First aphidiine wasp from the Sakhalinian amber

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Aphidiinae is a small, globally distributed subfamily of specialized aphid parasitoids belonging to Braconidae, Hymenoptera (Yu et al. 2016; Chen and van Achterberg 2019), but it was once considered a separate family within Ichneumonoidea (Starý 1970;Tobias and Chiriac 1986;Davidian 2007Davidian , 2018Davidian , 2019)).According to different estimates, there are 505 (Žikić et al. 2017) to 619 (Yu et al. 2016) extant species of aphidiines recognized worldwide, and the process of generic revision and new species description continues (Rakhshani et al. 2017;Čkrkić et al. 2019;Kocić et al. 2019Kocić et al. , 2020;;Tomanović et al. 2020).More than half of all species are known from the Palaearctic Region (Yu et al. 2016).Aphidiines are an essential part of the aphidophagous guild, and due to their practical importance, this group is well studied (Žikić et al. 2017; Chen and van Achterberg 2019); however, questions remain regarding the evolution and phylogeny of the group (Belshaw and Quicke 1997;Belshaw et al. 2000;Sanchis et al. 2000;Ortega-Blanco et al. 2009; Chen and van Achterberg 2019) and genera therein (Gӓrdenfors 1986;Kocić et al. 2019Kocić et al. , 2020;;Čkrkić et al. 2020).The study of fossil material may contribute to resolving these problems.
Ephedrus contains about 50 living and extinct species altogether, most of which are known from the Palaearctic Region (Yu et al. 2016;Kocić et al. 2019;Tomanović et al. 2020).Among Ephedrini, the Ephedrus is the only genus with rich extant fauna and includes two fossil species described from Europe (Oligocene of France and Baltic amber; Yu et al. 2016).Diagnostic morphological characters of the genus are 11-segmented antennae in both sexes (an exception is E. antennalis Tomanović, 2020, described from a single female with 12-segmented antennae), complete venation of the forewing, with present 2RS and r-m veins, and also seven complete cells (marginal, 1st and 2nd submarginal, 1st discal, basal, subbasal, and 1st subdiscal).The ovipositor sheaths are more or less elongate, straight or slightly curved upward, usually with sparse setae.

Material and methods
Amber insects were collected in the southern part of Sakhalin Island, Russian Far East, by an expedition of the Paleontological Institute of Academy of Science of USSR in 1972 (Dietrich and Perkovsky 2019, and references therein).
In total, 36 amber specimens were studied under Axio Imager M1 Carl Zeiss microscope in FSBSI VIZR and under Leica Z16 APO microscope equipped with a Leica DFC 450 camera and LAS V3.8 software in SIZK.Photos were made using Axio Imager M1 Carl Zeiss microscope in FSBSI VIZR.The examined material housed in PIN.
Classification of aphids is given after Heie and Węgierek (2009).The morphological terminology used in this paper follows Sharkey and Wharton (1997) and Hymenoptera Anatomy Ontology Project, the latter is an illustrated glos sary of morphological terms (Hymenoptera Anatomy Consortium available online at http://glossary.hymao.org).
Description.-Description is based on a single female, male forms are unknown.
The venation (Figs.1A 1 , A 2 , 2) of the forewing complete, including 2RS and r-m veins and seven closed cells, however, only marginal, 1 st and 2 nd submarginal and basal cells are clearly visible.Pterostigma approximately two times as long as wide.3RSa slightly longer than 2RS; 3M not reaching wing margin.Hind wing with complete basal cell.The surface of both wings densely covered with long setae.The setae along the wing edge are longer than on the wing surface.
Legs densely pubescent.First fore tarsomere 2.0 times as long as second tarsomere, first hind tarsomere 2.7 times as long as second tarsomere.
