Culex (Culiciomyia) nebulosus Theobald, 1901

Cornel, Anthony John, Mayi, Marie Paul Audrey, Kowo, Cyril, Foncha, David, Andongma, Esack, Anong, Damian Nota, Elad, Mirabel, Djomo, Charlene, Tchuinkam, Timoleon, Brisco, Katherine K. & Sehgal, Ravinder, 2020, New species of Culex (Culiciomyia) (Diptera: Culicidae) from Talangaye Forest in Cameroon and descriptions and identification keys for males of the Afrotropical species of the subgenus, Zootaxa 4858 (4), pp. 451-506 : 485-490

Culex (Culiciomyia) nebulosus Theobald, 1901

Male. A small brown to greyish mosquito with no obvious distinguishing features. Integument of thoracic pleura generally not uniform in colour, with mesanepimeron, metepisternum and coxae whitish and antepronotum, proepisternum, postspiracular and subspiracular areas, mesokatepisternum and mesomeron light to dark brown. Scutal integument light brown. Wing 2.70 mm. Proboscis 1.87 mm. Forefemur 1.60 mm.

Head: Row of broad white decumbent scales along eye margin ( Fig. 25A,B,E ), pale narrow decumbent scales numerous on vertex ( Fig. 25A,B,E ), erect scales numerous, pale brown except for white to very light brown apices, broad white scales along eye margin tend to be more numerous towards sides of head and form a more distinct lateral patch ( Fig. 25A,E ). Maxillary palpus slightly longer than proboscis, palpomeres 4 and 5 bearing setae, palpomere 4 shorter than palpomere 5 (ratio 0.45–0.33), palpal comb scales described by Edwards (1941) as “the proximal part of this comb formed of scales shaped like spear-heads, the distal part of more close-set scales which are also broader and have fine recurved points” ( Fig. 25C ), 3 or 4 most basal of proximal set of 7 or 8 (rarely 9) with longer points, significant gap between proximal and distal sets, distal set with 9–10 scales more closely spaced, proximal scales often darker than distal set of scales ( Fig. 25C ); we prefer to describe distal scales as spatulate or oblanceolate with recurved fine points (aristate apices), proximal 3 or 4 scales of proximal set as lanceolate and other distal scales as narrowly ovate with aristate apices and cuneate bases. Antenna and proboscis similar to those of other Culiciomyia .

Thorax: Variation in colour of thoracic integument may be dependent on age of mosquito or environmental conditions, such as larval diet, habitat or perhaps degree of exposure to UV light. Scutal and pleural integument light brown (in most specimens) to greyish (in some) creates some confusion about general colouring of this species ( Fig. 25A,D ). Scutum covered with short brown to shiny translucent setae, narrow white scales on scutellar lobes. Colour of thoracic pleural integument highly variable and mostly non-uniform. Mesanepimeron, metepisternum and coxae whitish, integument of antepronotum, proepisternum, postspiracular and subspiracular areas, mesokatepisternum and mesomeron light to dark brown; middle region of metepisternum light brown in some specimens, which gives pleura a more uniform brown appearance, but in others pleura appear more greyish, thus more closely fitting Edwards (1941 “greyish mesonotum”); pleura devoid of scales except for small patch among setae on upper mesokatepisternum and occasionally a row along posterior margin of lower mesokatepisternum, scales absent on mesepimeron in majority of specimens but a few have 1 or 2 below mesepimeral seta; setae present in following regions: antepronotum, a row of 6 on posterior margin of postpronotum, 3 on proepisternum, prealar knob, all coxae, a few on upper and lower posterior margin of mesokatepisternum, and 1 in lower mesepimeral area. Capitellum of halter darker than pedicel.

Wings: Scales all dark.

Legs: Coloured similar to those of other Culiciomyia , except Cx. cambournaci .

Abdomen: Terga uniformly brown with paler small lateral spots in a few specimens; sterna light brown to beige.

