Aedes (Aedimorphus) abnormalis (Theobald)

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 : 9-10

Aedes (Aedimorphus) abnormalis (Theobald)

subspecies abnormalis ( Theobald, 1909) —original combination: Bathosomyia abnormalis .

Distribution: Burkina Faso, Central African Republic, Côte d’Ivoire, Ghana, Nigeria, Senegal ( Wilkerson et al. 2021).

subspecies kabwachensis Edwards, 1941 —original combination: Aedes (Aedimorphus) abnormalis ssp. kabwachensis .

Distribution: Kenya, Uganda ( Wilkerson et al. 2021).

Theobald (1909, 1910) described abnormalis as the only species in his new genus Bathosomyia . The description was based on two males, one unlabelled. Townsend (1990) wrote: “ Syntype — Ghana: 1 male [poor condition], Ashanati, Obuasi.” A drawing of a slide-mounted clasper [gonostylus] accompanies the description. The male genitalia were remounted by Edwards (1917), who illustrated the opposite side of the Theobald-illustrated structure. Some selected characters for the genus follow. “Head with loose flat scales, except for a few small narrow curved ones in the middle at the base.” “Thorax with rather large narrow-curved scales, also the scutellum….” “Male clasper swollen and with large spines and one large apical curved spine. First posterior cell [cell R 5] almost uniform in breath [emphasis by Theobald]. …this presents a very marked genus on account of the squamose characters of the head, the marked first posterior cell, and the peculiar claspers to the male genitalia.” Additional selected characters in the species description Include: “Abdomen brown with basal creamy bands broadened in the middle. Legs uniformly brown, hind tibiae with pale apex.” In the male: “Thorax deep brown, clothed with rather large pale creamy narrow-curved scales and brown chaetae [setae]; scutellum ochreous brown with narrow-curved pale creamy scales. …Clasper of genitalia very marked, broadly expanded apically with several large spines and one large curved broad spine at apex. …The genitalia are very peculiar, and the general pale scaled head and thorax, and the large pale basal abdominal patches, should at once separate it.”

To our knowledge, the nominotypical subspecies remains known only from those two males. Hopkins (1952) described the larva of abnormalis and included it in a key, but his observations were based on larval exuviae of paratypes of subspecies kabwachensis . There have been a number of virus isolations from Ae. abnormalis sensu lato but no mention has been made about how identifications were carried out ( Worth & de Meillon 1960; Mutebi et al. 2012).

Edwards (1941) described subspecies kabwachensis based on reared specimens from Kabwach, Kenya. He designated a male as the holotype and provided brief descriptions of the male, female and pupa. Hopkins (1952), as noted above, described the larva as Ae. abnormalis . Townsend (1990) wrote [square brackets from original]: “ kabwachensis Edwards, 1941: 181–182 , 395, 432 ( Aedes (Aedimorphus) abnormalis subsp.). Holotype male [P & L skins on slide]— Kenya: [Kavirondoj], Kabwach Forest, [Kisii]. Paratypes (7)— Kenya: 7 female. …Edwards labelled the male as holotype, but the label was obscured beneath the locality label. Mattingly’s (1956b: 38–39) lectotype designation is therefore invalid. I have removed Mattingly’s and Edwards’ labels and replaced them with a standard BMNH ‘holotype’ label. The genitalia of paratypes on two pinned mounts are supernumerary to pinned series.”

The hindfemora of subspecies kabwachensis and abnormalis lack an apical pale spot. The two differ in that abnormalis has all three scutellar lobes with narrow scales whereas kabwachensis has broad scales on the lateral lobes and narrow scales on the middle lobe; and the vertex of abnormalis has mostly broad decumbent scales, while kabwachensis has the vertex with mostly narrow decumbent scales. Since the female of abnormalis is not known it is possible that these differences are due to sexual dimorphism.

Edwards (1941) redescribed the male genitalia of abnormalis as follows: “Style [gonostylus] with slender stem and greatly expanded distal portion, with a fairly long horn [gonostylar claw], a row of five sharp-pointed spines on the terminal margin, and a stronger spine adjacent to which is a small pubescent point, lower part of expanded portion bare; coxite [gonocoxite] broad in middle.” For kabwachensis : “almost as in the type of A. abnormalis , the only obvious difference being in the shape of the expanded portion of the style.” The drawings provided by Edwards (fig. 52a, type form; fig. 52c, kabwachensis ) show that the shape of the apical structures of the gonostylus of both are similar, as described. The stem [stalk, basal portion of the gonostylus] of the type form, however, appears much narrower than for kabwachensis , and the median expansion of the gonocoxite is broader and more rounded in kabwachensis than in the type form. Although not discussed, it appears to us from the drawings that the basal piece of the phallosome is much narrower and almost pointed in the type form, broader in kabwachensis , and tergum IX of the type form is concave posteriorly while in kabwachensis it is narrowed anteriorly and posteriorly. Other features shown in the illustrations of the male genitalia are not distinct enough for comparison.

It is not clear, except for similar adult morphology, why Edwards thought the two forms should be subspecies rather than full species. There is immense geographical distance between the two forms, type form from far western Africa, kabwachensis from eastern Africa. This of course could be an artefact of so few specimens available for study. For comparisons, only the males are known for both. The larval and pupal exuviae of the holotype and paratypes of kabwachensis exist but only the male has been described in any detail. However, we think the few characters that separate males of the two forms are significant and indicate two genetically independent species. For this reason, we hereby elevate kabwachensis to species status: Aedes (Aedimorphus) kabwachensis Edwards, 1941 . Aedes kabwachensis is currently listed as a species in the Encyclopedia of Life.

As an aside, Wigglesworth (1929), accepting the identification by Edwards, described and illustrated the larva and pupa of what they both thought was abnormalis , but which later was recognized by Edwards as a misidentification of a new species, which he named Aedes (Aedimorphus) wigglesworthi Edwards, 1941 . No subsequent taxonomic catalog has recognized the misidentification or that Wigglesworth (1929) was the source of the description of the species named in his honor.