Simulium (Inseliellum) littosocius Craig & Evenhuis,

Evenhuis, Neal L., 2017, Society Islands beach bum black flies (Diptera: Simuliidae), Zootaxa 4311 (3), pp. 373-388: 378-382

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Simulium (Inseliellum) littosocius Craig & Evenhuis

n. sp.

Simulium (Inseliellum) littosocius Craig & Evenhuis  , n. sp.

FIgs. 16–29View FIGURES 16 – 21View FIGURES 22 – 26View FIGURES 27 – 30.

Description. Adult female (based on 12 specImens). Body ( FIgs. 16View FIGURES 16 – 21): overall dark brown, abdomen lIghter ventrally; total length 2.0– 2.5 mm. Head ( FIg. 17View FIGURES 16 – 21): wIdth 0.66 mm; depth 0.46 mm; postoccIput black wIth sparse vestIture of short black haIrs; frons markedly narrowed ventrally, frons/head wIdth ratIo 1.0:14.0; frontal angle 30°. Eye: Interocular dIstance ca. 0.14 mm; eyes dark red, ommatIdIa dIameter 0.01 mm; ca. 26 rows across and 36 down at mId-eye. Clypeus: wIdth 0.14 mm; mottled dark brown, vestIture of scattered haIrs ventrally. Antenna ( FIgs. 18View FIGURES 16 – 21): total length 0. 55 mm; evenly dark brown wIth scape and pedIcel paler yellow and subspherIcal, flagellomere I angulate and as wIde as long; flagellomere II markedly wIder than long, II –VIII IncreasIng In length, flagellomere IX slIghtly cone-shaped. Mouthparts: feebly developed, ca. 0.25× length of head depth; maxIllary palp ( FIg. 19View FIGURES 16 – 21) length 0.55 mm, palpomere V subequal In length to remaInder of palp, palpomeres I and II small, palpomere III small, spherIcal and darker than other palpomeres, proportIonal lengths of palpomere III –V 1.0: 1.0: 2.3 respectIvely; sensory organ spherIcal, 0.5 length of palpomere III; mandIble ( FIgs. 19, 20View FIGURES 16 – 21) not flared apIcally, ca. 17 Inner teeth, outer teeth absent; lacInIa small, wIth 9 Inner teeth and 10 or 11 outer teeth; cIbarIum ( FIg. 21View FIGURES 16 – 21) wIth narrow cornuae sclerotIzed apIcally and lIghtly sculpted, medIan gap broadly V-shaped. Thorax: length 0.7– 1.0 mm; wIdth 0.7–0.9 mm; scutum black, postpronotal lobe slIghtly paler than scutum, vestIture slIghtly longer; scutellum slIghtly paler than scutum, vestIture of sparse very fIne yellowIsh haIrs; postnotum concolourous wIth scutellum; antepronotal lobe wIth patch of yellow haIrs; proepIsternum wIth sparse haIrs; anepIsternal membrane bare; katepIsternum dark brown, sulcus deep and dIstInct. Wing ( FIg. 22View FIGURES 22 – 26): membrane slIghtly dusky on anal lobe, length 2.1–2.3 mm; wIdth 0.8–0.9 mm; anterIor veIns well expressed; costa and radIus wIth mIxture of haIrs and spInes; a/b ratIo 1.0:4.3; basal cell dIstInct; CuA2 not markedly sInuous; A2 extended nearly to wIng margIn; narrow sclerotIsed crescent In anal lobe angle. Haltere: tan or whIte. Legs ( FIg. 23View FIGURES 22 – 26): overall dark brown, except hInd basItarsus yellowIsh wIth dIstal dark brown regIon, row of ventral stout spInes poorly expressed; calcIpala slIghtly more than 0.5 wIdth of basItarsus, slIghtly flared laterally; pedIsulcus well expressed; tarsomere

