Gnathoncus rotundatus ( Kugelann, 1792 )

Lackner, Tomáš, 2010, Review of the Palaearctic genera of Saprininae (Coleoptera: Histeridae), Acta Entomologica Musei Nationalis Pragae (suppl.) 50, pp. 1-254 : 118-122

Gnathoncus rotundatus ( Kugelann, 1792)

( Figs. 36 , 55 , 90 , 119 , 360–378 )

Hister nanus: SCRIBA (1790) : 73, nec PILLER & MITTERPACHER (1783): 34 (misidentification).

Hister rotundatus Kugelann, 1792: 304 .

Saprinus deletus J. E. LeConte, 1844: 186 . Synonymized by MARSEUL (1855): 503.

Saprinus rotundatus: J. E. LECONTE (1845) : 70; MARSEUL (1855): 348, 503; HORN (1873): 314; BLATCHEY (1910): 618, 619.

Gnathoncus rotundatus: SCHMIDT (1885a) : 317; MAZUR & KASZAB (1980): 45, Figs. 22A ,I–J, 23A; MAZUR (1981a): 88, Figs. 111–114 ; MAZUR (1984): 105; DAVIES (1991): 138; LAPLANTE et al. (1991): 44; ÔHARA (1994): 215, 220, Figs. 130, 131, 133, 135 ; DOWNIE & ARNETT (1996): 612; MAZUR (1997): 215; BOUSQUET & LAPLANTE (1999): 144; YÉLAMOS (2002): 246, 248, Figs. 124A,B, 126A,B; MAZUR (2004): 92; BOUSQUET & LAPLANTE (2006): 87, 90, Figs. 64, 65 .

Gnathoncus ovulatus Casey, 1916: 256 . Synonymized by MAZUR (1997): 215.

Gnathoncus nanus Reichardt, 1941: 159 , 161. Synonymized by HOFFMANN (1803): 87.

Gnathoncus nanus: MCGRATH & HATCH (1941) : 64; HINTON (1945): 322; STOCKMANN (1957): 67; HATCH (1962): 265; HALSTEAD (1963): 13; HANSEN (1968): 317; WITZGALL (1971): 166; MAZUR (1973): 27, Figs. 25–28 , 37 ; KRYZHA- NOVSKIJ & REICHARDT (1976): 114, 116, Figs. 125, 130, 135, 140 , 145 ; VIENNA (1980): 120, Fig. 47 .

Gnathoncus rotundatus var. pygidialis Ganglbauer, 1899 .

Gnathoncus rotundatus var. subsuturalis Reitter, 1896 .

Note. Larva was described by PERRIS (1877): 21. Sensory structures of the antennal club and spermatheca were

studied by DE MARZO & VIENNA (1982a,b).

Type locality. Poland, East Prussia, Ostróda.

Material examined. CZECH REPUBLIC: BOHEMIA: Čelákovice, vi.1955, 1 ♁ 1 ♀, A. Olexa lgt. JAPAN: HOKKAIDO: Shimohoro, Tsurui, Kushiro moor, 1.vi.1992, 1 spec., M. Ôhara lgt. KAZAKHSTAN: Jambol Akkul, 8.v.1979, 2 ♀♀, A. Olexa lgt. UKRAINE: Odessa, vi.1957, 1 ♁ 1 ♀, A. Olexa lgt. ( TLAN).

Redescription. Body length: PEL: 1.75–2.50 mm; APW: 0.625 –0.825 mm; PPW: 1.20–1.725 mm; EL: 1.175 –1.675 mm; EW: 1.375–2.00 mm.

Body ( Figs. 360–361 ) oval, moderately convex, slightly flattened from above, cuticle dark brown to black without metallic luster; legs, mouthparts and antennae rufous.

Antennal scape ( Fig. 363 ) not thickened, with very few short setae; club ( Fig. 362 ) comparatively large, oval, without visible articulation, entire surface covered in dense short sensilla, intermingled with sparse somewhat longer erect sensilla; sensory structures of antennal club ( Fig. 36 ) in form of two sensory areas on ventral side and five vesicles; one of them is larger than other four; vesicles arranged in two pairs on ventral and dorsal side respectively.

Mouthparts. Mandibles ( Fig. 90 ) with rounded outer margin curved inwardly, acutely pointed, subapical tooth on inner margin of left mandible very small; labrum ( Fig. 55 ) flattened, punctate, with very shallow median excavation; labral fold significantly less developed; labral pits very small, one short seta present in each pit; terminal labial palpomere elongated, its width about one-third its length; palpal organ present on both labial and maxillary palpi; mentum ( Fig. 365 ) sub-trapezoid, anterior angles slightly produced, anterior margin with a shallow medial notch ( Fig. 119 ), surface around it with two long setae, lateral margins with a single one row of much shorter sparse ramose setae, disc glabrous; cardo of maxilla with few short setae on lateral margin; stipes triangular, with three short setae; lacinia with lacinial hook; terminal labial palpomere elongated, its width about one-third its length, about three times as long as penultimate palpomere.

