Pholioxenus Reichardt, 1932

Lackner, Tomáš, 2010, Review of the Palaearctic genera of Saprininae (Coleoptera: Histeridae), Acta Entomologica Musei Nationalis Pragae (suppl.) 50, pp. 1-254 : 181-182

Pholioxenus Reichardt, 1932

Pholioxenus Reichardt, 1932: 16 , 26. Type species: Hypocacculus phoenix Reichardt, 1929 , original designation.

Pholioxenus: REICHARDT (1941) : 156, 275; PORTA (1939): 151, 152; KRYZHANOVSKIJ & REICHARDT (1976): 111, 197; OLEXA (1984): 113; MAZUR & KASZAB (1980): 7, 51; VIENNA (1980): 116, 168; MAZUR (1984): 83; MAZUR (1997): 245; YÉLAMOS (2002): 245, 305; MAZUR (2004): 96.

Diagnosis. Body rather flattened dorsally, cuticle light to dark brown, occasionally with greenish or bronze metallic tinge, surface often imbricate-punctate; eyes moderately to strongly convex; anterior margin of clypeus not elevated; frontal stria weakly impressed, at times weakened or even interrupted; pronotum only slightly convex so that both lateral margins are visible along their entire length (seen from dorsal view), lateral pronotal margins evenly arcuate; pronotal foveae absent; pronotal hypomeron usually glabrous. Sutural elytral stria especially on apical half often strongly carinate, in large round punctures; inner subhumeral stria often long, basally sometimes connected with humeral elytral stria forming an additional fifth dorsal elytral stria. Pre-apical foveae small and inconspicuous (occasionally absent); meso-metaventral sutural stria occasionally sinuate, distanced from meso-metaventral suture; protibia rather dilated, outer margin with up to six low teeth topped with tiny thin denticle; protarsal groove shallow; meso- and metatibiae slender, long, tarsal claws long, usually longer than apical tarsomere itself.

Differential diagnosis. Species of Pholioxenus are most similar to the members of the genus Hypocacculus , chiefly differing from them by the more dilated protibiae, more flattened pronotum, more convex (often almost semi-spherical) eyes, and usually imbricate-punctate dorsal and ventral body surface. Also, the meso- and metatibiae are longer and slenderer with Pholioxenus than with Hypocacculus , and sutural elytral stria is often strongly carinate (especially on its apical half) and in large punctures.

Biology. All species of Pholioxenus live as inquilines of various mammals (e.g. Spermophilopsis , Jaculus , Rhombomys , etc.) and birds. Pholioxenus schawalleri Mazur, 1987 has been recorded near the colony of Northern Bald Ibis ( Geronticus eremita ( Linnaeus, 1758)) , or even in burrows of tortoises (e.g. Testudo horsfeldi Gray, 1844 ) (OLEXA 1984). Pholioxenus species occur especially in the arid, semidesert or desert biotopes. They are occasionally also collected on dung, carrion, etc., but can be primarily collected in the nests of animals, where they most probably prey upon dipteran or siphonapteran larvae.

Distribution. Twenty-five species, distributed in the Palaearctic and Afrotropical Regions, have been hitherto described ( MAZUR 1997, 2006; YÉLAMOS 2001).

Species examined. Pholioxenus krali Olexa, 1984 , P. kodymi Olexa, 1984 , P. mesopotamicus Olexa, 1984 , P. normandi Olexa, 1984 , P. orichalceus Reichardt, 1941 , P. phoenix (Reichardt, 1929) , P. pickai Olexa, 1984 , P. quedenfeldti ( Schmidt, 1887) , P. rutilus ( Erichson, 1834) , P. schatzmayri ( Müller, 1910) .

Discussion. Pholioxenus is probably a monophyletic taxon that is supported by few synapomorphies, e.g. imbricate-punctate surface of body, long and slender metatibiae, very small (occasionally even absent) pre-apical foveae and carinate sutural elytral stria. It can be regarded as an evolutionary branch of its presumably related sister taxon Hypocacculus that became adapted to nidicolous way of life, speciated there and its members have probably been a part of this niche for a long time. Large convex eyes and a rather small vesicle of the sensory structures of antennal club could be listed among the possible morphological adaptations to the inquilinous way of life.