Simulium (Pomeroyellum) santomi Mustapha, 2004

Mustapha, M., Jarvis, W. & Post, R. J., 2004, The Simuliidae (Diptera) of the Republic of São Tomé and Príncipe, including the description of a new species, African Invertebrates 45, pp. 143-156 : 146-149

Simulium (Pomeroyellum) santomi Mustapha sp. n.

( Figs 4–11 )

Etymology: The species name is derived from São Tomé, the island from which the species has been collected and described, and where it is probably endemic.

Below is a list of characters that distinguish this new species from S. alcocki , followed by a full description.

Larvae: Gothic arch­shaped postgenal cleft ( Fig. 9 ), presence of minute broad fanshaped thoracic setae and abdominal setae ( Fig. 11 ), presence of three or four secondary lobules on the rectal organ and presence of accessory sclerites.

Pupae: Eight pupal gill filaments aligned in mirror image to S. alcocki ( Fig. 4 ) and abdominal segment 4 with a pair of ventral spines ( Fig. 6 ).

Adults: Golden scales spread evenly over scutum of ơ and ^, male genitalia differences ( Figs 5, 8 and10 ) and sub­basal dark band on the female hind tibia absent ( Fig. 7 ).

Adult female.

General body colour silvery grey.

Head: Eye facets mostly silver but some black; frons greyish with golden scales; antennae brownish with basal segments paler; postcranial hairs golden.

Thorax: Grey when viewed with anterior or posterior light source; no apparent scutal pattern except evenly clothed with golden scales; pleural membrane and katipisternum pruinose silvery­grey with no scales; scutellum silvery­grey with golden scales and long black hairs; wing stem vein tufts dark; subcostal wing vein with hairs along proximal two­thirds; arculus medium brown; halteres with dark stem and beige to dark brown crown; legs all dark except the tibiae which are golden on the top half and the hind basitarsi which are golden on the top two­thirds, hind tibia ( Fig. 7 ) lacks sub­basal band present on female S. alcocki ; claw curved with well developed basal tooth.

Abdomen: Basal scale of short golden hairs; abdominal tergites black, shiny distally, dorsally covered in golden scales, distally mostly with dark hairs, laterally covered with golden scales on 2–5.

Terminalia: Eighth sternite lightly sclerotised, covered in minute setae with groups of about 30 long thin setae on each side; gonopophyses well developed, membranous and covered in minute setae; paraprocts conical; genital fork with thin base and thin lateral arms with well formed anterior processes; spermatheca oval with no apparent external sculpturing or internal hairs; area of insertion of spermathecal duct membranous.

Adult male.

General body colour black.

Head: Upper eye facets reddish brown; lower eye facets grey to black, golden hairs along line where upper facets abut; postcranial hairs golden; antenna brownish.

Thorax: Scutum silvery when viewed with anterior light source, velvety black with posterior light source, and with no apparent pattern except evenly distributed golden scales; scutellum dark with golden scales and dark hairs; pleural membrane pruinose silver, no scale patch; katepisternum prinose brownish; legs all dark except tibiae and hind basitarsi which are both golden on the top half; wings stem vein tufts dark; arculus medium brown; subcostal vein bare; halteres entirely dark.

Abdomen: Basal fringe of long golden hairs; background colour velvety black; silver patches laterally on segments 2, 5 and 6; short dark hairs all over abdomen.

Terminalia: Style slightly tapered and in opposite orientation on coxite ( Fig. 5 ) to that of S. alcocki ; ventral plate broad, trilobed at base and indented at top ( Fig. 8 ); median sclerite flat and strap­like and abruptly expanded apically ( Fig. 8 ); paramere with multiple hooks (approximately 4–6) ( Fig. 10 ).

Pupa.

Pupal length ventrally 1.90–2.60 mm (mean = 2.30, n =11). Gill length 2.05–2.50 mm (mean = 2.28, n =9). Cocoon length dorsally 2.00–2.70 mm (mean = 2.32, n =11).

Light brown slipper shaped cocoon with variable median anterior projection; cocoon slightly strengthened anteriorly and loosely woven with medium to large fibres; respiratory organ with 8 filaments, bifurcating from outside­in 2+((2+2)+2) ( Fig. 4 ); gill filaments long and delicate with tips easily broken off, the lengths between the branches off the main stalk are usually longer than S. alcocki ; cephalothorax with numerous dome­like tubercules and a few long single and bifid trichomes; abdomen dorsally with usual 4 hooks on each side of segments 3 and 4, whilst segments 7–9 each have a row of miniature spines; ventrally segment 4 with one hook on each side, segment 5 with pair of closely set hooks on each side and segments 6 and 7 with pair of more evenly set hooks on each side ( Fig. 6 ).

