Aedes (Stegomyia) Theobald
Creators: name: Yiau-Min Huang
Publisher: name: Zenodo
Year: 2004
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Culicidae
Aedes

description: Subgenus Stegomyia Theobald
Stegomyia Theobald 1901a (June 1), in Howard 1901: 235; Theobald 1901b (July 15): 235; Theobald 1901c (Sept.): 4, App. ii; Theobald 1901d (Nov. 23): 283. Type­species: Culex aegypti Linnaeus 1762 (see Mattingly, Stone and Knight 1962).
Quasistegomyia Theobald 1906: 69. Type­species: Q. unilineatus Theobald 1906,Bahr­el­Ghazal, Sudan; monobasic.
Pseudostegomyia Ludlow 1908: 10. Type­species: Stegomyia gardnerii Ludlow 1905, Bulacao, Mindoro Island, Philippines; monobasic [Apparently an error for Quasistegomyia Theobald 1906 (see Theobald 1910: 135)].
Kingia Theobald 1910: 135 (non Schloenbach 1866). Type­species: Stegomyia luteocephala Newstead (Brunetti 1914: 63).
Aniella Enderlein 1923: 26. Type­species: Stegomyia africana Theobald.
Characteristics
The subgenus Stegomyia is characterized by the following combination of characters: ADULT (both sexes). (1) Vertex with all broad, flat decumbent scales, erect forked scales not numerous, restricted to occiput; (2) male maxillary palpi not very short, more than 0.5 length of proboscis, 5­segmented, segment 4, 5 subequal, slender and with only a few short setae, total length of apical 2 segments not very short, at least 0.4 length of the remaining segments; in female about 0.14–0.32 length of proboscis, 3­ or sometimes 4­ segmented, when present segment 4 minute; (3) maxillary palpi with white scales; (4) acrostichal setae absent; (5) prespiracular setae absent; (6) postspiracular setae present; (7) postprocoxal membrane without scales; (8) scutum with all, or mainly narrow scales; (9) scutellum with broad scales on all lobes; (10) mesopostnotum bare; (11) wing with plume scales narrow; (12) hindtarsus with basal white band at least on one tarsomere. Male Genitalia. (13) Aedeagus strongly toothed; (14) claspette well developed, with numerous setae; (15) gonostylar claw present. Female Genitalia. (16) Insula longer than broad, with minute setae and with 2–10 larger setae on apical 0.25–0.50; (17) cerci short and broad; (18) 3 spermathecae, one larger than the other 2. PUPA. Subgeneric characters not evident. LARVA. (19) Head seta 4­C well developed, branched, closer to 6­C than 5­C, cephalad and mesad of 6­C; (20) 4, 6­C cephalad of antennal base; (21) 6­C cephalad of 5, 7­C; (22) seta 12­I not developed; (23) seta 2­VIII distant from 1­VIII; (24) comb scales in a single row; (25) ventral brush (4­X) with 4, 5 pairs of setae on grid; (26) without precratal tufts. This combination of characters differs from other subgenera of Aedes.
Systematics
Edwards (1932) divided the subgenus Stegomyia into four groups, which he designated as A, B, C and D. In "Group A (aegypti group)" he included 18 species from Africa (except for Ae. aegypti). Edwards assigned Aedes chemulpoensis Yamada and Ae. mascarensis MacGregor to Group B (w­albus group). Mattingly (1953) transferred Ae. chemulpoensis and Ae. mascarensis from Group B to Group A (aegypti group). Huang (1974c) redescribed the type­specimens of Ae. chemulpoensis and designated a lectotype for this species and also confirmed the assignment of Ae. chemulpoensis to Group A (aegypti group). Aedes amaltheus was described by de Meillon and Lavoipierre (1944) from Livingstone, Zambia (as Northern Rhodesia). Mattingly (1952, 1953) noted difficulty of fitting this species into Edwards' (1932) system of grouping. Later, Mattingly (1965) began a revision of the main groups of the subgenus Stegomyia as defined by Edwards (1932) and summarized the characteristic of the species groups (A, B and D) and subgroups. He recognized three subgroups in Group B (w­albus group) and assigned Ae. amaltheus to his subgroup B3 (Ae. amaltheus subgroup). Huang (1974a) transferred Ae. amaltheus from Group B (Mattingly's Ae. amaltheus subgroup) to Group A (aegypti group) on the basis of a critical examination of this species (male and female) and comparison with other members of Groups A, B and C.
