Aedes (Ochlerotatus) fulvus (Wiedemann)

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 : 34-36

Aedes (Ochlerotatus) fulvus (Wiedemann)

subspecies fulvus ( Wiedemann, 1828) —original combination: Culex fulvus . Distribution: Argentina, Belize, Bolivia, Brazil, Colombia, Costa Rica, Cuba, Ecuador, French Guiana, Guatemala, Guyana, Mexico, Panama, Peru, Suriname, Trinidad and Tobago, Venezuela ( Wilkerson et al. 2021, South Korea listed in error).

subspecies pallens Ross, 1943 —original combination: Aedes (Ochlerotatus) fulvus pallens . Distribution: United States (continental) ( Wilkerson et al. 2021).

Distributions listed in Wilkerson et al. (2021) for fulvus sensu stricto from the continental United States and for pallens from Cuba and Mexico could not be documented and should be omitted.

The nominal forms are members of the Chrysoconops Group of Wilkerson et al. (2015) —genus Chrysoconops Goeldi, 1905 ; Group C, fulvus -group of Edwards (1932a); Ochlerotatus subgenus Chrysoconops of Reinert et al. (2008, 2009). In addition to the two nominal taxa, the group also includes bimaculatus ( Coquillett, 1902b) ; jorgi Carpintero & Leguizamón, 2000 ; pennai Antunes & Lane, 1938 ; and stigmaticus Edwards, 1922.

Wiedemann (1828) described the nominotypical subspecies from “ Brazil ”. The holotype female was seen by Belkin (1968) in the collection of the Senckenberg Naturmuseum Frankfurt, Germany. Belkin et al. (1971) later restricted the type locality to Salvador, Bahia, Brazil .

Goeldi (1905) described the egg of fulvus (as Taeniorhynchus fulvus ) from a female captured in Murutucú, near Belém, Brazil. He was, however, unable to rear immature stages for study. Goeldi provided a description of the adult from separate observations: “Among our mosquitoes it is one of the largest species. It is characterized, in addition to its distinct size, by the beautiful general yellow coloration, color of gold, that extends over all [body] parts, including a good part of the anterior margin of the wings, contrasting here on the wing with the distal margin having a dark spot, while the rest shines giving a beautiful iridescent effect. Also ostensibly distinctive are the dark middle articulations of all six pairs [sic] of legs, the tarsi, the tip of the proboscis and the tip of the palps [maxillary palpi]. The back of the thorax [scutum] and the posterior margins of the abdominal rings [bands] exhibit some areas of a slightly different tint, darker than the beautiful general golden yellow [translated from the Portuguese].”

In his description of subspecies pallens, Ross (1943) contrasted the subspecies with fulvus , and with the very similar Ae. bimaculatus . For reference, Ross included detailed illustrations of the male genitalia and larvae of fulvus pallens and bimaculatus . He wrote:“This paper presents evidence to show that two distinct species of Aedes occurring in the United States are both at present identified as Coquillett’s bimaculatus . The true bimaculatus , described from Brownsville, Texas, and ranging from central Texas to El Salvador, is very distinct from the ‘ bimaculatus ’ collected throughout the southeastern United States which is here described as a new subspecies of the Neotropical fulvus (Wiedemann) . Vargas’s rozeboomi, recently described from Campeche, Mexico, is shown to be a synonym of the true bimaculatus .” After describing the “true bimaculatus ”, Ross compared the species with fulvus as follows: “The male terminalia [genitalia] characters of bimaculatus are very distinctive and set the species well apart from fulvus [sensu lato]. The larval differences between bimaculatus and fulvus pallens , on the other hand, are relatively slight. Adults of both sexes of these species may be separated as follows: fulvus [sensu lato] has apical triangular areas of black scales on all abdominal tergites [terga], thoracic pleura with at least one black integumental spot ( fulvus pallens ) or two longitudinal black stripes ( fulvus fulvus ); bimaculatus , with scarcely any black scales on tergites except toward base of abdomen, thoracic pleura yellow—no integumental maculation”.

Before describing fulvus fulvus, Ross (1943) stated: “The writer has before him the fulvus material in the U. S. National Museum from many localities in Central and South America. Representatives from Panama [not Brazil] are described...”. The following are pertinent excerpts from his description of the male: “Thorax with mesonotal [scutal] integument lemon-yellow except for the subbasal spots [posterolateral spots]; each spot is transversely divided medially by a yellow area, the spots are brownish-black with blending margins.... Pleural integument lemon-yellow with two longitudinal brownish-black bands, one extending caudad from side of anterior promontory of mesonotum to prealar sclerite [prealar area], the lower band crossing middle of sternopleural sclerite [mesokatepisternum] and covering lower half of mesepimeron. ... Male terminalia [genitalia] without significant differences from that described later for fulvus pallens (fig. 1) [figure number from original].”

