Thinophilus inaequalis Samoh & Grootaert

Samoh, Abdulloh, Satasook, Chutamas & Grootaert, Patrick, 2019, New marine Thinophilus species (Diptera: Dolichopodidae: Hydrophorinae) from the Thai Andaman Sea coast and new records from peninsular Thailand, European Journal of Taxonomy 505, pp. 1-20 : 4-7

Thinophilus inaequalis Samoh & Grootaert sp. nov.

urn:lsid:zoobank.org:act:04B69217-31C2-4DB8-86CB-E2855CC47954

Figs 2–4

Diagnosis

A small species from the ‘ Thinophilus simplex -group’. Fore coxa entirely yellow with a single short black bristle near middle. Legs yellow, but apical tarsomere of all legs black. Fore femur with a few long ventral bristles near base and a row of about eight posteroventral bristles in apical 2 / 3. Mid femur with a row of five to six strong black bristles in apical third. Hind femur with three to four ventral bristles on basal quarter and a row of fine anteroventral bristles over entire length about half as long as femur is wide. Sternite 3 and 4 with very long pale bristles at side near tip. Left surstylus pointed, right surstylus blunt.

Etymology

The name ‘ inaequalis ’ alludes to the asymmetric surstyli: the left surstylus is pointed while the right surstylus has a blunt tip.

Type material

Holotype THAILAND – Phang Nga Prov. • 1 ♂; Ko Phra Thong, Andaman Sea ; 9°03′58.6″ N, 98°15′09.9″ E; 25 Apr. 2018, A. Samoh leg.; sweep netting; PSUNHM.

Paratypes

THAILAND – Phang Nga Prov. • 12 ♂♂, 14 ♀♀; same data as for the holotype; PSUNHM (1 ♂ PSUZCDIP0011, 1 ♀ PSUZCDIP0012) • Ko Phra Thong, Andaman Sea ; 9°03′29.5″ N, 98°15′02.4″ E; 15 Sep. 2017, A. Samoh leg.; sweep netting; 11 ♂♂, 13 ♀ ♀ PSUNHM, 1 ♂, 1 ♀ RBINS .

Description

Male ( Fig. 2 )

MEASUREMENTS. Small species. Body 2.5–2.7 mm; wing 2.2–2.6 mm.

HEAD. Ocellar bristles long, vertical bristles half as long as ocellars. Postvertical bristle indistinct. Upper postoculars small, black, uniseriate; lower postoculars a little longer and paler than upper, uniseriate, but with a few longer bristles behind the row. Antenna yellow, postpedicel dusky yellow and arista black. Palpus large, about half as long as height of an eye, covered with a few thin bristles. Proboscis black, rather long.

THORAX. Shining metallic green. Four equally long dorsocentrals preceded by a small bristle. Wing clear with pale yellowish veins. Squama white with a few white cilia. Haltere white.

COLOUR OF LEGS. Yellow, including fore coxa, but mid and hind coxae brown. Apical tarsomere of all legs black.

FORE LEG. Coxa with a single short black bristle near middle. Femur with a few long ventral bristles near base and a row of about eight posteroventral bristles in apical 2 / 3. Tibia with a short dorsal and posteroventral bristle near middle, lacking spine-like ventral bristles.

MID LEG. Coxa with one long exterior. Femur with a row of five to six strong black bristles in apical third. Tibia with one anterodorsal and one posterodorsal bristle at basal quarter and one anterodorsal and one posterodorsal bristle just beyond middle.

HIND LEG. Coxa with an exterior bristle. Femur with about three to four ventral bristles on basal quarter and a row of fine anteroventral bristles over entire length about half as long as width of femur. One distinct anterior bristle before middle and a longer anterodorsal on apical third. Tibia with two anterodorsal and two dorsal bristles.

ABDOMEN. Tergites subshining metallic greenish black, set with short black bristles. Sternite 3 and 4 with long, fine pale bristles at side near tip. Terminalia ( Fig. 4 ). Cerci widely separated over more than half their length, joining at base but not fused ( Fig. 4D ). Cercus with only a few long bristle at apex, the rest of the cercus sparsely set with bristles. Left surstylus pointed ( Fig. 4C ), right surstylus blunt ( Fig. 4B ). A distinct epandrial bristle present ( Fig. 4C ).

Female ( Fig. 3 )

Body 2.4–2.9 mm; wing 2.2–2.4 mm. Similar to male but lacking the posteroventral bristle on the fore femur while posteroventrals in apical half of mid femur are present. Hind femur also lacking the row of long ventral and anteroventral bristles. Apical three tarsomeres of all legs more dusky than in male and thus tarsomere 5 is not so contrastingly darkened. Sternites with minute white hairs only.

Comments

The new species belongs to the ‘ Thinophilus simplex -group’ sensu Grootaert (2018). Having entirely yellow fore coxa with only a single short black bristle, the new species runs to couplet 27 leading to T. evenhuisi Grootaert, 2018 and T. minor Grootaert, 2018 . It is, however, very distinct from both species in that T. evenhuisi has two very long, black ventral bristles near middle of the fore femur (twice as long as femur is wide), not present in the new species. Thinophilus minor has a row of very long ventral bristles on the fore tibia.

Figures

Fig. 2. Thinophilus inaequalis Samoh & Grootaert sp. nov. Male habitus (Abdulloh Samoh leg., PSUNHM (PSUZCDIP0011)).

Fig. 3. Thinophilus inaequalis Samoh & Grootaert sp. nov. Female habitus (Abdulloh Samoh leg., PSUNHM (PSUZCDIP0012)).

Fig. 4. Thinophilus inaequalis Samoh & Grootaert sp. nov. Male terminalia (Abdulloh Samoh leg., PSUNHM (PSUZCDIP0011)). A. Ventral view on epandrium. B. Tip of right surstylus. C. Lateral view on left side of epandrium with a pointed left surstylus. D. Dorsal view on cerci. Scale = 0.1 mm.