Simulium (Hebridosimulium) subparadisium Craig., 2006

Craig, Douglas A., Currie, Douglas C., Hunter, Fiona F. & Spironello, Mike, 2006, A taxonomic revision of the southwestern Pacific subgenus Hebridosimulium (Diptera: Simuliidae: Simulium), Zootaxa 1380 (1), pp. 1-90 : 69-72

Simulium (Hebridosimulium) subparadisium Craig. n. sp.

( Figs. 6f , 7d , 10c , 11i&j , 14b , 17b , 19b , 21b )

Types

Holotype. Larva : last instar in alcohol. Label data – “ S. (Hebridosimulium) subparadisium , Vanuatu, Santo, Millennium Cave Stream, S15.45547° E167.07158°, alt. 192 m. 13.ix.2004. Coll. D. & R. Craig. HOLOTYPE. No. 16611” ( BPBM) . Paratypes. Adults: one double-pinned male dried from alcohol; one partially dissected and cleared male in genitalic tube on pin. Label data – as for Holotype, but with “ PARATYPE ”. Both with pupal exuviae and cocoon as subsidiary material (males; BPBM). Larvae and pupae: in alcohol. Label data – as above. (larvae, pupae; DAC. larvae; BPBM, LCNZ, ROM) .

Diagnosis

Large species. Larva: female, head, dark brown with pale nimbus surrounding semineutral head spots; male head light brown with blackish lateral areas on apotome. Abdomen: female evenly mottled grey; male pale anteriorly, evenly yellow-grey

posteriorly. Pupa: cuticle with numerous dark granules; gill filament petioles elongated; filaments finely tapered.

Description

Adult female. Unknown.

Adult male (based on 2 reared individuals). Body: overall rich dark brown; total length 3.4 mm. Head: width 1.0 mm; depth 0.83 mm. Eyes: interocular hairs markedly long and black; upper ommatidia dark orange, large, 0.06 mm in diameter, ca. 14 across and 15 down, decreasing is size towards smaller ommatidia; lower ommatidia brown, darker ventrally, 0.015 mm in diameter, ca. 26 across and 35 down. Clypeus: dark brown, pruinose, 0.24 times as wide as head; vestiture of sparse black hairs. Antenna: total length 0.63 mm; all parts light yellow. Mouthparts: length 0.3 times head depth; mandibles insubstantial, finely tapered with apical hairs; lacinia broad basally, finely tapered apically with terminal hairs; palpus dark, 0.6 mm long, proportional lengths of 3rd, 4th, and 5th articles 1.0:0.8:1.0, sensory vesicle barrel shaped, occupying 0.25 times width of article, opening 0.33 times width of vesicle. Thorax: length 1.2 mm; width 0.9 mm; postpronotal lobes pale; anterior scutum evenly rich brown, darker posteriorly, faint vittae; vestiture of fine pale hairs; anterior scutellum lighter than scutum, concolourous posteriorly, apical angle distinctly obtuse; vestiture of thin pale hairs and markedly long stiff black hairs laterally; postnotum mottled brown; pleuron concolourous with scutum, pleural membrane well haired. Wing: 2.6 mm in length, 1.2 mm at maximum width. Legs: markedly bicolourous, tarsi and tibial apices black, remainder yellow; pretarsal claws with ca. 25 grappling hooks dorsally. Abdomen: anterior segments pale, remainder medium grey, vestiture of dense, fine, pale hairs; basal scale black with markedly long, pale yellowish hairs. Genitalia ( Fig. 6f ): gonocoxa 1.5 times longer than basal width, basal pigmented band narrow than in other species, vestiture of numerous substantial hairs, anterolateral apodeme not well developed; gonostyle approximately 3.0 times longer than basal width, subequal in length to gonocoxa, mediobasal strengthening ridge not distinct; ventral plate small, sloped laterally, proximal arms distinctly curved medially and evenly tapered; median keel relatively large, in ventral view flattened, markedly angulate in posterior view, stem broad, vestiture of markedly small, evenly spaced hairs; parameral spines as for other species; dorsal sclerite broadly rounded apically, less V-shaped than other species; median sclerite 1.8 times as long as apical width, stem expanded apically, sclerotized irregularly. Cerci: distinct.

Pupa (based on 1 female and 2 males). Body length: female 3.9–4.2mm, male 3.7 mm. Cuticle with numerous dark granules, those anterior rounded, posterior sharply pointed. Gill ( Fig. 10c ): filaments fine, gradually tapering, dorsal filaments subequal in length, petioles 0.3 time length of filaments; branching pattern ((2+2) +2) +2 +1+1; maximum length 1.4–1.8 mm; annulations fine. Cocoon ( Fig. 7d ): distinctly shoe shaped, of substantial construction; not splayed laterally at base.