Mattingly (1965) subdivided Group A into three subgroups known as Subgroups A1 (Ae. aegypti subgroup), A2 (Ae. africanus subgroup) and A3 (Ae. chemulpoensis subgroup). In "Subgroup A1 (Ae. aegypti subgroup)," he included 28 species from the Mascarenes and Africa (except for Ae. aegypti). Aedes pseudonigeria (Theobald) was assigned by Mattingly (1965: 22) to his Subgroup A1. In "Subgroup A3 (Ae. chemulpoensis subgroup)" he included only one species, Ae. chemulpoensis from Korea and N.E. China. Huang (1988b) removed Ae. pseudonigeria from Mattingly's Subgroup A1 and defined a new group (pseudonigeria group) for it and three related species. Ae des chemulpoensis from Mattingly's Subgroup A3 was assigned by Huang (1988b: 4) to the pseudonigeria group. Huang (1990) defined the africanus group, which is practically the same complex of species as Mattingly's Subgroup A2 (Ae. africanus subgroup). Huang (1997) removed Ae. dendrophilus Edwards from Mattingly's Subgroup A1 and defined a new group (dendrophilus group) for it and 13 related species. Ae des amaltheus was assigned by Huang (1997: 7) to the dendrophilus group.
The remaining species in Mattingly's Subgroup A1 (Ae. aegypti subgroup) can be further divided into five species groups, the aegypti, apicoargenteus, metallicus, poweri and simpsoni groups. These eight groups in the present paper comprise Mattingly's Subgroup A1, Subgroup A2 and Subgroup A3.
Edwards (1932), in his “Group C (scutellaris group),” included 10 species from the Oriental and Australasian Regions, Crete and Africa. Huang (1972c) redefined Group C (scutellaris group) and subdivided the scutellaris group into two subgroups, the albopictus subgroup and the scutellaris subgroup. (1) The albopictus subgroup is characterized by having the supraalar white line incomplete, not clearly defined and with only narrow scales over the wing root. (2) The scutellaris subgroup is characterized by having the supraalar white line complete and well developed, with broad flat scales over the wing root and toward scutellum. Aedes albopictus was assigned by Huang (1972c: 4) to the albopictus subgroup. Aedes galloisi Yamada was originally assigned to Group C (scutellaris group), by Edwards (1932). Mattingly (1965) transferred it from Group C. to Group B. Huang (1972a) redescribed the type­specimens of Ae. galloisi and designated a lectotype for this species. Based on the great similarity to members of the scutellaris group, Huang (1972a) transferred Ae. galloisi back to the scutellaris group and placed it in the albopictus subgroup. Aedes granti (Theobald) and Ae. unilineatus (Theobald) were assigned by Edwards to his Group C (scutellaris group).
In the following treatment I recognize three species groups from the Afrotropical Region: (1) the granti group is erected for the nominate species, Ae granti (Theobald) 1901d, from Socotra, (2) the scutellaris group is represented by the recently introduced Ae. albopictus, and (3) the unilineatus group is erected for the nominate species, Ae. unilineatus (Theobald) 1906, from Sudan.
