On the identity of Paracacoxenus kaszabi Okada, with the formal description of a new closely related species (Diptera, Drosophilidae)

In order to clarify the identity of Paracacoxenus kaszabi Okada, 1973, a species described from Mongolia, the morphological structures of one male paratype, collected at 1,750 m altitude, were analyzed and redescribed. In addition, one of the male specimens, previously referred to in literature as ‘sp. aff. kaszabi’, is restudied and described as Paracacoxenus macai sp. nov. (type locality: Schmelz, Parco Nazionale dello Stelvio, Province of Bolzano, Region of Trentino-Alto Adige, Italy). The former species seems to be distributed in central and eastern Asia while the latter is supposed to have an exclusively European distribution. The midtibial preapical seta of male Paracacoxenus argyreator (Frey, 1932), which is unusually long, is illustrated by photomicrographs. A key to the European species of Paracacoxenus Hardy, 1960 is presented.


Introduction
Paracacoxenus kaszabi was described from Mongolia by Okada (1973). Further detailed records were published from the Czech Republic (Máca 1980, Máca and Laštovka 1986, Máca and Barták 2001 as well as from Siberia (Watabe et al. 1995, Vinokurova 2003. In a former paper (Bächli and Vilela 2011), we provided a description of a species from northern Italy, provisionally named as 'Paracacoxenus sp. aff. kaszabi sp. nov.', because some doubts existed as to whether this species was really different from P. kaszabi, of which only the rather short description by Okada (1973) was known. This was later complemented by some additional characters added by Máca (1980). Máca (1980), while discussing one male and three female Paracacoxenus specimens found in Veselí nad Lužnicí (South Bohemia, Czech Republic), provided some illustra-tions and additional characters, primarily to distinguish it from P. exiguus, a species originally found in Silesia (Poland). He mentioned that the specimen at hand showed minor differences from Okada's description and figures, but his decision to identify them as P. kaszabi was sound because P. kaszabi was then the only species which had been described.
Through the assistance of Dr Jan Máca, we were able to analyse three European male specimens from his collection, formerly identified by him as P. kaszabi. Because both species are morphologically very similar, we had some hope that at least the male terminalia would demonstrate clear differential characters.
The general morphology and the male terminalia of 'Paracacoxenus sp. aff. kaszabi sp. nov.' have already been published (Bächli and Vilela 2011). In this paper, we want to describe the differences between P. kaszabi and 'Paracacoxenus sp. aff. kaszabi', formally described here as Paracacoxenus macai sp. nov.

Material and methods
The redescription of Paracacoxenus kaszabi Okada, 1973 is based on a male paratype specimen on loan from the Hungarian Natural History Museum (HNHM), Budapest (Bächli 1984, Bächli andRocha Pité 1984). For comparison purposes, three Paracacoxenus male specimens on loan from our colleague Dr Jan Máca, collected  Data labels attached to each type specimen are cited in full with a slash [/] indicating a line change and a double slash [//] a label change. Our own notes or interpretations are included in brackets (also in other items throughout the text).
The preparation of microscope slides were made following Wheeler and Kambysellis (1966) and Kaneshiro (1969). The abdominal sclerites, including the disarticulated male terminalia, are preserved in microvials filled with glycerin and attached by the stopper to the pin of the respective specimen. Refer to Vilela and Bächli (2000) and Bächli et al. (2004) for further details.
Male pinned specimens and their dissected terminalia were photomicrographed with a Smartphone's back camera (Samsung S8) attached to both a stereomicroscope and to a compound microscope respectively. Several images in different focal planes were obtained for every specimen and they were then digitally stacked using the "All Methods" mode of Combine ZP free software (Hadley 2010) and the final all-in-focus image was improved using the Adobe Photoshop Elements 2.0 software. Male dissected terminalia were also drawn using a camera lucida (1.8x) attachment on a compound microscope under a 20x objective. For measurements and indices see Vilela and Bächli (1990); for morphological terminology see Vilela and Bächli (2000) and Bächli et al. (2004).
Complementary redescription. The photomicrographs of the habitus of a male paratype (Figs 23-28) presented in this paper are intended to complement the original description of this species (Bächli and Vilela 2011). Three analysed male specimens from South Bohemia (PCJM) cited above were illustrated (Figs 29-59) for the purposes of geographical distribution only, as they represent new records, and they are not considered as belonging to the type series of Paracacoxenus macai sp. nov.   Etymology. Epithet: a genitive patronym to honour of our colleague Dr Jan Máca who first detected this species in Europe (Czech Republic).

Discussion
Species of Cacoxenus and Paracacoxenus do not show a particular Alpine distribution (Máca 1977, Máca et al. 2015. However, almost all specimens of Paracacoxenus macai n. sp. were collected in Schmelz (South Tyrol), using a Malaise trap. The biology of Paracacoxenus species is virtually unknown, but a connection with stem rust is suggested (McAlpine 1968) and the Schmelz locality is covered with many broad-leave trees (Ziegler 2008). We suppose that there are additional such localities in the Alps where Paracacoxenus macai be abundant.

Conclusion
The identity of Paracacoxenus kaszabi was clarified through the analyses of the male terminalia of a paratype from Mongolia. The previous suspicion that similar specimens collected both in Italy and Czech Republic do not belong to this species was confirmed. However, we were not able to check all specimens previously identified as P. kaszabi that have been recorded from Europe. Given that P. kaszabi and P. macai sp. nov. are sibling species, fully differentiated only by the male terminalia, we suggest that all western Palaearctic specimens previously identi- fied as the former species belong to P. macai sp. nov., and that P. kaszabi is most probably a species of central and eastern Asian distribution.