Alavesia Waters and Arillo

Sinclair, Bradley J. & Grimaldi, David A., 2020, Cretaceous diversity of the relict genus Alavesia Waters and Arillo (Diptera: Empidoidea: Atelestidae), American Museum Novitates 2020 (3961), pp. 1-40 : 4-6

Alavesia Waters and Arillo

Alavesia Waters and Arillo, 1999: 60 . Type species Alavesia subiasi † Waters and Arillo , by original designation.

Neoalavesia Poinar and Vega, 2020: 2. Type species Neoalavesia hadroceria † Poinar and Vega, by original designation, new synonymy.

NOTE ON SYNONYMY: The genus Neoalavesia is considered a junior synonym of Alavesia . The characters proposed by Poinar and Vega (2020) justifying their new genus (e.g., length of cell dm, apical curvature of CuA+CuP, slanting h crossvein, M 1+2 straight, length of R 1, shape of postpedicel) all fall within the present definition of Alavesia and identify only species differences. For this reason Neoalavesia is proposed as a new synonym of Alavesia .

DIAGNOSIS: Readily differentiated from all other empidoid genera by the diminutive cell dm, M 1+2 and M 4 long, greater than half length of wing and widely divergent, postpedicel very long and lanceolate (longer in males than females), stylus three-articled, legs with parallel rows of setulae, scutal chaetotaxy thickened; vein CuA straight, convex or arched to CuA+CuP.

GENERAL DESCRIPTION (updated from Sinclair and Kirk-Spriggs, 2010): Male. Dichoptic, frons broad (fig. 8A); inner margin of eye near antenna with shallow notch. Ocellar triangle slightly raised. Antenna (figs. 1, 8): postpedicel elongate, lanceolate to long triangular shape, tapered to apical point, micropubescent; stylus aristalike, terminal, 1/3 to 3× length of postpedicel (very long in males of two fossil species, which also have broadened apical “flags” on stylus), with 2 minute, ringlike basal articles. Proboscis (fig. 9): Short, labellum fleshy, with ~10 pseudotracheae per lobe; labrum well developed, lacking epipharyngeal blades; laciniae and hypopharynx well developed; palpus from short and paddlelike to long and digitate or spatulate.

Thorax: Antepronotum without setulae; postpronotal lobe protruding (fig. 5), with short, stout setulae. Scutum moderately to strongly arcuate (figs. 12–17). Acrostichal setulae usually biserial (fig. 5), sometimes uniserial; dorsocentrals similar to acrostichals, minute, irregular, prescutellar dorsocentrals macrosetose; 2–5 notopleural setae, 1 stout supraalar seta, 1 stout postalar seta; 2–4 pairs marginal scutellar setae. Laterotergite bare. Legs: Length moderate, with distinct rows of setulae, mostly lacking large setae, except for subapical tibial setae. Fore- and mid femora slightly swollen, hind femur more strongly so; mid and hind femora with shallow longitudinal furrow, bare of setulae (fig. 11) on lateral or lateral + mesal surfaces; tibiae sometimes with such thin furrows (see below, Femoral Furrows). Tibiae slender, subequal in length to femur, foretibial gland absent; 1–2 stout apical setae present. Tarsi slender; pretarsal claws short, pulvilli small, padlike.

Wing (figs. 2–4, 10A): Hyaline to slightly tinted/infuscate; with fine microtrichia over entire membrane. Pterostigma absent. Vein C terminating slightly beyond apex of M 1+2; Sc apically evanescent, ending slightly before costal margin; Rs arising near or distant from level of humeral crossvein; R 1 ending at or slightly beyond midlength of wing; R 2+3 shortly curved to C apically, ending closer to apex of R 1 than R 4+5; R 4+5 unbranched, slightly divergent to parallel to M 1+2; cell dm very small, nearly or more than half length of basal cells, emitting two veins M 1+2 and M 4; M 1+2 and M 4 moderately to strongly divergent; CuA straight, curved, or sharply recurved; apex of cell cua truncate or acute. Anal lobe broad to very shallow, alula reduced.

