Thinophilus plektron 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 : 7-11

Thinophilus plektron Samoh & Grootaert sp. nov.

urn:lsid:zoobank.org:act:B560D3B5-AD31-43C2-9C67-10438E4C7104

Figs 5–7

Diagnosis

A large species with all coxae black and fore coxa bearing long white bristles. All femora strongly thickened, hind femur strongest. Hind tibia with a long, blunt flattened apical spur.

Etymology

The specific name is from the Greek ‘ plektron ’ (‘thing to strike with’: cock’s spur, pick for a lyre) alluding to the apical spur on the hind tibia. It is used as a noun in apposition.

Type material

Holotype THAILAND – Ranong Prov. • 1 ♂; Khlong Chanut, Ban Bang Ben, Kapoe district , Andaman Sea ; 9°36′32.9″ N, 98°29′12.6″ E; 12 Jul. 2018; A. Samoh leg.; sweep netting; PSUNHM.

Paratypes THAILAND • 2 ♂♂, 1♀; same data as for the holotype; 1 ♂, 1 ♀ PSUNHM (1 ♂ PSUZCDIP0013, 1 ♀ PSUZCDIP0014), 1 ♂ RBINS .

Description

Male ( Fig. 5 )

MEASUREMENTS. Large species. Body 7 mm; wing 6 mm.

HEAD. Both frons and face wide, subshining bluish. Ocellars long, verticals also long, about ¾ of ocellars. Postverticals as long as verticals ( Fig. 5 ). Postoculars black, uniseriate above, long, white, and multiseriate below. Clypeus protruding over the robust proboscis that is about half as long as the eye height. Palpus yellow, but black at base and covered with long black bristles.Antenna yellowish, with all segments darkened above. Scape longer than pedicel, the latter with long dorsal bristle and a few short bristles below. Postpedicel slightly longer than high, triangular in lateral view, with a blunt tip ( Fig. 5 ). THORAX. Black in ground-colour, subshining (faint cover of dusting), and with a greenish bluish metallic shine. All bristles black and long. Six equally long dorsocentrals. Upper and lower propleural bristles densely set, white. Upper propleurals shorter than lower.

COLOUR OF LEGS. Largely yellowish. All coxae black with extreme tip yellowish. All trochanters contrastingly pale (whitish) with a black stripe at connection with femur. All femora darkened brown above and laterally, ventrally more yellowish. All tibiae yellow. All tarsi whitish yellow, with extreme tips of all tarsomeres black above (ventrally white). Apical tarsomere of all legs entirely black above.

FORE LEG. Coxa with only white bristles, including the apicals. Longest bristles with long white bristles near base. Femur swollen, with a double row of ventral bristles about half as long as width of femur; a row of posteroventrals with a few longer bristles near base. Most basal bristle longer than femur width. Fore tibia with a row of long ventral bristles, the longest near base, strong and three times as long as width of tibia. The bristles decrease in length toward tip of tibia; the row continues on the first tarsomere. A set of six strong dorsal and posterodorsal bristles on median third of tibia.

MID LEG. Coxa with a long black exterior. Femur as wide as fore femur. Anteroventrally with multiple rows of long black bristles in basal ¾. Row of posteroventral long bristles in basal half, longest near base of femur, nearly as long as femur width, the bristles become gradually shorter toward apex. Tibia as long as femur, with a ventral row of short spine-like bristles over the entire length. A strong black curved spine at tip. Tarsomere 1 very long, nearly 1.5 times as long as all following tarsomeres together.

HIND LEG. Coxa with a long exterior. Femur broader and longer than mid femur; spindle shaped; with four strong dorsal black bristles in apical half; ventrally densely set with bristles, a patch of longer bristles near middle. Tibia ending in a long flattened apical spur as long as tibia width at that point; ventrally and posteroventrally with a row of fine bristles over entire length, nearly as long as tibia width; near base with two to three long black ventral to posteroventral bristles. Dorsally with unusually long dorsal bristles.

WING. With a faint brownish tinge, veins pale brownish in basal half, black in apical half. Squama white with short white cilia. Haltere white.

ABDOMEN. Subshining metallic green, tergites densely covered with short black bristles, except for the sides of tergite 5 that have very long bristles. Posteromarginal bristles a little longer. Sternites with short bristles on basal segments. Sternite 5 densely set with bristles, basal bristles even spine-like. Terminalia ( Fig. 7 ) black. Cercus pale at base, darkened at tip, covered with long pale bristles and a long strong black bristle near tip ( Fig. 5B ). Cerci separated near tip over a short distance and eventually fused ( Fig. 7B ). Phallus long, wide, black ( Figs 5 , 7 C–D). Apex of surstylus widened and ventrally covered over the whole length with long black bristles ( Fig. 7A ). Epandrial lobe indistinct and no epandrial bristle distinct from other bristles.

Female ( Fig. 6 ) Body 6.7 mm; wing 7.3 mm. Resembling male, but all femora slender and bristling on legs simple. No apical spur on hind tibia.

Comments

Having entirely black fore coxa with white bristles, the new species will lead to T. boonrotpongi Samoh et al., 2017 in couplet no. 5 of the key in Grootaert (2018). Additionally, in the latter species, the fore femur also has white bristles mixed with black ventral bristles. In the new species, there are only black ventral bristles on the fore femur. The most distinctive and hitherto unique character in oriental Thinophilus is the long flattened apical spur on the hind tibia.

At first sight, the new species seems to belong to the ‘ Thinophilus murphyi -group’ sensu Grootaert (2018). This is a group of medium to large-sized, robust species with large mouthparts. The cerci are long and separated apically. The arista is partly white on the apex. However, the new species differs in several aspects. The tip of the cercus is not fused at the extreme tip, but shortly behind the tip. The arista is indeed paler but not white on the apex. The bristling of the surstylus is unusually long and dense and this is a situation we find in the Chinese species T. zhuae Grootaert et al., 2017 , but in this species the cerci are much wider, keel-shaped and seem to form a protection for the phallus and surstyli. In the latter species, the tip of the surstylus is also set with numerous bristles. In the present species, the bristles are denser set over the entire length of the surstylus. Thus, we consider this species as yet unplaced.

The new species resembles also superficially T. nigrilineatus Grootaert, 2018 , but the hind femur in the latter is not as strongly swollen as in the new species and a little twisted. The shape of the cerci is also different.

Figures

Fig. 5. Thinophilus plektron Samoh & Grootaert sp. nov. Male habitus (Abdulloh Samoh leg., PSUNHM (PSUZCDIP0013)).

Fig. 6. Thinophilus plektron Samoh & Grootaert sp. nov. Female habitus (Abdulloh Samoh leg., PSUNHM (PSUZCDIP0014)).

Fig. 7. Thinophilus plektron Samoh & Grootaert sp. nov. Male terminalia (Abdulloh Samoh leg., PSUNHM (PSUZCDIP0013)). A. Ventral view of tips of surtstyli. B. Dorsal view of tip of fused cerci. C. Ventral view of epandrium. D. Lateral view on epandrium. Scale = 1 mm.