Sakhalinencyrtus Simutnik, 2021

Simutnik, Serguei A., Perkovsky, Evgeny E. & Vasilenko, Dmitry V., 2021, Sakhalinencyrtus leleji Simutnik gen. et sp. nov. of earliest Encyrtidae (Hymenoptera, Chalcidoidea) from Sakhalinian amber, Journal of Hymenoptera Research 84, pp. 361-372 : 361

Genus Sakhalinencyrtus Simutnik gen. nov.

Type species.

Sakhalinencyrtus leleji , sp. nov.

Species composition.

Type species.

Etymology.

From “Sakhalin” and " Encyrtus ". Gender masculine.

Diagnosis.

Habitus not ‘encyrtiform’, body not compact, without metallic shine; vertex above upper level of eyes (frontal view); interantennal prominence not high, without carina; eyes relatively small, convex, almost circular, height of eye as long as malar space; pedicel shorter than first two funicular segments combined; clava with an oblique truncation extending along entire ventral surface and without sutures; pronotum short; all coxae large; parastigma distinctly widened, but not triangular; mesotibial spur slightly longer than basitarsus, cerci located at almost non-dilated apex of gaster; Mt8 small, U-shaped; hypopygium short, almost reaching apex of metasoma, genitalia weakly sclerotized, transparent, with a long phallobase and short aedeagus (excluding apodemes), without visible digiti.

Remarks.

Placement of the new genus and species into the family Encyrtidae is supported by: presence of the linea calva with long covering setae at distal margin; mesotibial spur thick and long; axillae large, triangular, transverse, medially touching each other; scutellum large, as long as mesonotum; mesopleuron enlarged, convex, mesocoxa inserted at its middle; Mt8 U-like; cercal setae long.

However, cerci of the new genus are located extremely close to the apex of gaster. As in other known males in Sakhalinian amber, such a position of the cerci is not found among the extant Encyrtidae or among the late Eocene ones.

The new genus somewhat resembles the extant genus Eucoccidophagus Hoffer, 1963 by widened parastigma, relatively small and almost circular eyes, and cerci situated close to the apex of gaster. However, Sakhalinencyrtus well differs by the extremely apical position of cerci which are close to each other, long marginal vein, linea calva with a well-developed row of long covering setae on its basal margin (Fig. 3B , cs); long mesotibial spur (longer than mesobasitarsus) and absence of digiti on phallobase. All species of Eucoccidophagus have a short, almost absent marginal vein (Fig. 4D and figs I, II6, IV4 in Guerrieri 1994), mesotibial spur always shorter than mesobasitarsus, cerci substantially advanced toward gastral base and located far from each other (fig. 12e in Simutnik 2020 and figs I, II8 in Guerrieri 1994). It should be noted that all known late Eocene encyrtids from European ambers also retain long veins of forewings including the marginal vein. Reduction to complete absence of the marginal (as, for example, in the species of Eucoccidophagus ) and postmarginal veins, the subsessile stigmal vein is common in many extant encyrtids, but has not been found among fossil encyrtids from either the middle or late Eocene. More detailed comparison of the fossil encyrtids with the extant genera having an apical or near apical position of the cerci is provided by Simutnik (2020) and Simutnik and Perkovsky (2006, 2018).

A close relationship of some examined but undescribed fossil Encyrtidae from the Baltic amber to the extant genera Eucoccidophagus , Quadrencyrtus Hoffer, 1953, Oriencyrtus Sugonjaev & Trjapitzin, 1974, and Aphycoides Mercet, 1921 with apical or near apical position of the cerci was also earlier reported by Noyes and Hayat (1994). The taxonomic position of these genera is uncertain. The presence or absence of filum spinosum (fs) is one of the main characters used to subdivide the Encyrtidae into two subfamilies ( Trjapitzin 1968). These short and thickened setae on apical margin of linea calva are an exclusive characteristic of the wasps of the subfamily Encyrtinae as a part of the wing coupling mechanism at the moment of jumping. Another important diagnostic feature of the encyrtid subfamilies is the presence or absence of the special paratergites in the gastral structures of females. Genera Eucoccidophagus , Quadrencyrtus , and Oriencyrtus are characterized by the absence of fs and presence of the paratergites, but the latter structures are not homologous to those found in other Tetracneminae ( Noyes 2004). According to Noyes (2004), these three extant genera are most closely related to Aphycoides , species of which have fs and should be included into the subfamily Encyrtinae . Therefore, without studying the paratergites of females, it is difficult to determine relationships of the taxa described based on males from Sakhalinian amber. The taxonomic position of the new genus is also considered unplaced within the Encyrtidae .

The forewing venation of the new genus is very similar to that of Sugonjaevia Simutnik, 2015, which was also described from Sakhalinian amber. However, Sugonjaevia is characterized by large and elliptical (not circular) eyes; interantennal prominence in the form of carina; clava without an oblique truncation and with suture; Mt8 M-shaped between and around cerci, with long and narrow part between cerci; very long hypopygium; genitalia distinctly sclerotized, with digiti and margins of aedeagus dark; aedeagus longer than phallobase (figs 4a-e, 13e, f in Simutnik 2020). The new genus also differs from Encyrtoides Simutnik, 2020 by a short pronotum (fig. 7d in Simutnik 2020), and from Kotenkia Simutnik, 2015 by size and structure of antennae (figs 5b, c, e in Simutnik 2020).

Figures

Figure 3. S. leleji gen. et sp. nov., holotype female A head and mesosoma, dorsal B venation of fore and hind wings, dorsal C venation of fore and hind wings, metasoma and part of genitalia, ventral, cs- covering setae.

Figure 4. A-C S. leleji gen. et sp. nov., holotype female A apex of metasoma with cercus arrowed, dorso-lateral B apex of metasoma with cercus arrowed and genitalia, dorsal C habitus, lateral D Eucoccidophagus sp., venation of fore and hind wings.