New long-legged flies from mangroves on Pulau Ubin (Singapore) (Insecta: Diptera: Dolichopodidae) Author Grootaert, Patrick Author Velde, Author Isabella Van de text Raffles Bulletin of Zoology 2024 2024-09-19 72 303 323 journal article 10.26107/RBZ-2024-0025 2345-7600 14683054 079CC651-8D4D-4B95-B022-388B2FA51FE2 Medetera stigma , new species ( Figs. 10 , 11 ) Type material. Holotype male. Pulau Ubin, Sungei [= River] Sempit, Malaise trap along creek in back mangrove, 19 March 2019 , PU23 , 1°25′05.3″N 103°56′06.5″E , (in 70% ethanol, ZRCBDP0317875 _Jayanthi_JPP930_ PU23 _ 19Mar2019 ; LKCNHM ). GenBank accession code: PP893304. Paratype . Pulau Ubin, male, Sungei [= River] Maman, creek, 29 March 2018 , PU17 , 1°24′44.48″N 103°57′59.17″E ), front mangrove (70% ethanol) ZRCBDP0288845 , PU17 _ 29Mar2018 LKCNHM ). GenBank accession code: PP893305 . Etymology. The new species is named stigma , referring to the presence of a brown spot at the base of the costa. The name stigma is used as a noun. Diagnosis . A small-sized species (about 2.5 mm ). Base of wings with a brownish streak at both sides of R 1 . Face and palpus metallic green. Antenna yellow, postpedicel brownish on apex. Scutum without yellow colouration. Acrostichals biserial; 9 dorsocentrals, anterior 7 short, posterior 2 bristles long. Fore legs entirely black. Mid legs with trochanter and basal half of femur yellow, apical half femur, tibia and tarsus brown. Hind tibia with a black posterodorsal tooth beneath the preapical comb of bristles. Male terminalia with base of aedeagus not recurved, bent at a right angle. Tip hypandrium lacking denticles. Cercus undivided. Male. Length: body 2.6 mm ; wing 2.1 mm . Head. Face wide, with a pruinosity, but shiny metallic green with some bluish reflection at base. Frons very short (shorter Thorax . Brownish black as base colour with a green metallic green shine, covered with a fine pruinosity. All bristles black. Acrostichals biserial, about 8 pairs; 9 dorsocentrals, anterior 7 bristles short, posterior 2 much longer, prescutellar bristle longest. Apical pair of scutellar bristles twice as long as bristles outside. A long white propleural bristle. Squama white with apical border brown, set with a row of pale brown bristles a little longer than squama is wide. Knob of haltere white, but with a brownish cap. Legs. Fore legs entirely black. Mid legs with tip of coxa pale brown, trochanter, basal half of femur yellow; apical half femur, tibia and tarsus brown. Hind legs with coxa brown, trochanter yellow, basal half femur yellow, but apical half yellowish brown, basal half tibia pale brown, apical half brown, tarsus entirely brown. Fore legs. Coxa with apical bristles yellow, shorter than coxa is wide; anterior bristles short, black. Femur with a posterior row of short brown bristles. No distinct bristles on tibia. Mid legs. Coxa with whitish bristles; exterior bristle near apex coxa. Mid femur swollen on basal half with pale bristles, brown in apical half, half as long as femur is wide. Tibia with a short anterodorsal and posterodorsal bristle at basal quarter, as long as tibia is wide and a preapical ventral a little longer than tibia is wide. Hind legs. Coxa near middle with a pale brown bristle, shorter than coxa is long. Femur somewhat dorsoventrally bent in basal third; with 5 long black dorsal bristles near base; 4 anterior bristles on apical third and 3 anteroventral bristles as long as femur is wide; basal half of femur with short ventral whitish bristles. Tibia with a black posterodorsal tooth-like projection composed of 4 closely set bristles, beneath the preapical comb of pale bristles; apical quarter more densely set with short ventral bristles than the basal ¾ of tibia. Basal tarsomere much shorter than second tarsomere. Length ratio tarsomeres 1–5 in mm: 0.16: 0.36: 0.22: 0.08: 0.95. Abdomen . Brown in ground-colour with a faint green metallic shine. Tergites with all bristles brown, marginal bristles a little longer. Sternites with minute white bristles. Male terminalia. Fig. 11 . Entirely brown. A pair of apicoventral epandrial bristles of equal length inserted on globular papilla. Basal epandrial bristle minute ( Fig. 11B, D ). Tip hypandrium much widened before tip, lacking denticles ( Fig. 11G ). Base of aedeagus not recurved, bent at a right angle ( Fig. 11G ). Dorsal and ventral surstylus well separated. Dorsal surstylus with an apical slit, bearing a lateral ( Fig. 11C–E ) and reflexed appendage at the outside. Postgonite pointed in lateral view ( Fig. 11G ). Cercus undivided ( Fig. 11F, G ), with a digitiform ventral appendage near middle ( Fig. 11G ). Fig. 11. Medetera stigma , new species , male terminalia. A, Ventral view; B, Hypandrium, epandrial bristles, ventral; C, Apex dorsal surstylus, right side; D, Ventral surstylus; E, Apex dorsal surstylus, left side; F, Cerci dorsal; G, Hypopygium lateral. Scale bar = 0.1 mm. Drawings by P. Grootaert. Female. Unknown. Comments. Medetera stigma , new species , is quite characteristic in having at the base of the wings a brownish streak between the costa and R 1 and below R 1 . As far as we know, this characteristic is not observed in other Medetera species. Only two specimens are known: the holotype from a back mangrove near the mouth of Sungei Sempit ( PU23 ) and a paratype from a front mangrove along Sungei Maman ( PU17 ) . None of the species handled by Bickel (1987) in his revision of the Oriental and Australasian Medetera and by Yang et al. (2011) in the Fauna sinica, correspond to the present new species. Bionomics. Adults of most Medetera species are known to dwell on tree trunks where they hunt for small insects. The larvae of most species are predacious and live inside the burrows of bark beetles where they feed on the larvae of these beetles. Having this type of biology that on first sight is independent of the saline mangrove conditions, it is remarkable that a number of these Medetera species are exclusive for back mangroves and occur in the terrestrial forests behind the mangroves. At present, four of the eleven species actually known from Singapore are exclusive for mangroves. Some species are dominant in mangroves and rarely occur in other biotopes, while some are exclusive for terrestrial forests.