Exaesiopus glaucus (Bickhardt, 1914) Bickhardt, 1914

Lackner, Tomas, 2015, Revision of the genus Exaesiopus Reichardt, 1926 (Coleoptera, Histeridae, Saprininae), ZooKeys 479, pp. 65-108 : 87-90

Taxon classification Animalia Coleoptera Histeridae

Exaesiopus glaucus (Bickhardt, 1914) comb. n. Figs 98, 99-106, 107-113

Pachylopus glaucus Bickhardt 1914: 280.

Hypocaccus (Hypocaccus) glaucus : Mazur (1984): 94; Mazur (1997): 259; Mazur (2011): 206.

Type locality.

Gobabeb, Namibia.

Type material examined.

Neotype, ♂, side-mounted on a triangular mounting point, right antennal club broken off, both terminal metatarsomeres broken off, with male genitalia mounted in Canada balsam on a separate slide under specimen, with the following labels: "S.W. Afr., Namib / Gobabeb / 23.34 S– 15.03E " (printed); followed by: "24.9.1974; E–Y: 376 / shore washing / leg. Endrödy-Younga” (printed); followed by: " Exaesiopus / glaucus / Bickh. / det. J. Thérond” (printed-written); followed by: “D08-029” (yellow, pencil-written label, written by myself); followed by: " Pachylopus glaucus / Bickhardt, 1914 / NEOTYPE det. T. / Lackner 2014" (red label, written) (TMSA).

Note.

This species has been described based on a single specimen collected in Okahandja (Namibia) ( Bickhardt 1914: 280). According to the personal information by the curator of ZMHUB B. Jaeger, the specimen was deposited at the Hamburg Museum of Natural History (Germany), which has been destroyed during WWII. The type specimen of this species can thus be considered as lost and hence a Neotype is designated herein.

Additional material examined.

NAMIBIA: 1 ♂ + 1 ♀, Gobabeb, 23.34S - 15.03E, 24.ix.1974, Endrödy-Younga leg., shore-washing (TMSA); 1 ♂ + 1 ♀, ibid, but MNHN; 1 ♀, Swakop River, 3 miles S of Okahandja, 7.iv.1972, floating refuse (MNHN). REPUBLIC OF SOUTH AFRICA: 1 ♂, Cape-Cedarbg, Olifants R., Boshof, 32.20S - 18.59E, 20.viii.1983, Endrödy-Younga & Penrith leg., sand banks, river (TMSA).

Diagnostic description.

