Athliini, Smith & Evans, 2018

Smith, Andrew B. T. & Evans, Arthur V., 2018, Taxonomic review of Athliini (Coleoptera: Scarabaeidae: Melolonthinae), a new tribe of scarab beetles endemic to South America, Zootaxa 4471 (2), pp. 279-308 : 280-281

Athliini Smith & Evans, new tribe

http://zoobank.org/urn:lsid:zoobank.org:act:1EF3248F-813E-4307-AD07-43E4F3 F75677

Type genus. Athlia Erichson.

Diagnosis. Labrum transverse, originating below and fused to anterior clypeal margin so that they are coplanar; labroclypeal suture evident. Clypeus and frons are coplanar. Ocular canthus present, margin continuous with lateral clypeal margin. Antennae with 8 or 9 antennomeres, club with three short, thick, subequal lamellae. Mentum with insertions of labial palpi not exposed. Pronotum with anterior margin membranous. Abdomen with 6 ventrites, 2–5 equal in length and not strongly narrowed medially, 5 and 6 not separated by a membrane, with ( Apteroathlia , Athlia ) or without carinae on sides, and a distinct propygidial-sternal suture. Propygidium plain, fused to tergite with suture more-or-less evident, spiracle not within or immediately adjacent to suture. Procoxae conical and protuberant, anterior height greater than basal width. Protibial spur present. Metepimeron triangular with a distinct ridge. Outer surfaces of mesotibiae and metibiae with indication of partial or complete ( Athlia ) transverse carinae. Metatibial apex transverse, inner margin distinctly notched with two spurs, each set above and below tarsal articulation so that the first tarsomere passes between them. Opposing claws symmetrical, incised, toothed, or simple, with a short and bisetose onychium; claws of Dihymenonyx with a fleshy lobe underneath each side of claw.

Composition. Apteroathlia Smith & Evans , new genus, Athlia , Dihymenonyx , and Ulata .

Distribution. Southern half of South America.

Notes. Athliini new tribe is distinguished from all Neotropical Sericoidini and Australian Liparetrini (and similar Australian tribes) by the distinct labrum that is fused to and coplanar with the anterior clypeal margin, a morphological feature that superficially resembles that found in the Sericini . Sexual dimorphism in this tribe is very subtle and difficult to detect. The antennal club is reduced in both sexes (generally less than half the length of the funicle) and there are no sexually dimorphic characters in the head or legs. The convexity of the abdomen is generally sexually dimorphic but the differences are subtle since the abdomen in both sexes appears convex or inflated.

Three of the genera in this tribe ( Apteroathlia , Athlia , Dihymenonyx ) include species with reduced or absent metathoracic wings, thus indicating a general evolutionary trend of flightlessness in this group for species living in arid habitats. Scholtz (2000) hypothesized that some scarab taxa have an increased evolutionary propensity towards flightlessness when they evolve in certain environments such as deserts, mountains, and islands.

The immature stages have not been described for any species in this tribe. Studying the larval natural history and morphology of this group may provide insights into the placement of this taxon among other Melolonthinae tribes.