Ripidius undetermined

Batelka, Jan, Perkovsky, Evgeny E. & Prokop, Jakub, 2020, Diversity of Eocene Ripiphoridae with descriptions of the first species of Pelecotominae and larva of Ripidiinae (Coleoptera), Zoological Journal of the Linnean Society 188, pp. 412-433 : 417-419

RIPIDIUS SP. , PRIMARY LARVA

( FIGS 5, 6A–L, 7A, 7B)

Examined specimen: PIN No. 3387/739 deposited in the Palaeontological Institute of the Russian Academy of Science (PIN RAS); Sakhalin amber, Sakhalin Oblast, Dolinsky District, Starodubskoye; dimensions of block: 3.20 × 2.25 × 0.45 mm.

Description

Habitus ( Figs 5–7): Body elongate, subcylindrical, length excluding terminal setae c. 0.373 mm, widest part posterior edge of metathorax c. 0.16 mm. Moderately sclerotized, with smooth cuticle. Head large, wider than long, as wide as prothorax; mandibles, antennae and maxillary palpi prominent and exposed. Thorax well sclerotized, with segments distinctly wider than long. Legs elongated, with long and slender tibiotarsus. Paired minute finger-shaped sensilla arranged in a mirror-like position along imaginary anterio-posterior mid-line on head and thorax. Paired long erect bristle-like setae on head, thorax and abdomen arranged in a similar manner. Abdomen suddenly tapering posteriad, abdominal segments superimposed on each other.

Head ( Figs 6D, 6E, 7A, 7B): Hexagonal, 1.5× wider than long, from antennal foramina suddenly tapering anteriad, with greatest width at its posterior margin. At least three small and one minute stemmata positioned laterally on head, just behind antennal foramina, visible from ventral side. Transverse frontoclypeal ridge strengthening and dorsal ecdysial sutures invisible. Labrum not recognizable as a separate structure, apparently fused with clypeofrons.

Dorsal surface of head with two types of setae ( Figs 6D, 7A). Two paired, minute, finger-shaped sensilla present: first pair (dcs1) placed just posteriad of each mandibular base, second pair of sensilla (dcs2) placed close to each other just before posterior margin of head. Three paired bristle-like seta discernible: one pair of short setae, with each one located above mandibles, extending slightly beyond front margin of head. Two paired long bristle-like setae located more or less adjacent to finger-shaped sensillae dcs1 and dcs2. Ventral surface with two paired long bristle-like widening posteriorly, slightly convex posteriad, with rounded posterolateral corners and margins that converge slightly anterialy.

setae located on lateral edge of head: first one placed posteriad of maxillary palpus and second just before antennal foramina ( Figs 6E, 7B). Putative finger-shaped sensilla on ventral side (vcs) indiscernible and probably absent.

Antennae three-segmented, slightly curved between antennomeres II and III; basal segment small, lenticullar, partly hidden under margin of head; antennomere II long, slender, cylindrical, with long bristle-like antennal sensorium at its apex, almost as long as antennomere II; antenomere III cylindrical, about half as long as antennomere II, with long, bristle-like terminal seta with a distinctly ring-shaped base ( Fig. 6C). One short microtrichia visible just before distal part of antennomere II.

Mandibles movable inwards in an anteroventral plane, apices of closed mandibles touch each other ( Fig. 6E). Base greatly expanded, elliptical, apices long and slender, falciform, strongly incurved, without teeth or ridges. Maxillae long and slender, cardo indiscernible, stipes present as a short, slightly longer than wide segment with oblique apex, extending slightly beyond margin of head; palpus long, probably two-segmented but without visible articulation, with two short microtrichia on the first-half of its length and opposite one bristle-like seta sloping at an angle of 45°, as long as both palpomeres combined ( Fig. 6E). Palpus terminates in a bristle-like seta, distinctly longer than palpomeres and stipes combined.

Thorax ( Figs 6I–K, 7A, 7B): 1.75× as long as head, about 2.8× as wide as long, thoracic segments slightly Prothorax: Pronotal base as wide as posterior cephalic margin. Two paired, finger-shaped sensilla discernible: one pair (pns1) located close to lateral margins, second pair (pns2) closer to midlength of posterior margin ( Fig. 6I). Two paired, long and erect bristle-like setae located close to posterolateral corners. Prosternum with three paired, finger-shaped sensilla (pss1–3) arranged in a semicircle around interior margin of procoxa. Procoxa prominent, elliptical, inserted postero-laterally, only slightly protruding beyond lateral pronotal margin ( Fig. 6J). Lateral procoxal margin with two long, thick spines, reaching about half the length of profemur. Trochanter small, cylindrical, slightly longer than wide, indistinctly widening distally, broadly connected with femur, devoid of any setae. Profemur elongate, robust, contracted in distal fifth of its length, with four long preapical setae that extend more or less beyond distal edge of profemur. Tibiotarsus elongated (c. 0.191 mm), about 1.75× longer than femur, thin, in distal half with irregular row of three extremely small semi-erect, laterally directed spines, and three similar spines directed in the opposite direction. Pretarsus consisting of a minute claw-like process and opposing prominent, elongated, slightly curved terminal pad ( Fig. 6F).

Mesothorax only slightly wider than prothorax, about 2.8× as wide as long, with margins more convergent anteriad. Mesonotum with paired finger-shaped sensilla (msns1) located close to lateral margin, and two paired long bristle-like setae located along posterior margin of mesonotum between finger-shaped sensilla and lateral margin of mesonotum ( Fig. 6I). One paired short bristle-like setae on postero-lateral mesonotal corner. Mesosternum with two paired finger-shaped sensilla (msss1, 2) directed towards metanotum. Middle legs similar to forelegs.

Metathorax shorter than mesothorax, about 3.7× as wide as long. Metanotum with one paired finger-shaped sensilla (mtns1) located close to lateral margin, and one paired long bristle-like setae on posterior margin of mesonotum between finger-shaped sensilla and lateral margin of metanotum. One paired, shorter, bristle-like setae on postero-lateral metanotal corner. Metasternum with two paired, finger-shaped sensilla (mtss1, 2) in a position similar to that of msss1 and msss2, directed towards abdomen ( Fig. 6K). Hind legs similar to front and middle legs.

Abdomen ( Figs 6A, 6B, 6L, 7A, 7B) probably shortened due to desiccation. Edges of segments indiscernible. The whole abdomen covered with long, erect, bristle-like setae, about three pairs on dorsal side of each segment, making counting of abdominal setae and segments difficult. Terminal pair of setae about as long as abdomen. Abdomen terminated by long, narrow, tubular, three-segmented appendage, each segment is similar in length, last segment triangular, widest distally ( Fig. 6L).