Philothis Reichardt, 1930

Lackner, Tomáš, 2010, Review of the Palaearctic genera of Saprininae (Coleoptera: Histeridae), Acta Entomologica Musei Nationalis Pragae (suppl.) 50, pp. 1-254 : 164-166

Philothis Reichardt, 1930

Philothis Reichardt, 1930: 293 . Philothis: REICHARDT (1941) : 157, 337; PEYERIMHOFF (1936): 224; KRYZHANOVSKIJ & REICHARDT (1976): 112, 243; MAZUR (1984): 109; OLEXA (1990): 146; MAZUR (1997): 268; MAZUR (2004): 96.

Type species: Philothis arcanus Reichardt, 1930 , original designation.

Diagnosis. Body strongly vaulted, especially ventrally, cuticle castaneous to dark brown, often with metallic luster; eyes inconspicuous from above; clypeus and frontal disc smooth, frontal stria usually broadly interrupted medially, rarely complete; supraorbital stria usually present, rarely absent; labrum smooth, flattened, labral pits and setae absent; pronotum usually conspicuously narrowed anteriorly with deep anterior incision for head, pronotal angles prominent; pronotal hypomeron setose, pronotal disc rarely with vague bulges in postero-median part; pronotal foveae absent. Elytral epipleura glabrous; inner subhumeral stria usually well developed; marginal elytral stria complete, apical elytral stria at times erased by punctation; sutural elytral stria on basal half distanced from elytral suture (in some species doubled) and at times continuous as basal elytral stria surrounding large transverse bulge situated on median part of elytral base; in subgenera Philothis and Farabius only first and sometimes second dorsal elytral striae developed; in subgenus Atavinus all four, or even five dorsal striae developed; disc of elytra usually entirely punctate, punctures very dense, shallow, often confluent, occasionally leathery at apex; scutellum very small. Propygidium and pygidium with large, shallow and very dense punctures, rarely lateral sides of pygidium glabrous; pygidium (and partly also propygidium) of at least one species, Philothis (Atavinus) pierrei (Thérond, 1963) , setose. Prosternum without pre-apical foveae, with long yellow setae; lateral prosternal striae absent, carinal prosternal striae usually absent as well (in subgenus Farabius present on prosternal apophysis), in some cases marginal prosternal stria complete. Mesoventrite of at least one species, Philothis (Philothis) alsiosus Peyerimhoff, 1936 , setose; lateral metaventral stria shortened (in some species extremely). Lateral striae of first abdominal sternite weakened, often shortened apically. Lateral parts of pleura and sterna with long yellow setae. Protibia anteriorly truncated, anterior margin of protibia formed by apical margin of most-distal large triangular tooth; outer margin of protibia with two large triangular teeth, topped with tiny round denticle, occasionally followed by several indistinct minuscule denticles; protarsi shortened, at times rudimentary, in subgenus Atavinus completely absent; apical protarsomere occasionally with single long, thin straight claw. Meso- and metatarsi with basal-most tarsomere the thickest, tarsomeres gradually diminishing in diameter apically; each tarsomere of mesotarsus with two strongly sclerotized lamelliform setae, one posteriorly and one anteriorly; mesotarsal claws thin, hair-like, several times as long as fifth tarsomere itself. Outer margin of metatibia with one double row of morphologically different sets of denticles: denticles of the first type short, thick-set with rounded apices, denticles of the second type much longer and thinner, with pointed apices; another row markedly shifted from outer margin, situated on anterior side of metatibia, observable only from ventral view.

Differential diagnosis. Species of this genus could be confused with the genera Ctenophilothis , Xenophilothis , Xenonychus , and perhaps also with Styphrus or Ammostyphrus . From Ctenophilothis they differ chiefly by the shape of protibia that is with two large distal triangular teeth instead of numerous long movable denticles; furthermore in Ctenophilothis the elytral epipleuron is setose, whereas in Philothis it is glabrous. From the genus Xenophilothis the members of this genus differ also chiefly by the shape of protibia, that is with two rounded teeth each topped with a triangular denticle, followed by the two shorter triangular teeth topped with a denticle (whereas in Philothis it is with two large triangular distal teeth, see above), as well as the shape of mentum (sub-trapezoid to square-shaped in Philothis and broadening anteriorly in Xenophilothis ); furthermore, the lateral prosternal striae are well developed, straight in Xenophilothis (whereas they are absent in Philothis ) and the elytral epipleuron is likewise setose (glabrous with Philothis ). From the genus Xenonychus they differ by the usually reduced dorsal elytral striae, whereas they are well developed and almost complete in Xenonychus (in the subgenus Atavinus these striae are likewise well developed, but they rarely surpass the elytral half apically, whereas they are almost complete in Xenonychus ); furthermore, Xenonychus has a setose elytral epipleuron, whereas in Philothis it is glabrous. From the genus Styphrus the members of Philothis differ chiefly by present both sets of prosternal striae (absent in Philothis ) as well as the shape of protibia and different chaetotaxy of the antennal club and differently shaped pro-, meso- and metatibiae. Ammostyphrus possesses lateral pronotal stria, which is absent in Philothis ; furthermore, Ammostyphrus has lateral prosternal striae well developed, whereas they are absent in Philothis .

Biology. A strictly psammophilous genus. The biology and distribution of Philothis was elaborated by OLEXA (1990). Beetles burrow deep in sand, often near roots of various desert plants or shrubs recently entombed by shifting sands and still having faded leaves buried in the sand where they prey on larvae of various arthropods, like other Histeridae ( OLEXA 1990) . They are extremely well adapted to the psammophilous way of life.

Distribution. This genus has 14 described species from Algerian and Egyptian Sahara, Iranian and Omani deserts and desert regions of Central Asia ( Kazakhstan, Uzbekistan and Turkmenistan) as far west as Azerbaijan ( MAZUR 1997).

Discussion. Philothis ranks among most derived psammophilous Saprininae , containing most of the peculiar morphological adaptations linked with its special habits. It is probably monophyletic and sister to Ctenophilothis . The monophyly of Philothis is supported by several synapomorphies e.g. vesicle of the antennal club situated under apical surface (instead of internal distal margin), peculiar shape of prosternal process, flattened smooth labrum without labral pits or setae and cupuliform 8 th antennomere.