Following his description of “ fulvus pallens , new subspecies ”, Ross noted: “Because of the lack of apparent terminalia differences between the United States series and that from Panama, and because the more superficial characters such as color and vestiture are relatively slight, though constant, the United States series is placed as a subspecies of fulvus . Pallens can be separated at once from typical fulvus by the almost complete absence of pleural maculation of the thorax and by the greater development of the mesothoracic [posterolateral scutal] spots.”

We could not find any evidence of sympatry or intermediate forms of the two subspecies— pallens is found only in the southeastern United States and fulvus is distributed from southern Mexico and the Caribbean ( Cuba) to Brazil, but does not occur in the United States.

We disagree that lack of male genitalia differences is a reason to ignore significant diagnostic characters and quite disparate distributions. Because of these factors, we believe that fulvus and pallens are separate species. We therefore afford species status to Aedes (Ochlerotatus) pallens Ross, 1943 . Aedes pallens is currently listed as a species in the Encyclopedia of Life.

Aedes pallens has one synonym, Culex flavicosta Walker, 1856 . Edwards (1932a) was apparently the first to treat flavicosta as a synonym of fulvus . Alan Stone saw the type specimen, and in an unpublished taxonomic catalog research note (1955) he wrote: “British Museum: A ♀ type labeled Amaz. [Amazon] in BM, lacking head. The triangular apical areas of dark scales on the abdomen are scarcely visible, but it’s [sic] synonymy with fulvus [sic] is probably correct.” The holotype was also examined by Belkin et al. (1971) in the Natural History Museum, London, who, instead of “Amazon Region,” restricted the type locality to “Manaus (Amazonas)”. Townsend (1990) also examined the holotype and noted “head missing”, but he did not note that Belkin had restricted the type locality.

While it is clear to us that pallens should be accorded species status, variation can be found in adult characters of fulvus in Central and South America and the Caribbean. This variation, and the highly unlikely occurrence of any mosquito species naturally occurring in very different zoogeographic areas, make the existence of a species complex likely. In addition, we are not aware of studies of specimens from the generalized Amazonian type localities, nor the restricted type localities, of fulvus or the synonym flavicosta . A few examples of morphological variation follow.

Gutsevich & Garcia-Avila (1969) described Ae. fulvus from Cuba. Their description is not entirely clear but, in part: “The lateral surface of the thorax is also of two colors: upper half dark brown; lower half yellowish. A spot of broad silvery scales on the upper part of the sternopleuron [mesokatepisternum] and on the upper mesepimeron.... The specimens we have collected occupy an intermediate position between the southern and North American forms [between fulvus fulvus and fulvus pallens ] [translated from the Spanish].” The thoracic pleura being dark above and yellowish below has not been described for any other taxon related to fulvus . The broad silvery scales usually have not been emphasized but are of possible significance in the Chrysoconops Group. These scales were also noted by Carpenter & LaCasse (1955) for fulvus pallens and by Ross (1943) for fulvus fulvus .

Rodriquez-Martinez et al. (2020) documented the sympatry of bimaculatus and fulvus in southern Mexican states bordering the Gulf of Mexico and Guatemala. To identify fulvus : “I distinguish this species from the preceding [stigmaticus, which was shown by them not to occur in Mexico] by the dark bands of the pleura, by the gold-colored scales in the region of the subcosta, and by the initial dark apical part [of the wing] at the point where the subcosta ends on the costal vein [translated from the Spanish].” Martini (1935) also mentioned the apically dark wings of fulvus : “A series of example specimens from South America has, without exception, the characteristic of a dark spot at the end of the wings [translated from the Spanish].” We found wide variability in the descriptions of the extent of yellow scales and dark apical areas of the wings in this group of species. The division of the posterolateral dark scutal spots, a character used by Ross (1943) as characteristic of fulvus , is not mentioned by Rodriguez-Martinez et al. (2020), but an undivided dark scutal spot is clearly shown in a photograph (their fig. 1b). The dark pleural lines, also characteristic of fulvus according to Ross (1943), are present in a photograph of Rodriguez-Martinez et al. (2020: fig. 1d), but the authors of both publications only pointed out that there is a dark spot in the hypostigmal area, but did not discuss the two obvious dark pleural bands.

In keys to the mosquitoes of Guatemala ( Clark-Gil & Darsie 1983), the characters used to identify adult females of fulvus were “Scutal integument yellow with posterolateral dark marks” and “Thoracic pleuron with dark hypostigmal spot [not two dark bands]; abdominal terga yellow-scaled basally, dark-scaled apically.”