Electroadicella unipetra, Melnitsky & Ivanov & Perkovsky & Vasilenko, 2024

Melnitsky, Stanislav I., Ivanov, Vladimir D., Perkovsky, Evgeny E. & Vasilenko, Dmitry V., 2024, Electroadicella unipetra sp. nov., a new fossil species of Leptoceridae (Insecta: Trichoptera) from Eocene Rovno amber, Ecologica Montenegrina 72, pp. 11-18 : 12-18

Electroadicella unipetra sp. nov.

https://zoobank.org/ urn:lsid:zoobank.org:act:902F21BD-133B-4015-A5AA-82F09CA3899A

( Figs 1 – 4 )

Type material: Holotype. Male. SIZK UA –29640, Rovno amber, late Eocene. Syninclusions: stellate hairs.

Description. Body length 5.2 mm; forewing length 6.5 mm. Head, antennae yellow, abdomen and thorax grey-brown. Antennae very slim, with light trichoid sensilla. Pedicellus very narrow smaller than scapus. Wings light brown with long dark brown hairs. Mxp with long brown hairs, lbp with short white hairs. In forewing fork I short, DC closed. Legs narrow, spurs 1–2–2.

Male genitalia. Inferior appendages have two branches: long medial finger-shaped with rounded apex, and short tubercle-shaped lateral. The apex of lateral branch with bunch of long hairs; medial branch with numerous long hairs. A pair of long, narrow, pointed and recurved processes of unknown homology visible above inferior appendages are attached to the base of the inferior appendages. Segment X shorter than inferior appendages with extended elongate lateral processes. Preanal appendages elongate with numerous very long setae.

Comparison. Wing venation and genital structures suggest the new species to belong to the genus Electroadicella Wichard, 2013 . The new species is similar to Electroadicella succina Wichard, 2013 from Baltic amber ( Wichard 2013) in the general shape of genitalia. The new species Electroadicella unipetra sp. nov. differs from that species in very long medial branches of inferior appendages, reduced lateral branches, and in broad short X segment significantly shorter gonopods.

Etymology. From Saint Petersburg State University (Universitas Petropolitana, in Latin) to commemorate its 300 th anniversary in 2024.

Distribution. Priabonian Rovno amber.

Discussion

Thirty-eight named species of caddisflies are currently known from Rovno amber ( Ivanov et al. 2016; Perkovsky 2017; Melnitsky et al. 2021a, 2021b, 2021c; Melnitsky & Ivanov 2010, 2013, 2016b, 2023a, 2023b; this paper). Only ten of these species (26%) are known also from Baltic amber. All Baltic amber species are reported from Rovno amber years ago ( Melnitsky & Ivanov 2016b; Perkovsky 2017); on the other hand, many endemic species still await the description ( Melnitsky & Ivanov 2016b). With addition of the undescribed species ( Melnitsky et al. 2021c) these common faunal elements comprised only 17% of all Rovno caddisfly species ( Melnitsky et al. 2021c); later three Rovno amber endemic species were added to the list ( Melnitsky & Ivanov 2023 a, 2023b; this paper).

Supposed share of Rovno amber caddisflies species common with Baltic amber looks comparable with the share of beetles (14–15%, Sokolov et al 2024; Legalov et al. 2024a). Specifically, only one Baltic amber leptocerid species (20% of all named Rovno amber leptocerid species), i.e. Erotesis aequalis Ulmer, 1912 , is known from Rovno amber ( Perkovsky 2017; this paper); Ceraclea sp. is reported from Rovno amber ( Melnitsky & Ivanov 2016b) but the species remains undescribed; with addition of this species (genus Ceraclea Stephens, 1829 is unknown from Baltic amber) the share of Baltic amber species in Rovno leptocerid fauna will be 16.7%. Leptocerids are known as good fliers, but also thermophile or cryophobic (extant relict species Erotesis baltica McLachlan, 1877 is a rare exception), and this could be the main reason of the rarity of the common leptocerid species in the different amber faunas. Electroadicella and Erotesis McLachlan, 1877 (Bitterfeld Erotesis species missed in Ivanov et al. 2016) are two long-horned caddisflies genera reported from three European amber faunas.

The degree of similarity between the Baltic and Rovno amber faunas, strongly varies depending on the studied orders and superfamilies ( Telnov et al. 2023). It was supposed that the high degree of similarity between the Danish and Baltic amber faunas ( Legalov et al. 2024b) for a particular group might depend on a predominance of temperate elements in their compositions and/or a close connection with the resin-producing tree and the amber forest community as a whole. The Baltic and Rovno amber faunas also have apparent similarity. Both Baltic and Rovno amber caddisfly faunas include certain temperate elements such as genera Beraeodes Eaton, 1867 and Plectrocnemia Stephens, 1836 ( Perkovsky 2013; Ivanov et al. 2016). The aquatic larvae of caddisflies have no connections with the amber trees, although the adult insects might have localities for mating and estivation. Warmer ( Belokobylskij et al. 2023; Kirichenko-Babko & Perkovsky 2023) and supposedly more dry climate of Rovno as compared with Baltic amber forest as well as insularity of the Volhynian Uplift in late Eocene may result in more than 80% of Rovno amber caddisfly species being endemics or having northern distribution boundary at the late Eocene lying along the southern coast of the Subparathetys ( Sokolov & Perkovsky 2020). The caddisflies of Baltic amber are well-studied ( Ulmer 1912; Wichard 2013, etc.); with this background, importance of the Rovno amber caddisflies studies for the better understanding of European amber biota is difficult to overestimate.

Acknowledgements

We are very thankful to Aleksandr P. Rasnitsyn (Paleontological Institute, Moscow) and Dmitri Telnov (Natural History Museum, London) for discussion and to reviewers for their useful comments.

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Figures

Figure 1. Electroadicella unipetra sp. nov. (holotype, male, Rovno amber, SIZK UA–29640, photo), general view, ventral. Scale bar = 1 mm.

Figure 2. Electroadicella unipetra sp. nov. (holotype, male, Rovno amber, SIZK UA–29640, photo), genitalia, ventral view. Scale bar = 0.1 mm.

Figure 3. Electroadicella unipetra sp. nov. (holotype, male, Rovno amber, SIZK UA–29640, drawing), general view, ventral. Abbreviations: Ant – antenna, Fl – fore leg, Hl – hind leg, Ml – middle leg, Ocu – compound eye, Plb – labial palp, Pmx – maxillary palp; Latin numbers – wing forks I and V.

Figure 4. Electroadicella unipetra sp. nov. (holotype, male, Rovno amber, SIZK UA–29640, drawing), genitalia, ventral view. Hairs are omitted. Abbreviations: X – 10th segment; ia – inferior appendages, lp – lateral processes, pa – preanal appendages, rp – recurved processes.