Species of the genus Chrysotus Meigen, 1824 (Diptera: Dolichopodidae) from Japan, with descriptions of two new species

Two new species of the genus Chrysotus Meigen, 1824 are described: Ch. masunagai Negrobov, Kumazawa, Tago sp. nov and Ch. saigusai Negrobov, Kumazawa & Tago sp. nov. Chrysotus parilis Parent, 1926 is recorded from Japan for the first time. An identification key to all known species of the genus Chrysotus of Japan is presented together with a tree diagram showing relationships among them.


Taxonomic descriptions
Class Hexapoda Blanville, 1816 Order Diptera Linnaeus, 1758 Family Dolichopodidae Latreille, 1809 Genus Chrysotus Meigen, 1824 We found the following six species in the collection of Mr. T. Tago and of the Schmalhausen Institute of Zoology of National Academy of Sciences Ukraine, including a species new to Japan and two species new to science.

Distribution
Japan and Russia: Sakhalin, Primorye, Khabarovsk, Magadan, Chukotka. The species was described from Japan and the Far East of Russia by Negrobov & Maslova (1995).

Diagnosis
Face narrow; postpedicel small; lower postocular setae white; fore coxa with black hairs; femora mostly yellow; mid tibia with 2 anterodorsal and 2 posterodorsal setae; hind femur and with long setae, hind tibia with short hairs; phallus with two lateral processes on tip.

Etymology
The species is named after the famous dipterologist Dr. Kazuhiro Masunaga from Japan. Head. Frons green with purple tinge, without pollen. Face narrow, its width narrower than the width between ocellar bristles in lower part. Frons green at the top, with pollinosity at the bottom. Antenna black, postpedicel small, triangular, length 1.3 times greater than height. Arista subapical, with short hairs. Length of arista more than two times longer than length of postpedicel. Proboscis and palpus brown with black hairs without pollen. Lower postocular setae pale. tHorax. Metallic green, scutum with bronze tinge and without pollen. Pleura with pollen, propleuron with 1-2 setae. 5 pairs of strong dorsocentral setae. Acrostichal setae long, irregular 6-7 pairs, arranged in two rows. Scutellum with 2 long and 2 short lateral setae.
Leg. Fore coxa yellowish brown, mid and hind coxa dark; femora mostly yellow, except dorsal surfaces of fore femur, middle part of the mid femur and apical third part of the hind femur dark; fore and mid tibiae yellow, hind tibia dark; tarsi yellow except hind tarsus and apical parts of fore and mid tarsus dark. All coxae with dark hairs and setae. Fore femur with long white anteroventral hairs, length approximately equal to the width of femur. Fore tibia with 1 anterodorsal seta and short posteroventral hairs. Ratio of fore tibia and tarsus (from 1 to 5) 2.6: 1.5: 0.6: 0.5: 0.3: 0.4. Mid femur with a short preapical seta. Mid tibia with 2 anterodorsal and 2 short posterodorsal setae. Ratio of mid tibia and tarsus (from 1 to 5) 3.4: 1.6: 0.8: 0.6: 0.4: 0.3. Hind femur with several long preapical setae and short anteroventral hairs on entire length femur. Hind tibia with 3-4 short anterodorsal setae and short erect anteroventral hairs, its length approximately equal to the diameter of tibia. First segment of hind tarsus with short erect hairs. Ratio of hind tibia and tarsus (from 1 to 5) 3.7: 1.2: 1.0: 0.6: 0.4: 0.3.
Wing. Hyaline with dark veins; R 4+5 and M 1+2 parallel at apex. Length of costal section between R 4+5 and M 1+2 more than 2 times longer than that between R 2+3 and R 4+5 ; m-cu distinctly shorter than apical part of CuA 1 . Halter and cilia on lower calypter yellow.
abdoMen. Metallic green, grey pollinose laterally, covered with black hairs. Epandrium oval in the basal part of the oval; apical part of surstylus bent. Apex of phallus with two short lateral processes, left process is rounded. Cercus with brown hairs, top of the left side with long processes.

Female
Unknown.

