Agathidium triangularum Miller and Wheeler, 2005

MILLER, KELLY B. & WHEELER, QUENTIN D., 2005, Slime-Mold Beetles Of The Genus Agathidium Panzer In North And Central America, Part Ii. Coleoptera: Leiodidae, Bulletin of the American Museum of Natural History 2005 (291), pp. 1-167 : 102-103

Agathidium triangularum Miller and Wheeler , new species Figures 130 , 213–215, 361

TYPE MATERIAL: Holotype, Ƌ in CMNC labeled ‘‘ MEX:Hgo ; 18 KmE Jacala , nr. El Alamo 10. VI.83, 1700 m S&J.Peck, moist oak for.litter/ HOLOTYPE Agathidium triangularum Miller and Wheeler, 2003 [red label with black line border]’’. The only specimen examined of this species was the holotype .

TYPE LOCALITY: Mexico, Hidalgo, 18 km E Jacala nr El Alamo.

DIAGNOSIS: Members of this species can be distinguished from other species by the combination of a distinct ventral prominence on the gula which is foveate on the anterior surface, the prominent flat, triangular flange formed where the oblique metasternal carinae meet medially, moderately large and finely faceted eyes, the small male metafemoral tooth (fig. 130), and the male genitalia, which are relatively simple (figs. 213–215). The median lobe is relatively slender and straight and the apical portion is fairly short, apically pointed, and undifferentiated (fig. 213). The operculum is moderately slender and apically slightly expanded and rounded (fig. 213).

DESCRIPTION: Moderately large (TBL = 3.14 mm), body broad, robust, rounded (PNW/TBL = 0.5), strongly contractile.

Head and pronotum dark red­brown; elytra dark red­brown, iridescent laterally; venter yellow­brown; antennae, palpi, and legs yellow to yellow­red.

Head broad (MDL/OHW = 0.59), dorsal surface flattened, dorsoventrally compressed; with very fine punctures, each with a short, very fine seta, surface between punctures shiny, smooth; frontoclypeal suture obsolete medially; eyes protruding and prominent but dorsoventrally compressed; gula with prominent anteromedial tumidity which is strongly foveate on anterior surface; antennomere ratios: length I:II:III = 1.9:1.0:2.2, width VII: VIII:IX = 1.0:1.0:1.9. Pronotum very large, broad (PNL/PNW = 0.73), strongly convex, anterolateral lobes strongly produced, lateral margin broadly curved, not angulate; with very fine, sparse punctures, each with a short, very fine seta, surface between punctures smooth. Elytra broad, lateral margins strongly rounded, apically rounded (SEL/ELW = 0.74); punctation similar to pronotum; sutural stria absent. Flight wings strongly reduced. Mesosternum broad, not declivitous; medial carina well­developed, prominent medially. Metasternum narrowed (MTL/MTW = 0.14), anteriorly sloping dorsad, concave medially; oblique femoral carinae well­developed, meeting medially in strongly­produced, triangular, posterior flange.

Male tarsi 5­5­4; pro­ and mesobasotarsomeres only somewhat laterally expanded, with moderate field of ventral spatulate setae; mandibles not modified; metafemur moderately slender, posteroapical angle produced into small tooth, apical margin sinuate (fig. 130); metasternal fovea prominent, large, transversely oval, with large, dense brush of fine setae. Median lobe in lateral aspect slen­ der, curved basally, apical portion short, broad, directed slightly dorsad, apex slightly sinuate and pointed (fig. 214); in ventral aspect slender, lateral margins parallel, apical portion broad, tapered, apex formed into a narrow process (fig. 213); operculum long, flat, lateral margins convergent apically, apex a parallel­sided, apically rounded process (fig. 213); lateral lobes long, slender, apically expanded, apex pointed with 2 subapical stout setae (fig. 215).

Female not examined.

ETYMOLOGY: Named from the Latin word triangularus, meaning ‘‘triangle’’, for the distinctly triangular shape of the medial metasternal flange.

DISTRIBUTION: This species is known only from the type locality in Hidalgo (fig. 361).

DISCUSSION: The single type specimen was collected from moist oak forest litter at 1700 m elevation.

Figures

Figs. 118–144. Agathidium concinnum­ and A. oniscoides­group species, left male metafemur, ventral aspect: 118, A. concinnum. 119, A. kimberlae. 120, A. vaderi. 121, A. bituberculum. 122, A. oedema. 123, A. gomezae. 124, A. hidalgoense. 125, A. skoliosternum. 126, A. erythromelas. 127, A. rhamphastes. 128, A. megoniscoides. 129, A. grumum. 130, A. triangularum. 131, A. lobosternum. 132, A. potosii. 133, A. popocatepetlae. 134, A. hyle. 135, A. stenomma. 136, A. tribulosum. 137, A. tribulograndum. 138, A. invisitatum. 139, A. multidentatum. 140, A. sejunctum. 141, A. grandidentatum. 142, A. andersoni. 143, A. disgregum. 144, A. oaxacaense. Bars = 0.5 mm.

Figs. 361, 362. Geographic distribution of Agathidium oniscoides­group species: 361, A. erythromelas = •; A. rhamphastes = -; A. triangularum = ^. 362, A. grumum = -; A. lobosternum = ^; A. megoniscoides = *.