Platypalpus pilifer Grootaert et van der Weele, 2020

Grootaert, P., van der Weele, R., Oboňa, J. & Kustov, S. Yu., 2020, Description of a peculiar new species of the genus Platypalpus Macquart, 1827 (Diptera: Hybotidae) from the Caucasus, Caucasian Entomological Bulletin (Caucas. entomol. bull.) 16 (1), pp. 85-90 : 86-88

Platypalpus pilifer Grootaert et van der Weele , sp. n.

( Figs 1, 2)

Material. Holotype, ♂ ( RBINS): Azerbaijan, Zaqatala District, tributary of the Talacay River , 41°40ʹ40.7″N / 46°41ʹ57.9″E, 950 m a.s.l., from rocks and tree trunks, 9.05.2019 (P. Manko) . Paratypes: Azerbaijan: 1♂, 1♀ ( ZIN), Pirkuli , 22 km N Shemachi, forest, 20.05.1972 (V. Richter) ( ZIN) ; 2♀ ( ZIN), Kahi, 26.05.1978 (V. Richter) ; 2♂ ( RMNH), Şəki District, Kish resort garden , 41°14ʹ41.3″N / 47°11ʹ23.6″E, 905 m a.s.l., from walls of buildings and tree trunks, 5.05.2019 (J. Oboňa) ; 1♂, 2♀ ( KSU), Şəki District, Şəki, Quirxbulaq, small tributary of the Ayrychay River , 41°08ʹ51.6″N / 47°15ʹ38.0″E, 650 m a.s.l., from rocks and tree trunks, near bush, 6.05.2019 (J.Oboňa) ; 2♀ (RvdW), Qabala District,tributary/sidebrook of the Demiraparanchay River , below Durca , 41°02ʹ16.1″N / 47°53ʹ12.2″E, 1310 m a.s.l., close to the resort, steep small brook (mesolithal) in forest/ meadow area + small pond, from rocks and tree trunks, 10.05.2019 (J. Oboňa) . Georgia: 1♂ ( RBINS), Kakheti Region, Khornabuji, Eagle Gorge , 41°29.375ʹN / 46°05.857ʹE, 750 m a.s.l., from rocks and tree trunks, 4.05.2019 (J. Oboňa) . Russia: Republic of Dagestan: 1♂ ( ZIN), Terekli-Mekteb, 16.05.1972 (V. Richter); Republic of Adygea: 2♂ ( KSU), Teuchezhskiy District, Tlustenhabl, bank of Kuban River , 2.05.2010 (V. Gladun); Krasnodar Region: 4♂, 3♀ ( KSU), Goryachiy Klyuch District, Oktyabrskiy env., 25.04.2010 (S. Kustov) ; 3♂, 4♀ ( KSU, ZIN), Krasnodar, Vostochno-Kruglikovskiy , 15.04.2013 (S.Kustov) ; 7♂, 2♀ ( KSU, ZIN), Krasnodar, park 30 let Pobedy , 21.04.2013 (S. Kustov) ; 1♀ ( KSU), Abinsk District, Shapshugskaya env., bank of Adegoy River , 2.05.2013 (S. Nesterenko) ; 1♀ ( KSU), Anapa District, Utrish Nature Reserve , Dolgaya Niva natural boundary, 17.04.2014 (S. Kustov) ; 2♂ ( KSU), same data, 28.04.2014 (S. Kustov) ; 3♂ ( KSU), Anapa District, Utrish Nature Reserve , 28.04.2014 (S. Kustov) .

Description. Male ( Figs 1, 2). Body length 3.2–3.8 mm; wing length 3.7–3.8 mm.

Head. Black in ground-colour. Frons just below ocellar triangle 2 times as wide as front ocellus, narrowing toward base of antenna, grey dusted (in dorsal view). Face as wide as frons in front, silvery grey dusted including clypeus. A pair of short pale anterior ocellar bristles, shorter than verticals, a pair of minute posterior ocellars. Antenna black. Postpedicel elongate triangular, almost 2.5 times as long as wide. Arista 1.5 times as long as third segment. Postocular bristles pale, short above, longer below and some bristles near neck more dusky. Palpus brown in ground-colour, covered with long white fine bristles, a long white subapical bristle nearly twice as long as palpus. Proboscis shiny black, 3/4 eye height.

Thorax. Black in ground-colour, entirely thinly grey dusted and covered with pale hairs and bristles. One thin short humeral; acrostichals biserial, rather long, rows close together, diverging; dorsocentrals mostly as long as acrostichals, uniserial, becoming longer along prescutellar depression, rows ending in 1–2 long prescutellar. Two notopleural bristles with some shorter bristles aside, but no anterior notopleural (= posthumeral) bristle present. Scutellum with a pair of strong long apical bristles and a bristle at each side finer, nearly half as long as apicals. Pleura grey dusted, sternopleura polished.

Wing ( Fig. 1) with hyaline membrane, apical half with a brownish hue. Costa yellowish at base, becoming dark brown just before tip. Vein R 1 yellowish, tips of R 2 + 3, R 4 + 5 and M 1 dark brown. Crossveins separated but nearly contiguous. Vein closing anal cell straight, perpendicular on anal vein. Anal vein pale at base, disappearing in apical half and thus not reaching wing border. Bristling on costa pale at extreme base farther becoming darker. Pair of long pale basal costal bristles.

Squama white with long white cilia. Haltere entirely white.

Legs yellow including all coxae. Black parts are: border where mid and hind coxae are attached on thorax, border of apex of trochanters; mid femur with black stripe along the double row of ventral spinules; sides of mid and hind knees black; tip of mid tibial spur and sharply black annulated tarsomeres. Fore tarsomere 1 (basitarsus) is entirely yellow and tips of mid and hind tarsomere 1 are faintly brown.

