Myrmica rudis

†Myrmica rudis; Temporal range: Bartonian, Middle to Late Eocene K Pa Eo Ol Mi Pl Baltic amber, Baltic Sea region
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Myrmicini
Genus:	Myrmica
Species:	†M. rudis
Binomial name
	†Myrmica rudis; (Mayr, 1868)

Photo Gallery

Radchenko (2023), Figure 2. Myrmica rudis, worker, neotype: (A) body, right side lateral view; (B) body, left side dorso-lateral view; (C) hind tibia; Myrmica intermedia, workers: neotype (D) body, left side lateral view; (E) body, right side dorso-lateral view; specimen GPIH 4942: (F) head, dorsal view; (G) body, dorsal view; specimen F-650: (H) body, dorso-lateral view; (I) antenna. Scale bars: A, B, D, E, G–I – 1 mm, C, F – 0.5 mm.

Identification

Radchenko (2023) - Meso- and metatibiae without spur; head, mesosoma and waist coarsely sculptured; upper lateroventral corners of head somewhat pointed; eyes located distinctly in front of midlength of sides of head; scape gradually, but quite strongly curved at base, without any angle, lobe or carina; mesosoma long and low; petiole very long and low; propodeal spines directed backward and upward at an angle ca. 45° (seen in profile) and distinctly divergent (seen from above).

For differences from Myrmica longispinosa, see there. In Myrmica dictyosa the entire mesosoma is very coarsely reticulate, while in M. rudis at least the propodeal dorsum has sinuous longitudinal rugae. Like M. longispinosa, M. rudis differs from Myrmica electrina and Myrmica saxonica by the longer and more slender mesosoma and long and low petiole. By the eyes located in front of midlength of sides of head, it resembles Myrmica intermedia and differs from Myrmica eocenica and Myrmica damzeni. In addition, it is distinguished from M. eocenica by the absence of spurs on the meso- and metatibiae and by the scape more strongly curved at the base, and from M. damzeni by a much more abundant erect or suberect pilosity on the body and appendages and longer propodeal spines (ESL/HL ≥ 0.60 vs. 0.45). It differs from M. intermedia by the somewhat longer propodeal spines, directed backward and upward at an angle ca. 45° and more divergent.

This species was originally assigned to the genus Macromischa (now junior synonym of Temnothorax), then it was transferred by Wheeler (1915) to the established by him extinct genus Nothomyrmica, and finally was transferred to Myrmica by Radchenko et al. (2007).

Mayr (1868) described M. rudis based on two workers from Baltic amber, but later André (1895), Wheeler (1915), Carpenter (1927) and Radchenko et al. (2007) studied 13 more specimens of this species from Baltic amber. Taking into account current data (see Material examined in Rachenko (2023)), the total number of found specimens of this species is 17, which is twice as many as the number of specimens of all other species of amber Myrmica combined. Moreover, one of these specimens was first discovered in Rovno amber.

The designated neotype specimen of M. rudis agrees well with the original description of this species, further Wheeler’s (1915) comments and an excellent drawing (loc. cit., Fig. 23).

Keys including this Species

Distribution

This taxon was described from Baltic amber (Bartonian, Middle to Late Eocene) and is known from Rovno amber (Priabonian, Late Eocene).

Castes

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

†rudis. †Macromischa rudis Mayr, 1868c: 85, pl. 4, fig. 85 (w.) BALTIC AMBER (Eocene).
- Combination in †Nothomyrmica: Wheeler, W.M. 1915h: 60; in Myrmica: Radchenko, Dlussky & Elmes, 2007: 1495.
- See also: Radchenko & Elmes, 2010: 655.

Type Material

Neotype worker (designated by Radchenko, 2023), complete specimen, Baltic amber, No. JDC 8482 (SIZK); worker, complete specimen (badly preserved), Baltic amber, No. 1945/6 (MZPAN); worker, complete specimen (mostly covered by whitish film), Rovno amber, No. F-256 (CMKHU).

Type locality: Poland, Baltic amber (neotype worker); Ukraine, Rivne Prov., Volodymerets Distr., Rovno amber; both late Eocene, Priabonian age, 37.8–33.9 Ma.

Description

References