Clypeus ( Fig. 363 ) large, rectangular, rounded laterally, with sparse fine punctures, separated several times their own diameter; frontal and supraorbital striae absent; frontal disc ( Fig. 363 ) with sparse fine round punctures; eyes convex, well visible from above.

Pronotal sides ( Fig. 360 ) feebly convergent anteriorly, apical angles obtuse, marginal pronotal stria complete, thin, slightly carinate, somewhat weakened behind head; disc entirely covered with deep, round punctation, becoming coarser and denser laterally; pronotal base with ante-scutellar depression; pronotal hypomeron glabrous; scutellum very small.

Elytral epipleura with scattered punctures of various sizes; marginal epipleural stria double, both striae weakly impressed but complete; marginal elytral stria well impressed, continuous along elytral apex as apical elytral stria, stopping short of sutural elytral stria; humeral elytral stria impressed on basal fourth; inner subhumeral stria present medially, very short; elytral disc with four dorsal elytral striae 1–4, first the longest, almost complete, becoming very fine and almost invisible on apical half, second to fourth striae well impressed, reaching about elytral half; between fourth dorsal elytral and sutural striae a characteristic hooked appendix present; sutural elytral stria present usually only on basal fourth to basal sixth. Entire elytral disc with regular dense round punctation, becoming sparser anteriorly and especially around scutellum; punctures separated by about their own to twice their own diameter; around apical elytral stria with longitudinal rugae.

Propygidium transverse, about four times as broad as long, partly concealed by elytra, with dense and coarse punctures; pygidium with dense elliptic punctures, separated by about their own diameter, becoming sparser towards apex.

Anterior margin of median portion of prosternum ( Fig. 366 ) rounded; marginal prosternal stria present only laterally; prosternal process flattened, broad, dorso-laterally with sparse punctures, intermingled with alutaceous microsculpture; carinal prosternal striae carinate, parallel on basal two-thirds, thence strongly convergent anteriorly, vaguely united under a sharp angle terminating in shallow tiny prosternal apical fossa; lateral prosternal striae strongly convergent anteriorly, attaining carinal striae in middle of prosternal process.

Anterior margin of mesoventrite ( Fig. 367 ) moderately emarginate medially; discal marginal mesosternal stria well impressed, somewhat carinate; disc flattened, with round punctures separated about their own to three times their diameter; meso-metaventral suture indistinct, meso-metaventral sutural stria marked as a sinuate row of large punctures; intercoxal disc of metaventrite ( Fig. 368 ) laterally and along apical margin with deep round punctures of various sizes; in male longitudinally somewhat concave, with narrowly-defined longitudinal area along median line bordered with microscopic setae; surface mesad of it glabrous. Lateral metaventral stria well impressed, carinate, almost straight, reaching metacoxa; lateral disc of metaventrite ( Fig. 368 ) flattened, with round shallow large punctures fringed with microscopic setae; metepisternum + fused metepimeron ( Fig. 368 ) evenly covered with even coarser and denser punctation, punctures without setae.

Intercoxal disc of first abdominal sternite with lateral depressions, almost completely striate laterally; surface of disc with dense oblong punctation, punctures becoming sparser and finer medially.

Protibia ( Fig. 369 ) flattened and somewhat dilated, outer margin with three low teeth topped with short denticle (first tooth topped with double denticle) followed by three minuscule denticles; setae of outer row rather dense, regular and short; setae of median row similarly dense and regular, but even shorter than those of outer row; protarsal groove deep; anterior protibial stria ridge-like; two thin, rather long tarsal denticles present apically; protibial spur large, bent, growing out from apical protibial margin; apical margin of protibia posteriorly with two tiny apical denticles; outer part of posterior surface of protibia ( Fig. 369 ) finely imbricate, with a row of about 10 minute denticles; delimitation from median part of posterior surface vague, marked by a row of sparse minuscule setae; posterior protibial stria complete, with rather dense sclerotized setae that become thicker towards apical margin; inner margin with double row of short setae.

Mesotibia ( Fig. 370 ) slender, outer margin with a single row of thin denticles growing in size apically; setae of outer row sparse, regular, rather dense but short; setae of median row irregular, much shorter than those of outer row; posterior mesotibial stria complete; anterior surface of mesotibia ( Fig. 370 ) with dense row of well sclerotized short setae, with another similar row of much shorter and finer setae situated below it; anterior mesotibial stria complete, terminating in three tiny inner anterior denticles; mesotibial spur stout, short; apical margin with two tiny denticles; mesotarsus shorter than mesotibia; claws of apical tarsomere about one-third its length; metatibia basically similar to mesotibia, but denticles of outer margin much sparser than those of mesotibia; claws of apical tarsomere somewhat longer, about half its length.

