Myrmica andryushchenkoi Zharkov & Dubovikoff, 2025

Zharkov, Dmitry M., Dubovikoff, Dmitry A. & Abakumov, Evgeny V., 2025, A new spineless species of the genus Myrmica Latreille, 1804 (Hymenoptera: Formicidae: Myrmicinae) from late Eocene Baltic amber, Ecologica Montenegrina 87, pp. 224-229 : 226-228

† Myrmica andryushchenkoi Zharkov & Dubovikoff sp. nov. ( Figure 1 )

https://zoobank.org/ urn:lsid:zoobank.org:act:D54F496D-FE89-4F5C-AE98-97111B2FC731

Etymology. After Konstantin Andryushchenko (Kalinigrad, Russia), our friend and Baltic amber enthusiast, who provide amber for this study and donated it to our Museum.

Type material. Holotype and paratype, workers (paratype without head), are found in a small piece of late Eocene Baltic amber. Types are stored in the collection of the Paleontological Museum of the St. Petersburg State University, St. Petersburg city, Russia, accessioned KA-122 .

Type locality and age. The piece of amber is found by Konstantin Andryushchenko (https://paleoamber.ru) in Baltic amber. The material originated from Yantarny , on the Sambia Peninsula , Kaliningrad region, Russia. Late Eocene , Priabonian age (37.8–33.9 Ma), the Prussian Formation ( Iakovleva et al. 2022) .

Diagnosis (worker). Anterior clypeal margin broadly rounded, not prominent, shallowly notched medially. Frontal carinae very weakly curved to merge with the rugae, which surround antennal sockets. Eyes of moderately small, weakly bulging, situated approximately at the midlength of lateral margins of head. Antennae 12-merous with distinct three-segmented club. Antennal scape relatively short, at least not reaching the occipital margin of head, gradually curved at the base. Propodeum with two short denticles, straight, sharp at the apex, directed backward. Petiole (abdominal segment II) with relatively short but distinct peduncle, forming a distinct triangular node. Meso- and metatibiae without spurs. Femora strongly swollen.

Measurements (in mm) and indices. Holotype: HL – 1.05; HW – 0.78; FW – 0.30; SL – 0.60; PdL – 0.10; Fl1 – 0.13; Fl2 – 0.14; OL – 0.18; MdL – 0.32; WL – 1.38; PnW – 0.45; ESL – 0.20; ESD – 0.07; PrdL – 0.33; PrdH – 0.45; PtL – 0.30; PtW – 0.25; PPL – 0.25; PPH – 0.24; PPW – 0.26; HFL – 0.85; HTL – 0.50; GL – 1.25; TL – 4.55.

CI – 1.35; SI 1 – 0.57; SI 2 – 0.77; FLI – 0.38; OI 1 – 0.17; OI 2 – 0.23; MdI – 0.30; PI 1 – 1.20; PI 2 – 0.32; PPI 1 – 1.04; PPI 2 – 0.92; PPI 3 – 1.04; PPI 4 – 0.33; ESLI – 0.26; ESDI – 0.35; MI – 3.07; PRI – 0.73.

Description. Head: Mandibles with a small striped sculpture, six sharp teeth. Anterior clypeal margin broadly rounded, not prominent, shallowly notched medially, with pair of long median setae and fringe of shorter setae on the anterior margin. Clypeus with a few straight longitudinal rugae. Palp formula – 6:4 (partially concealed). Frontal carinae feebly curved outward, merging with the rugae surrounding the antennal sockets that not reach to middle of head. Head longer than broad, with convex sides and occipital margin, and broadly rounded, barely marked occipital corners. Head longitudinally striate. Eyes of moderately small, weakly bulging, situated approximately at the midlength of lateral margins of head. Antennae 12-merous with distinct three-segmented club, second to ninth funicular joints distinctly longer than broad. Antennal scape relatively short, at least not reaching the occipital margin of head, gradually curved at the base. Sparse suberect setae mostly occur dorsally over the head. Antennal scape with subdecumbent to suberect hairs.

Mesosoma: Mesosoma relatively short and robust. Promesonotum feebly convex (in lateral view) and in dorsal view with broadly rounded anterior-lateral corners, distinctly narrowing posteriorly (approximately twice wider anteriorly than posteriorly) and with trace of promesonotal suture (in dorsal view). Metanotal groove distinct, but not very deep. Dorsal surface of propodeum with reticulate sculpture, longer than posterior one. Propodeum bearing two short denticles, straight, sharp at the apex, directed backward. Whole mesosoma with coarse reticulation.

Metasoma: Petiole (abdominal segment II) with relatively short but distinct peduncle, forming a distinct triangular node. Its dorsum also with moderate (not coarse) reticulation. Postpetiole (abdominal segment III) subglobular, in dorsal view with longitudinal rugae. Proximal part of abdominal tergum IV with numerous longitudinal striae. Gaster ovoid, the first tergite much larger than following one. Gaster smooth and shiny, covered with long, erect hairs, the distance between the hairs is approximately equal to their length.

Legs: Legs relatively short and robust. Metacoxa not distinctly larger than pro- and mesocoxae. Femora strongly swollen. Meso- and metatibiae without spurs.

Notes. † Myrmica andryushchenkoi sp. nov. is well distinguished from all other fossil Myrmica species by short propodeal denticles (instead of spines), and a three-segmented funicular club. However, these features combine the new ant with the species † Myrmica paradoxa Radchenko, Dlussky & Elmes, 2007 , which was described from the late Eocene Bitterfeld amber. † Myrmica andryushchenkoi sp. nov. differs from † M. paradoxa in the following features: smaller size, shorter scape, head longitudinally striate, femora and tibiae strongly swollen, meso- and metatibiae without spurs.

Figures

Figure 1. †Myrmica andryushchenkoi sp. nov., photomicrographs showing certain key features. Worker KA- 122a (holotype): A— dorsolateral oblique view; B— ventrolateral oblique view; C— dorsolateral oblique view. Worker KA-122b (paratype): D— dorsal view. Abbreviations: antennal club (clb), clypeal margin (clm), longitudinal rugae (lr), mesofemur (msf), metanotal groove (mtg), petiole (pt), postpetiole (ppt), promesonotal suture (pms), propodeum denticle (pd).