Thursday 26 August 2021

Sakhalinencyrtus leleji: A new species of Encyrtid Wasp from Middle Eocene Sakhalinian Amber.

The Encyrtidae are a large family of parasitoid Chalcid Wasps, primarily targeting members of the Hemiptera (True Bugs), although some target of Ticks and others are hyperparasites, with their larvae growing inside the parasitic larvae of other Wasps. The first known fossil species assigned to the family, Encyrtus clavicornis, was described from an Oligocene shale from Rott in Germany in 1938. Since this time a further eighteen species have been discovered, Archencyrtus rasnitsyni, Sugonjaevia sakhalinica, Kotenkia platycera, and Encyrtoides pronotatus, from Middle Eocene Sakhalinian Amber, Eocencyrtus zerovae, Eocencnemus sugonjaeviEocencnemus vichrenkoi, Eocencnemus gedanicus, Glaesus gibsoni, Rovnosoma gracile, Sulia glaesaria, Protocopidosoma kononovae, Dencyrtus vilhelmseni, Archaeocercus schuvachinae, Trjapitzion cylindrocerus, Ektopicercus punctatus, and Efesus trufanovi, from Late Eocene Baltic Amber, and Copidosoma archeodominica, from Miocene Dominican Amber.

In a paper published in the Journal of Hymenoptera Research on 24 August 2021, Serguei Simutnik and Evgeny Perkovsky of the I.I. Schmalhausen Institute of Zoology of the National Academy of Sciences of Ukraine, and Dmitry Vasilenko of the Borissiak Paleontological Institute of the Russian Academy of Sciences, and the Cherepovets State University, describe a new species of Encyrtid Wasp from Middle Eocene Sakhalinian Amber.

Sakhalinian Amber is mainly collected on a beach near the village of Starodubskoye, close to the mouth of the Naiba River in Dolinsk District on Sakhalinian Island in the Sea of Okhotsk in the Russian Far East. For a long time the age of this amber was uncertain, but in 1999 it was found in situ in strata of the Naibuchi Formation, making it Middle Eocene in origin, and older than the Baltic and Rovno ambers.

The new species is named Sakhalinencyrtus leleji, where 'Sakhalinencyrtus' implies an Encyrtid Wasp from Sakhalinian Amber, and 'leleji' honours Arkady Stepanovich Lelej for his expertise on the Hymenoptera. The species is described from a single male specimen preserved within a piece of Sakhalinian Amber, which also contains an undescribed female Ant.

 
(A) Piece of Sakhalinian Amber containing inclusions (B), (C) syninclusion of Mymaridae, female (B) dorso-lateral (C) ventral (D)–(F) Sakhalinencyrtus leleji holotype male: (D) antennae, head, mesosoma, ventral (E) antennae, head, frontal (F) antennae, head, and anterior part of metasoma, dorso-lateral. Simutnik et al. (2021).

The specimen is 0.9 mm in length, and brownish black in colour. The lower jaw is longer than the upper, the head is wider than the thorax. The eyes are small and almost circular, although details of the face are unclear as this has been deformed during preservation. The sockets in which the antennae are fitted are half way between the lower margin of the eyes and the margin of the mouth. The first segment of the antannae is extended and flattened, being four times as long as it is wide. The mesosoma (middle section of the body) is shorter than the metasoma (final section), and is not flattened. The forewing is glassy in appearance, with a row of hairs on its basal margin. 

 
Sakhalinencyrtus leleji, holotype male (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. Simutnik et al. (2021).

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