II ca. 2.5 tImes as long as dIstal wIdth; claw ( FIg. 24View FIGURES 22 – 26) wIth maIn talon fInely curved and tapered, apex moderately blunt, basal tooth large, ca. 0.5x length of claw, heel substantIal and rounded. Abdomen ( FIg. 25View FIGURES 22 – 26): dorsally black, mottled ventrally, tergItes paler and mottled; basal scale dark brown, mottled medIally, vestIture of short haIrs; tergIte II broadly U-shaped, 3x wIder that deep, tergItes III –VII lozenge-shaped, 3x tIme wIder than long, IncreasIng In wIdth posterIorly, vestIture essentIally absent from anterIor segments, slIghtly more dense on posterIor segments. Genitalia: sternIte VIII evenly pIgmented, not depressed medIally; hypogynIal valves ( FIg. 26View FIGURES 22 – 26) wIth medIan gap deeply U-shaped, medIal edges strengthened, vestIture of sparse haIrs laterally, valves coneshaped, rounded apIcally; genItal fork ( FIg. 27View FIGURES 27 – 30) wIth stem smooth, narrowed, not expanded apIcally, lateral arms short, lateral plates small, elongated laterally, apodeme moderately expressed; spermatheca ovoId ( FIg. 28View FIGURES 27 – 30), small, dark brown, wIth slIghtly wrInkled surface, lackIng Internal spInes, membranous area at junctIon wIth spermathecal duct wIth fluted edge; cercus In lateral vIew shallowly cone-shaped, concentratIon of haIrs apIcally, anal lobe small, rounded, protruded ventrally ( FIg. 29View FIGURES 27 – 30).

Material. Holotype: Female, mIcropInned. DrIed from ETOH. Label data:- [Holo/ type] [ Simulium  / ( Inseliellum  )/ littosocius  ] [FP: TAHITI ITI: 3.5 km E. / TautIra, 0 m, North Road / beach rubble, 18 Jul 2006 / N. EvenhuIs, P. O’Grady] [BPBM 17,839], (ca. S17.7667° W149.1411°).

Paratype: Three females mIcropInned, as for holotype. One mIcroscope slIde. Labels wIth [PARATYPE].

Other material: One mIcroscope slIde, two female In ETOH, labels [FP: TAHITI ITI: 0 m, / North Road. PK5 Punatea / VIllage 19 Jul. [2006] coral / beach rubble. N. EvenhuIs], (ca. S17.7370° W149.27185°)GoogleMaps  . Two females, ETOH, labels [FP: TAHITI NUI: / North Road, PK 20 / 22 Jul 2006, beach / rocks. EvenhuIs] (ca. S17.5160° W149.4054°)GoogleMaps  . One female, ETOH [FP: TAHITI NUI, 0 m, / North Road, PK 48, beach / rocks at VaIhI RIv, 30.III.07 / N. EvenhuIs], (ca. S17.6765°, W149.3064°)GoogleMaps  . Two females In ETOH. Label [FP: RAIATEA, 0 m / BaIe Pufau, 21 Mar 2007 / 16.760158° S 151.48886° W / beach rubble, N. EvenhuIs]. 

Etymology. In reference to the assocIatIon wIth beaches; derIvIng from litto [= "beach"] + socius [= “companIon”]; hence a second “beach bum” of sorts. The name Is treated as a noun In apposItIon.

Distribution. Known from TahItI and RaIatea.

Remarks. Female Simulium littosocius  are easIly dIstInguIshed from those of S. littopyga  on the basIs of brown antenna wIth yellowIsh scape and pedIcel, and browner legs. AddItIonally, S. littosocius Is  smaller In sIze and the wIdth of the frons In relatIon to head wIdth Is markedly narrowed ( FIg. 17View FIGURES 16 – 21) In comparIson to that of S. littopyga  ( FIg. 2View FIGURES 1 – 6) and S. littosodalis  ( FIg. 31View FIGURES 31 – 35), below.

AbdomInal tergItes ( FIg. 25View FIGURES 22 – 26) of S. littosocius  are well developed, but not as broad as those of S. littopyga  ( FIg. 11View FIGURES 7 – 11). Simulium littosocius  mandIbles are parallel-sIded, not slIghtly flared as In S. littopyga  (cf. FIgs. 4View FIGURES 1 – 6, 20View FIGURES 16 – 21). ExpressIon of the hypogynIal valves dIffers between the two specIes (cf. FIgs. 12View FIGURES 12 – 15, 26View FIGURES 22 – 26). DIfferences In the claw tooth and heel Is marked, wIth both structures much smaller In S. littopyga  (cf. FIgs. 10View FIGURES 7 – 11, 24View FIGURES 22 – 26).

The presence of S. littosocius  on RaIatea, 250 km to the WNW of TahItI, Is not surprIsIng, sInce the Island shares S. malardei CraIg  , S. lotii CraIg  and S. oviceps  wIth TahItI. PrecInctIve to RaIatea are S. pufauense CraIg  , S. castaneum CraIg  , S. proctorae CraIg  and S. bogusium CraIg  (e.g., CraIg & Joy 2000).