Addition to the key
In the key to the Palearctic species of Chrysotus (Negrobov et al. 2000

Diagnosis
Face narrow, width in lower part less than distance between ocellar bristles; antenna black; postpedicel transverse-oval, with a triangular tip; lower postocular setae white; fore coxa with black hairs; femora mainly green-brown; mid tibia with 2 anterodorsal and 2 posterodorsal setae; hind femur with long setae, hind tibia with short hairs; phallus with two lateral processes on tip.

Etymology
The species is named after the famous dipterologist Dr. Toyohei Saigusа from Japan. Head. Frons green with purple tinge, without pollen. Face narrow, its width narrower than the width between ocellar bristles in lower part. Frons green at the top, with pollinosity on the bottom. Antenna black, postpedicel small, a right-angled triangular, its length about equal to its height. Arista subapical, with short hairs. Length of arista approximately five times longer than length of postpedicel. Proboscis and palpus brown with black hairs without pollen. Lower postocular setae pale.
Leg. All coxae dark; femora mostly dark, except apical part of fore femur, apical and basal part of mid femur and basal part of hind femur yellow; trochanters yellow or yellowish-brown; fore and mid tibiae yellow, hind tibia yellowish-brown; most part of mid and hind tarsi yellow, basal parts hind tarsus yellowish-brown. Coxae with dark hairs and setae. Fore femur with 3 long preapical setae. Fore tibia with 1 anterodorsal seta and short posteroventral hairs. Fore tarsus with short hairs. Ratio of fore tibia and tarsus (from 1 to 5) 2. Wing. Hyaline with dark veins; R 4+5 and M 1+2 slightly divergent at apex. Length of costal section between R 4+5 and M 1+2 about twice longer than that between R 2+3 and R 4+5 ; m-cu distinctly shorter than apical part of CuA 1 . Halter and cilia on lower calypter yellow.
abdoMen. Metallic green, pollinose laterally, covered with black hairs. Epandrium oval in the basal part with the small projection; apical tip of surstylus bent. Phallus with two lateral processes at apex. Cercus oval with black hairs.

Female
Unknown.

Cladistic analyses
According to Capellari (2013), the absence of a small projection in the basal part of the epandrium represents the plesiomorphic character state. The combination of this character state with such character states as pale palpus, dark fore coxae, yellow hind tibia with short erect anteroventral hairs and short erect hairs on the first segment of hind tarsus separate the group of Ch. saigusai and Ch. tagoi from all other Japanese Chrysotus (Fig. 6). The species Ch. saigusai can be separated from Ch. tagoi by having anteroventral hairs on the entire length of find femora and mostly dark fore femora. The species Ch. laesus, Ch. nudisetus and Ch. kumazawai compose the group with the least stable internal connections. Their association is based on the similarity of color of fore, middle and hind femora and the absence of the anteroventral hairs on entire length of hind femur.

Discussion
The genus Chrysotus is paraphyletic or possibly polyphyletic within the subfamily Diaphorinae (Capellari & Amorim 2012). Bickel (2010) considers species of Chrysotus as various small-size Diaphorinae species, mostly with inadequate description. Knowledge on the phylogenetic relationships of the genus is poor. Therefore, it is important to investigate phylogenetic relationships of Chrysotus species using both morphological and biogeographical data.  The present cladistic analysis was made in two ways. When we consider the characteristics used in the Palearctic keys of the genus, we were considering the possible relationship between the endemic and trans-Palearctic species, thus inserting the endemic species in the general scheme.
The morphology of the genus Chrysotus is relatively variable, and the most important diagnostic characters are the morphology of the apical part of the phallus, the color of the legs and the form of the postpedicel. It should be noted that the use of the full list of characteristics does not allow for allocating the endemic species in a separate cluster on any of the cladistic trees.
The cladistic analysis was carried out on the basis of a different combination of characters. It allowed for the identification of groups of characters that separate the Japanese endemic species from the trans-Palearctic species. This group of characters includes color of coxae and trochanter, ratio of apical part of CuA 1 and dm-cu, the presence of erect hairs at hind tibia and the first segment of hind tarsus and morphology of hypopygium. Most of the characteristics, including head morphology and color of legs, which are used for the diagnosis of the Palearctic species, cannot be used for the Japanese species. Thus, further study of the phylogenic relationships of Chrysotus species should be carried out, using a wider range of species, including both trans-Palearctic and endemic species.