The 59 species and subspecies of the African Stegomyia can be further divided into two sections, A and B. (1) Section A is characterized by having the scutum with a distinct patch of broader crescent­shaped white or yellow scales on the fossal area. It is represented by eight species groups, the aegypti, africanus, apicoargenteus, dendrophilus, metallicus, poweri, pseudonigeria and simpsoni groups. Included also in the aegypti group is one Malagasy species, Ae. mascarensis from Mauritius. In addition, one Palearctic species, Ae. chemulpoensis from Korea, and N.E. China, is included in the pseudonigeria group. These two species are not found in the Afrotropical Region and are treated here for comparison. There is one species, Ae. vinsoni Mattingly, also from Mauritius, that is not treated here, awaiting more adequate material for study. (2) Section B is characterized by having the scutum with a long, median longitudinal white stripe of narrow scales extending from anterior margin to about the level of wing root. It is represented by three species groups, the granti, scutellaris and unilineatus groups. Thus, the African Stegomyia now consists of 11 species groups. These 11 groups with their constituent subgroups, 59 species and subspecies are listed in Table 1.
MacGregor (1924: 409) described Aedes (Stegomyia) mascarensis from Mauritius. Edwards (1932) assigned Ae. mascarensis to his Group B (w­albus group), and Mattingly (1953) transferred it from Group B to Group A (aegypti group). After a critical examination of this species, I agree with Mattingly's (1953) assignment of Ae. mascarensis to the aegypti group. The adult of Ae. mascarensis differs from all the members of the aegypti group by the absence of white knee­spot on all femora. This same character state of Ae. mascarensis is extremely similar to all the species of the africanus group. However, Ae. mascarensis can be distinguished from all the species in the africanus group by the diagnostic characters given in the key. The male genitalia of Ae. mascarensis are extremely similar to those of Ae. aegypti in having the apical margin of tergum IX with the middle part deeply concave, with large conical lateral lobes, each with a few very short setae at the tip. However, Ae. mascarensis can be distinguished from those of Ae. aegypti by the gonostylus, which is not swollen in the middle and strongly elbowed at about apical 0.35 (see Fig. 48 C). In Ae. aegypti, the gonostylus is somewhat swollen in the middle, with the apical 0.28 rather narrow and curved (see Fig. 35A).
Evans (1925: 121) described Aedes (Stegomyia) blacklocki from Daru, Sierra Leone. Stegomyia fraseri was originally described by Edwards (1912: 11) from a single female from Mpumu Forest, Uganda. Later, Edwards (1917: 210) reported "Since then a good series including both sexes has been received by the Imperial Bureau of Entomology from Southern Nigeria; unfortunately the names of the locality and collector have been lost. These specimens agree perfectly with the type female." Edwards (1941: 139) considered Aedes (Stegomyia) fraseri (Edwards) as a single species and synonymized Ae. blacklocki with Ae. fraseri.
A careful study of Evans' type­specimens of blacklocki, Edwards' type­specimen of fraseri, and other available material indicates that Ae. blacklocki Evans is a distinct species. Thus, Ae. blacklocki is removed from synonymy with Ae. fraseri and is restored to specific status. The adult male and female of Ae. blacklocki are very similar to those of Ae. fraseri but can be easily distinguished from Ae. fraseri as follows: hindfemur with anterobasal 0.20–0.25 white and with a large white spot 0.60–0.64 from base (white spot not connected with the basal white area). In Ae. fraseri, the hindfemur has a broad, white, anterior stripe on the basal 0.50–0.53.
The male genitalia of Ae. blacklocki are extremely similar to those of Ae. fraseri in having the claspette with distal expanded portion square in dorsal aspect (apicomesal angle formed a narrow thumb­like projection, with a 90° basolateral angle), with numerous simple setae on the expanded distal portion and bearing 3–4 setae on the apicomesal angle. However, Ae. blackloci can be distinguished from those of Ae. fraseri by the gonostylar claw, which is rather short and stout. In Ae. fraseri, the gonostylar claw is long and slender (see Figs. 38 B and 38A). Aedes blacklocki is most similar to Ae. fraseri, and I consider Ae. blacklocki to be the sister species of Ae. fraseri.
