Agathidium dioperculum Wheeler and Miller, 2005

WHEELER, QUENTIN D. & MILLER, KELLY B., 2005, Slime-Mold Beetles Of The Genus Agathidium Panzer In North And Central America, Part I. Coleoptera: Leiodidae, Bulletin of the American Museum of Natural History 2005 (290), pp. 1-95 : 54-56

Agathidium dioperculum Wheeler and Miller , new species Figures 82 , 94, 95

TYPE MATERIAL: Holotype, Ƌ in AMNH (deposited from California Department of Food and Agriculture) labeled ‘‘ CALIF:Del Norte Co. Crescent City IX­19 –1978 T. R.Haig,Coll. [date handwritten]/ Berlesed from Redwood Duff/ HOLOTYPE Agathidium dioperculum Wheeler and Miller, 2002 [red label with black line border]’’.

TYPE LOCALITY: United States, California, Del Norte Co., Crescent City, redwood duff.

DIAGNOSIS: This species is separable from other A. brevisternum group members by the male median lobe with operculum deeply di­ vided into two elongate plates diverging apically, with halves connected by a broad, truncate, hyaline plate (fig. 95).

DESCRIPTION: Body very broadly rounded, strongly convex, and partially contractile; TBL = about 2.2 mm. Color reddish­brown; antenna pale, concolorous; venter and appendages testaceous.

Head large, very wide, broadly rounded in front, more or less quadrate and dorsoventrally flattened; OHW/MDL = 2.0; eyes very large, elongate, situated on sides of head, with large, coarse facets numbering less than 36 in dorsal view; postocular temporum short, inconspicuous; OHW/PHW = 1.1; anterior marginal carina very conspicuous from edge of labrum to point posterior to eye, narrowly bordering eye; antenna with abrupt 3­ segmented club; antennomere III elongate, narrow, longer than II, subequal to length of I; II:III = 1:1.8; VII, VIII subequal, small, submoniliform; VII:VIII:IX = 0.7:1:1.4; frontoclypeal suture absent, extremely faint hint of suture under high magnification; surface of head shiny, nearly impunctate; under high magnification, sparse, microscopic punctules exist bearing very fine setae; labrum narrow, elongate, distally tapered with blunt apex slightly emarginate medially. Pronotum very broad, convex; anterior margin broadly rounded; posterior angles weakly defined; surface shiny, nearly impunctate, as on head, except punctures slightly less dense; PNW/PNL = 1.8; PNL/PNH = 1.6; PNW/ PNH = 2.8. Combined elytral width, in dorsal view, about equal to length (ELW/SEL = 1.3); in posterior view, extreme apex attenuate; sutural stria evident in apical half; surface shiny, nearly impunctate, as on pronotum; epipleuron very wide, bordered by sharp carinae, ending shortly before apex of elytron. Mesosternum large, simple; without lateral carinae; without median carina; surface microscopically alutaceous; MSL/MTL = 2.1. Metasternum very short medially, sides at widest point shorter than mesosternum medially, narrowed to bands between meso­ and metacoxae, narrower than onehalf maximum width of metacoxa; surface with microscopic alutaceous pattern; MTL/ MTW = 0.11.

Male tarsi 5–5–4; pro­ and mesobasotarsomeres slightly expanded, with spatulate ventral setae; metasternal fovea median, punctiform, with few long setae; metafemur narrow, without tooth; left mandible with dorsally directed, curved, apically blunt tusk arising dorsally from side near base mandible; with tuft of apical setae. Aedeagus with short, stout median lobe, narrowed at apex in ventral view, curved ventrad with apex recurved dorsad (fig. 95); operculum with sclerotized basal and lateral areas forming deeply emarginate, divided parts, the apices of which bear two pores and the medial surfaces of which are not excavated, the distal region between two sclerotized ‘‘arms’’ connected by truncate, transparent, extremely fine, membranelike structure (fig. 95); lateral lobes gradually narrowed apically, subapical setae similar in size (figs. 94, 95) (foreshortened due to angle of vision in ventral drawing, fig. 95).

Female tarsi 5–4–4; spermatheca not examined.

ETYMOLOGY: This species is named from di, Latin for ‘‘two’’, and operculum, Latin for ‘‘lid’’, in reference to the deeply divided operculum of the median lobe in males of this species.

DISTRIBUTION: This species is only known from the type locality in extreme northwestern California (fig. 82).

PARATYPES: UNITED STATES: California: Del Norte Co.: Crescent City, 24 Apr 1991, pine duff, berlese, TR Haig (4, CASC, deposited from California Department of Food and Agriculture).

DISCUSSION: This form is hypothesized to be a distinct species largely because the connective structure between the two sclerotized lateral arms of the operculum was not seen in individuals of related species. Because this form appears to by sympatric with related species and because variation in some structures have been observed, including the number of pores on the operculum, it is possible that this is simply a variant of A. brevisternum . The type series was collected from pine duff.

Figures

Fig. 82. Agathidium brevisternum group geographic distribution: A. brevisternum Fall = •; A. dioperculum, n.sp. = ·; A. rhinocerellum, n.sp. = ^.

Figs. 94, 95. Agathidium dioperculum, n.sp., aedeagus: 94, lateral; 95, ventral.