Desicasta Thomson, 1878

Ratcliffe, Brett C., 2013, A Revision of the Neotropical Genus Desicasta Thomson (Coleoptera: Scarabaeidae: Cetoniinae: Gymnetini), The Coleopterists Bulletin 67 (4), pp. 447-456 : 449-450

Desicasta Thomson, 1878

Desicasta Thomson, 1878: 14 . Type species: Desicasta sculptilis Thomson, 1878: 15 , by original designation. Desicasta sculptilis is a junior synonym of Desicasta reichei ( Thomson, 1860) .

Moscheuma Thomson, 1880: 268 . Type species: Stethodesma reichei Thomson, 1860: 362 , by original designation (synonym).

Description. Scarabaeidae ,Cetoniinae, Gymnetini .

Form: Rhomboidal, robust, sides slightly tapering

from humeri towards apex of elytra, dorsum nearly flat. Color black to bright reddish brown, shiny or velutinous. Length 19–26 mm. Surface of pygidium with short setae, especially in females. Head: Subrectangular, longer than wide. Clypeus at apex with deep, U-shaped emargination, not reflexed, sides constricted just before antennal insertion. Frons weakly, longitudinally tumid at middle and slightly depressed on either side. Antenna with 10 antennomeres. Pronotum: Subtrapezoidal, widest near base, gradually convergent to anterior angles, basomedian lobe strongly produced, lobe covering all but tip of scutellum. Sides with broad bead or marginal line, anterior and basal margins lacking bead. Elytra: Widest at base, posthumeral emargination distinct. Bead present on lateral margins. Pygidium: Surface densely, concentrically strigulose or rugulopunctate, nearly flat to weakly convex. Venter: Mesometasternal process, in lateral view, usually subrectangular, bluntly to subquadrately rounded, obliquely projecting away from ventral axis of body (sometimes only weakly) ( Fig. 1 ). Males with abdomen weakly to distinctly concave in lateral view. Females with abdomen flat to slightly tumescent. Legs: Protibia in males slender, with either 1, 2, or 3 teeth; protibia in females wider and always tridentate. Metatibia at apex with 3 acute teeth and with 2 long, slender spurs. Parameres: In caudal view, form subrectangular, form of apices variable: narrowly to broadly rounded, with or without small tooth apicolaterally, divergent or convergent at apices.

Diagnosis. Species of Desicasta are distinguished from other genera of New World Gymnetini by a distinctly bilobed and emarginate clypeal apex, frons weakly and longitudinally tumid at middle (lacking armature that is present in most species of Cotinis and males of Allorrhina ), and, in lateral view, a mesometasternal process that is subrectangular or bluntly rounded and usually projecting obliquely downwards and away from the ventral axis of the body ( Fig. 1 ).

Only three other New World gymnetine genera possess a distinctly emarginate, or bilobed, clypeal apex: Amithao , Guatemalica , and Hadrosticta Kraatz. Species of Amithao have a mesometasternal process that is, in lateral view, dorsoventrally flattened and in the same plane as the ventral axis of the body ( Fig. 2 ), while species of Guatemalica and Hadrosticta have a mesometasternal process that is short, attenuate, and curving downwards and then recurving upwards at the apex ( Fig. 3 ). Hadrosticta is unique because of its metallic green color both dorsally and ventrally and the slender form of the parameres. Some species of Hologymnetis Martínez (all species are velutinous) have an emarginate clypeal apex (not bilobed), but they all lack a prosternal “throat spur”, a distinguishing character for the genus since all other New World gymnetines possess this character.

Distribution. Species of Desicasta are known from central Panama to South America, and one species extends as far south as Argentina.

Natural History. Adults have been found from near sea level to 2,500 m and are usually attracted to traps baited with ripe fruits. Adult activity seems to coincide with the rainy season, although additional data is needed to verify this for all species. Krell et al. (2002) found two larvae of Desicasta laevicostata ( Neervoort van de Poll, 1886) (= D. reichei ) in living stalk tissue of Vriesea sanguinolenta Cogn. and Marchal (Bromeliaceae) in Panama and surmised the larvae were feeding on living plant tissue. The larval stages remain undescribed.

Nomenclature. The genus Desicasta has languished in obscurity for the last 115 years. Aside from checklists that enumerated eight species in the genus, the most recent paper discussing species was that of Schoch (1898), and a note on natural history was provided by Krell et al. (2002). After examining the available types of most of the species, I have concluded that there are only three species in the genus. Early workers often had only the brief, original descriptions of species described by other authors upon which to distinguish their own new species, and so extensive synonymy resulted since actual comparisons of specimens were not then made.

The holotype female of Desicasta nonfriedi Schoch, 1896 is actually Amithao erythropus ( Burmeister, 1842) , and I transferred it from Desicasta to Amithao ( Ratcliffe 2013) .

CHECKLIST OF THE SPECIES OF DESICASTA THOMSON

Desicasta lobata ( Olivier, 1789)

Cetonia coracina Herbst, 1790 (synonym)

Desicasta sculptilis Thomson, 1878 New synonymy.

Desicasta sebosa ( Neervoort van de Poll, 1886) New synonymy.

Desicasta opaca ( Kraatz, 1898) New synonymy.

Desicasta purpurascens ( Schoch, 1898) .

Desicasta reichei ( Thomson, 1860)

Desicasta laevicostata ( Neervoort van de Poll, 1886) New synonymy.

KEY TO THE SPECIES OF ADULT DESICASTA THOMSON

1. Pronotum and elytra velutinous, reddish brown to black................. D. purpurascens (Schoch)

1′. Pronotum and elytra glabrous, opaque to shiny black....................................................2

2. Elytral apices behind apical umbones rugulose; elytral disc with 2 distinctly elevated, longitudinal costae; surface “greasy” in males, shiny in females .............. D. lobata (Olivier)

2′. Elytral apices behind apical umbones sparsely punctate; elytral disc nearly flat, lacking distinctly elevated, longitudinal costae; surface shiny in both sexes....... D. reichei (Thomson)

Figures

Figs. 1–3. 1) Desicasta reichei showing large, oblique mesometasternal process (image courtesy of the Natural History Museum, London, UK); 2) Amithao haematopus (Schaum) showing slender, subparallel mesometasternal process; 3) Guatemalica hueti Chevrolat showing recurved mesometasternal process.