Adelaeus Ratcliffe, 2014

Ratcliffe, Brett C., 2014, A New Genus and Species of Dynastinae (Coleoptera: Scarabaeidae) from the Galápagos Islands, Ecuador, other New Species of Cyclocephalini, Pentodontini, and Phileurini from South America, and a Revised Key to the Genera of New World Pentodontini, The Coleopterists Bulletin 68 (4), pp. 663-680 : 663-680

Adelaeus Ratcliffe , new genus

Type Species. Adelaeus anachoretus Ratcliffe , here designated.

Description. Body form short, suboval ( Fig. 17 ), elytra together wider than long. Length about 16 mm. Color reddish brown. Clypeus subtriangular, apex narrowly subtruncate. Interocular distance equals about 5 transverse eye diameters. Antenna with 9 antennomeres, club subequal in length to antennomeres 2–6. Mandibles exposed, rounded, with small, subapical tooth. Pronotum with punctures moderate in density and size; base margined except in front of scutellum where bead obsolete. Elytra with moderately dense, shallow punctures, striae indistinct. Hind wings reduced. Pygidium nearly flat, rugose across base, disc with few small punctures. Protibia tridentate. Metatibia at apex subtruncate. Prosternal process thick, subrectangular, slightly recurved, apex truncate.

Distribution. San Cristóbal (Chatham) Island, Galápagos Islands, Ecuador.

Diagnosis. The only other Dynastinae occurring on the Galápagos Islands are five species of the endemic genus Neoryctes , and one might naturally expect for this new species to belong to that genus. Adelaeus anachoretus , while superficially similar to Neoryctes species in body form, is unique and differs from Neoryctes as follows: clypeal apex narrowly subtruncate (narrowly bidentate in Neoryctes ); mandibles rounded with small, subapical tooth (mandibles with external edge rounded, entire in Neoryctes ); prosternal process long, subrectangular, thick, slightly recurved, apex truncate (process short, laminate, subtriangular in Neoryctes ); propygidium glabrous and lacking stridulatory bands (propygidium finely setose and with two longitudinal stridulatory bands in Neoryctes ); pygidium in males nearly flat (strongly convex in males of Neoryctes ); and parameres long, slender, and with acute apices ( Figs. 18–19 ) (parameres generally subrectangular in caudal view in Neoryctes ) ( Cook et al. 1995). Only N. linelli occurs sympatrically on San Cristóbal (Chatham) Island, but that beetle is much larger, has quadridentate protibiae, and the parameres are broadly subrectangular. Neoryctes species and A. anachoretus have hind wings so greatly reduced that they cannot be used for flight, and it is possible that the short, suboval body form seen in both is a result of reduced wings.

In size and gestalt, A. anachoretus also resembles in body form species of Eremobothynus Ohaus. The three species of Eremobothynus occur in Argentina and have a central frontoclypeal tubercle or horn, a declivous pronotum in males, functional flight wings, and generally subtriangular parameres, none of which are character states shared with A. anachoretus .

Etymology. The generic epithet is derived from the Greek stem adelos, meaning unknown or obscure and is used here as a masculine noun to mean “that which is unseen” in reference to the long hidden nature of this genus.

Figures

Figs. 17–19. Adelaeus anachoretus, holotype. 17) Habitus; 18) Parameres, caudal view; 19) Parameres, lateral view.