Male genitalia. Eighth sternite ( Figs. 371–372 ) separated medially, vela with sparse microscopic setae ( Fig. 371 ); eighth tergite and eighth sternite not fused laterally ( Fig. 373 ). Ninth tergite ( Figs. 374–375 ) longitudinally divided medially; spiculum gastrale ( Fig. 376 ) expanded on both ends. Aedeagus ( Figs. 377–378 ) slender; basal piece of aedeagus short, ratio of its length: length of parameres 1: 5; parameres fused along their basal three-fourths; aedeagus curved ventrad ( Fig. 378 ).

Figures

Figs. 29–38. Saprininae, sensory structures of the antennal club (vesicles marked with grey; sensory areas shaded): 29 – Xenophilothis choumovitchi (Thérond, 1965); 30 – Zorius funereus (Schmidt, 1890); 31 – Alienocacculus neftensis (Olexa, 1984); 32 – Philothis (Philothis) arcanus Reichardt, 1930; 33 – Philothis (Atavinus) atavus (Reichardt, 1931); 34 – Philothis (Farabius) hexeris Reichardt, 1930; 35 – Euspilotus (Neosaprinus) perrisi (Marseul, 1872); 36 – Gnathoncus rotundatus (Kugelann, 1792); 37 – Eremosaprinus vlasovi (Reichardt, 1941); 38 – Microsaprinus therondianus (Dahlgren, 1973).

Figs. 47–73. Saprininae, labral structures, dorsal view (left half showing external and right half showing internal structures): 47 – Alienocacculus neftensis (Olexa, 1984); 48 – Ammostyphrus cerberus Reichardt, 1924; 49 – Chalcionellus amoenus (Erichson, 1834); 50 – Chivaenius kryzhanovskii Olexa, 1980; 51 – Eopachylopus ripae (Lewis, 1885); 52 – Eremosaprinus vlasovi (Reichardt, 1941); 53 – Euspilotus (Neosaprinus) perrisi (Marseul, 1872); 54 – Exaesiopus grossipes grossipes (Marseul, 55); 55 – Gnathoncus rotundatus (Kugelann, 1792); 56 – Hypocaccus (Hypocaccus) rugiceps (Duftschmid, 1805); 57 – Hypocacculus (Hypocacculus) metallescens (Erichson, 1834); 58 – Hypocacculus (Colpellus) praecox (Erichson, 1834); 59 – Hypocacculus (Nessus) rubripes (Erichson, 1834); 60 – Microsaprinus therondianus (Dahlgren, 1973); 61 – Myrmetes paykulli Kanaar, 1979; 62 – Paravolvulus lateristriatus (Solskij, 1876); 63 – Philothis (Philothis) arcanus Reichardt, 1930; 64 – Philothis (Atavinus) atavus (Reichardt, 1931); 65 – Philothis (Farabius) hexeris Reichardt, 1930; 66 – Pholioxenus phoenix (Reichardt, 1930); 67 – Reichardtiolus duriculus (Reitter, 1904); 68 – Saprinus (Saprinus) semistriatus (Scriba, 1790); 69 – Saprinus (Hemisaprinus) subvirescens (Ménétries, 1832); 70 – Saprinus (Phaonius) pharao (Marseul, 1855); 71 – Styphrus corpulentus Motschulsky, 1845; 72 – Xenonychus tridens (Jacquelin-Duval, 1852); 73 – Xenophilothis choumovitchi (Thérond, 1965).

Figs. 90–98. Saprininae, mandibles, ventral view: 90 – Gnathoncus rotundatus (Kugelann, 1792); 91 – Hypocaccus (Baeckmanniolus) dimidiatus dimidiatus (Illiger, 1807); 92 – Hypocacculus (Hypocacculus) metalescens (Erichson, 1834); 93 – Hypocacculus (Colpellus) praecox (Erichson, 1834); 94 – Hypocacculus (Nessus) rubripes (Erichson, 1834); 95 – Myrmetes paykulli Kanaar, 1979; 96 – Paravolvulus lateristrius (Solskij, 1876); 97 – Philothis (Philothis) arcanus Reichardt, 1930; 98 – Philothis (Atavinus) atavus (Reichardt, 1931).

