West Palaearctic species of the Hercostomus species-group III ( Diptera , Dolichopodidae ) , with description of a new species from Turkey

The West-Palaearctic species of the Hercostomus species-group III are reviewed, a species-list and a revised key to males is provided. Hercostomus angustus (Loew, 1857) is restored from synonymy with Hercostomus nanus (Macquart, 1827) based on differences in male genitalia. Hercostomus griseifrons Becker, 1910 is redescribed and a lectotype is designated. Hercostomus tonguci sp. n. is described from Turkey.

The traditional definition of Palaearctic species-groups of Hercostomus is based on the following characters: -Femora yellow; lower postocular setae yellow or white; antennae partly yellow ...........

Material and methods
The material examined is from the collection of the Czech University of Life Sciences Prague (CULSP) and from the University of Berlin (Museum für Naturkunde, Leibniz-Institute for Evolution and Biodiversity Science).Distribution data are taken mainly from Pollet (2004) and Yang et al. (2006), but doubtful records are omitted.
Body length is measured from the base of the antennae to the tip of abdominal segment 6; wing length from wing base to wing apex.The positions of features on elongate structures such as leg segments are given as a fraction of the total length, starting from the base.The following ratios are used: relative podomere ratios: femur, tibia, tarsomere 1/2/3/4/5; length of crossvein dm-cu to distal section of CuA (= CuAx ratio); distance between veins R 2+3 and R 4+5 to distance between R 4+5 and M at costal margin (= RMx ratio).Describing the hypopygium, dorsal and ventral refer to the position prior to rotation and flexion, i.e. in figures top is morphologically ventral and bottom is dorsal.If not otherwise indicated, the coloration of hairs and setae is black.Morphological terminology follows Cumming and Wood (2009), except for male genitalia which follows Brooks (2005).

Description of the new species
Hercostomus tonguci sp.n.
Diagnosis.Antenna black, postpedicel as long as high; arista dorsoapical; face narrow, with dense grey pruinosity; lower postocular setae black; abdominal segments 1-3 with yellow lateral spot; legs including coxae yellow; veins R 4+5 and M parallel; CuA about 2.5 times as long as crossvein dm-cu; cercus yellow, with claw-like apical setae.
Etymology.The new species is dedicated to the Turkish dipterist and Dolichopodidae worker Alper Tonguç.
Remarks.H. tonguci belongs to the species-group III according to Stackelberg (1933) which is defined by the following characters: femora yellow, postocular setae black.In the recent key to Palaearctic species of the species-group III (Selivanova et al. 2012) the new species runs to H. acutangulatus Yang & Saigusa, 1999 described from China based on the yellow lateral spots on the abdomen.H. tonguci can be distinguished as follows: mesonotum without yellow coloration, first flagellomere as long as high, cercus apically with claw-like setae; wing length 2.2 mm.In H. acutangulatus the mesonotum is partly yellow, the postpedicel is 1.6 times as long as high, the cercus has no claw-like setae apically, and the wing length is 5 mm.Type locality.Asia Minor," Kleinasien".

Species list of the
When studying the types at the University of Berlin, the species is restored from synonymy with H. nanus based on differences in the male genitalia.Greece, Hungary, Italy, Luxembourg, Netherlands, Norway, Poland, Romania, Russia, Slovakia, Spain, Sweden, Switzerland, Turkey, Ukraine.Nearctic: Canada, USA.Oriental: India.
Redescription of Hercostomus griseifrons based on type material (Museum für Naturkunde, Leibniz-Institute for Evolution and Biodiversity Science).Since Becker has not designated a holotype, a lectotype is designated on order to stabilize the nomenclature.
Female: differs from the male by a broader face and a more intense darkening of the apex of the hind femora.

Discussion
Originally the Hercostomus species-group III was more expanded including species now transferred to other genera.The genus Gymnopternus Loew, 1857 earlier treated as synonym or subgenus of Hercostomus is now accepted as a separate genus (Brooks 2005).The West Palaearctic species Hercostomus chalybeus (Wiedemann, 1817) was transferred to the genus Ethiromyia Brooks & Wheeler, 2005. Becker (1917) stated that H. nanus and H. chetifer have lower postoculars yellow or black and thus he listed both species twice in his key.I have examined series of H. nanus and H. chetifer from different localities in Europe but could not find specimens with yellow lower postocular setae, although there could be the illusion of yellowish-brown setae depending on light reflections.Stackelberg (1933) and subsequent workers omitted H. nanus in the male key of species-group III but included it in species-group II.
Moreover, it should be noted that in the current key to Palaearctic species of the Hercostomus species-group III (Selivanova et al. 2012) H. separatus d'Assis Fonseca, 1976and H. nanus (Macquart, 1827) are lacking.
In this work a species list and a revised key to the species-group III is provided, and a new species from Turkey is described.