The subgeneric classification of the genus Zelus Fabricius, 1803 (Hemiptera: Heteroptera: Reduviidae: Harpactorinae) has had a troubled history (see Zhang et al. 2016 for a detailed review) and would need further study in a worldwide and phylogenetic context.

Stål (1862) proposed the first classification, subdividing the genus into three subgenera, the names of which have been treated variously as of generic or subgeneric rank by subsequent authors (Zhang et al. 2016). Zelus renardii Kolenati, 1857, a species introduced into several areas of the world (Kment & van der Heyden 2022) was included in the subgenus Diplodus Amyot & Serville, 1843 (originally proposed as a genus by Amyot & Serville (1843: 370)). Kirkaldy (1900: 242) noticed that the latter name was preoccupied by Diplodus Rafinesque, 1810 (Osteichthyes: Sparidae) and proposed the new name Diplacodus Kirkaldy, 1900 for replacing the junior homonym. The replacement name, however, was preoccupied by Diplacodus Davis, 1884 (Chondrichthyes: Cochliodontidae, fossil) (Davis 1884: 632).

Payne (1909: 122) and Wilson (1911: 89) first used the incorrect subsequent spelling Diplocodus for D. exsanguis Stål, 1862 (probable misidentifications pertaining to Z. luridus Stål, 1862 or Z. renardii, see Zhang et al. 2016) in a study involving hemipteran specimens identified by E.P. Van Duzee. Van Duzee (1912: 324) also used the name Diplocodus without an explanation for this incorrect subsequent spelling. The combination Diplocodus luridus was cited within quotation marks by Fracker (1912: 241), referring to the above mentioned contribution of Van Duzee. In a subsequent paper Van Duzee (1913: 123) clearly attributed the incorrect subsequent spelling Diplocodus to Kirkaldy (as author of the name). Most subsequent authors (among the few who mentioned the subgenera) continued to use the latter spelling (e.g., Van Duzee 1916: 30, 1917: 260; Costa Lima 1940: 218; Barth 1953: 325).

Aukema et al. (2013: 149) introduced another alternative spelling, Diplodacus, very likely by mistake since they cited “ Kirkaldy, 1900 ” as the author of the name. This name, actually to be considered as an incorrect subsequent spelling, was subsequently quoted as the valid name of the subgenus containing Z. renardii by several authors, including Çelik et al. (2021: 32), Kment & van der Heyden (2022: 7), Cianferoni (2023: 220), and Aukema (2023).

The incorrect subsequent spellings listed above cannot be used as the valid generic name, since they have no separate availability (ICZN 1999, Art. 33.3). The same is true for Diploda, an incorrect subsequent spelling for Diplodus, used by Walker (1873: 49). Therefore, according to the International Code of Zoological Nomenclature (ICZN 1999, Articles 60.1 and 60.3), proposal of a new replacement is necessary to remove the homonymy (see also Rees 2023).

Accordingly, I hereby propose Diplocodus nom. nov. (an incorrect subsequent spelling of Diplacodus used by several authors in the early 20 th century, itself not an available name) as a new name to replace the preoccupied Diplodus Amyot & Serville, 1843. Its grammatical gender is masculine.