Culex (Lophoceraomyia) curtipalpis (Edwards)

Harbach, Ralph E. & Wilkerson, Richard C., 2023, The insupportable validity of mosquito subspecies (Diptera: Culicidae) and their exclusion from culicid classification, Zootaxa 5303 (1), pp. 1-184 : 98-99

Culex (Lophoceraomyia) curtipalpis (Edwards)

subspecies curtipalpis ( Edwards, 1914 c) —original combination: Lophoceratomyia curtipalpis . Distribution: Cambodia, Indonesia, Malaysia, Singapore, Thailand, Vietnam ( Wilkerson et al. 2021).

subspecies sumatranus Brug, 1931 —original combination: Culex (Culex) sumatranus (subspecific status by Meng & Chen 1980). Distribution: Cambodia, Indonesia, Macau, People’s Republic of China, Vietnam ( Wilkerson et al. 2021).

Edwards (1914 c) described curtipalpis from five males collected at Kuching Reservoir in Sarawak, Malaysia. His description did not mention or include an illustration of the male genitalia. Edwards (1928) added some details to his previous description, including a brief description of the genitalia and an illustration of the gonostylus. The larva and pupa were described by Edwards & Given (1928) based on association with reared adults. The male and larva were later described and illustrated in more detail by Colless (1965), Bram (1967) and Sirivanakarn (1977), and the pupa was described by the last author.

Subspecies sumatranus was originally described by Brug (1931) as a species of the subgenus Culex , described from a single male reared from a larva taken from a pitcher plant in the vicinity of Dermajoe, Benkoelen, Sumatra. Brug illustrated the male genitalia and the head and terminal abdominal segments of the larval exuviae. The species was transferred to the subgenus Neoculex by Brug & Edwards (1931), and this was accepted (see Stone et al. 1959) until Sirivanakarn (1971) recognized it as a species of the subgenus Lophoceraomyia . It was later regarded as a subspecies of Cx. curtipalpis by Meng & Chen (1980).

As revealed by Barraud (1934), in a footnote on page 351, and discussed by Sirivanakarn (1977), the larva described and illustrated by Brug (1931) was wrongly associated with the adult male, and adults reared from larvae collected in Hong Kong and elsewhere are identical with the larva of curtipalpis described by Edwards & Given (1928). Sirivanakarn treated sumatranus as a distinct species, but noted that “All stages of sumatranus are exceedingly similar to and indistinguishable from curtipalpis except for the male which differs from the latter rather strikingly in the absence of the modified tufts of the male antenna.” For clarity, unlike curtipalpis , the flagellar whorls of sumatranus are weakly verticillate or comprised of relatively fewer long setae and tufts of modified setae/scales are absent on flagellomeres 5–9 or a rudimentary or inconspicuous tuft of four very short setae may be present on the mesal surface of flagellomere 7. Contrary to Sirivanakarn (1977), Meng & Chen (1980) considered this striking difference to be nothing more than interspecific variation.

In view of the poor illustration of the male genitalia of sumatranus provided by Brug (1931), we decided it was important to examine the holotype in the Natural History Museum, London. The dissected genitalia of the holotype are poorly mounted on a microscope slide. The left gonocoxite seems to be positioned differently than indicated in Brug’s illustration, and the gonostylus, which is tapered to the apex in the illustration, is expanded and strongly modified as illustrated by Colless (1965: fig. 29d), Bram (1967: fig. 22) and Sirivanakarn (1977: fig. 69). The setae of the subapical lobe are inaccurately drawn, but the two setae proximal to setae a–c are clearly present. Setae a–c are more tapered and pointed than illustrated, and also tapered more distally than illustrated by Colless, Bram and Sirivanakarn for curtipalpis . Foliform seta g is not shown in the drawing, but it probably was not seen by Brug because it is very faint and difficult to see even under differential interference contrast microscopy, which we used to examine the genitalia. Surprisingly, it is much longer and narrower than seta g shown in the illustrations of the genitalia of curtipalpis provided by Colless, Bram and Sirivanakarn, which is short and very broad, about as broad as long. It is likely that Sirivanakarn (1977) also did not see seta g when he examined the holotype of sumatranus (he undoubtedly used traditional bright-field microscopy), otherwise he would have noted this obvious difference in his description of the species. These differences, along with the absence of modified tufts of setae or scales on the antennal flagellum, are a clear indication that sumatranus is a species distinct from curtipalpis . Based solely on the antennal characteristics, both forms have been found in areas of Cambodia, Indonesia (Sumatra) and Vietnam. Considering this apparent sympatry and the morphological distinctions exhibited by the adult male, we believe curtipalpis and sumatranus are genetically distinct species and hereby reinstate the latter to its original specific status: Culex (Lophoceraomyia) sumatranus Brug, 1931 . Culex sumatranus is currently listed as a species in the Encyclopedia of Life.

Culex sumatranus has a single synonym, Cx. gudouensis Chang, Zhao, Hang & Chen, 1975 (type locality: Xin-hui Shien, Kwangtung Province, People’s Republic of China), which was synonymized with sumatranus by Meng & Chen (1980). The illustration of the subapical lobe of Cx. gudouensis provided by Chang et al. (1975) is very poor. There is no indication of seta g, but Meng & Chen examined the type specimens and noted the presence of a “broad leaf” that was “ignored in the original description” (translated from the Chinese). This does not clearly indicate, however, whether seta g is like that of Cx. curtipalpis or Cx. sumatranus , but Meng & Chen also noted that a tuft of specialized short setae was present only on the seventh flagellomere of the antenna, and used this as the primary character to support the synonymy of Cx. gudouensis . Unless other information becomes available to indicate otherwise, Cx. gudouensis should continue to be recognized as junior synonym of Cx. sumatranus .