Simulium (Hebridosimulium) undulatum 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 : 74-75

Simulium (Hebridosimulium) undulatum Craig. n. sp.

( Figs. 11i , 14d , 17d , 19d , 21d )

Types

Holotype. Larva : Pre-penultimate instar larva in alcohol. Label data – “ Simulium (Hebridosimulium) undulatum . Vanuatu, Banks Islands, Vanua Lava, Tahiti River. S13.84727° E167.52191°, alt. 12.5m, 28.viii.2004. Coll. D. & R. Craig. HOLOTYPE. No. 16613” ( BPBM) . Paratypes. Larvae: Prepenultimate instar larvae on slide. Label data as for Holotype, but with “ PARATYPE ” (larva; BPBM) .

Diagnosis

Larva: anterior cephalic apotome markedly pale anteriorly, head spot pattern in Eiffel Tower configuration; posterior edge of cephalic apotome markedly emarginated, postocciput extended between cervical sclerites and apotome, hypostomal teeth not markedly developed; abdomen moderately steatopygous, posterior circlet directed posteriorly; dorsal tubercles absent.

Description

Adult female. Unknown.

Adult male. Unknown.

Pupa. Unknown.

Larva (based on 1 penultimate and numerous prepenultimate instar larvae). Body ( Fig. 11i ): total length ca. 6.1 mm; females evenly mottled grey, with metathoracic segment slightly orange, males more yellowish. Head ( Fig. 14d ): anterior frontoclypeal apotome markedly pale; labral fan stalks pale to light brown; head-spot pattern positive, medial head spots in Eiffel Tower configuration, ecdysial lines pale and distinct; width 0.62 mm, length 0.65 mm; distance between antennal bases 0.38 mm; lateral margins of head subparallel; posterior edge of apotome markedly emarginated; postocciput extended between distinct cervical sclerites emarginated apotome. Antenna: distal article light brown, remainder pale; total length 0.44 mm; distal article 0.3 times as long as basal articles, extended well beyond labral fan stalk. Labral fan: stalk very light brown, anterior palatal bar markedly developed; 47 rays, 0.70 mm in length, 16–19 rays less substantial; microtrichia 1.3 times longer than ray width, distinct pattern of 6 smaller microtrichia to 1 larger one. Postgenal cleft ( Fig. 17d ): arrowhead shaped, 1.3 times deeper than wide with slightly convex edges; posteroventral elongated muscle spots positive. Postgenal bridge: 0.4 times as long as cleft depth, bridge pale yellow; ventral genae and postgenae light brown. Hypostoma ( Fig. 19d ): overall cone-shaped; ratio 4.4; teeth not markedly protruded anteriorly; median tooth prominent, lateral teeth small, directed anteriorly, but scalloped medially; medial sublateral teeth larger, others smaller with subsidiary basal tooth; paralateral teeth just apparent; lateral serrations essentially absent; 9 hypostomal setae per side. Mandible ( Fig. 21d ): apical teeth normally developed, 6 spinous teeth; spinous teeth gap normal; serration and sensillum broadly based and distinct; blade region smooth and straight. Abdomen: expanded evenly posteriorly to 5th abdominal segment, slightly steatopygous; posterodorsal tubercles absent. Posterior circlet: directed posteriorly; 180 rows of hooks; 28–30 hooks per row (total ca. 5,200).

Additional material examined

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

Etymology Named in reference to the emarginated posterior edge of the larval cephalic apotome.

Distribution VANUATU: Vanua Lava (Banks Islands).

Comments

This species is found in the same riverine habitat as S. banksi ( Fig. 23d ). Although described only from one penultimate instar larva and some earlier instar larvae, S. undulatum is considered here a separate species — one related to the steatopygium species group. Simulium undulatum has a markedly emarginated apotome posteriorly. It is expected that in the last-instar larva, the emarginations will be even more developed, because they increase in size from earlier to later larval instars. With lack of reared adult material from the Banks Islands simuliids ( S. banksi , S. callipygium , S. undulatum ), adults collected by Cheesman in the late 1920s from Vanua Lava and deposited in the BM, cannot as yet be assigned to species (see Incertae sedis).

Figures

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 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.