Neomida Latreille, 1829

Nabozhenko, Maxim V., Kairišs, Kristaps & Bukejs, Andris, 2020, The oldest fossil darkling beetle of the genus Neomida Latreille, 1829 (Coleoptera: Tenebrionidae) from Eocene Baltic amber examined with X-ray microtomography, Zootaxa 4768 (3), pp. 435-442 : 436

Genus Neomida Latreille, 1829

Notes. The specimen considered here was assigned to the subfamily Diaperinae and subtribe Diaperini within Tenebrionidae on the basis of the following combination of morphological characters: tarsal formula 5-5-4; head armed between eyes ( Figs 1B , 2F , 3B ); base of antennomere 1 dorsally covered by lateral extension of gena ( Fig. 2B ); antennae gradually widened and clubbed, with slightly asymmetrical antennomeres 5–11 ( Fig. 3A ); mouthparts tenebrioid, open ( Figs 2B,E ); mentum with median elevation ( Figs 2B,E ); labro-epistomal membrane exposed; procoxal cavities externally closed, with ventrally convex prosternal process ( Fig. 3C ); mesocoxal cavities partly closed by mesoventrite, mesepimeron and metaventrite; mesotrochantine present ( Fig. 3C ); each elytron with nine striae and short striole ( Figs 2 A–G); legs not fossorial; abdominal membranes between ventrites 3–5 exposed (supporting presence of defensive glands) ( Fig. 2E ); and apical piece of aedeagus without ventral alae ( Fig. 4A ).

The genus Neomida has a diverse combination of characters, and sometimes can be confused with Platydema Laporte et Brullé, 1831 . This is because some Neotropical and Oriental Platydema , such as Platydema orientaloides ( Grimm 2016) , also have a subcylindrical body and subparallel elytra as in Neomida ( Grimm 2016) . However, the new fossil species (male) distinctly belongs to Neomida based on the presence of very small paired marginal epistomal tubercles ( Figs 3A,B ), and the structure of the prosternal process, which is not beaded but convex and sharply declivitous immediately posterior to the procoxae, with the apex of the prosternal process bearing a tubercle at the level of the basal part of the procoxae ( Fig. 3C ). Platydema has a prosternal process that is beaded, and “prominent, prolonged caudally horizontal or deflected behind” procoxae according to Triplehorn (1965). In addition, the new fossil species has fovea intercoxal process of mesoventrite ( Fig. 3C ), which is also found in at least two Palaearctic Neomida .

Usually, species of Neomida have epipleura that are abruptly abbreviated at or near the last abdominal suture (between ventrites 4 and 5), while epipleura in Platydema are extending or almost extending the elytral apex. The new Eocene species has epipleura similar to those in Platydema ( Fig. 2B,E ), but at least two extant Neotropical Neomida species also have the same epipleural structure ( Triplehorn 1965).

Figures

FIGURE 1. Neomida groehni sp. nov., holotype, photomicrograph: A – habitus, latero-dorsal view; B – details of forebody, dorsal view; C – habitus, ventral view. Not reproduced to the same scale.

FIGURE 2. Neomida groehni sp. nov., holotype, habitus, X-ray micro-CT rendering: A – dorsal view; B – ventral view with legs; C – lateral view, without legs and antennae; D – the same, with legs an antennae; E – ventral view without legs and antennae; F – anterior view; G – caudal view. Scale bars represent 1 mm.

FIGURE 3. Neomida groehni sp. nov., holotype, X-ray micro-CT rendering:A – details of forebody, dorso-lateral view, arrows show marginal epistomal tubercles; B – head, dorsal view, arrows show marginal epistomal tubercles; C – pro-mesothoracic junction, ventral view. Abbreviations: Pstr – prosternal process, MstrE – mesosternal Y-shaped elevation, MstrF – mesosternal intercoxal fovea, Mtrch - mesotrochantine. Not reproduced to the same scale.

FIGURE 4. Neomida groehni sp. nov., holotype, aedeagus, X-ray micro-CT rendering: A – ventral view; B – dorsal view; C – lateral view; D – apical piece. Abbreviations: ap – apical piece, bp – basal piece, ml – median lobe.