Empria improba (Cresson, 1880)

Liston, Andrew, Mutanen, Marko, Heidemaa, Mikk, Blank, Stephan M., Kiljunen, Niina, Taeger, Andreas, Viitasaari, Matti, Vikberg, Veli, Wutke, Saskia & Prous, Marko, 2022, Taxonomy and nomenclature of some Fennoscandian Sawflies, with descriptions of two new species (Hymenoptera, Symphyta), Deutsche Entomologische Zeitschrift 69 (2), pp. 151-218 : 151

Empria improba (Cresson, 1880)

Fig. 22A-E

Emphytus improbus Cresson, 1880: 11. ♀, ♂. Syntypes. Type locality: Nevada, USA. Lectotype ♂ (type No. 365) designated by Smith (1979). ANSP.

Tenthredo (Poecilostoma) hybrida Erichson in: Ménétriés in: Middendorff, 1851: 60-61. ♀. Syntypes (assumed). Primary homonym of Tenthredo (Tenthredo) hybrida Eversmann, 1847. Type locality: Udskoj Ostrog [Russia, Khabarovsk Krai, Udskoe]. Lectotype ♀ designated by Prous et al. (2011). ZIN. syn. nov.

Poecilosoma plana Jakowlew, 1891: 31. ♀. Type locality: Irkutsk, Russia. ♀. Holotype. ZIN. syn. nov.

Empria itelmena Malaise, 1931b: 23. ♀, ♂. Syntypes. Type locality: Kamtschatka, E[lisowo] [Russia, Kamchatka Krai]. Lectotype ♀ designated by Prous et al. (2011). NHRS. syn. nov.

Empria camtschatica Forsius, 1928: 46-47. ♀. Holotype. Type locality: Russia, Kamchatka Krai, Bolsheretsk [Bolscheretsk]. MZH. syn. nov.

Notes.

The species boundaries between willow-feeding taxa of the Empria immersa group ( E. immersa , E. camtschatica , E. plana , and E. improba ) have proved to be difficult to elucidate ( Prous et al. 2014, 2020). In Fennoscandia, two forms can commonly be found at the same time and place ( Prous et al. 2014): E. immersa with a dark pterostigma and short antenna, and E. camtschatica with a pale pterostigma and long antenna. These two forms can also be distinguished by larval morphology (Fig. 22 ). Based on ex ovo rearings by M. Prous (two females from Sweden and Estonia) and ex larva rearings by Ponomarev (2022) of E. immersa , and ex ovo rearings by M. Prous of E. camtschatica (using two females from Sweden), the main difference seems to be in head coloration: E. immersa with an occipital fleck or stripe (Fig. 22F-M ) and E. camtschatica with occipital and parietal stripes (Fig. 22A-E ). An additional difference may be that glandubae (white conical warts) are more prominent in E. immersa than in E. camtschatica . Although based on limited specimen sampling, genome scale data ( Prous et al. 2020) support E. immersa as a distinct species most consistently compared to the other species in the E. immersa group. In Fennoscandia, taxonomy is complicated by the presence of occasional specimens identifiable as E. plana , somewhat intermediate in morphology between E. immersa and E. camtschatica (pterostigma like E. camtschatica , saw intermediate). Genome scale data of one E. plana female from Sweden do not indicate affinity with E. immersa , but do show at least some affinity with E. camtschatica (Sweden), E. improba (Canada), and one other E. plana (Hokkaido, Japan) (see fig. 5 in Prous et al. 2020). Given the above, we synonymize E. plana and E. camtschatica with E. improba , because clear boundaries between these taxa cannot at present be drawn. Thus, in Europe, the specimens with dark pterostigma, short antennae and more prominent serrulae of the saw can be identified as E. immersa , and those with pale pterostigma, usually longer antennae, and less prominent serrulae as E. improba (see Prous et al. 2014). In North America, however, at least some E. improba specimens look externally more like E. immersa (dark pterostigma and metafemur), while the serrulae of the saw resemble E. camtschatica . Lacourt (2020) suggested that E. camtschatica could be a synonym of E. improba , but genetically these taxa are not necessarily closer to each other than they are to E. plana ( Prous et al. 2020). If the circumscription of E. improba as proposed here is considered incorrect, then it remains unclear how many additional species should be recognized, and how these should be delimited. For example, in Europe the morphological distinction between E. camtschatica and E. plana is not clear, although these forms can be more reliably distinguished from E. immersa .

Figures

Figure 22. Larvae of Empria on Salix. A-E. E. improba (Cresson, 1880); F-M. E. immersa (Klug, 1818).