Aedes (Collessius) elsiae (Barraud)

subspecies elsiae (Barraud, 1923a) —original combination: Finlaya elsiae. Distribution: Cambodia, India, Malaysia, Nepal, People’s Republic of China, Taiwan, Thailand, Vietnam (Wilkerson et al. 2021).

subspecies vicarius Lien, 1968 —original combination: Aedes (Finlaya) elsiae vicarius. Distribution: Taiwan (Lien 1968).

The nominotypical subspecies was described from male and female cotypes (Barraud 1923a) and other conspecifics from Shillong, Assam, India. Using exuviae from the cotypes and additional specimens to document variation, Barraud (1923c) described the larva with illustrations of the siphon and antenna. Barraud (1934) then described in more detail the adults (both sexes) and larva, with illustrations of the larval head, thorax and siphon. Darsie (2010) described the pupa of elsiae (as a species of Ochlerotatus Lynch Arribálzaga, 1891a) from sites in Nepal relatively close (about 400 km) to the type locality of elsiae in northern India. Townsend (1990) reported 19 syntypes of elsiae in the collection of the Natural History Museum, London, but not the cotypes or larval exuviae.

Subspecies vicarius was described and illustrated in all life stages, except the egg, from Chuchi, Chiai Hsien, Taiwan, but was also documented from many other localities in the original description. It is apparently found only on Taiwan. It and elsiae are similar in many respects in the adult and larval stages. In the larval stage, the two nominal forms have setae 1-M and 1-T very stout and borne on prominent tubercles, and seta 1-S stout and aciculate. The unusual character of these stout thoracic setae is also found in Aedes (Collessius) shortti (Barraud, 1923a) and Ae. (Col.) macfarlanei (Edwards, 1914). The larval cuticle of subspecies vicarius is, however, densely covered with spicules, a significant difference from elsiae. Lien (1968) summarized the differences between elsiae and vicarius in the original description: “ The mosquito [vicarius], in most respects, shows a close resemblance to Aedes elsiae and is therefore described here as a new subspecies of Aedes elsiae. It differs from type species chiefly as follows: The venter of adults mainly dark brown instead of ‘mainly yellowish’; a patch of broad dark scales sandwiched by two patches of broad white scales on upper and middle aspects of ppn [postpronotum] instead of ‘narrow yellow and broad white scales on lower border of ppn ’; antennal hair [seta] 1-A of larva inserted at about basal third of shaft and bifid instead of ‘at about middle’ and ‘with 3–5 branches’; thoracic and abdominal integument densely spiculate. The male terminalia is [sic] almost indistinguishable from that of type species.” We instead judge these differences to clearly indicate separate species. We do not accept the reasoning that since the two forms are similar that they should be subspecies.

The pupal stage of elsiae was not available to Lien (1968) when he published a detailed illustration of the pupa of vicarius. The description and illustration of the pupa of elsiae by Darsie (2010) allowed direct comparison of the pupae of the two nominal forms. Darsie (2010) wrote: “From the illustration it can be separated from the subspecies elsiae pupa as follows: in Oc. e. vicarius seta 1-II has 4 branches and Oc. e. elsiae has 10–16 branches; seta 9-VII has 4 branches in the former and 8–10 branches in the latter.” We compared the illustrations of the two nominal forms and confirm the differences noted by Darsie. However, we also note many other obvious differences, such as nearly universal differences in the length and number of branches of setae (shorter and fewer in vicarius) and a very differently shaped paddle (~1.25 times longer than wide in vicarius; nearly round in elsiae). It is always possible that this is attributable to an undetected species complex, misidentification or a mix-up of specimens or illustrations, but the differences in the larval stage and adults remain to support our conclusions.

Given the significant morphological differences and the geographic isolation of subspecies vicarius, we hereby recognize its status as a species: Aedes (Collessius) vicarius Lien, 1968. Aedes vicarius is currently listed as a species in the Encyclopedia of Life.

Aedes (Col.) elsiae has one synonym: Aedes (Finlaya) simulatus Barraud, 1931. It was described from a single female from Assam, Haflong, Cachar Hills, India and was listed as a synonym, without comment, in Barraud (1934). There are no synonyms of Ae. (Col.) vicarius.