Genus Tanakaius Reinert, Harbach & Kitching, 2004
Tanakaius togoi (Theobald, 1907), original combination: Culicelsa togoi.
Subfamily Culicinae, tribe Aedini. Tanakaius includes two species. Genus abbreviation – Ta.
Characters that diagnose Tanakaius in the phylogeny of Aedini recovered in the study of Reinert et al. (2009) are indicated by an asterisk (*). ADULTS – Vertex of head with narrow decumbent scales, occiput and most of vertex with numerous erect forked scales; eyes narrowly separated above antennal pedicels; maxillary palpus about 0.25 length of proboscis in females, *about 0.75 in males (comprised of 5 palpomeres); scutum with narrow scales, pale scales in lines and stripes on acrostichal and dorsocentral areas, anterior margin of scutal fossa, posterior margin of scutal fossa to middle of supraalar area and laterally on antealar and supraalar areas; *scutal fossal scales sparse; acrostichal setae (anterior and posterior) and dorsocentral setae (anterior and posterior) present; paratergite with broad pale scales; scutellum with narrow falcate scales on all lobes; lower mesepimeral setae present or absent; wing dark-scaled, costa with small pale spot at base; *remigial setae absent; alula with row of narrow scales on margin; upper calypter with numerous setae on margin; ante- and postprocoxal membranes bare; femora with knee spots and incomplete pale stripes on anterior and posterior surfaces; tarsi dark-scaled or with narrow basal and apical pale bands on some tarsomeres; both hindungues toothed in *females and *males; laterotergite of abdominal tergum I pale-scaled, terga II–VII with basolateral pale patches; sterna with basolateral pale patches often connected mesally; segments VII and VIII of females laterally compressed. FEMALE GENITALIA – *Intersegmental membrane long between segments VII and VIII; tergum VIII with *setae on distal 0.70 or more; sternum VIII with shallow posterior emargination, *seta 2-S inserted lateral to and more or less on level with seta 1-S; tergum IX with V-shaped caudal margin; *upper and lower vaginal sclerites absent; insula lip-like, with setae on either side of midline; 3 spermathecal capsules, one slightly larger. MALE GENITALIA – Tergum IX narrowly connected laterally to sternum, posterior margin bilobed, lobes with setae; gonocoxite with numerous spatulate scales on dorsolateral, lateral and ventral surfaces, ventral surface with irregular or double row of numerous fusiform scales, gonostylus attached apically, gonostylar claw at apex; claspette comprised of columnar stem and *long strongly curved claspette filament, *stem ≤ 0.85 length of aedeagus; aedeagus simple, scoop-like with narrowed apex; paraproct narrow, apex strongly curved into short beak-like point, 2–5 cercal setae. HABITAT OF IMMATURE STAGES – *Brackish-water ground and rock pools. LARVAE – Antenna short, *≤ 0.40 length of dorsal apotome; seta 1-A with 3–6 branches (rarely double), not reaching apex of antenna; setae 2,3-A inserted apically; seta 4-C branched; setae 4–6-C arranged in a transverse row, inserted anterior to level of seta 7-C; seta13-C single, inserted laterad of seta 12-C; seta 19-C absent; seta 4-P single; *seta 5-P as long as or shorter than seta 6-P; *seta 7-M as long as or longer than setae 5-M; *seta 3-VII inserted at same level or posterior to seta 1; seta 6-I–III with 3 or more branches, seta 7-I,II long, with 2 or 3 branches; seta 12-I single or double; setae 2,10-VII single; comb scales in patch; siphon short, acus attached, pecten spines evenly spaced; seta 1-S inserted distal to pecten; saddle small, incomplete ventrally, without acus; seta 1-X single to triple, *not inserted on saddle; seta 2-X with 5–11 branches; seta 3-X single; ventral brush (seta 4-X) comprised of 12–14 multiple-branched setae attached to grid with both lateral and transverse bars, occasionally 1 precratal seta. PUPAE – Trumpet with weakly developed tracheoid area; seta 1-CT longer than seta 3-CT; seta 7-CT > 3.5 length of seta 6-CT; *seta 3-I branched; seta 6-I single to 5-branched, distinctly shorter than seta 7-I; seta 2-II single or double, inserted lateral to seta 1; seta 5-II single to 4-branched, *inserted mesad of seta 4; seta 5-V single to triple, longer than following tergum; seta 3-VI inserted laterad of setae 1; seta 6-VII single to 7-branched, inserted posteromesad of seta 9-VII; paddle broad, without fringe of hair-like spicules, midrib distinct to near apex; seta 1-Pa single. See Aedini.
Tanakaius was recovered as sister to a clade comprised of Hulecoeteomyia + (Gilesius + Collessius) in the phylogenetic study of Reinert et al. (2009) based on morphological data of the adult, larval and pupal stages of Aedini. Tanakaius and subgenera Collessius, Gilesius and Hulecoeteomyia comprised a polyphyletic clade in the phylogeny of Wilkerson et al. (2015). Tanakaius was recovered as as the sister to a clade comprised of species of Collessius, Hulecoeteomyia and Rhinoskusea in the maximum likelihood phylogeny of Soghigian et al. (2017) based on molecular markers. In a phylogenetic analysis of mtDNA COI sequences (Somboon et al., 2023), Tanakaius was recovered as a weakly supported clade in a polytomy with two clades comoprised of 12 other generic-level taxa.
The immature stages of Tanakaius species usually inhabit brackish-water ground and rock pools in coastal areas, but Ta. togoi has been found on occasion in fresh water containers. Females of Tanakaius are known to bite humans during diurnal hours.
Tanakaius togoi is a vector of Brugia malayi; females have been found naturally infected with Japanese encephalitis virus and transmission of the virus has been demonstrated in laboratory studies (Gutsevich et al. 1974; Tanaka et al., 1979; Rattanarithikul et al., 2010). It is also an experimental vector of Semliki Forest virus (Nye & Lien, 1960).
The type species of Tanakaius is known to occur naturally in eastern areas of China and Russia, and in Japan, South Korea, Malaysia (peninsular), South Prymorye, Southern Kurile Islands, Taiwan, Thailand and Vietnam. It was introduced to British Columbia, Canada, and subsequently extended its range into Washington State, USA. Tanakaius savoryi is indigenous to Ogasawa-guntô (the Bonin Islands) of Japan.
Reinert et al., 2004, 2009 (generic status, morphology, phylogeny); Reinert, 2008 (female genitalia); Rattanarithikul et al., 2010 (Thailand, keys, bionomics); Wilkerson et al., 2015 (as subgenus of Aedes, phylogeny); Soghigian et al., 2017 (as subgenus of Aedes, phylogenetic relationships).
