Podmosta, Ricker, 1952

Chen, Zhi-Teng, 2018, Females of the genus Podmosta (Plecoptera: Nemouridae): comparison of terminalia and a new female record in Baltic Amber, Zootaxa 4407 (2), pp. 293-297 : 293-294

Podmosta sp.

Figs. 1 –7.

Description. Macropterous; body length ca. 5.7 mm, generally yellow and patterned with brown ( Fig. 1).

Head ( Figs. 1, 2 ): Head brown, wider than pronotum. Ocelli pale, compound eyes dark. Antennae filiform and mostly brown, almost equal with body length, with about 50 segments. Maxillary palp short, stout and foursegmented.

Thorax ( Figs. 1, 3): Pronotum mostly brown, sub-quadrate, with sparse rugosities; cervical gills absent; cervix elongated, laterally with reduced oval nubs. Mesothorax and metathorax sclerotized, with similar length to prothorax. Forelegs shortest, hindlegs longest; femur and tibia mostly pale except for the darker joints; tibia longer and thinner than femur, ventroapically with two giant spurs; tarsus with three segments, second segment shortest, first and third segments subequal in length; claws sharp. Wings with the X-structure; the terminal costal crossvein Sc2 joins the radius R1.

Abdomen ( Figs. 3–5): Abdomen near half of the body length; segments 1–7 pale. Posterior of sternum 7 slightly extended backwards. Sternum 8 indented posteromedially, with a “rabbit-shaped” sclerite, the sclerite with a bilobed anterior tip and widened posteriorly. Sterna 9–10 darkly sclerotized and shorter than sternum 8. Paraprocts subtriangular with blunt corners. Cerci sclerotized, unmodified and short, approximately twice as long as wide.

Material. Female, an almost complete specimen in a clear and well-preserved piece of Baltic amber from Lithuania, Eocene (ca. 40–50 Mya). The specimen is deposited in the Chen Amber Collection, No. CZT-PLE-BA1.

Syninclusions. Plant remains and mineral substances.

Remarks. The new female is assigned to the extant genus Podmosta due to the following characters: cervical gills absent; sternum 8 narrow and shorter than sternum7; sternum 8 with a distinct median sclerite; the terminal costal crossvein Sc2 joins the radius R1 ( Caruso & Wichard 2010). This specimen differs from females of other extant congeners by the posteromedially indented sternum 8 which has a rabbit-shaped sclerite ( Fig. 5). When compared to the two unnamed females proposed by Caruso & Wichard (2010) from Baltic amber, the new specimen has a more indented sternum 8, a more modified median sclerite, but has no lateral sclerites ( Fig. 5). However, accurate species-level assignment of the new female and determination of the relationship between the new female and the fossil species P. attenuata Caruso & Wichard, 2010 is not currently possible.

Currently, no extant species of the Podmosta has been reported from Europe, the source of Baltic amber. Historical dispersal of this genus may have occurred due to the climate change ( Caruso & Wichard 2011). More morphological and genetic studies are needed to discovery evolutionary trends of stonefly taxa know from Baltic amber.

Figures

FIGURE 2. Podmosta sp. Antennae, lateral view;