Eobroscus masumotoi Morita 1990

Eobroscus masumotoi Morita, 1990

TAIWAN: Alishan [locus typicus], 2400 m, 17–26 June 1995, Dalihod leg. (1 female, cWR); same data but: P. Moravec leg. (1 female, cSCI).

The genus Eobroscus Kryzhanovskij, 1951 was described for Broscus lutshniki, a species from the Siberian Far East and Japan. More than 30 years later a second species, E bhutanensis Morvan, 1982 was described from Bhutan. Still later, Morita (1990), when describing a third species (E. masumotoi from Taiwan) created the subgenus Orobroscus for the two species E. bhutanensis and E. masumotoi. Finally, in 1995 the same author described a third species of that subgenus, E. uenoi Morita, 1995, from Vietnam. The distinguishing characters of Orobroscus mentioned by Morita (1990: 159) were:

(i) the occurrence of two setae at each side of the last abdominal sternite of the male,

(ii) the presence of adhesive hairs on the proximal two (instead of three) protarsomeres in the male, and

(iii) the lack of dorsal strigosity of the onychium.

We had the opportunity to examine additional Eobroscus material covering the whole geographical distribution of that genus and all the known species. As a result we observed the great similarity of the three taxa attributed to Orobroscus as well as the remarkable variability of the characters used for the separation of the latter taxon. For example, concerning the setosity of the last abdominal sternite we observed that in both the species, E. masumotoi and E. lutshniki, some male specimens had a single seta on one side but two on the opposite side. In most of the E. bhutanensis males we found two pairs of setae, but in a specimen from Vietnam we found only one pair. Also the holotype specimen of E. uenoi Morita, 1995, bears a single pair of setae at the apical margin of the last abdominal sternite. Moreover, we found an E. lutshniki female specimen from Sakhalin that bears three setae on the right and two on the left side. Based on these observations we conclude that within the genus Eobroscus the number of setae developed at the apical margin of the last abdominal sternite is not a speciesspecific constant. For this reason, abdominal setation seems inappropriate to be used as a differential character to define natural lineages within Eobroscus. This conclusion was already reached by Morita (1995: 11) in the paper with the description of E. uenoi Morita, 1995; however, the author still maintained the validity of Orobroscus.

Concerning protarsal adhesive vestiture of males we confirm the observation of Morita (1990) who found adhesive vestiture on the proximal three tarsomeres of E. lutshniki (Figure 4D) and on the proximal two tarsomeres of E. bhutanensis (Figure 4G) and of E. masumotoi. However, as a result of a comprehensive phylogenetic analysis of the tribe Broscini Roig-Juñent (2000) showed that this character has several parallel gains and losses, and it is therefore of low phylogenetic value (zero in the cladistic analysis of Roig-Juñent 2000). Species of the same genus and even of the same subgenus have or lack this structure. Those conditions Roig-Juñent (2000) found also regarding the mesotarsal adhesive vestiture. The different extent of adhesive vestiture on male mesotarsomeres in Eobroscus species is shown in Figure 4E (E. lutshniki, adhesive vestiture covers approx. 75% of the ventral surface of tarsomere 2) and Figure 4H (E. bhutanensis, adhesive vestiture covers less than 50% of the ventral surface of tarsomere 2).

Concerning the surface morphology of the onychium we found traces of dorsal longitudinal strigosity also in E. bhutanensis (see Figure 4I) and in E. masumotoi. This is in contrast to the statement of Morita (1990: 156) that members of Orobroscus have a smooth onychium dorsally. It is true that strigosity of the onychium is much more markedly developed in E. lutshniki (Figure 4F).

In summary, we state that separation of a subgenus Orobroscus as defined by Morita (1990) is highly questionable. Therefore, we propose Orobroscus Morita, 1990 as a junior synonym of Eobroscus Kryzhanovskij, 1951.

This decision is supported by our observation that species diversity in the genus Eobroscus is lower than expected: We could compare several specimens from Vietnam (coming from the type locality of E. uenoi Morita 1995) with the holotype of E. bhutanensis Morvan, 1982, and with additional specimens from China, Myanmar, Nepal and northeast India, and we could determine identity. Based on a careful examination of this material we can state that all differential characters of E. uenoi mentioned by Morita (1995) fall in the variability of the species E. bhutanensis: (i) body size 15.7–16.1 mm (15.9–16.3 mm in E. uenoi); (ii) coloration of dorsal side of body brown to black with + / – prominent metallic lustre (see Figure 2B; body almost black in E. uenoi with greenish lustre on elytra); (iii) aedeagus relatively robust (see Figure 5 C– F; identical in E. uenoi, see Morita 1995: 9); (iv) lateral and dorsal wing-like expansions of aedeagal median lobe markedly produced (see Figure 5 C–F; identical in E. uenoi, see Morita 1995: 9). Therefore, we propose E. uenoi mentioned by Morita (1995) as a junior synonym of E. bhutanensis Morvan, 1982, a macropterous species with a wide distribution along the Himalayan chain and in neighbouring mountainous areas of South East Asia (Figure 7).

Hence, the genus Eobroscus encompasses actually no more than three species. We believe that this is an additional argument against splitting the genus into two subgenera.

In addition, we have doubts about the status of E. masumotoi Morita, 1990 as a distinct species. Based on the comparison of two female specimens from the type locality with the E. bhutanensis material listed above we have to reject four of the six differential characters mentioned by Morita (1990: 164) because they fall within the variability of the species E. bhutanensis: (i) the colour of the body surface; (ii) the length of the temples in proportion to the length of the eyes; (iii) the shape of the pronotum; (iv) the shape of the elytra. We have to confirm the observation of Morita (1990) that specimens of the Taiwanese population (E. masumotoi) are somewhat smaller (14.9 mm; Morita 1990: 160: 14.5–15.2 mm) than specimens from the continent (E. bhutanensis, 15.7–16.1 mm). By comparing our preparations of E. bhutanensis aedeagi (e.g. Figure 5 C–F) with the figuring of the E. masumotoi holotype specimen (Morita 1990: 163) we also confirm that the median lobe of the latter is slightly shorter. In addition, lateral wing-like expansion on the right seems lesser developed in the E. masumotoi holotype than in specimens of E. bhutanensis. However, apart from the holotype no additional male specimens of E. masumotoi have been described or recorded in the literature and so, the true variability of the external shape of the aedeagus remains unknown for us. For this reason the decision to confirm or to reject the species status of E. masumotoi has to wait until further material from Taiwan becomes available.