Larva.

Length laterally 3.10–3.90 mm (mean = 3.56, n =13).

Head: Head capsule creamy yellow with very faint pigmentation and a negative head pattern, length 0.46–0.58 mm (mean = 0.53, n = 6), width 0.41–0.46 mm (mean = 0.43, n = 6); cephalic fan with 25–33 rays; postgenal cleft large, shaped like gothic arch ( Fig. 9 ); ratio of postgenal cleft to postgenal bridge 2.0–2.4; hypostomium bearing 9 apical teeth with middle and corner teeth prominent; 4 hypostomial setae in each row parallel to margin of hypostomium; mandible as in S. alcocki .

Thorax: Speckled greenish­greyish; cuticle with minute broad fan­shaped setae and long single hairs; proleg circlet with about 27 rows of 2–6 hooks; pupal gill histoblast with 8 thin tightly coiled filaments.

Abdomen: Mottled greyish­brown dorsally, milky white ventro­apically; cuticle covered with minute fan­shaped setae and long single hairs ( Fig. 11 ); rectal organ with 3–4 thick secondary lobules on each lobe; ventral papillae pointed; anal sclerite present; accessory sclerites present; posterior circlet with 60–70 rows of 2–12 hooks.

Type material: SÃO TOMÉ ISLAND: Holotype ơ (pinned) with associated pinned pupal exuviae, abdomen and genitalia on slide, site 4, 10.x.1998, RJP ( BMNH) . Paratypes: 2 larvae, 1 pupa, site 3, 10.xi.1998, RJP ( BMNH) ; 1^ (pinned), 6 larvae, site 3, 10.xi.1998, RJP ( ST &P) ; 1ơ (slide), 3^ (slides), 10 larvae, site 4, 10.xi.1998. RJP ( BMNH) ; 1ơ (slide), 3^ (pinned), 3^ (slides), 19 larvae, site 4, 10.xi.1998, RJP ( ST &P) ; 20 larvae, site 5, 10.xi.1998, RJP ( BMNH) ; 45 larvae, 3 pupae, site 5, 10.xi.1998, RJP ( ST &P) ; 3 larvae, site 7, 12.xi.1998, RJP ( BMNH) ; 1^ (pinned), 1^ (slide), 12 larvae, 2 pupae, site 8, 12.xi.1998, RJP ( BMNH) ; 2^ (pinned), 36 larvae, 6 pupae, site 8, 12.xi.1998, RJP ( ST &P) ; 28 larvae, site 11, 11.xi.1998, RJP ( ST &P) ; 1ơ (pinned, abdomen and genitalia on slide), 1^ (pinned), 12 larvae, 2 pupae, site 12, 11.x.1998, RJP ( BMNH) ; 1ơ (pinned), 3^ (pinned), 14 larvae, 2 pupae, site 12, 11.x.1998, RJP ( ST &P) ; 1 pupa, site 13, 13.xi.1998, RJP ( BMNH) ; 6 larvae, site 14, 13.xi.1998, RJP ( ST &P) ; 17 larvae, site 14, 13.xi.1998, RJP ( ST &P) ; 6 larvae, site 15, 11.xi.1998, RJP ( ST &P) ; 3 larvae, site 16, 11.xi.1998, RJP ( BMNH) .

Material seen from the Instituto de Higiene e Medicina Tropical ( IHMT), Portugal (for full explanation of river sites and bioecological data see dos Santos Grácio 1999): SÃO TOMÉ ISLAND: 1 dissected pupal slide, no 129, site 9, 05.viii.1988, AJSG ; 1 dissected pupal slide, no 230, site 36, 24.vii–07.viii.1988, AJSG; 2 dissected larval slides, no 467 & 468, 5 dissected pupal slides, no 96, 98, 99, 100 &135, site 39, 24.vii– 07.viii.1988, AJSG.

Remarks: Simulium santomi constituted approximately 40 % of all specimens from São Tomé. It is clearly a member of the subgenus Pomeroyellum and all life stages key out as such following Crosskey (1969). With respect to species­groups, S. santomi keys out to the alcocki species­group following Freeman & de Meillon (1953), and clearly fits the alcocki species­group description of Crosskey (1969) better than any other speciesgroup within Pomeroyellum .

Figures

Figs 4–11. Simulium santomi sp. n. 4. Pupal gill. 5. Gonocoxite and gonostyle. 6. Pupal ventral onchotaxy. 7. Female hind leg. 8. Ventral plate and median sclerite. 9. Larval postgenal cleft. 10. Parameres. 11. Larval abdominal setae.