Megauchenia Macleay, 1825

Dasgupta, J., Pal, T. K. & Hegde, V. D., 2015, Review of the Megauchenia Macleay of India (Coleoptera: Nitidulidae: Prometopinae), Zootaxa 4058 (4), pp. 551-560 : 553-555

Genus Megauchenia Macleay, 1825

Megauchenia Macleay 1825: 45 . Type species: Megauchenia setipennis Macleay, 1825 ; Arrow 1909:191; Kirejtshuk 1990:77. Ischaena Erichson 1843: 287. Type species: Ischaena angustata Erichson, 1843 ; Lacordaire 1854: 301, 306; Reitter 1873: 10, 54; Grouvelle 1908: 340, 357. Synonymized by Grouvelle (1913a).

Orvoenia Dajoz 1980: 190. Type species: Orvoenia borneensis Dajoz, 1980 . Synonymized by Kirejtshuk (2008).

Characterization. General appearance ( Figs. 1–30 ): Elongate-subparallel, feebly convex dorsally and subdepressed ventrally, moderately shiny, punctate-pubescent, elytral punctation arranged in longitudinal rows, with short squamous setae, color reddish-brown to black, antenna with a compact three-segmented club, pronotum and elytra carinate laterally and feebly explanate; abdominal segments almost completely covered by elytra dorsally, abdominal sternite I with deeply diverging metacoxal lines, meso- and metacoxae widely separated, tarsomeres simple, sexual dimorphism indistinct.

Head ( Fig. 1 ) hypognathous, transverse, narrower than prothorax, mandibles partly exposed, fronto-clypeal suture absent; eyes moderately large and slightly projecting, coarsely facetted, slightly developed lateral sulcus beneath eye, tempora short and rounded behind; slightly marked neck constriction. Tentorium with two long tentorial arms and a transverse corpotentorium present in posterior third. Antenna longer than head; antennal insertions partially hidden under projections of frons, scape broadly elongate, segment 2 short, segment 3 about 3x as long as segment 2; segments 4 to 6 short, subequal, about as broad as long or slightly elongate; segment 7 slightly transverse; segment 8 more transverse and broader than preceding segments; club 3-segmented, about as broad as long, segments compactly arranged. Ventrally antennal grooves narrow and convergent posteriorly. Mandible ( Fig. 8 ) about as broad as long, tip of mandibles broadly pointed, mola well-developed, prostheca setose, no distinct mandibular cavity. Maxilla ( Fig. 9 ) devoid of galea; lacinia broadly elongate, apex rounded, apex and inner margin densely hairy; palpi with palpomere 1 short, palpomeres 2 and 3 subequal and transverse; palpomere 4 (apical palpomere) longer than preceding segments and fusiform, sparsely setose. Labium ( Fig. 10 ) with mentum distinctly transverse, large pits on surface, apical margin bi-sinuate; ligula about as broad as long with lobes projecting and horn-like; palpi with palpomere 1 short, palpomere 2 longer and about as broad as long, palpomere 3 longest and fusiform. Labrum ( Fig.11 ) transverse, apically bilobed, deeply incised medially; two types of dense setae: shorter setae laterally, longer setae medially.

Prothorax ( Fig. 2 ) transverse, about as broad as elytra; apical margin emarginate; anterior and posterior angles devoid of any denticle; lateral carinae beaded and often arcuate; pronotal disc rather convex; prosternal process somewhat narrower between coxae, feebly broader towards apex; front coxae contiguous internally; coxal cavities distinctly transverse, externally and internally closed, trochantins exposed; notosternal sutures convergent anteriorly and extending to border of foramen.

Meso-metathorax ( Fig. 3 ): Mesoventral process narrower than prosternal process. Mesocoxae less widely separated than front coxae, mesocoxae narrowly separated internally, bordered by coxal lines reaching beyond middle of the distance along metaventral-metanepisternal suture, forming distinct axillary space; coxal cavities open outwardly, mesoventral process contacting metaventral process between mesocoxae almost in a straight line. Metaventrite somewhat transverse, discrimen extending to about two-thirds of length of metaventrite from base, metacoxae more widely separated than mesocoxae (external separation). Metendosternite ( Fig. 18 ) well developed, with a broad basal stalk bifurcated into two lateral arms, anterior tendons rather closely situated.