Genitalia: Lobes of tergum IX each with 5–9 (mostly 6, rarely 9) setae along upper margin ( Fig. 27A ). Description below includes details that were not mentioned in Edwards (1941). Gonocoxites moderately broad with distinct patch of gold ventrolateral setae, mostly confined to middle 0.33 of gonocoxite, patch of 3 to 4 setae wide with each seta about 0.66 length of gonocoxite ( Fig. 26A,B ); dorsal surface of gonocoxite with few setae, each about same length as gonocoxite, distinct apical dorsal lobe bearing 4–7 setae (mostly 4), 3 rod-like setae (a–c) with 1 placed slightly more ventrally than other 2 and rod-like setae not necessarily as close together as described by Edwards (1941), with tip of seta a slightly shorter and sharper apically than b and c, b and c slightly hooked apically and b noticeably darker than a and c ( Fig. 26B ), a consistently short seta present below or next to a; 1 very broad slightly striated foliform seta (g) and shorter narrower foliform seta (f) half as broad as g; a stout striated seta (e) between bases of f and g slightly longer than f and g and 4 setae of which 2 (d 1 –d 2) longer and slightly broader than other 2. Gonostylus bent in middle with a large membranous flange dorsally, a single subapical seta and 1–5 (mostly 3 or 4) setae pre-dorsally positioned in proximity where gonostylus bends downwards ( Fig. 26A ), tip of gonostylus bent upwards into a hook and with a small broad foliform seta. Aedeagus broadened basally with distinct tooth at base of each lateral plate ( Fig. 27A,B ); from dorsal aspect lateral plate smooth and rounded apically, resembling what Edwards (1941) described as being “finger like processes”, however, from ventral and lateral aspects lateral plate clearly toothed along one margin and apex ends sharply, resembling the description provided for Cx. nebulosus by Hamon & Lambrecht (1959), who described the lateral plate as sharp and having strong lateral teeth. Paraproct with typical dense crown of spicules and 3 or 4 small subapical setae ( Fig. 27A ).

Additional notes: None of the Cx. nebulosus males from the Talangaye Forest have white scaling on the propleuron (proepisternum) and there was always only one lower mesepimeral (mesanepimeral) seta with no accompanying short setae, which precludes them from identification as Cx. pseudocinereus , which according to Edwards (1941) occurs more in eastern and southern Africa. Males of Cx. nebulosus , Cx. furlongi , Cx. cinereus , Cx. lanzaroi and Cx. muspratti have similar external features. The genitalia of Cx. cinereus are most easily distinguished from the genitalia of the other three species by the dense patch of delicate setae at the base of the subapical lobe, and Cx. cinereus also has no gap between the proximal and distal sets of palpal comb scales. Hamon & Lambrecht (1959) noted that the apices of the lateral plates of Cx. nebulosus are sharp whereas they are rounded in Cx. muspratti . In our opinion, the apices of the lateral plates of Cx. nebulosus appear rounded depending on the angle of the slide mount, we caution relying on using this feature to distinguish these two species. Culex nebulosus and Cx. muspratti have a strong basal tooth at the base of the lateral plate, whereas this is absent in Cx. furlongi . The only character that likely separates Cx. nebulosus from Cx. muspratti is the number of narrower accessory appendages on the subapical lobe of the gonocoxite, with three in Cx. muspratti and two in Cx. nebulosus . Van Someren (1954) reported the presence of three short “narrow leaflets (d–f), which sometimes appear as “stout setae”, but did not mention or figure them as having barbs. The most distal palpal comb scales in Cx. furlongi end in fine short straight points whereas in Cx. nebulosus , Cx. lanzaroi and Cx. muspratti they are longer, strongly recurved and shaped much like the top bill of a hawk’s beak. Flat scales on the upper mesokatepisternum and the scales on the mesepimeron are easily rubbed off, and when present, these scales are often translucent and can be easily overlooked. The larvae of Cx. muspratti and Cx. lanzaroi are unknown. The larva of Cx. nebulosus is quite different from the larvae of Cx. furlongi and Cx. cinereus ( Hopkins 1952; van Someren 1954). The only noticeable difference in the larvae of the latter two species is that the comb is composed of scales in Cx. cinereus and spine-like scales in Cx. furlongi ( van Someren 1954) .