Fore leg. Coxa densely set with white bristles. Fore femur much swollen, ventrally with a double row long white fine bristles, most about as long as femur is wide. Fore tibia spindle-shaped dilated, half as wide as femur; dorsally with some brownish bristles and with numerous long ventral and very long anteroventral and posteroventral fine bristles (at tip nearly 3 times width of tibia). Tarsomere 1 with 4–5 very long posteroventral bristles (similar to posteroventral bristles on fore tibia).

Mid leg.Coxa densely set with long white bristles.Trochanter with a single more dusky long ventral bristle. Mid femur very strong, about 1.5 times as wide as fore femur and 2 times as wide as hind femur; some longer anterior white bristles near tip, numerous posteroventral bristles, a little longer than half width of femur. A long pointed spur on tibia with black tip.

Hind leg. Coxa with white apical bristles. Femur narrow, posterodorsally and ventrally densely set with pale fine bristles about as long as femur is wide. Tibia also dorsally and ventrally densely set with fine white bristles as long as tibia is wide and a dorsal row of five black bristles as long as tibia is wide.

Abdomen. Shiny black but tergites 1 and 2 with a small grey dusted patch at sides, further entirely set with white bristles.

Male terminalia globular ( Fig. 2). Cerci short, concealed in epandrial lamellae. Right cercus with widened apex, left cercus pointed ( Fig. 3). Left epandrial lamella with truncate rounded tip and left border with small protuberance below middle. Left border set with long pale bristles, those below longest with somewhat entangled tips ( Fig. 4).

Female. Body length 4–4.6 mm; wing length 4.3–4.6 mm. In most respects similar to male. Tergites and sternites with pale yellow hairs, denser laterally. Apical two segments and cerci dusted.

Fore femur with shorter bristles ventrally. Fore tibia only weakly spindle-shaped with posteroventral bristles much shorter than in male and fore basitarsus covered with only short bristles.

Diagnosis. A medium-sized black species (3.2–4.6 mm) of the P. pallidiventris-cursitans group with a single pair of short pale vertical bristles, close together (about 1.5 times as wide as frons below anterior ocellus). Antenna black with third antennal segment 2.5 times as long as wide, arista 1.5 times as long as third segment. Humeral bristle present but short and thin. Acrostichals biserial. Legs yellow including all coxae. Tarsi distinctly annulated black. Male with fore tibia spindle-shaped dilated with numerous long ventral and very long anteroventral and posteroventral fine bristles. Mid femur much thickened with pale posteroventral bristles and a ventral black stripe upon which the double row of spinules are inserted. Mid tibia with long, pointed apical spur. Abdomen entirely shiny black, anterior two tergites with small lateral patches of greyish pollinosity.

Habitat. The new species was found in a wide variety of habitats on one hand rather anthropogenic habitats like gardens in a city and an orchard as well on vegetation along a stream ( Figs 5, 6). All specimens were collected from rocks or walls of buildings and tree trunks.

Distribution. Recorded from the Caucasus ( Azerbaijan, Georgia and Russia).

Etymology. The name pilifer alludes to the presence of the long ventral bristles on the male fore tibia.

Notes. We classify Platypalpus pilifer sp. n. in the P. pallidiventris-cursitans group, though the presence of a weak humeral bristle and the thinly dusted mesonotum (seen on dried specimens) would classify P. pilifer sp. n. in the P. minutus group.

The pallidiventris group is a very large group while the P. minutus group contains only a few species and is probably a part of the P. pallidiventris-cursitans group. Using the key for the Caucasian Platypalpus in Kustov et al. [2015] only three species belong to the minutus -group: P. minutus (Meigen, 1804) , P. pseudociliaris and P. ruficornis (von Roser, 1840) . The latter two species have the posterior part of the mesonotum polished while P. minutus has the mesonotum thinly dusted except for a median shiny stripe. In addition, the fore tibia in P. minutus bears an apical brown rim, absent in the new species described here. None of these species of the region have a very thickened spindle-shaped fore tibia with very long pale ventral bristles. In addition, the black ventral stripe of the mid femur is also a rare characteristic in Platypalpus .

If one considers the dusting of the mesonotum as dense and considers that the humeral bristle is strong and distinct, the new species will lead in the key of Kustov et al. [2015] to P. infectus ( Collin, 1926) . In that species the antenna is entirely black, the clypeus is dusted and the vertical bristles are not wide apart (at most 1.5 times the width of the frons below the anterior ocellus). In addition the fore tibia is swollen and the mid femur is very thickened in both species. However, the true P. infectus has only short ventral bristles on the swollen fore tibia, shorter than the tibia is wide, weakly annulated tarsomeres, there is generally a distinct anterior notopleural bristle, the humeral bristle is stronger, there is no black ventral stripe on the mid femur and the male terminalia are different in many distinct characters as can be seen in the notes below on P. infectus .

In the key of Caucasian Platypalpus [ Kustov et al., 2015] the new species can be included instead of P. infectus as follows:

22(21). Clypeus polished black. Postpedicel about 2.5 times longer than wide. Mid femur without a ventral black stripe. Tarsomeres of all legs broadly sharply black annulated. Abdomen black, entirely shiny ....................... ......... P. arzanovi Kustov, Shamshev et Grootaert, 2014

– Clypeus grey dusted ............................................................ 23 23(22). Fore tibia with very long (nearly 3 times width of tibia at apex) anteroventral and posteroventral fine bristles. Mid femur with a ventral black stripe ........... ........................................................................ P. pilifer sp. n.