Electromethes alleni Kazantsev, 2012

Kazantsev, S. V., 2022, Description of a female of Electromethes alleni Kazantsev, 2012, the only fossil omethid taxon (Insecta: Coleoptera) from Baltic amber, Russian Entomological Journal 31 (3), pp. 276-277 : 276-277

Electromethes alleni Kazantsev, 2012

Figs 1–2 .

MATERIAL: Female, specimen No. KA-001, Baltic amber, Eocene (K. Andruschenko coll., Kaliningrad) .

DESCRIPTION. Female. Dark brown, with lighter distal margin of penultimate ventrite.

Eyes relatively small, interocular dorsal distance ca. 2 times greater than eye diameter. Ultimate maxillary palpomere narrow, ca. 2 times longer than wide, almost parallel-sided and flattened distally. Antennae dentate, attaining to elytral third, gradually narrowing distally, antennomere 3 ca. 2.5 times longer than pedicel (antennomere 2) and ca. 1.2 times shorter than antennomere 4 and consequent antennomeres; antennal vestiture short and sub-erect ( Figs 1–2 ).

Pronotum transverse, ca. 2 times as wide as long, almost straight posteriorly, with broadly rounded posterior angles ( Fig. 1 ).

Elytra elongate, flattened, ca. 2.8 times as long as wide at humeri, somewhat widened in distal third; with three weak longitudinal costae, interstices densely granulate ( Fig. 1 ).

Tarsomere lengths ratio: 2: 1: 1: 0.7: 2 ( Fig. 2 ).

Ultimate ventrite elongate, semi-triangular, rounded distally; penultimate ventrite transverse, slightly rounded distally ( Fig. 2 ).

How to cite this article: Kazantsev A. V. 2022. Description of a female of Electromethes alleni Kazantsev, 2012 ,

Length (from anterior head margin to end of elytra): 6.1 mm. Width (humerally): 1.8 mm.

Syninclusions. Aphid.

Male. Similar to female, but eyes somewhat smaller, antennae ramose, body length 6.4 mm [ Kazantsev, 2012].

Electromethes , distinguishable from other omethids by the combination of more prominent and more sclerotised labrum, almost parallel-sided or securiform ultimate palpomeres, non-ramose male antennomere 3, location of the bases of rami of male antennomeres 4–10 at the apices of antennomeres, triangular prosternum, absent elytral epipleuron, present plantar pads on tarsomeres 1–2 [ Kazantsev, 2012, also Fig. 2 ], actually does not fit into any of the extant subfamilies of Omethidae . However, erecting a new higher level taxon to accommodate the genus seems premature; prior to that further studies should carried out to define the family more clearly, with, preferably, premature stages taken also into consideration.

Acknowledgements. It is my pleasant duty to express my sincere gratitude to Mr. Konstantin Andruschenko (Kaliningrad) for the possibility to study this remarkable amber specimen .

Figures

Figs 1–2. General view of Electromethes alleni, female: 1 — dorsally; 2 — same, ventrally. Scale bars: 1 mm. Рис. 1–2. ОбЩий вид Electromethes alleni, самка: 1 — сверху; 2 — сниЗу. Масштабные линейки: 1 mm.