Aedes (Stegomyia) denderensis Wolfs (1949: 190) was originally described as a var. of Aedes (Stegomyia) apicoargenteus (Theobald) from Dender, Costermansville, DEMO­ CRATIC REPUBLIC OF THE CONGO (Zaire). Mattingly (1952, 1953) stated that the larva of Ae. denderensis differs from Ae. apicoargenteus in having an entirely dark siphon. Mattingly (1953: 13) treated Ae. denderensis as a subspecies. However, it is clearly a distinct species. The adult male and female of Ae. denderensis are very similar to those of Ae. apicoargenteus in having the scutellum with broad white scales on midlobe and with broad, dark scales on lateral lobes. This species can be distinguished easily from Ae. apicoargenteus as follows: hindtarsomere 5 with basal 0.33 white to all white on dorsal surface. In Ae. apicoargenteus, the hindtarsomere 5 is all dark. Based on discovery that the male genitalia of Ae. denderensis differ from other species in the apicoargenteus group, I have accorded it specific status. The differences are: claspette with distal, expanded portion square in dorsal aspect, apicomesal angle forming a broad thumb­like projection, and basolateral corner rounded, expanded distal portion bearing numerous simple setae and apicomesal angle with 8–9 setae (see Fig. 37 A).
Edwards (1932) originally assigned Aedes granti to his Group C (scutellaris group). Knight and Hurlbut (1949) subdivided the scutellaris group into three subgroups known as Subgroup I. scutellaris s. str., Subgroup II. albopictus and Subgroup III. mediopunctatus, and placed Ae. granti in Group C, Subgroup II. (albopictus subgroup). Mattingly (1953: 17) considered Ae. granti to be clearly the scutellaris subgroup, which it resembles in pleural markings. The taxonomic position of Ae. granti has been further discussed by Marks (1954: 353). Marks (1954: 353, 382) considered Ae. granti by itself as a separate subgroup of Group C (scutellaris group). Mattingly and Knight (1956: 100) stated that Ae. granti "... is intermediate in its characters between the Aedes scutellaris Walker and Aedes albopictus Skuse groups of Stegomyia."
A careful study of Theobald's type­specimen of Stegomyia granti from Dahamish, Sokotra, Leeson's specimens of Aedes (Stegomyia) granti (Theobald) from Mouri, Socotra, and other available material indicates that Ae. granti is clearly a remarkable species. It differs from all the members of the scutellaris group (the albopictus subgroup and the scutellaris subgroup) in markings of proboscis, female maxillary palpus, legs, scutellum (see Figs. 5 B,D and Figs. 7 B,C) and wings (costa with white line on basal 0.5–0.6). Based on the discovery that the male genitalia of Ae. granti are differentiated from all other species in the scutellaris group by the claspette, which has the distal elevated portion long and narrow in dorsal aspect, with numerous simple setae on the elevated distal portion and bearing no widened specialized setae, and by the gonostylar claw which is long and slender (see Fig. 49 A), I have here placed Ae. granti in a distinct monotypic species group, the granti group (Aedes granti (Theobald)).
The larva of Ae. granti is very similar to those of all members of the scutellaris group, in having the comb scales in a single row and not arising from a sclerotized plate, but can be distinguished from those of the scutellaris group by the basal spine of meso­ and metapleural setal groups which is strong and bluntly pointed. In this respect it resembles Ae. desmotes (Giles) of the desmotes subgroup, the w­albus group. However, Ae. granti can be distinguished easily from that of Ae. desmotes by the comb of 9–12 scales in a row, without a sclerotized plate (Leeson and Theodor 1948: 226, 227, Fig.4). In Ae. desmotes, comb of 3–5 scales in a row, which is arising from a sclerotized plate (see Huang 1977a: 26, 28, Fig.15 C).
The granti group shows the strongest affinities with the scutellaris subgroup of the scutellaris group but can be distinguished easily from the latter by the diagnostic characters given in the key.
