Baconia chujoi (Cooman, 1941)

Caterino, Michael S. & Tishechkin, Alexey K., 2013, A systematic revision of Baconia Lewis (Coleoptera, Histeridae, Exosternini), ZooKeys 343, pp. 1-297 : 172-174

Baconia chujoi (Cooman, 1941) Figs 49 A–B51A–C, E, G–HMap 15

Binhister chujoi Cooman, 1941: 332; Baconia (Binhister) chujoi : Mazur 1984: 26.

Type locality.

JAPAN: Tokyo: Inokashira Park [35.70°N, 139.58°E].

Type material.

Not found; should be in MNHN.

Other material.

JAPAN, 1: Honshu: Kanagawa, Kawasaki, Masukata-yama, Tama-ku, 13.v.1995, K. Kawada (CHSM); 1:Mt. Daihi, 23.vi.1951 (FMNH).

Diagnostic description.

Length: 1.9-2.0mm, width: 1.4-1.7mm; body elongate oval, subdepressed, glabrous; color rufopiceous to piceous, with faint metallic sheen; head with frons flat, wide, ground punctation fine, secondary punctures sparse anteriorly, markedly coarser dorsad, frontal stria present only along inner margin of eye, obsolete across middle, supraorbital stria absent; antennal scape short, club nearly circular; epistoma straight to faintly emarginate apically; labrum about 4 ×wider than long, weakly emarginate apically; both mandibles with strong, acute basal tooth; pronotum with sides weakly convergent, rounded to apex, lateral marginal stria descending to ventral edge in posterior half, continuous anteriorly with complete anterior marginal stria, lateral submarginal stria present in basal three-fourths, pronotal disk weakly depressed in anterolateral corners, with fine ground punctation, conspicuous secondary punctures interspersed more or less throughout, much denser toward sides; elytra with two complete epipleural striae, outer subhumeral stria absent, inner subhumeral stria present in basal one-fourth or less, occasionally also as apical fragment, dorsal striae 1-4 complete to base, apex progressively shortened mediad, 4th arched mediad in front, stria 5 slightly abbreviated at base and apex, sutural stria present in middle one-third, abbreviated at base and apex, elytral disk with scattered secondary punctures in apical one-third; prosternum moderately broad, keel weakly emarginate at base, with carinal striae complete, separate, weakly convergent in basal one-fourth, weakly divergent anterad; prosternal lobe slightly over half keel length, apical margin bluntly rounded, with marginal stria more or less complete; mesoventrite weakly produced at middle, with marginal stria absent from middle one-third; mesometaventral suture weakly arched forward, mesometaventral stria arched more strongly forward, rounded to subangulate at middle, continuous laterally with oblique lateral metaven tral stria, metaventral disk coarsely punctate at sides, impunctate at middle; abdominal ventrite 1 with complete inner lateral stria and fragments of outer lateral behind metacoxa, disk with coarse secondary punctures only laterad stria, ventrites 2-5 with sparse secondary punctures at sides, the punctures becoming almost obsolete at middle; protibia tridentate, the middle tooth closer to the apical than the basal, outer margin serrulate between teeth; mesotibia with two very weak marginal spines; outer metatibial margin smooth, edentate; propygidium lacking basal stria, with sparse, fine ground punctation, with coarse secondary punctures evenly interspersed, propygidial gland openings inconspicuous; pygidium with sparse ground punctation and coarser, secondary punctation denser toward base. Male genitalia (Figs 51 A–C, E, G–H): T8 with base narrowly, rather deeply emarginate, ventrolateral apodemes with inner apices separated by about one-half T8 width, projecting beneath nearly to ventral midpoint, obsolete apically, apical margin shallowly emarginate; S8 with halves fused along midline, basal emargination broad, narrowed to subacute, basal apodemes narrowly rounded, subparallel, weakly arcuate, apices narrow, obliquely truncate, setose, widely separated by deep, acute apical emargination; T9 with short basal apodemes, halves well separated dorsally, ventrolateral apodemes bluntly produced beneath, nearly meeting, apices narrowly rounded, with single subapical seta on each side; T10 elongate, apical emargination not well defined; S9 with long narrow, medially keeled stem, head rounded to near apex, apices subacute, apical emargination broad, sinuate; tegmen with sides subparallel in basal half, weakly narrowed to apex, apices narrowly rounded, tegmen evenly curved in lateral aspect; median lobe about one-fourth tegmen length, with eversible subapical denticles; basal piece about one-third tegmen length.

Remarks.

This and the following six species are Asian, and no attempt is made to differentiate them from American species. They probably represent a single lineage, although they are quite varied, and clear synapomorphies for such a lineage are not obvious. Baconia chujoi is the only species occurring in Japan, and it also differs from all other Asian species by dark bronze metallic coloration (Fig. 49A), the 4th stria being barely arched at base, by the coarsely punctate pronotum, and by the presence of only a single lateral metaventral stria (Fig. 49B).

Ôhara (1989) has provided additional illustrations of the species, as well as more comprehensive documentation of its distribution, apparently only on Honshu, Japan. It is unfortunate that the type specimen cannot be located. However, as the only species of this group in Japan, its identity is not in question. The species has been found in association with fungi, including Polystictus versicolor (L.) and Coriolus hirsutus (Wulf.) Quel. ( Ôhara, 1989).