Metasoma (Fig. 1A 1 , A 2 , A 4 ) elongate, lanceolate, densely pubescent.Petiole inverted and its shape is difficult to observe; approximately two times as long as wide at the level of the spiracular tubercles.Eight metasomal tergites clearly visible.Hypopygium and elongate ovipositor sheaths completely covered with short dense setae.Ovipositor sheaths elongate, 3.0 times as long as wide in the middle; dorsal margin of ovipositor sheaths straight, apex rounded, ventral margin slightly curved upwards.Left ovipositor sheath broken at midlength (Fig. 1A 4 ).
Coloration of the body is brown, antennae and legs are slightly lighter; palpi are light yellow.
Body length 1.2 mm, the length of antennae 0.5 mm.
Remarks.-Left side of the specimen is convex towards observer.The head is strongly deformed, it is not possible to observe the eyes and clypeus.The specimen has clearly visible mesosoma, legs, metasomal tergites, ovipositor sheaths; the wings and petiole are partly visible.
Ephedrus rasnitsyni Davidian and Kaliuzhna sp.nov. is the first Aphidiinae species described from Sakhalinian amber, and the oldest named female of subfamily.

Concluding remarks
Among studied aphidiine specimens from Sakhalinian amber, the most abundant species are from the genus Ephedrus, tribe Ephedrini Haliday, 1833 (29 out of 36 specimens).
Ephedrus rasnitsyni Davidian and Kaliuzhna sp.nov.clearly belongs to the Ephedrus.We compared this specimen with all known genera of Ephedrini according to the electronic catalog Taxapad (Yu et al. 2016): Ephedrus Haliday, 1833, Parephedrus Starý and Carver, 1971, Toxares Haliday, 1840, Diospilites Brues, 1933, Indoephedrus Samanta, Pramanik, and Raychaudhuri, 1983, and Archephedrus Ortega-Blanco, Bennet, Delclòs, and Engel, 2009.Among these genera, Diospilites and Indoephedrus have been erroneously assigned to Aphidiinae in Taxapad (Yu et al. 2016).We agree with Tobias (1987), who redescribed the fossil Diospilites brevicornis Brues, 1933, from Baltic amber and erected for him the monotypic subfamily Diospilitinae.The Indoephedrus was erected for two parasitoids of Greenideidae from Meghalaya (northeast India): I. reticulata Samanta, Pramanik, andRaychaudhuri, 1983, andI. neoficicola Samanta, Pramanik, andRaychaudhuri, 1983.According to the description by Samanta et al. (1983), the structure of the head (oval head shape, long temples, narrow face with sparse setae, reticular region between the antennal fossae and simple eyes), venation of the forewings, long antennae (25-segmented in I. neoficicola and 33-in I. reticulata) as well as the structure of the long narrow ovipositor sheaths completely covered with setae, are similar to those of some genera of the subfamily Braconinae Nees, 1811 (Sergey A. Belokobylskij, personal communication 2020) and does not belong to Aphidiinae.This opinion is also shared by other aphidiine specialists (Ehsan Rakhshani, personal communication 2020), and the genus was not included to the list of world aphidiine parasitoids of greenideids (Starý et al. 2010).
The fossil Archephedrus stolamissus Ortega-Blanco, Bennet, Delclòs, and Engel, 2009, was described based on a single male from Early Cretaceous (late Albian) Álava amber (Peñacerrada I) from Spain.It differs from the new species by having 16-segmented antennae that clearly narrow towards the apex and by the 5-segmented maxillary palps.
The Parephedrus and Toxares are represented exclusively by extant species.The Australian Parephedrus, despite the absence of notauli, is characterized by sparse pubescence of the ovipositor sheaths, as well as having two thickened setae at the apex of the sheath, similar to species of the Praon Haliday, 1833.The Toxares occupies an isolated position in the group because it has 16-23-segmented antennae and a plow-shaped ovipositor sheath that is curved downward and widens towards the apex.