Aedes unilineatus was assigned by Edwards (1932) to his Group C (scutellaris group). As noted above, Knight and Hurlbut (1949) subdivided the scutellaris group into three subgroups and provisionally placed Ae. unilineatus in Group C, Subgroup II. (albopictus subgroup). Examination of type­specimen of Quasistegomyia unilineatus Theobald from Bahr­el­Ghazal, Sudan, type­specimen of Stegomyia gebeleinensis Theobald from Gebelein, Sudan and other available specimens of Aedes (Stegomyia) unilineatus (Theobald) from Erkowit, Sudan, Malawi (Nyasaland), South Africa and Cote d’Ivoire (Ivory Coast), and comparison with other members of the albopictus subgroup shows that Ae. unilineatus is a remarkable species. The adult is very similar to Ae. albopictus, Ae. seatoi Huang and Ae. galloisi in having the scutum with a patch of broad flat white scales on the lateral margin just before the level of the wing root. It differs from Ae. albopictus and Ae. seatoi in pleural scaling, and in particular in the presence of broad white scales on the hypostigmal, postspiracular and metameron areas. In this respect it resembles Ae. galloisi. However, Ae. unilineatus can be distinguished easily from all other species in the albopictus subgroup by the midfemur with a large, white spot on anterior surface (see Figs. 6 B,C). Based on the discovery that the male genitalia of Ae. unilineatus are differentiated from all other species in the scutellaris group (the albopictus subgroup and the scutellaris subgroup) by the claspette, which is long, slender, with numerous simple setae and several stouter widened setae on distal part, with a small median mesally directed projection bearing one large seta and with 3–4 smaller setae near to it, and by the gonostylar claw which is long and slender (see Fig. 49 B), I have here placed Ae. unilineatus in a distinct monotypic species group, the unilineatus group (Aedes unilineatus (Theobald)).
The larva of Ae. unilineatus is extremely similar to those of Ae. gardnerii gardnerii (Ludlow), Ae. gardnerii imitator (Leicester) of the w­albus subgroup, the w­albus group, in having the similar shape of the comb scale (with very small and inconspicuous basal denticles), the ventral brush (4­X) with 4 pairs of unbranched setae, and the basal spine of meso­ and metapleural setal groups small and straight, but can be distinguished from those of Ae. g. gardnerii, g. imitator by the anal segment with complete saddle (Hopkins 1952: 158). In Ae. g. gardnerii, saddle is incomplete (see Huang 1977a: 48, 52, Fig. 30 C). (The larva of Ae. g. gardnerii is indistinguishable from that of Ae. g. imitator). The larva of Ae. unilineatus is also extremely similar to that of Ae. albopictus, but can be distinguished from that of Ae. albopictus by having 4d­X which is single, very small, much smaller than 4a, b, c­X and without bars, whereas in Ae. albopictus 4d­X is well developed, single and with bars (see Huang 1972c: 14, Fig.3 C).
The unilineatus group shows the strongest affinities with the albopictus subgroup of the scutellaris group but can be distinguished easily from the latter by the presence of a large, white spot on anterior surface of the midfemur.
Savage et al. (1992: 101) reported that “Eggs of Aedes albopictus were collected in oviposition cups from 3 forested areas of Delta State in south­central Nigeria during September 1991 as part of a post­yellow fever outbreak investigation. These eggs were shipped to the Centers for Disease Control in Colorado, where they were reared to the adult stage and identified. This is the first record of breeding populations of Ae. albopictus in continental Africa.” Eleven adults (6 M, 5 F) and six male genitalia slides are in the mosquito collection of the USNM. The identity of Nigeria specimens with Ae. albopictus (Skuse) from the Oriental Region are confirmed (see Fig. 35B).
A new species, Aedes ealaensis, from Eala, Democratic Republic of the Congo (Zaire), is recognized. The collection of Ae. denderensis and Ae. ealaensis from the same area, Eala, Democratic Republic of the Congo (Zaire), suggests that the two species are specifically distinct. Aedes ealaensis combines some of the features of Ae. denderensis and Ae. apicoargenteus. Difference between the adults of Ae. ealaensis and Ae. denderensis, and the adults of Ae. ealaensis and Ae. apicoargenteus, are slight but apparently constant. These species form a complex of closely related and very similar mosquitoes within the apicoargenteus group.
Two new species: Aedes ethiopiensis, from Ethiopia, and Aedes mpusiensis, from Mont Mpuse, Democratic Republic of the Congo (Zaire), are recognized. There are two other members of the poweri group: Aedes angustus Edwards, from SW. Uganda, and Aedes usambara Mattingly, from Amani, Tanzania (Tanganyika). All these species share the following derived characters: (1) posterior dorsocentral pale yellow line of narrow scales present, reaching forward to fuse with the fossal white or pale yellow patch; (2) scutellum with broad white or pale yellow scales on all lobes; (3) midfemur with a large, white spot on anterior surface; (4) hindtibia with a white stripe on ventral surface in basal area; (5) hindtarsomere 4 almost all white to all white and (6) hindtarsomere 5 all white on dorsal surface. These species form a small group of closely related and very similar mosquitoes within the poweri group.
A new species, Aedes hogsbackensis, from Hogsback, Cape Province, South Africa, is recognized. The collection of Ae. poweri (Theobald) and Ae. hogsbackensis from the same areas, Drakensberg, Natal and Kologha Forest, Cape Province, South Africa, suggests that the two species are specifically distinct. The new species, Ae. hogsbackensis, is most similar to Ae. poweri, and I consider Ae. hogsbackensis to be the sister species of Ae. poweri.
In addition, two new species: Aedes gandaensis, from Ganda, Coast Region of Kenya, and Aedes sampi, from Mataara (Matahara), Central Region of Kenya, are recognized. The new species, Ae. gandaensis, is most similar to Ae. woodi Edwards, and I consider Ae. gandaensis to be the sister species of Ae. woodi.
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TABLE 1 (continued)
*** Species which does not occur in the Afrotropical Region.
In the identification of the species of the subgenus Stegomyia, the adult stages appear to be more useful than the immature stages. However, it must be remembered that specific differences between the members of this subgenus tend to be very slight. Some members are highly variable in both adult ornamentation and in the immature stages. Although males of all species can be recognized on the basis of morphological features, females and immatures are extremely difficult or impossible to distinguish in many instances. The male genitalia of all species are distinct and the most diagnostic feature is the claspette of the gonocoxite. In dealing with this structure, special preparations must be made and care taken to study both lateral and mesal views of the dissected claspette as well as undissected aspects.
Affinity
The subgenus Stegomyia possesses some rather important basic characters in common with the subgenera Aedimorphus Theobald, Albuginosus Reinert, Diceromyia Theobald and Pseudarmigeres Stone and Knight of the genus Aedes in the Afrotropical Region: male maxillary palpus 5­segmented, aedeagus with conspicuous teeth, claspette developed, female insula longer than broad, larval seta 12­I not developed, and pecten teeth present. These shared characters indicate the affinity of Stegomyia to these four subgenera. Of these four subgenera, Stegomyia shares more important characters in both adult and immature stages with Diceromyia than with any other subgenus, suggesting the strongest affinities with that subgenus. However, it differs from Diceromyia in the development of the male maxillary palpus and in the position of seta 4­C of the larva. The male maxillary palpus of Stegomyia has the total length of the apical two segments not very short, at least 0.4 the length of the remaining segments, while in Diceromyia the total length of the apical two segments is very short, at most 0.3 the length of the remaining segments, or segment 5 is much shorter than segment 4. The larva of Stegomyia has seta 4­C cephalomesad of 6­C while in Diceromyia, seta 4­C is caudomesad of 6­C.
description: Published as part of Yiau-Min Huang, 2004, The subgenus Stegomyia of Aedes in the Afrotropical Region with keys to the species (Diptera: Culicidae), pp. 1-120 in Zootaxa 700 on pages 6-15, DOI: 10.5281/zenodo.166051