minimize this paragraph: Many of the occurrence records for Cx. pipiens and Cx. quinquefasciatus in the KSA are problematic. Culex pipiens generally occurs north of a line transecting the KSA between Jeddah in the west and Al-Hasa in the east. Culex quinquefasciatus occurs in the more southerly region of the Arabian Peninsula, with isolated populations of Cx. pipiens occurring in the southwestern mountains [5]. Introgression occurs between the two species where their distributions overlap in central KSA (see figure 3 in Harbach [101]). Both species exhibit considerable variation in the larval and adult stages, and they cannot always be distinguished with certainty. They are paraonly reliably distinguished by characters of the male genitalia; however, their separation is complicated by the occurrence of hybrid forms in the central transitional zone and eastern coastal region of the country. Hybrids are morphologically more variable than the parental species, and are only reliably distinguished from the parental species by the DV/D ratio calculated from measurements based on the form and relationships of the dorsal and ventral arms of the male genitalia [102, 103]. It is not possible to distinguish hybrid larvae and females from the parental species. For this reason, some hybrid specimens collected in and around the zone of introgression have undoubtedly been misidentified as either Cx. pipiens or Cx. quinquefasciatus. Larvae and adults collected north of the hybrid zone that have been identified as Cx. quinquefasciatus are misidentified specimens of Cx. pipiens, and those collected south of the zone that have been identified as Cx. pipiens, with the possible exception of those collected in the southwestern mountains, are misidentified specimens of Cx. quinquefasciatus. Future studies based on dissections of male genitalia or DNA sequence analysis of larvae and adults are needed to substantiate species identifications and collection records. Culex quinquefasciatus is an important vector of the microfilariae that cause lymphatic filariasis.

Culex torrentium is listed as a species of the KSA in the online catalogue of the Walter Reed Biosystematics Unit [24] based on a number of reports, including Alahmed et al. [18, 19], Al Ahmed et al. [20, 28], Kheir et al. [34], Alahmed [35] and Hassan et al. [41]. However, it is obvious that the identification of Cx. torrentium in the KSA by these authors is based on unreliable characters of larvae and adult habitus principally using the keys of Harbach [4, 5]. This species can only be distinguished from members of the Cx. pipiens complex with certainty based on features of the male genitalia. Additionally, Cx. torrentium is a Palaearctic species whose distribution only extends south into Turkey and possibly into northern Iran [90, 104, 105]. As noted by Harbach [5], early records of Cx. torrentium in Iraq are doubtful, and the species is not now listed as present in that country [106, 107]. For these reasons, Cx. torrentium is excluded from the list of mosquito species known to occur in the KSA.

Four species of the subgenus Culex of the genus Culex occur in the southwestern Afrotropical Region of the Arabian Peninsula, i.e. Cx. decens, Cx. duttoni, Cx. simpsoni and Cx. univittatus. These species were only known to occur in Yemen [5, 108] until they were more recently found in the Asir Region [63], Jizan (Jazan) Region [18] and Najran Province [28], which border Yemen in the southwest corner of the KSA. The records of two of these species, Cx. simpsoni and Cx. univittatus, require confirmation because their identification was based on larvae and adults. They are only reliably distinguished from Cx. sinaiticus and Cx. perexiguus, respectively, based on the morphology of the male genitalia. Records of the two species in more northerly areas of the country are more doubtful.

Since Culex salisburiensis has been known to be present in Yemen since 1953 [108], there is no reason to doubt its occurrence in the adjacent Afrotropical area of the KSA [21, 67]. On the contrary, the reported finding of Cx. wigglesworthi in the Asir Region by Al Ashry et al. [67] is certainly a misidentification. The authors collected 4307 Culex larvae, two of which were identified as Cx. nebulosus, three as Cx. perexiguus and two as Cx. wigglesworthi. Larvae were identified using the keys of Hopkins [109], Mattingly & Knight [2] and Harbach [4, 5]. The identification of Cx. nebulosus and Cx. perexiguus may be correct as these two species are included in the keys of Mattingly & Knight (Cx. nebulosus) and Harbach (Cx. nebulosus and Cx. perexiguus). Use of the badly outdated keys of Hopkins [109] for African species published in 1952, leading to the identification of Cx. wigglesworthi, is problematic, nonetheless because it is a sub-Sharan species with closest records in southern Sudan, South Sudan and Kenya. Consequently, as it seems likely that the two larvae were misidentified specimens of either Cx. perexiguus or Cx. univittatus, Cx. wigglesworthi is excluded from the list of mosquito species known to occur in the KSA.