. catus_, but in practice almost all biologists have used _F. silvestris_. In 2003, the Commission issued a ruling ( Opinion 2027 ) that "conserved the usage of 17 specific names based on wild species, which are pre-dated, by or contemporary with those based on domestic forms", confirming _F. silvestris_ for the wild cat. Taxonomists who consider the domesticated cat the same species as the wild cat should use _F. silvestris_; taxonomists who consider the domesticated cat a subspecies of the wild cat should use _F. silvestris catus_; taxonomists who consider the domesticated cat a separate species should use _F. catus_.

The latest amendments enacted by the Commission concern electronic publishing, which is now permitted for works published under an ISBN or