Larva (based on 8 mature last-instar larvae). Body ( Fig. 11i, j ): total length, female 8.2–8.7 mm, male 7.4–8.3 mm; female, evenly granular light gray, continuous posteroventrally, male prothorax orange-brown, mesothorax pale, metathorax markedly orange coloured, remainder evenly yellowish brown. Head ( Fig. 14b ): female, width 0.76–0.79 mm; length 0.71–0.81 mm; distance between antennal bases 0.45–0.46 mm; male, width 0.66–0.74 mm; length 0.74–0.83 mm; distance between antennal bases 0.41–0.44 mm; colour: female markedly bicolourous, anterior apotome pale brown, lateral apotome dark brown, medial spots slightly positive, surrounded by pale yellow nimbus, posterior spots negative; male, apotome yellow with lateral dark brown region, medial head spots slightly positive, ecdysial lines irregular, inflexion at maximum width broadly rounded, posterior margin of apotome slightly emarginate; genae dark brown laterally; lateral margins of head slightly convex; postocciput extended finely between cervical sclerites and apotome. Antenna: total length, female 0.46–0.55 mm, male 0.43–0.50 mm; distal article 0.28 times as long as basal articles; longer than labral fan stalk; distal article light brown, remainder pale. Labral fan: stalk lightly pigmented, anterior palatal bar well developed, 47–51 dark rays, 0.78–0.81 mm in length, medial rays 0.018 mm in width, 10–14 posterolateral rays finer than others; microtrichia well developed, subequal in length to ray width, pattern not distinct. Postgenal cleft ( Fig. 17b ): sharply V-shaped with slightly concave edges; 1.3 times longer than maximum width; postgenal bridge 0.4 time as long as cleft depth, pale; genae pale laterally, medium brown ventrally, posteroventral elongated muscle spots positive. Hypostoma ( Fig. 19b ): overall broadly cone-shaped; ratio 1:4.7; median tooth markedly prominent, lateral teeth broadly based, sublateral teeth small; paralateral teeth absent, lateral serrations absent; 10 or 11 hypostomal setae per side; supernumerary hairs on hypostomal base substantial. Mandible ( Fig. 21b ): apical teeth prominent, but not markedly developed; spinous teeth clumped, gap absent; serration and sensillum normally developed; blade region slightly irregular, but straight. Abdomen: thorax decreased in size to abdomen; anterior segments subequal in width, expanded gradually to maximum width, markedly steatopygous; posterodorsal tubercles absent. Posterior circlet: directed posteriorly; 208–210 rows of hooks, 33–36 hooks per row (total hooks ca. 7,100).

Additional material examined

Santo, Millennium Cave Stream , S15.45547° E167.07158°, alt. 192 m. 13.ix.2004. Coll. D. & R. Craig (larvae; DAC, ROM). Tafwakar Str. trib Sarakata River, S 15.43839° E167.07425°, alt. 126m. 13.ix.2004. Coll. D. A. & R. Craig (larvae; DAC) .

Etymology Named for its apparent close relationship to S. paradisium .

Distribution VANUATU: Santo, Millennium Cave region.

Comments

Known, so far, only from the Millennium Cave region (Sarakata River watershed) on Santo, the larvae of S. subparadisium are similar to those of S. paradisium in that they are habitat specialists of fast water ( Fig. 24e ). Larvae were taken in moderately large numbers from smooth basalt substrate in fast flow (1.7 m /s), along with those of S. steatopygium and S. callipygium . Larvae show marked steatopygy of the abdomen, in addition to possessing, along with larvae of S. paradisium , a large number of hooks on the posterior circlet. Both of these attributes are adaptations to fast-flowing water ( Craig 2003, Palmer and Craig 2000). Similar to larvae of S. paradisium , those of S. subparadisium possess a large number of substantial labral fan rays and are highly colourful, albeit less so. It is not known if larvae of S. subparadisium lack the ability to twist their bodies, as is characteristic of S. paradisium .

Figures

FIGURE 6. Hebridosimulium. Male genitalia. a–b callipygium species group, c–f steatopygium species group. e. Paramere spines shown in detail. Scale bar = 0.1 mm. Abbreviations: adg mbm — aedeagal membrane; d plt — dorsal plate; goncx — gonocoxite; gonst — gonostyle; m scl — median sclerite; pm th — paramere teeth; v plt — ventral plate.

FIGURE 7. Hebridosimulium. Pupal cocoons. a & b. Lateral and dorsal views. c & d. Lateral view. Scale bar = 0.5 mm.

FIGURE 10. Pupal gill filaments of Hebridosimulium species (continued). Scale bar = 0.2 mm.

FIGURE 11. Left lateral views of Hebridosimulium species larvae. Last-instar larvae, except l & n, which are penultimate. Arrowheads indicate dorsal tubercles. Scale bar = 1.0 mm.

FIGURE 14. Dorsal views of larval heads of Hebridosimulium species. steatopygium species group. Last instars, except d & f, which are penultimate instars. Scale bar = 0.2 mm.

FIGURE 17. Postgenal clefts and hypostoma of larvae of Hebridosimulium species. Last instar except b, d, & f, which are penultimate. Scale bar = 0.1 mm.

FIGURE 19. Hypostomal teeth of larvae of Hebridosimulium species. Last instar, except d & f, which are penultimate. Scale bar = 0.05 mm.

FIGURE 21. Mandibular teeth of larvae of Hebridosimulium species, steatopygium species group. Last instar, except d & f, which are penultimate. Scale bar = 0.025 mm.

FIGURE 24. Habitats of larvae of Hebridosimulium species. a–e. Vanuatu.a. Santo, Adsone River. Type locality of S. adsonense. b. Santo, upper cascade, tributary of Sarakata River. Type locality of S. paradisium. c. Efate, Mele Cascade. Type locality of S. steatopygium. Note travertine terraces. d. South Pentecost, Warbot River. Type locality of S. supercilium. e. Santo, small stream, Millennium Cave region. Typical locality of S. subparadisium. f–i. Fiji. Habitats of S. laciniatum larvae. f. Viti Levu, Abaca Village, above Vereni Falls. Type region. g. Taveuni, Wairiki, Devo Peak, looking down water slide. h. Kadavu, Kadavacoro Village, Wailea Waterfall. i. Vanu Levu, Waisala Rain Forest Reserve, Ravini River.