89. Rhipicephalus linnaei.

Šlapeta et al. (2021) reinstated the name Rhipicephalus linnaei (Audouin, 1826) from Egypt for the Rhipicephalus sanguineus from Australia described by Roberts (1965), which is thought to represent many “tropical lineages” of this tick worldwide. While we agree that the species described by Roberts (1965) is new, the name selected by Šlapeta et al. (2021) has no scientific basis for adoption.

Rhipicephalus linnaei was originally named Ixodes linnaei Audouin, 1826, a tick that was imprecisely described from specimens collected from unknown hosts in Egypt, and the type material is not available. Rhipicephalus linnaei (Audouin, 1826) is a nomen dubium, a synonym of Ixodes linnaei Audouin, 1826, in Guglielmone & Nava (2014) and Guglielmone et al. (2015 and updates) and also here, while Neumann (1897) treated this tick as a nominal species. Camicas et al. (1998) and others regarded Rhipicephalus linnaei as a synonym of Rhipicephalus sanguineus. However, the proposed synonymy of Rhipicephalus linnaei with Rhipicephalus sanguineus is taxonomically unsupported because there are no type specimens of Rhipicephalus linnaei for morphological and molecular comparison (Guglielmone et al. 2015 and updates). Thus, Walker et al. (2000) defined Rhipicephalus linnaei as “New combination for Ixodes linnaei Audouin, 1826 [= Unknown species].”

There are several species of Rhipicephalus in Egypt, among them Rhipicephalus camicasi, Rhipicephalus guilhoni, Rhipicephalus sanguineus “southern Europe lineage,” Rhipicephalus sanguineus “tropical lineage” and alleged Rhipicephalus turanicus (Chitimia-Dobler et al. 2017 b, Perveen et al. 2021), plus Rhipicephalus limbatus (type available) and Rhipicephalus rutilus (type available), both described by Koch (1844a) and considered to be synonyms of Rhipicephalus sanguineus by Camicas et al. (1998, among others). Specimens of any of these ticks may actually represent the lost specimens of Ixodes linnaei Audouin, rather than the Australian tick described by Roberts (1965), but all these names were ignored and were not compared with the Australian species by Ŝlapeta et al. (2021).

In summary, there is no scientific basis for reinstating Rhipicephalus linnaei (type material not available) as a valid species; this name is still considered to be a nomen dubium and a synonym of Ixodes linnaei (nomen dubium), following Guglielmone & Nava (2014) and Guglielmone et al. (2015 and updates). A new name should be selected for the species described by Roberts (1965). Meanwhile, this tick will not be further discussed in the present analysis.

Note: following the final revision of this monograph, Šlapeta et al. (2022 Ticks and Tick-borne Diseases, 13 (6) (article 102204) 12 pp.) provided an additional study of the validity of Rhipicephalus linnaei, including morphological and molecular definition of a neotype, and a convincing comparison with other species of Rhipicephalus from Egypt. Consequently, Rhipicephalus linnaei is now treated as a valid species, but other data from Šlapeta et al. (2022) are not included in our monograph.