Abdomen: Sclerites covered in distinct, short setae, posteromarginal setae slightly thicker on largest sclerites. Segments 1–5 broad, with remaining gradually narrowed. Tergum 8 very narrow, straplike, greatly prolonged laterally with triangular dorsomedial posterior extension. Sternite 8 greatly reduced, as pair of slender sclerites, weakened and partially folded at midlength; longer than sternite 7. Terminalia (figs. 6, 7; 10B): Symmetrical, unrotated, held posterodorsal to abdomen. Cercus small, flat, oval, and weakly sclerotized; hypoproct subtriangular. Epandrium U-shaped with dorsal bridge anterior to cerci. Surstylus subapical, commonly with small dorsal lobe at base. Hypandrium (in Recent species) short, divided into slender, straplike sclerites; anterolateral corner extending to articulate with epandrium. Postgonites caplike, joined or fused medially. Paired ventral apodemes extending anteriorly from postgonites; gonocoxal apodeme with slender rodlike process longer than hypandrium; ejaculatory apodeme articulated at base of phallus (observed in Recent specimens). Phallus tubelike, arched and pointing ventrally; apex bifid in fossil species.

Female. Similar to male except postpedicel shorter; abdomen well sclerotized, tergites nearly twice as broad as long. Postabdomen (fig. 10C, D) weakly sclerotized, telescoping into segment 5. Tergites 6 and 7 reduced to pair of slender sclerites; sternites 6 and 7 rectangular, slender; tergite 10 absent; cercus well developed, pubescent, length about twice width. Spermathecal capsule spherical, darkly pigmented.

SPECIES COMPOSITION: The two species in Early Cretaceous amber from Spain, Alavesia subiasi Waters and Arillo and A. prietoi Peñalver and Arillo , exhibit all the diagnostic features of the living species. Distinctive features in both of these fossil species are: (1) the position of vein CuA, which is straight but strongly recurved, such that it is in line with crossvein m-cu or nearly so, and (2) veins R 4+5 and M 1+2 straight and parallel for their entire length. The species in Burmese amber with these features are A. angusta , sp. nov., A. latala , sp. nov., A. longicornuta , sp. nov., and A. longistylata Zhang and Wang. Alavesia longicornuta and A. longistylata are distinguished from the Spanish amber species by the very long stylus with apical flag. Alavesia latala has a distinctively broad wing. The wing of Alavesia angusta is quite similar to A. prietoi , in size (i.e, 1.4 and 1.5 mm, respectively), in the slender shape, and venation, including the slanted crossvein m-m. The postpedicel of A. prietoi is triangular and slightly broader (L/ W 3.0), that of A. angusta is slender and fusiform (L/ W 4.47).

The extant species from Namibia, Alavesia brandbergensis Sinclair and Kirk-Spriggs and A. daura Sinclair and Kirk-Spriggs , have a distinctively arched vein M 1+2 that is widely divergent with M 4, and cell dm is very small. Burmese amber species sharing these features are A. brevipennae , sp. nov., A. myanmarensis , and A. pankowskiorum , sp. nov., although in the last-named species there is significantly less arching. Of the seven species in Burmese amber where details of the male genitalia could be observed, all except one have a fringe of long setae on the distal margin of the ventral epandrial lamella and a slender, digitiform surstylus. The surstylus has at its base a slender or small dorsal lobe in A. longistylata , and A. magna , sp. nov. Like the Namibian species A. brandbergensis , the phallus in A. longistylata , A. magna , sp. nov., A. pankowskiorum , sp. nov., and A. zigrasi , sp. nov., is bent ventrad, but significantly longer in the fossil species and with a bifid, “feathered” apex. The male genitalia of A. lanceolata , sp. nov., and A. spinosa , sp. nov., are each unique and very different from other species in the genus, as described under those species.

FEMORAL FURROwS: In the course of this study it was noticed that some species and specimens possess a shallow longitudinal furrow along the lateral (sometimes medial) surface of the femora (especially mid and hind legs), and sometimes on the tibiae (fig. 11). The furrow readily appears to be an artifact of preservation, and in fact when the legs are slightly compressed or shrivelled the furrow is unapparent. However, the structure is certainly not preservational since in fully distended legs the furrow area is devoid of microsetae/setulae (which otherwise cover the rest of the femur), it is symmetrical between legs of the same pair, and there is often an even row of setulae bordering the furrow. Femoral furrows are well developed in Alavesia longistylata , A. magna , A. pankowskiorum and A. zigrasi , and are faint in A. angusta and A. lanceolata , suggesting this may be a distinctive feature for Alavesia , or at least the Burmese amber species. Preservation of specimens in the other species may be insufficient to determine if the furrows are present or absent. Available living specimens have compressed legs due to air drying, but a longitudinal region devoid of setulae is apparent and likely represents a shallow furrow. The condition is Spanish amber species is unknown.