Marmarina argentina ( Moser, 1917 )

Ratcliffe, Brett C., 2015, A Review of the Neotropical GenusMarmarinaKirby, 1827 (Coleoptera: Scarabaeidae: Cetoniinae: Gymnetini), with Description of a New Species from Argentina, The Coleopterists Bulletin 69 (2), pp. 183-201 : 186-188

Marmarina argentina ( Moser, 1917) ( Figs. 1–6 )

Gymnetis argentina Moser 1917: 3 (original combination). Holotype male at ZMHU, labeled “ Corrientes, Argentina // Gymnetis argentina Moser , Type //type” [on red paper], examined. Type locality: “ Corrientes, Argentinien.”

Description. Length 13.9–17.1 mm; width across humeri 8.0– 10.8 mm. Ground color and punctures black, opaque to weakly shiny, with extensive enamel-like or opaque. pale yellow marks as follows: Head enamel-like pale yellow except for short, longitudinal, black line on center of frons and on apical rim of clypeus. Pronotum completely covered with opaque pale yellow except for slender to thick, broken, black bands radiating anteriorly from pronotal lobe. Elytra each covered by opaque pale yellow except for transverse or oblique, broken, black bands ( Figs. 1–2 ). Pygidium completely pale yellow (usually enamel-like) except for black spot either side of midline at base in males, spots often coalescing; females similar to more commonly basal half black, occasionally entirely black. Venter of males shiny black with variable, enamel-like pale yellow marks on mesepimera, metepisterna, metepimera, metasternum, and abdominal sternites; females usually with yellow marks reduced or almost absent. Metacoxae, meso- and metafemora, and meso- and metatibiae each with enamel-like pale yellow. Yellow areas of venter and legs may be variably reduced or absent. Setae of venter and legs black, occasionally ferruginous. Head: Males with frons and clypeus vaguely tumescent at center, punctures small to moderate in size, sparse to moderate in density; females with punctures larger, denser, especially on dark areas. Clypeal apex slightly thickened, weakly emarginate, slightly reflexed. Interocular width equals 4.5 transverse eye diameters in males and 4.0– 4.5 in females. Antenna with 10 antennomeres, club subequal in length to entire stem in males, slightly shorter in females. Pronotum: Surface with punctures small, sparse to moderate in density on yellow areas, punctures larger and often denser on black areas, especially in females. Lateral margins weakly emarginate or evenly arcuate between middle and basal angle (2 specimens lacking emargination), with slen- der marginal line usually not reaching basal angle. Elytra: Surface similar to that of pronotum. Sutural costa and usually costae on disc each elevated on apical halves. Apices at suture subquadrate. Pygidium: Black areas in both sexes with sparse, transversely vermiform punctures or densely, transversely rugulose and with minute to short, black or ferruginous setae in pristine specimens; surface on colored areas usually with small, round (occasionally kidney-shaped) punctures. In lateral view, surface weakly convex in both sexes. Venter: Metasternum with moderate to large, sparse to usually dense, round to crescent-shaped, setigerous punctures either side of impunctate mesometasternal process. Mesometasternal process, in lateral view, short, blunt, parallel to subparallel to ventral axis of body, apex rounded ( Fig. 3 ); in ventral view, sides tapering to broadly rounded apex ( Fig. 4 ). Abdominal sternites 1–6 of both sexes with small, sparse punctures on yellow areas and moderately large, sparse punctures on dark areas near lateral margins. Legs: Protibiae of males with strong tooth at apex, occasionally with weak second tooth behind apical tooth (1 male with tridentate protibiae). Females similar (1 specimen with tridentate protibiae). Parameres: In caudal view, form elongate, subrectangular, apices blunt and subacute on apicolateral angle ( Figs. 5–6 ).

Distribution. Marmarina argentina is known from Argentina, Brazil, and Uruguay.

Locality Records. 26 specimens from AMNH, BCRC, CASC, CMNC, FMNH, MZSP, UCCC, USNM, VMDM, and ZMHU. ARGENTINA (14): BUENOS AIRES (7) : Bahía Blanca , Buenos Aires. CORRIENTES (1) : No data. CHUBUT (1): Gaiman Norte. MENDOZA (1): No data. SALTA (1): Ampascachi. SAN LUIS (2): San Jerónimo. NO DATA (1). BRAZIL (2): RIO GRANDE DO SUL (1) : Tramandaí. SANTA CATARINA (1): No data. URUGUAY (10): MALDONADO (1) : Sierra de Mataojo. MONTEVIDEO (8) : Montevideo. NO DATA (1).

Temporal Distribution. January (9), February (8), April (1), December (1). Most specimens are old and have no date of collection.

Diagnosis. Di Iorio (2013) observed that “Except in cataloges (sic) and/or lists ( Schenkling 1921, Schürhoff 1937, Blackwelder 1944, Krajík 1998), M. argentina was never mentioned again after the original description by Moser (1917), probably because it is not possible to identify the species among the numerous individual variations of M. tigrina .” But in reading Moser’ s (1917) description, he characterized M. argentina by its shiny pronotum (an atypical specimen), darker overall color (a melanistic specimen), and by the short, blunt, mesometasternal process. “Normal” specimens of M. argentina are nearly identical with M. tigrina except for the distinctive form of the mesometasternal process (compare Figs. 3 and 32 ). The short, blunt, subparallel process in M. argentina is substantially different from the large, thick, obliquely projecting process of M. tigrina , and this is the best way to differentiate the two species. The form of the mesometasternal process is important in the Gymnetini , and it is usually consistently expressed within any given species. I was unable to find any other characters that would help to separate these two species, especially since each varies so much in color, pattern, and surface sculpturing. The color of all the M. argentina specimens examined was pale yellow. A larger sample size, similar to that of M. tigrina , might reveal additional colors like the orange or grey seen in M. tigrina .

Moser (1917) stated that the type specimen is only 10 mm in length. My examination of the holotype at the Museum für Naturkunde in Berlin revealed a body length of 14.5 mm (pronotum to pygidium). While this difference may sound trivial, it helps to distinguish between M. argentina and the small, new species described below. The discrepancy in length measurements could be attributed to either (1) Moser did not measure correctly, (2) the measurement was erroneously printed in the publication, or (3) the holotype is not the same specimen examined by Moser. Inasmuch as the holotype agrees in all other respects with Moser’ s description, I conclude that this specimen in Berlin is the original type specimen, and that the length reported in the publication is incorrect.

Natural History. Nothing is known about the natural history of this species. Label data for two specimens indicate they were collected in the nest of Atta and Acromyrmex species ( Hymenoptera : Formicidae ).

Figures

Figs. 1–2. Marmarina argentina, habitus showing variation.

Figs. 3–6. Marmarina argentina. 3–4) Mesometasternal process, lateral and ventral views; 5–6) Parameres.

Figs. 32–35. Marmarina tigrina. 32–33) Mesometasternal process, lateral and ventral views; 34–35) Parameres.