Atissini Cresson, 1942

Zatwarnicki, Tadeusz & Mathis, Wayne N., 2019, New discoveries in New World Atissini as revealed in revision of Pelignellus Sturtevant & Wheeler (Diptera: Ephydridae), Israel Journal of Entomology (Oxford, England) 49 (2), pp. 11-26 : 14

Tribe Atissini Cresson, 1942

Atissini : Cresson 1942: 103. Type genus: Atissa Haliday in Curtis 1837; Wirth 1965: 735–737 [Nearctic catalog]; 1968: 77.4–77.6 [Neotropical catalog]; Cogan & Wirth 1977: 324–325 [Oriental catalog]; Cogan 1980: 657–658 [Afrotropical catalog]; 1984: 129–134 [Palearctic catalog]; Mathis 1989: 641 [Australasian/Oceanian catalog]; Mathis and Zatwarnicki 1995: 54–60 [world catalog].

Diagnosis: Atissini are distinguished from other tribes of the subfamily Hydrelliinae by the following combination of characters: Body length small to moderately small, 0.60–2.10 mm; generally densely microtomentose, silvery gray to brown. Head: Antenna with 4–6 dorsal rays (secondarily, as in Asmeringa , the arista is barely developed, just a stub without any aristal rays). Eye bearing numerous, short, interfacetal, fluted setulae. Thorax: Dorsocentral setae usually 0+1, rarely 1+1 (anterior seta sutural); posterior notopleural seta either at about same level as anterior seta or distinctly dorsad of anterior seta. Wing slightly pointed at apex of vein R 4+5; vein R 2+3 short; costal section III long, at least ⅔ length of section II, sometimes longer; costa extended to vein M; frequently area around and over crossvein dm–cu distinctly darkened. Midtibiae lacking dorsal, spine-like setae. Abdomen: Male terminalia: Epandrium in posterior view as an inverted U, sometimes discontinuous medially across dorsum; cercus separated from epandrium, rarely fused anteriorly with epandrium, from oval to clavate; surstylus (= gonostylus) present or reduced, if present, its shape and connection with epandrium variable: separated or fused with epandrium, small and narrow to robust and elongate or broad, or forming a genital plate; postgonite elongate, bearing some setulae, rarely connected with surstylus; pregonite small, short, more or less triangular or lobate, bearing 1–3 apical setulae; fused aedeagus/phallapodeme elongate, basal third (phallapodemal section) V-, or T-shaped or rod-like in ventral view, medial section more robust and wide, apical third tapered to acutely pointed apex; hypandrium as simple sclerite with rounded anterior margin, in lateral view flattened.

Discussion: The characters used to distinguish Atissini from other tribes in Hydrelliinae include both symplesiomorphies and synapomorphies. The synapomorphies that establish the monophyly of the tribe are: (1) Wing slightly pointed at apex of vein R 4+5; (2) Vein R 2+3 short, with costal section III long, at least ⅔ the length of section II, sometimes longer; and (3) Phallapodeme and aedeagus fused.

In addition to these synapomorphies, most specimens are densely microtomentose and are dull whitish or silvery gray to tan; often the posterior notopleural seta is inserted at an elevated position relative to the anterior seta; and specimens are frequently found in saline or alkaline aquatic habitats along maritime coasts or inland.

Although the tribe Atissini is a monophyletic clade, we have not definitively identified its sister group. Perhaps the tribe Hydrelliini Robineau-Desvoidy is a likely candidate, as both Hydrelliini and Atissini have eyes that bear conspicuous and numerous interfacetal setulae that are fluted.