Rovnoxestus rasnitsyni DIETRICH & DMITRIEV & PERKOVSKY 2021, sp. nov.

Rovnoxestus rasnitsyni sp. nov.

Material. Holotype (male): SIZK Pe-27, late Eocene Rovno amber. Ukraine: Rovno prov.: Perebrody. Syninclusions: male Sciaridae, two unidentified Nematocera, one Scelionidae, stellate hairs. Paratype: fifth instar nymph SIZK Pe-118, late Eocene Rovno amber. Ukraine: Rovno prov.: Perebrody. Syninclusions: two Psychodidae, female of Chironomidae, Сollembola: Entomobryomorpha, two Empididae, stellate hairs.

The holotype specimen is a complete, intact, adult female embedded in a piece of pale greenish yellow amber with extensive milky veil and plant/soil debris obscuring many morphological details of the specimen, particularly the face and ventral part of the thorax. The paratype is a complete, intact, fifth-instar nymph with the entire dorsum completely visible but with most of the venter concealed by a milky veil that obscures several details of the facial structure and leg chaetotaxy.

Etymology. The species name is a Latin noun in the genitive case honoring Prof A.P. Rasnitsyn in recognition of his many important contributions to knowledge of the fossil record of insects.

Description. Measurements (mm).

Adult: Body length 6.1; head width (dorsal aspect) 1.4, head length (medial) 0.4, pronotum maximum width 1.4, pronotum length (medial) 0.9; front femur length 0.95, tibia length 1.0; middle femur length 0.9; tibia length 1.3; hind femur length 1.6, tibia length 2.9; forewing length 4.7. Overall coloration uniformly black.

Head in dorsal view (Figs 1C, 3A) broader than pronotum, anterior margin parabolically rounded, crown moderately convex, slightly longer in middle than next to eyes, width between eyes approximately twice median length, eye width slightly less than crown width between eyes. Ocelli large, on anterior margin of head, separated from eyes by two ocellar diameters. Face slightly convex, frontoclypeus (Figs 1D, 3C) slightly longer than width between antennal bases, shagreen with some indistinct transverse rugae; lateral frontal sutures extended to ocelli. Antennae shorter than head width, arising from shallow pits closer to anterodorsal than to ventral corners of eyes. Rostrum slightly tapered, extended to middle trochanters.

Pronotum slightly more than twice as long as crown, lateral margin moderately long, divergent posterad (Figs 1C, 3A). Exposed part of mesonotum shorter than scutellum, scutellar sulcus arcuate (Fig. 3A).

Forewing macropterous, texture granulose, mostly opaque except near apex; clavus approximately two thirds total length; venation somewhat elevated and moderately well delimited, three anteapical cells present, appendix very narrow, wing apices not overlapping at rest, inner apical cell extended to apical margin (Fig. 3F). Hind wing membrane with reticulate pattern, submarginal vein narrowly separated from margin, complete distally.

Front femur with anteroventral macroseta near midlength and some additional ventral setae more distad; tibia row PD with three widely spaced macrosetae in distal half (possibly more basally), AD with single distal macroseta, AV with at least 12 long setae, PV with a few shorter, more widely spaced setae. Middle tibia row PD with several macrosetae, AD with only distal macroseta present. Hind femur macrosetal formula 2+2+1 with penultimate pair close-set (Fig. 3E). Tibial row AD with 11 macrosetae and 3–5 small setae between successive macrosetae, distal setae in each intercalary series progressively larger; row PD with 20 setae approximately uniform in length, slightly longer and thinner than AD macrosetae;AV with ~19 close-set setae; PV with ~29 setae (Figs 2C, 3E); tarsus ca. half length of tibia, tarsomere I as long as II and III combined, with dorsoapical pair of macrosetae, two ventral longitudinal rows of stout setae and pecten with 3 platellae, inner preapical ventral seta elongate (Figs 2B, 3D).

Female pygofer elongate with numerous scattered macrosetae, ovipositor approximately half total length of abdomen, extended slightly beyond pygofer (Fig. 2C).

5 th instar nymph: Body. Length 5.6 mm. Body slender, not flattened, without flattened setae, with only macrosetae organized into longitudinal rows (Fig. 4A, B).

Head. Without macrosetae. Crown (Fig. 4A) more than 1.5× wider than long, angulately rounded. Crown lateral margin carinately elevated above eye level. Lateral edges long, parallel to each other, only slightly shorter than middle line of head. Ecdysial line on dorsal surface of head. Angle formed by ecdysial line almost 180 degrees. Acrometope present, about 1/3 of the crown length. Median longitudinal carina on crown absent. Ocelli at fore margin of head, close to eyes. Crown-face transition narrowly rounded. Face (Fig. 4C) longer than wide, without longitudinal carina. Postclypeus longer than wide. Antennae attached near upper margins of eyes, first antennal segment visible from above, antennae short, not or just reaching apex of anteclypeus. Antennal flagellum not segmented.

Thorax. Thorax (Fig. 4A) without macrosetae on dorsum. Pronotum lateral margin shorter than pronotum medially.

Wings. Forewing pad moderately long, 1.6× as long as pterothorax (Fig. 4A).

Legs. Fore tibia rounded dorsally. Hind femur setal formula 2+2+1, setae of penultimate pair set close to each other. Cross section of hind tibia narrowly rectangular (distance AD-AV much greater than AD-PD). Hind tibia AD row with 9–11 macrochaetae. PD row of hind tibia with intercalary setae shorter than macrosetae (Fig. 4E). AD row of hind tibia with 1–3 setae between each pair of macrosetae. PV row of hind tibia with setae increasing in size towards apex of tibia. Pecten of hind tibia with platellae. Ventral surface of hind tarsomere I with two well developed longitudinal rows of setae, without platellae, last seta of PV row significantly enlarged. Apex of hind tarsomere I not pointed; pecten consists of several platellae (Fig. 4D).

Abdomen. Lateral margins of abdominal tergites not flattened. Abdomen without dorsomedial carina, without setal tubercles, with macrosetae of moderate size, about 1/3 of tergite length. Abdomen with eight longitudinal rows of macrosetae situated at hind margin and hind corners of each tergite (Fig. 4B). Fore and lateral margins of abdominal tergites without macrosetae.

Nymph terminalia. Pygofer dorsally more than 2× as long as tergite VIII, incised along the midline, with 2 groups of numerous macrosetae. Pygofer appendages set close to each other. Gonapophyses I shorter than pygofer length.

Coloration. Main coloration brownish. Red pigment absent. Without distinct color pattern; entire body, especially abdominal tergites covered with small pale dots. Setal areolae on abdomen not developed. Hind margin of metanotum without dark spots. Posterior half of each abdominal tergites slightly darker than anterior half, which has more pale dots. Legs without dark setal areolae.