Body length: PEL: 2.50-2.60 mm; APW: 0.80-1.00 mm; PPW: 1.83-2.00 mm; EW: 2.00-2.18 mm; EL: 1.50-1.60 mm. Body (Fig. 98) similar to the species Exaesiopus atrovirens , with feeble metallic tinge; legs, mouthparts and antennae light brown. Antennae as in Exaesiopus grossipes . Mouthparts: as in Exaesiopus grossipes ; labrum with median keel-like elevation, surface anterad of it semi-circularly depressed; mentum (Fig. 99) sub-trapezoid, anterior margin without median notch, fringed with several long setae, lateral margins with single row of sparse shorter ramose setae; stipes with four setae; other mouthparts similar to those of Exaesiopus atrovirens . Clypeus (Fig. 100) rectangular, obscurely variolate, anterior margin elevated, formed by two transverse tubercles that can occasionally be connected forming thus a ridge-like structure; clypeus and frons otherwise similar to those of Exaesiopus atrovirens , but without numerous irregular rugae. Pronotum: sides slightly convergent on basal 3/4, strongly convergent on apical ¼; disc with round dense punctation, laterally punctures larger in size and increasingly ellipsoid, occasionally confluent; postero-median part of disc smooth, punctation stops short of lateral pronotal margin leaving a narrow impunctate band; pronotal base with a single row of round punctures; pronotal hypomeron with short amber setae almost invisible from dorsal view; scutellum small, visible. Elytra: humeral elytral stria well impressed on basal fourth; inner subhumeral stria present medially as a short median fragment; elytral punctation confined to apical half of elytra, along elytral suture reaches up to 2/3 of elytral length anteriorly, punctures in most cases do not enter elytral intervals, regular and deep, separated by about their own diameter, punctation does not become denser apically; rest of elytra impunctate. Propygidium and pygidium (Fig. 101) similar to other congeners, with coarse and dense regular punctation. Prosternum (Fig. 102): prosternal foveae well impressed, rather small, but deep; prosternal process slightly concave, otherwise similar to that of other congeners. Mesoventrite (Fig. 103) slightly wider than long, almost smooth; meso-metaventral sutural stria well impressed, undulate; intercoxal disc of metaventrite with longitudinal depression in both sexes, more prominent in male, almost smooth, except for several rows of variously-sized deep punctures along base; lateral metaventral stria, lateral disc of metaventrite and metepisternum similar to those of Exaesiopus henoni . Intercoxal disc of first abdominal sternite as with the rest of congeners. Protibia (Fig. 104) on outer margin with two moderately large triangular teeth, topped by rounded denticle followed by another two lower teeth topped by small round denticle and another tiny denticle entombed in outer protibial margin; setae of outer row regular and short; setae of median row shorter than those of outer row; anterior protibial stria almost complete; protibial groove deep; protibial spur (Fig. 105) distinct but tiny, growing out from apical margin of protibia; outer part of posterior surface of protibia rugulose-lacunose, clearly separated from comparatively narrower glabrous median part; posterior protibial stria complete, terminating in two tiny inner posterior denticles; inner margin of protibia with single row of short lamellate setae. Mesotibia not particularly dilated or thickened, outer margin similar to that of Exaesiopus henoni ; posterior mesotibial stria fine, shortened apically; mesotibial spur stout, prominent and long; anterior surface of mesotibia smooth; anterior mesotibial stria shortened apically; claws of last tarsomere almost straight, their length approximately half the length of apical-most mesotarsomere. Metatibia (Fig. 106) slightly more dilated and thickened than mesotibia, but always more slender than that of the rest of the congeners; two rows of denticles on outer margin widely separated permitting for placement of another two denticles between the two rows; claws of apical-most metatarsomere shorter than half its length; otherwise metatibia similar to mesotibia. Male genitalia. Eighth sternite (Figs 107-108) entirely fused medially, apically with a setose velum; apex of eighth sternite with short dense setae. Eighth tergite apically weakly inwardly arcuate; eighth sternite and tergite fused laterally (Fig. 109). Ninth tergite (Fig. 110) on apical margin faintly inwardly arcuate; tenth tergite on apical margin regularly rounded, weakly inwardly arcuate basally. Spiculum gastrale (Figs 110-111) with typical ‘head’ and ‘tail’; aedeagus (Figs 112-113) tube-like, sub-parallel, slightly widening apically; parameres fused along their basal three-fourths, apex of aedeagus with pores; basal piece short, ratio of its length: length of parameres approximately 1:5.

Differential diagnosis.

Exaesiopus glaucus is arguably the most distinctive species of the genus differing from all other members by only slightly dilated metatibia (strongly dilated in all other species, compare Fig. 106 with e.g. 97); present and observable protibial spur (very tiny or absent in the rest of species, compare Fig. 105 with e.g. 43). Furthermore, the setae of the pronotal hypomeron are rather short and invisible from dorsal view (in all other species they are protruding from underside of the pronotum and are observable from dorsal view).

Biology.

Found on a beach by the technique of shore-washing as well as on a river bank on deposited debris.

Distribution.

Described from Namibia; newly recorded from the Republic of South Africa.

Remarks.

The placement of this species in Exaesiopus must be regarded as tentative, as it differs from the rest of the members chiefly by only slightly instead of strongly dilated metatibiae. Hypocaccus from the Old World, however, does not contain any species with ciliate pronotal hypomera, and keeping Exaesiopus glaucus in Hypocaccus would make it heterogeneous. Note that it was already Reichardt (1926) who remarked that this species should be, based on its ciliate pronotal hypomeron, moved into the genus Exaesiopus . Thérond, in the 1960's and 1970's identified this species as ' Exaesiopus ', rather than ' Hypocaccus ' glaucus.