Ephedrus rasnitsyni Davidian and Kaliuzhna sp.nov.has all of the plesiomorphic features of the Ephedrus: 11-segmented antennae, complete wing venation, propodeum with central areola, hind wings with a complete basal cell, a straight, triangular ovipositor sheath.The absence of notauli is characteristic to both previously described fossil Ephedrus species and modern Parephedrus (Starý 1973;Gӓrdenfors 1986).Apomorphic features of Ephedrini include posterior position of propodeal spiracles, an elongated petiole, free cuspises of male genitalia, and black colored aphid host mummies (Gӓrdenfors 1986).The only clearly visible apomorphy of the new species is an elongated petiole; other characters are hardly visible or not present in the available specimen.
The fossil species E. mirabilis and E. primordialis can be easily distinguished from the new species.The former has a short petiole and a very short 3M that is approximately equal to r (Timon-David 1944;Starý 1973).E. primordialis has a short, wide, and almost square petiole and a long 3M vein that reaches the apical margin of the wing, and rather short, narrow, triangular ovipositor sheaths (the character of pubescence is absent in the description) (Brues 1933;Starý 1973).The new species has a longer petiole, a long 3M vein that does not reach the forewing margin, and more elongated ovipositor sheaths that are completely covered with setae.
Ephedrus rasnitsyni Davidian and Kaliuzhna sp.nov. is most similar to the extant E. validus and E. carinatus in the pubescence of the ovipositor sheaths but differs from these species in the following characters: the F1 is shorter, 2.5 times as long as wide; notauli are absent; and the ovipositor sheaths are 3.0 times as long as wide.In the related extant species, the F1 is much longer (in E. validus, it is 4.2-4.7 times as long as wide, and in E. carinatus, 5.8 times as long as wide); the notauli are well developed; and the ovipositor sheaths are about two times as long as wide (Starý 1958;Tomanović et al. 2020).Interestingly, E. validus was at one time included in the monotypic subgenus Lysephedrus established based on morphological and ecological data (Starý 1958).The main diagnostic characters that differentiate Lysephedrus from the rest of the subgenera are the reticulated sculpture of the propodeum and petiole and the continuous pubescence of the ovipositor sheath.Lysephedrus was also considered a subgenus in the Ephedrus monograph by Gӓrdenfors (1986).In several other studies, Lysephedrus was considered as a genus (Mackauer 1968;Starý 2006;Davidian 2018Davidian , 2019)).On the other hand, Ephedrus carinatus (Ephedrus sensu stricto) from Austria was described from a single female already in the nominative subgenus (Tomanović et al. 2020).This species, like E. validus, is characterized by pubescent ovipositor sheaths.This morphological character could be an adaptation to the parasitization of root aphids (e.g., subfamily Eriosomatinae), such as in E. validus (Starý and Schlinger 1967;Tobias and Chiriac 1986;Davidian 2007;Yu et al. 2016) and a similar host was assumed by Tomanović et al. (2020) for E. carinatus.Eriosomatidae are known from Sakhalinian amber as well (Piotr Węgierek, personal communication 2020), and because E. rasnitsyni Davidian and Kaliuzhna sp.nov.has the same character, it could also be a parasite of root aphids.
Sakhalinian amber is potentially the best source to reveal the crucial information in understanding the early stages of aphid-aphidiine coevolution.The Sakhalinian amber biota existed after the rise of ants and after the establishment of close ant-aphid relationships (Perkovsky and Węgierek 2018, and references therein), but ants are rare in this amber-four times less abundant than in Baltic and Rovno ambers (Perkovsky et al. 2007;Radchenko and Perkovsky 2016, and references therein).
Institutional abbreviations.-FSBSIVIZR, All-Russian Insti tute of Plant Protection, St. Petersburg-Pushkin, Russian Federation; PIN, A.A. Borissiak Paleontological Institute of the Russian Academy of Sciences, Moscow, Russian Federation; SIZK, I.I.Schmalhausen Institute of Zoology of NAS of Ukraine, Kyiv, Ukraine.