Simulium (Hebridosimulium) banksi 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 : 25-29

Simulium (Hebridosimulium) banksi Craig , n. sp.

( Figs. 9b , 11b , 13b , 16b , 18b , 20b , 22a ,)

Types

Holotype. Larva : last instar larva in alcohol. Label data – “ Simulium (Hebridosimulium) banksi , Vanuatu, Banks Islands, Vanua Lava, Tahiti River. S13.84727° E167.52191°, alt. 12.5 m, 28.viii.2004. Coll. D. & R. Craig. HOLOTYPE #16607” ( BPBM) . Paratypes. Larvae: last and penultimate larvae in alcohol. Label data – as for Holotype, but with “ PARATYPE ” (larvae; BPBM, DAC, ROM) .

Diagnosis

Relatively small species. Pupa: gill with short dorsal filaments, short petioles. Larva: head with distinct spot below stemmata; hypostomal median and lateral teeth not well developed, sublateral teeth small; fan rays ca. 37; abdomen callipygous, dorsolateral tubercles present. Posterior circlet with ca. 2,800 hooks.

Description

Adult female. Unknown.

Adult male. Unknown.

Pupa (based on 1 pharate specimen). Thorax: cuticle with sparse small granules. Gill ( Fig. 9b ): dorsal filaments shorter; arising from short petioles, branching pattern (2+2)+2+2+1+1; filaments evenly tapered, brown; maximum length 1.3 mm.

Larva (based on 5 last-instar specimens with immature pharate pupal gills). Body ( Fig. 11b ): length 5.4–5.6 mm; mottled dark grey, with paler intersegmental regions; males slightly more yellowish and smaller than females; females darker. Head ( Fig. 13b ): light brown, paler anteriorly; labral fan stalks pale; head spots essentially neutral, slightly positive medially, posterolateral spots slightly negative; width 0.58 mm; length 0.64 mm; distance between antenna bases 0.11 mm; lateral margins convex; ecdysial lines straight, diverging posteriorly, broadly rounded at maximum width; posteromedial edge of apotome darker brown; posterior edge of apotome slightly eroded, cervical sclerites distinct, postocciput not extended to cervical sclerites; distinct brown spot anterodorsal of stemmata. Antenna: total length 0.50 mm; distal article 0.3 times as long as basal articles, subequal in length to labral fan stalk; basal and distal article pale brown, median article pale. Labral fan: stalk clear to pale brown, anterior palatal bar not markedly developed; 33–35 fine rays, 0.63 mm in length, 6–8 rays less substantial; microtrichia fine and elongate, 1.5 time longer than ray width, no distinctive pattern. Postgenal cleft ( Fig. 16b ): deeply V-shaped, slightly concave margins 1.5 times as long as width. Postgenal bridge: 0.3 times as long as cleft depth; genae evenly light brown; elongate ventrolateral muscle scars slightly positive. Hypostoma ( Fig. 18b ): ratio 5.4; overall shape domed; teeth well developed, but not prominent; lateral teeth short, sharp, scalloped medially, directed laterally; sublateral teeth small; paralateral teeth small but obvious; lateral serrations poorly developed; 8 or 9 hypostomal setae per side. Mandible ( Fig. 20b ) preapical and subapical teeth poorly developed; 5 or 6 spinous teeth, gap absent; serration and sensillum fused basally and markedly pointed, blade region concave and smooth. Abdomen: thorax and anterior abdomen subequal in width, expanded gradually posteriorly to maximum width, callipygous; tergites II–V with dorsolateral tubercles increased in size posteriorly. Anal sclerite ( Fig. 22a ). Posterior circlet: directed ventrally; 131 rows of hooks; 21–23 hooks per row (total ca. 2,880).

Additional material examined

Vanua Lava , Tahiti River. S13.84727° E167.52191°, alt. 12.5 m, 28.viii.2004. Coll. D. & R. Craig (immature larvae; DAC) .

Etymology

In honour of Joseph Banks, botanist on Captain James Cook’s first voyage to the Pacific (1768–1771) and after whom the Banks Islands were named, although he never visited Vanuatu.

Distribution VANUATU: Vanua Lava (Banks Islands).

Comments

This callipygous species is assigned to the tuberculum species subgroup on the basis of the dorsal paired tubercles on the larval abdomen. Larvae differ from others in the group in possessing smaller hypostomal teeth, distinct lateral head-spot pattern and a deeper postgenal cleft. The type habitat of S. banksi larvae is somewhat unusual for a member of

the tuberculum species subgroup in that it was a moderately sized river ( Fig. 23d ), although larvae attach themselves to vegetation in typical fashion.

Figures

FIGURE 9. Pupal gill filaments of Hebridosimulium species. 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 13. Dorsal views of larval heads of Hebridosimulium species. a–e. callipygium species group, f–h. part of steatopygium species group. Last instars, except f & h, which are penultimate instars. Arrows (b & e) indicate anterior palatal bar. Scale bar = 0.2 mm.

FIGURE 16. Postgenal clefts and hypostoma of larvae of Hebridosimulium species. a–e callipygium species group, d–h steatopygium species group. Last instar, except b, which is penultimate. Scale bar = 0.1 mm.

FIGURE 18. Hypostomal teeth of larvae of Hebridosimulium species. Last instar. Scale bar = 0.05 mm.

FIGURE 20. Mandibular teeth of larvae of Hebridosimulium species. a–e callipygium species group, f–h steatopygium species group. Last instar, except b, which is penultimate. Arrow (e) indicates the blade region; asterisk the spinous teeth gap. Scale bar = 0.025 mm.

FIGURE 22. Anal sclerite and circlet of hooks of larvae of Hebridosimulium species. Last instar. Ca. 2800 and 7300 hooks, respectively. Scale bar = 0.2 mm.

FIGURE 23. Habitats of larvae of Hebridosimulium species, Vanuatu. a. Santo, Sarakata River, UNELCO Hydro Station. Type locality of S. callipygium. Note limestone substrate. b. Santo, Upper Sarakata River, Millennium Cave region. Typical habitat of S. callipygium and S. subparadisium. c. Malekula, Wesso River, downstream of cascade. Type locality of S. spiroi. Note travertine substrate. d. Banks Islands, Vanua Lava, Tahiti River. Type locality of S. banksi and S. undulatum. e. Tanna, stream south of Bethel. Type locality of S. johnfrumi. f. Malekula, Pankumu River. Type locality of S. pankumuense. g. Efate, Ewor River, La Cressionnière. Type locality of S. tuberculum. Note the travertine terraces.