Elytra and hind wings: Elytra ( Fig. 4 ) elongate, apex separately rounded or obliquely truncate, punctation round and distinct, arranged in longitudinal rows; setae golden, squamous, short and semi-erect; epipleura moderately developed and extending almost to apex; pygidium marginally exposed or completely concealed beneath elytra. Hind wing ( Fig. 7 ) simple and venation reduced, with moderately long radial vein, cubitus vein branched, two anal veins; without subcubital fleck or radial cell.

Legs ( Fig. 6 ) moderately long and broad, trochanters short and simple, femora broadened; slender tibiae slightly broadened at apex with distinct apical spurs; tibiae longitudinally canaliculated, inner edge of canaliculi crenulated; tarsal formula 5-5- 5 in both sexes, tarsomere 1 to 3 slightly dilated apically, tarsomere 4 shortest, claws simple.

Abdomen ( Fig. 5 ) slightly longer than broad, pygidium seldom marginally exposed, usually hidden beneath elytra; ventrite 1 with posteriorly directed femoral lines, intercoxal process moderately broad and its apical margin truncate; ventrites 2–4 short and subequal, ventrite 5 longer than each of the preceding three ventrites. Ventrites with moderately large pits, rather densely arranged. An anal sclerite (tergite VIII) present in males (externally not visible, detectable only after dissection).

Genitalia: Aedeagus ( Figs. 14, 15 ) with pear-shaped median lobe, membranous, dorsoventrally flattened; a single median strut running along ventral face; tegmen forming a broadly elongate envelope, with a shallow median notch at apex, slender lateral lobes (parameres) blunt and setose apically, lateral edges subparallel; tegminal struts join basally to form a ring around median lobe. Anal sclerite and spiculum gastrale as in Figs. 13, 16 . Ovipositor ( Fig. 17 ) with well-developed paraprocts, valvifers transversely septate beneath an elliptical membrane, long and slender coxites, and short styli attached to apices of the coxites. Sexual Dimorphism: Externally not distinct.

Habitat. Most species inhabit subcorticolous habitat and presumably feed on fungi and decomposed plant sap. Distribution. Prevalent in the Eastern Hemisphere, but most diverse in the Indo-Malayan zone of the Oriental region.

Figures

FIGURES 1 – 7. Megauchenia angustata (Erichson, 1843), line drawings: 1, head, dorsal view; 2, prothorax, ventral view; 3, meso-metathorax, ventral view; 4, left elytron, dorsal view; 5, abdomen, ventral view; 6, front leg; 7, hind wing.

FIGURES 8 – 18. Megauchenia angustata (Erichson, 1843), line drawings: 8, mandible, dorsal view; 9, maxilla, ventral view; 10, labium, ventral view; 11, labrum, dorsal view; 12, mesoscutellum, dorsal view; 13, anal sclerite (tergite VIII); 14, male genitalia: tegmen, ventral view; 15, male genitalia: median lobe, ventral view; 16, spiculum gastrale; 17, ovipositor; 18, metendosternite.

FIGURES 19 – 30. 19, 21, 29 (dorsal habitus): 19, Megauchenia angustata (Erichson, 1843); 21, M. quadricollis (Reitter, 1883); 29, M. indica (Grouvelle, 1908); 20, 22, 30 (ventral habitus): 20, M. angustata; 22, M. quadricollis; 30, M. indica. 23 – 28: male genitalia: 23, tegmen and median lobe of M. angustata, microphotograph; 24, median lobe of M. angustata after separating from tegmen, microphotograph; 25, tegmen and median lobe of M. quadricollis, microphotograph; 26, median lobe of M. quadricollis after separating from tegmen, microphotograph; 27, tegmen of M. quadricollis, line drawing; 28, median lobe of M. quadricollis, line drawing.