Genus Skusea Theobald, 1903
Skusea pembaensis (Theobald, 1901), original combination: Aedes pembaensis.
Subfamily Culicinae, tribe Aedini. Skusea includes four species. Genus abbreviation – Sk.
Species of Skusea are characterised and distinguished from species of other genera of Aedini by the following combinations of characters. Characters that diagnose the genus in the phylogenetic analysis of Reinert et al. (2009), based on Sk. pembaensis, are indicated by an asterisk (*). The female, larva and pupa of Sk. moucheti are unknown.
ADULTS – Vertex of head with broad decumbent scales, erect forked scales confined to occiput; maxillary palpus of males about as long as proboscis, palpomeres 4 and 5 short, slightly thickened and setose; scutum with narrow scales, acrostichal setae and dorsocentral setae present; scutellum with broad decumbent scales; paratergite bare; *upper proepisternum with ≥ 20 setae; pleura with broad scales on postspiracular area, upper and lower areas of mesokatepisternum and upper area of mesepimeron; lower mesepimeral setae present (apparently absent in males of Sk. pembaensis); wing dark-scaled with short patch of pale scales at base of costa; femora without knee spots, ungues of females all simple; abdominal terga largely dark-scaled with basolateral pale patches, some terga usually with narrow pale basal bands. FEMALE GENITALIA – *Intersegmental membrane between segments VII and VIII short to intermediate; *tergum VIII with setae inserted on ≤ distal 0.60; *posterior margin of sternum VIII with median emargination separating sublateral lobes; tergum IX a single sclerite, wrinkled (at least in Sk. pembaensis); postgenital lobe without scales; *upper vaginal sclerite absent. MALE GENITALIA – Segment VIII unusually large; tergum IX unusually small; sternum IX without setae; gonocoxite short and broad, mesal surface not membranous, with double subapical lobe bearing row of long apically hooked setae on lateral side that extend to or beyond apex of gonostylus and a dense patch of short setae on mesal side (lobe apparently terminal part of uniquely modified claspette that extends as a narrow strip along mesal margin of gonocoxite); gonostylus short and stout, with distolateral fringe-like crest and *dorsal spur-like process immediately proximal to short spine-like gonostylar claw; aedeagus *widest in distal third, comprised of pair of simple elongate lateral plates, *teeth absent; paraproct very poorly developed. LARVAE – *Antenna without spicules, seta 1-A inserted about 0.25 from base; *seta 5-P branched, *no longer than seta 6-P; *seta 7-P single; *seta 7-M longer than seta 5-M; *seta 7-I with 4 or more branches, *< 0.45 length of seta 6-I; *seta 1-VIII ≤ 0.38 length of seta 2-VIII; *seta 2-VIII inserted approximately midway between setae 1- and 3-VIII; *seta 3-VIII simple; comb comprised of numerous scales in patch, scales bifid and trifid (branched from base), branches frayed at tip; siphon nearly cylindrical, relatively short, siphon index about 3.5, *acus absent; pecten more or less on proximal 0.5, *pecten spines evenly spaced; seta 1-S very short, multi-branched, inserted beyond pecten; saddle very small, weakly sclerotised, with dorsoposterior patch of coarse spicules; *seta 1-X not inserted on saddle, single; seta 2-X multi-branched, with about 8 branches; ventral brush (seta 4-X) with 6–7.5 pairs of multi-branched setae inserted on grid. PUPAE – *Trumpet without tracheoid area; *seta 7-CT ≥ 6.0 times length of seta 6-CT; *seta 11-CT, *seta 3-I and *seta 3-II branched; *seta 5-II inserted mesal to seta 4-II; *seta 5-II longer than seta 3-II; *seta 2-VI inserted lateral to seta 1-VI; *seta 9-VIII inserted slightly anterior or mesal to posterolateral corner of segment; paddle broad, round, margins smooth; seta 1-Pa single, long, *≥ 0.80 length of paddle. See Aedini.
Prior or Belkin (1962), Skusea included a collection of unrelated species whose adults exhibited similar scaling of the head and scutellum. He established Lorrainea (as a subgenus of Aedes) for the Oriental and Australasian species previously included in the group and recognised Skusea as a monobasic group represented by Sk. pembaensis in eastern Africa and Madagascar. Edwards (1928) noted that the position of this species relative to other aedine taxa was “a matter of uncertainty owing to the fact that no very close allies are known”. The genus now includes four closely related species whose affinities with other groups of Aedini remain uncertain. The genus was recovered as the sister of Indusius + Cancraedes in the phylogeny of Reinert et al. (2009) based on morphological characters of all life stages of the type species. It was recovered as the sister of Indusius, and this pair was sister to Fredwardsius, in the phylogeny of Wilkerson et al. (2015).
Larvae of Skusea are common in crab holes in tidal swamps and estuaries. Females of Sk. pembaensis are known to bite humans from early morning until dusk, with peak activity in late afternoon. Females of Sk. lambrechti are known to feed on mammals and are attracted to humans – both sexes have been collected inside houses in early morning and outdoors in the vicinity of larval habitats. Eggs of Sk. pembaensis have been found attached to crabs.
Microfilariae have been found in wild-caught females of Sk. lambrechti, but it is not known if species of Skusea are of medical importance to humans.
Species of Skusea are known to occur in Madagascar (three species), Seychelles (two species, including the type species) and Comoro Islands (one species also found in Madagascar). The type species, in addition to its occurrence in Madagascar and the Seychelles, is recorded from Mozambique and Tanzania.
Brunhes, 1977 (as subgenus of Aedes, male genitalia, taxonomy); Reinert, 2000 (as subgenus of Aedes, female genitalia); Reinert et al., 2004, 2009 (generic status, morphology, phylogeny); Wilkerson et al., 2015 (as subgenus of Aedes, phylogeny).
