W-albus Subgroup

Type species: 

Aedes w-albus (Theobald, 1905), original combination: Stegomyia w-alba.

Classification: 

Subfamily Culicinae, tribe Aedini, genus Aedes, subgenus Stegomyia, W-albus Group. The W-albus Subgroup includes three species.

Characteristics: 

Species of the W-albus Subgroup are characterised and distinguished by the following combination of characters (adapted from Huang, 1977). ADULTS ‒ Maxillary palpus with pale scaling; scutum with (i) broad longitudinal pale stripes on either side of midline extending from anterior promontory to middle of scutum and fusing with antealar pale patches, or (ii) with large median pale patch on anterior third, or (iii) with 2 lateral pale patches on anterior third; prescutellar area with broad dark scales on either side of bare space; dorsocentral setae and prescutellar setae absent; scutellum with broad pale scales on all lobes; hypostigmal area, subspiracular area, postspiracular area, prealar area and metameron with broad pale scales; mid- and hindfemora each with knee spot, absent on forefemur, midfemur with anterior pale spot near mid-length; anterior surface of all tibiae entirely dark-scaled; hindtarsomeres 1‒4 with basal pale bands, hindtarsomere 5 entirely dark-scaled or with basal pale band. FEMALE GENITALIA ‒ Tergum IX slightly broader than long to slightly longer than broad, with well-developed posterolateral lobes, each with 3 or 4 setae. MALE GENITALIA ‒ Caudal margin of tergum IX produced as a large lobe; gonostylus simple, as long as gonocoxite, with spiniform gonostylar claw at apex; paraproct with ventral arms. LARVAE ‒ Seta 9-M with 2 or 3 aciculate branches; setae 10,12-M single, long, stout, aciculate; basal support plates of meso- and metathoracic pleural groups with rather small pointed spine; comb plate present or absent, comb scales borne in a single row; seta 1-S inserted in line with and distal to pecten spines; saddle with inconspicuous spicules on posterior margin. PUPAE ‒ Seta 1-II usually well developed, dendritic or with 2 or 3 branches; seta 2-IV,V inserted mesad of seta 1; genital lobe of male short, broad, as broad as long or longer than broad. See subgenus Stegomyia.

Phylogenetic relationships: 

Huang (1977) indicated that adults of the W-albus Subgroup resemble those of the Annandalei Subgroup in having a patch of broad dark scales on each side of the prescutellar space and those of the Desmotes Subgroup in having similar pleural in scutellar markings. She also indicated that males and females share some characteristics of their genitalia with those of the Annandalei and Mediopunctatus Subgroups; pupae resemble those of the Scutellaris Group in having seta 2-IV,V inserted mesad of seta l; and the larvae resemble those of the Desmotes Subgroup in having inconspicuous marginal spicules on the saddle. She observed that the pupae and larvae are extremely similar and difficult or impossible to distinguish from those of the Scutellaris Group. Despite these observations, the phylogenetic relationships of the W-albus Subgroup are unknown and will remain so until the species of subgenus Stegomyia are better known and studied using objective methods of phylogenetic analysis.

Bionomics and disease relations: 

The immature stages of species of the W-albus Subgroup are mainly found in bamboo stumps, bamboo cups, tree holes and log holes. Rattanarithikul et al. (2010) noted that larvae of Ae. gardnerii imitator and Ae. w-albus have been found in banana stumps/axils and artificial containers, respectively, in Thailand. Females of Ae. gardnerii imitator and Ae. w-albus are known to bite humans.

Species of the W-albus Group are not known to be of medial importance to humans, but should be considered as potential vectors.

Distribution: 

The species of the W-albus Subgroup have distributions in the Oriental Region. Aedes gardnerii is recorded from countries in Southeast Asia (Indonesia, Malaysia, Philippines, Singapore and Vietnam) and Ae. w-albus is more widely distributed in the Oriental Region, with recorded presence in Bangladesh, China, India, Indonesia, Malaysia, Nepal, Pakistan, Sri Lanka, Thailand and Vietnam.

Principal references: 

Huang, 1977 (description, distribution, bionomics, keys to adults, pupae and larvae); Rattanarithikul et al., 2010 (as species of genus Stegomyia, distributions, bionomics, keys for identification of adults and larvae).

Species: 

gardnerii (Ludlow, 1905)
imitator (Leicester, 1908)
w-albus (Theobald, 1905)

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith