Aedes (Mucidus) aurantius (Theobald)

Harbach, Ralph E. & Wilkerson, Richard C., 2023, The insupportable validity of mosquito subspecies (Diptera: Culicidae) and their exclusion from culicid classification, Zootaxa 5303 (1), pp. 1-184 : 24-26

Aedes (Mucidus) aurantius (Theobald)

subspecies aurantius ( Theobald, 1907) —original combination: Pardomyia aurantia . Distribution: Australia (Queensland), Indonesia (Western New Guinea [formerly Irian Jaya]), Malaysia, Papua New Guinea ( Lee et al. 1984).

subspecies chrysogaster ( Taylor, 1927) —original combination: Mucidus chrysogaster (subspecific status by Knight et al. 1944).

Distribution: Australia, Irian Jaya [Western Papua New Guinea, Indonesia], Papua New Guinea ( Lee et al. 1984).

The two nominal taxa are members of Aedes subgenus Mucidus , Group B Pardomyia ( Edwards 1932a; Tyson 1970; subgenus Pardomyia of Reinert et al. 2004), which also includes Ae. quadripunctis (Ludlow, 1910) (in Theobald 1910) ( Philippines) and Ae. nigrescens (Edwards, 1929) (in Paine & Edwards 1929) (= painei Knight, 1948) ( Papua New Guinea, Solomon Islands). Species in the Pardomyia Group share some variable characters, which have led researchers to relate them to the nominotypical species. Aedes quadripunctis was considered a subspecies of aurantius by Basio (1971) and later returned to species status by Tsukamoto et al. (1985), and Ae. nigrescens was originally described as a variety of Pardomyia aurantia but elevated to species (as painei) by Knight & Hull (1951).

The nominotypical subspecies was described from an unknown number of adult females collected in the city of Kuching, Sarawak, Malaysia (Island of Borneo). Type specimens are in the Natural History Museum, London ( Townsend 1990). Characters given in the original description of aurantius have been used in keys and/or descriptions ( Knight et al. 1944; Knight 1947; Mattingly 1961; Tyson 1970; Lee et al. 1984), as indicated in the following extract from the original description ( Theobald 1907).

♀. Head pale brown, densely clothed with bright golden yellow narrow-curved scales, particularly dense around the borders of the eyes, numerous rich ochraceous to golden yellow long upright forked scales, becoming a little darker at the sides... the whole head presents a general golden yellow appearance.

Thorax bright brown, with a prominent band of brilliant golden yellow narrow-curved scales running across it behind the head [the extent of this band is not noted], the remainder clothed with deep black narrow-curved scales of almost sooty appearance....

Abdomen golden brown, the two basal segments [terga] clothed with almost entirely deep violet black scales, the third with some median spots of bright golden yellow scales, the remainder having gradually more golden yellow scales mixed with the violet black until the segments [terga] become brilliant metallic golden yellow; venter mostly golden yellow....

…femora and tibiae spotted with rich golden and violet-black… in the hind legs the base of the first tarsal [tarsomere 2], second tarsal, and to some extent the third tarsal, with a narrow yellow band, most pronounced on the first tarsal, the last hind tarsal pure white [hindtarsomere 5 not noted].…

Theobald also noted that “It varies to some extent in regard to the amount of golden scales on the abdomen and the spotting of the legs.”

Subspecies chrysogaster was described from Berner Creek, near Innisfail, in northeastern Queensland, Australia, just south of Cairns. A female holotype and a female paratype served for the description. Illustrations were promised for a future publication but we are not aware of it having been done. The types are in the School of Public Health and Tropical Medicine, University of Sydney, Sydney, New South Wales, Australia. The following characters from Taylor (1927) roughly parallel characters given above for the female of aurantius .

♀. Head covered with golden narrow-curved and dark upright forked scales, the latter very numerous; a dense median row of sickle-shaped golden ones in the middle; the narrow-curved golden scales round the eyes are very prominent, widening out laterally... palpi about one-quarter the length of the proboscis, densely covered with golden scales, except about the apical quarter, which is clothed with black scales... proboscis covered with golden scales with irregular patches of black ones.... Antennae with basal lobes pale testaceous, with a few small flat golden scales on inner surface.... Thorax: scutum chocolate-coloured, covered with mixed golden and chocolate-brown, narrow-curved scales; there is a moderately broad median transverse band of golden scales reaching right across the scutum, reaching this but not passing it is a broad (about a quarter the width of the scutum) stripe of golden scales; the golden scales are very pronounced on the anterior margin of the scutum... prothoracic lobes prominent, black, clothed with golden narrow-curved scales… pleurae blackish brown, with pale golden flat scales in the middle.... Abdomen: first segment dark chocolate-brown covered with black flat scales… also a narrow, median, basal patch of pale golden, loosely applied, flat scales... segments 2 to 4, inclusive... each with two small, submedian, basal, golden spots and golden, median, lateral patches, largest on the fourth; third segment with a small subapical, golden spot toward the edge on either side; fourth flecked with scattered golden scales; segments 5 to the apex black-scaled, profusely mottled with golden scales... venter clothed with golden scales except the apex, which is dark-scaled. Legs: femora of fore legs... heavily spotted with golden scales, with a basal golden band, knees golden; tibiae... profusely spotted with golden scales, apex golden; first tarsal joint with basal golden banding, apex narrowly golden, remainder mottled black and golden; second to fourth joints black-scaled with moderately broad basal banding, fifth golden with a few scattered dark scales; femora, tibiae and tarsi of mid legs similar to those of the fore legs... the fifth tarsals are entirely golden; femora and tibiae of hind legs similar to those of the fore and mid legs; first tarsals black-scaled, not mottled, with a basal golden band, second tarsal black with basal golden banding, third and fourth tarsals black with creamy-white basal banding, fifth tarsal creamy-white....

Except for the adult females there are no comprehensive comparisons of the other life stages of the two nominal taxa. Edwards & Given (1928) partially described and illustrated the pupal and larval stages of aurantius (as Pardomyia aurantia ) from Singapore. They noted a long pupal trumpet and rounded paddles lacking fringe; and a larva with mostly single setae and mandibles (illustrated) modified for grasping prey. In contradiction, in a key, Tyson (1970) wrote: “Paddle [of aurantius ] with the lateral margin densely and conspicuously spiculate.” Penn (1949) published a description and illustration of the pupa of subspecies chrysogaster , but apparently did not have specimens of subspecies aurantius , and did not find sufficient characters in Edwards & Given (1928) to contrast the two subspecies. Mattingly (1970) described the eggs of subspecies aurantius from Selangor, Malaysia, but we are not aware of a description of the eggs of subspecies chrysogaster .

Tyson (1970) separated the two nominal taxa by geographic area: chrysogaster in the Australasian Region and aurantius in the Oriental Region. He provided a key for separating females of aurantius , chrysogaster and painei (= nigrescens), but stated in a footnote that the males of the aurantius complex (these three nominal taxa) are “indistinguishable.”

Without comment, Knight et al. (1944) included chrysogaster as a subspecies of aurantius in a key to Aedes in the Australasian Region. They used the following characters to separate aurantius chrysogaster from aurantius nigrescens and aurantius aurantius :

chrysogaster —“Tarsal segments [tarsomeres] basally banded with golden scales (V of mid legs all golden), segments III and IV of hind legs with white basal bands, segment V of hind legs entirely creamy-white; abdominal segment I with narrow median patch of golden scales”.

aurantius and nigrescens —“Tarsal segments of fore and mid legs unbanded, brown, segments I, II and often III of hind legs basally yellow banded, segment V entirely white” Characters to distinguish aurantius from nigrescens included: “Abdominal tergites [terga] I and II almost entirely black, III with some median spots of golden scales, IV to VII with gradually more golden scales until the last segments are brilliant golden”.

Oddly, the key character of a basal white band on tarsomere IV of the hindleg of chrysogaster is not mentioned for aurantius .

Knight (1948) wrote a note about his efforts to corroborate the distinctness of subspecies chrysogaster : “Personal communications from Dr. W. V. King... and Mr. D. J. Lee ... both of whom have examined the types, have disclosed that this subspecies (at least the type specimens) differs from either [both?] aurantius aurantius (Theobald) or [and?] a. painei Knight [= nigrescens] in possessing a narrow basal white band on the fourth hind tarsal segment [hindtarsomere 4]. Also, Mr. Lee reported that the scutal scaling of the holotype is strictly as described by Taylor, but that the differentiation of the pattern in the paratype is less obvious.”

Mattingly (1961), in his treatment of Indomalayan Aedes , including the subgenus Mucidus , redescribed all stages of subspecies aurantius using specimens from throughout its range, and for females he noted: “Scutum covered mainly with narrow, dark brown scales, golden scales confined to anterior border and shoulders [this is also as later described and illustrated by Tyson 1970]…. Hind tarsus with first two segments pale at base, 3rd and 4th narrowly pale at base or entirely dark, 5th conspicuously pale, contrasting sharply with the dark apex of the 4th segment.” And in the key to females: “Abdomen with tergites [terga] IV‒VII largely or wholly golden scaled”. He did not discuss or describe chrysogaster except to contrast it with aurantius in a key to females: “Scutum with more numerous golden scales; fourth hind tarsal with narrow basal white band”. He did not compare subspecies chrysogaster to other life stages of aurantius .

Lee et al. (1984) distinguished adult females of the two nominal forms in a key (reformatted here to conform to journal style).

2(1) Scutum dark scaled [sharply] contrasting with prominent transverse area of narrow yellow scales on anterior margin and with a few yellow scales around prescutellar area, above wing root and (rarely) behind fossa; ppn [postpronotum] with narrow yellow scales on upper one third to one half...... aurantius aurantius

Scutum with more extensive yellow and/or golden-reflecting scaling; anterior yellow scaled margin not sharply contrasting...................................................................3

3(2) Ppn [postpronotum] with narrow yellow scales on upper one quarter to one half; scutum with yellow scaling variable but usually including a more or less distinct transverse band at mid length.................................................................................... aurantius chrysogaster

Ppn with small patch of narrow yellow scales on upper one fifth; scutum dorsally with areas of golden-reflecting (rather than yellow) scales, not forming a band at mid length..................... painei

In the above key, the description of the pattern of golden ornamentation on the scutum of chrysogaster is rather vague: “yellow scaling variable but usually including a more or less distinct transverse band at mid length”. Taylor’s (1927) description (see above) is more detailed but since it lacks an illustration it is rather difficult to visualize, and does not seem to follow closely the characteristics of the holotype. In notes recorded by Stone and Knight for their 1977 catalog, we found an unpublished sketch of the holotype of chrysogaster , presumably drawn by Stone, which we interpret as follows: Anterior promontory with a pair of small chocolate-brown spots, annotated by the illustrator as “(bare?)”; scutal fossa with “chocolate brown scales”, outlined anteriorly, laterally and posteriorly with “prominent golden scales”; dorsocentral area golden-scaled, anterior dorsocentral area “largely golden with some chocolate brown intermingled” and the posterior dorsocentral area “mainly golden, some brown”; antealar and supraalar areas “golden”, antealar area bordered anteriorly by a bare dark brown line, presumably along the prescutal suture.

There are two distinct scutal patterns outlined above. The nominotypical form has an anterior golden band, and chrysogaster has a variously described broad transverse band. There are also apparent differences in characteristics of the legs and abdomen, which we do not consider here but which could be of significance in separating the two nominal taxa, or could be indicators of a species complex.

Lee et al. (1984) included distributional notes which we believe are based on identifications by E. N. Marks that indicate sympatry of the two nominal forms: “ Ae aurantius aurantius is known from Malaya , Indonesia and Borneo and in the Australasian Region has been recorded a number of times from West Irian and Papua and from 2 locations in Queensland ( Innisfail and Lockhart R. Mission); the type locality of Ae aurantius chrysogaster is Innisfail, Qd. and it has also been recorded from West Irian , New Guinea and Papua....”

In summary, 1) Knight et al. (1944) provided no justification for regarding chrysogaster as a subspecies of aurantius , which has since been unjustifiably followed by others; 2) we believe the divergent patterns of golden scutal scales alone are sufficient to distinguish species; 3) aurantius and chrysogaster are sympatric and identifiable with no apparent difficulty in the area of overlap. For these reasons, we hereby reinstate chrysogaster to its original species status: Aedes (Mucidus) chrysogaster ( Taylor, 1927) . Aedes chrysogaster is currently listed as a species in the Encyclopedia of Life.

Aedes aurantius has a single synonym: Ekrinomyia aureostriata Leicester (1908) from Klang, near Kuala Lumpur [Selangor], Malaya [ Malaysia], synonymy with aurantius by Edwards (1913b), who stated “In Dr. Leicester’s collection in the British Museum are 3 ♂ and 4 ♀ cotypes of E. aureostriata ; the females agree exactly with the type of P. aurantia .” Aedes (Muc.) chrysogaster is without synonyms.