Specimens examined: The following males were reared from egg rafts laid in bamboo pots. Field accession numbers CAM 47 e 1a 2/VII/2017 , CAM 47 e1b 2/VII/2016 , CAM 47 e1c 2/VII/2016 , CAM 60 c.2 16/VII/2016 , CAM 113 ca 7/ V/2017, CAM 113 cb 7/ V/2017, CAM 230 c 1a 10/XI/2017 , CAM 230 c1b 10/XI/2017 and CAM 230 c1c 10/ XI/2017 . One male examined was reared from a pupa collected in a rain-filled coconut husk lying on the ground. Field accession number CAM 196 f3 16/VII/2017 .The other males examined from the Talangaye Forest were collected by sweep netting through vegetation on the forest floor. Field accession numbers CAM 50 b.1 16/VII/2016 , CAM 50 c.2 16/VII/2016 , CAM 62 h 18/VII/2016 , CAM 62g 28/VII/2016 , CAM 62 d 29/VII/2016 , CAM 86 ra 9/ XI/2016 , CAM 132 ya 31/I/2017 , CAM 132 yb 31/I/2017 , CAM 132 yd 31/I/2017 , CAM 132 ye 31/I/2017 , CAM 132 yh 31/I/2017 , CAM 132 yi 31/I/2017 , CAM 132 yk 31/I/2017 , CAM 132 o1d 1/II/2017 , CAM 132 b 1a 2/II/2017 , CAM 132 b1b 2/II/2017 , CAM 132 ka 5/II/2017 , CAM 132 kd 5/II/2017 , CAM 132 ke 5/II/2017 , CAM 132kg 5/II 2017 , CAM 132 kh 5/II/2017 , CAM 132 kj 5/II/2017 , CAM 132 kk 5/II/2017 , CAM 132 oa 6/II/2017 , CAM 132 oc 6/II/2017 , CAM 132 oe 6/II/2017 , CAM 132 of 6/II/2017 , CAM 132 og 6/II/2017 , CAM 132 ga 7/II/2017 , CAM 132 gc 7/II/2017 , CAM 132 gf 7/II/2017 , CAM 132 gi 7/II/2017 , CAM 132 gk 7/II/2017 , CAM 163 f 27/IV/2017 , CAM 163 ca 28/IV/2017 , CAM 163 cb 28/IV/2017 , CAM 163 ia 1/ V/2017, CAM 163 ib 1/ V/2017, CAM 163 ga 2/ V/2017, CAM 163 gb 2/ V/2017, CAM 163 sb 2/ V/2017, CAM 163 sc 2/ V/2017, CAM 163 fb 5/ V/2017, CAM 163 la 10/ V/2017, CAM 163lb 10/V/2017, CAM 163 la 26/ V/2017, CAM 202 j 5/VII/2017 , CAM 202 fb 6/VII/2017 , CAM 202 la 8/VII/2017 , CAM 202lb 8/VII/2017 , CAM 202 na 9/VII/2017 , CAM 202 nb 9/VII/2017 , CAM 202 nc 9/VII/2017 , CAM 202 ne 9/VII/2017 , CAM 202 nf 9/VII/2017 , CAM 202ng 9/VII/2017 , CAM 202 ni 9/VII/2017 , CAM 202 sb 10/VII/2017 , CAM 202 rc 12/VII/2017 , CAM 202 rd 12/VII/2017 , CAM 202 re 12/VII/2017 , CAM 202 rf 12/VII/2017 , CAM 202 qb 13/VII/2017 , CAM 202 qd 13/VII/2017 , CAM 202 jb 14/VII/2017 , CAM 202 jc 14/ VII/2017 , CAM 202 jd 14/VII/2017 , CAM 202 je 14/VII/2017 , CAM 202 hb 16/VII/2017 , CAM 202 c 17/VII/2017 , CAM 202 tc 19/VII/2017 , CAM 202 o 20/VII/2017 and CAM 202 na 21/VII/2017 .

For comparative purposes, we also examined males in the collection of the National Health Laboratory Services Museum in Johannesburg , South Africa. These were from: (i) Gwaliweni Forest , Kwazulu Natal , South Africa. Cx. nebulosus — 1 male. Collected and identified by Jim Muspratt , 1957; (ii) Port Shepstone , Kwazulu Natal , South Africa. Cx. nebulosus — 1 male. Field accession number T154 . No other collection information on the label; (iii) Livingstone , Zambia. Cx. nebulosus var. pseudocinereus — 1 male. Collected in 1945. No other collection information on the label; (iv) Tete District , Kwazulu Natal , South Africa. Cx. nebulosus var. pseudocinereus — 1 male. Collected and identified by Jim Muspratt , 1955; (v) Skukuza, South Africa. Cx. nebulosus var. pseudocinereus — 1 male. Collected and identified by Leo Braack, 22/III/1991. Man-biting .

Other specimens previously collected by one of us ( AJC) in Cameroon were also examined. These were from: (i) Ikange, Cameroon (4.12000º N; 9.44944º E). Cx. nebulosus — 2 males. Collected and identified by AJC, 2011. Reared from a larva found in a collecting cup on the side of a rubber tree; field accession number CAM 12.32 .1 6/IX/2011 . Reared from larva in road-side pool; field accession number CAM 12.34 .1 8/IX/2011; (ii) Beau , Cameroon (4.15333° N; 9.25333° E). Cx. nebulosus — 2 males. Collected and identified by AJC, 2011. Reared from a larva found in a bucket of water; field accession number CAM 12.22 .1 3/IX/2011 . Reared from larva collected in a concrete water reservoir; field accession number CAM 12.37 b 10/IX/2011; (iii) Niete , Cameroon (2.72617º N; 10.07096º E). Cx. nebulosus — 1 male. Collected and identified by AJC, 2013. Reared from larval collection in a banana leaf axil; field accession number CAM 12.58 .16 6/IX/2013 .

Figures

FIGURE 25. External features of Culex nebulosus. (A, D) Dorsolateral views of the head and scutum; (B,E) dorsal views of the head; (C) lateral view of the palpal comb scales (100x).

FIGURE 26. Gonocoxite of Culex nebulosus. (A) Drawn depiction; (B) image (100x).

FIGURE 27. Lateral plate-aedeagal sclerite and paraproct of Culex nebulosus. (A) Drawn depiction; (B) image (400x).