Figs. 109–141. Saprininae, anterior margin of mentum, ventral view: 109 – Alienocacculus neftensis (Olexa, 1984); 110 – Ammostyphrus cerberus Reichardt, 1924; 111 – Axelinus ghilarovi Kryzhanovskij, 1976; 112 – Chalcionellus amoenus (Erichson, 1834); 113 – Chivaenius kryzhanovskii Olexa, 1980; 114 – Ctenophilotis chobauti (Théry, 1900); 115 – Eopachylopus ripae (Lewis, 1885); 116 – Eremosaprinus vlasovi (Reichardt, 1941); 117 – Euspilotus (Neosaprinus) perrisi (Marseul, 1872); 118 – Exaesiopus grossipes grossipes (Marseul, 1855); 119 – Gnathoncus rotundatus (Kugelann, 1792); 120 – Hypocaccus (Hypocaccus) rugiceps (Duftschmid, 1805); 121 – Hypocaccus (Baeckmanniolus) dimidiatus dimidiatus (Illiger, 1807); 122 – Hypocacculus (Hypocacculus) metallescens (Erichson, 1834); 123 – Hypocacculus (Colpellus) praecox (Erichson, 1834); 124 – Hypocacculus (Nessus) rubripes (Erichson, 1834); 125 – Microsaprinus therondianus (Dahlgren, 1973); 126 – Myrmetes paykulli Kanaar, 1979; 127 – Paravolvulus ovillum (Solskij, 1876); 128 – Philothis (Philothis) arcanus Reichardt, 1930; 129 – Philothis (Atavinus) atavus (Reichardt, 1931); 130 – Philothis (Farabius) hexeris Reichardt, 1930; 131 – Pholioxenus phoenix (Reichardt, 1930); 132 – Reichardtiolus duriculus (Reitter, 1904); 133 – Saprinillus paromaloides Kryzhanovskij, 1974; 134 – Saprinus (Saprinus) semistriatus (Scriba, 1790); 135 – Saprinus (Hemisaprinus) subvirescens (Ménétries, 1832); 136 – Saprinus (Phaonius) pharao (Marseul, 1855); 137 – Styphrus corpulentus Motschulsky, 1845; 138 – Turanostyphrus ignoratus Tishechkin, 2005; 139 – Xenonychus tridens (Jacquelin-Duval, 1852); 140 – Xenophilotis choumovitchi (Thérond, 1965); 141 – Zorius funereus (Schmidt, 1890).

Figs. 360–370.Gnathoncus rotundatus (Kugelann, 1792), SEM micrographs:360 – habitus, dorsal view; 361 – ditto, ventral view; 362 – antennal club, ventral view; 363 – head, dorsal view; 364 – ditto, ventral view; 365 – mentum, ventral view; 366 – prosternum; 367 – mesoventrite and metaventrite; 368 – lateral disc of metaventrite, metepisternum and fused metepimeron; 369 – protibia, ventral view; 370 – mesotibia, ventral view.

Figs. 371–378. Gnathoncus rotundatus (Kugelann, 1792), male terminalia (after ÔHARA 1994): 371 – 8th sternite and tergite, ventral view; 372 – ditto, dorsal view; 373 – ditto, lateral view; 374 – 9th tergite, 10th tergite, dorsal view; 375 – ditto, lateral view; 376 – spiculum gastrale, ventral view; 377 – aedeagus, dorsal view; 378 – ditto, lateral view.

Figs. 9–28. Saprininae, sensory structures of the antennal club (vesicles marked with grey; sensory areas shaded): 9 – Saprinus (Saprinus) semistriatus (Scriba, 1790); 10 – Saprinus (Hemisaprinus) subvirescens (Ménétries, 1832); 11 – Myrmetes paykulli Kanaar, 1979; 12 – Styphrus corpulentus Motschulsky, 1845; 13 – Saprinus (Phaonius) pharao (Marseul, 1855); 14 – Ammostyphrus cerberus Reichardt, 1924; 15 – Chalcionellus amoenus (Erichson, 1834); 16 – Chivaenius kryzhanovskii Olexa,1980; 17 – Ctenophilothis chobauti (Théry,1900); 18 – Eopachylopus ripae (Lewis, 1885); 19 – Exaesiopus grossipes grossipes (Marseul, 1855); 20 – Hypocaccus (Hypocaccus) rugiceps (Duftschmid, 1805); 21 – Hypocaccus (Baeckmanniolus) dimidiatus dimidiatus (Illiger, 1807); 22 – Hypocacculus (Hypocacculus) metallescens (Erichson, 1834); 23 – Hypocacculus (Colpellus) praecox (Erichson, 1834); 24 – Hypocacculus (Nessus) rubripes (Erichson, 1834); 25 – Paravolvulus lateristrius (Solskij, 1876); 26 – Pholioxenus phoenix (Reichardt, 1930); 27 – Reichardtiolus duriculus (Reitter, 1904); 28 – Xenonychus tridens (Jacquelin-Duval, 1852).

Figs. 144–145. Left maxilla, ventral view. 144 – Eremosaprinus vlasovi (Reichardt, 1941); 145 – Xenophilotis choumovitchi (Thérond, 1965).