Saprininae Blanchard, 1845

Lackner, Tomáš, 2010, Review of the Palaearctic genera of Saprininae (Coleoptera: Histeridae), Acta Entomologica Musei Nationalis Pragae (suppl.) 50, pp. 1-254 : 57-60

Saprininae Blanchard, 1845

Saprininae Blanchard, 1845 (as Saprinites Blanchard, 1845)

Saprininae : FOWLER (1912)

Myrmetini Portevin, 1929. Synonymized by MAZUR (1984).

Saprinini: YÉLAMOS & FERRER (1988)

Diagnosis. Small to moderately sized beetles (PEL: 1.4–10.0 mm). Body oval, roundly oval, rarely elongate oval, usually convex to very convex, at times slightly flattened dorsally, or strongly vaulted ventrally. Cuticle often metallic, sometimes without metallic luster, usually brown, brown-red, black, at times light brown. Elytra occasionally with red, orange or yellow patches, maculae or transverse bands.

Head prognathous, much shorter than pronotum and well retractable. Frontal stria usually well developed, in some cases interrupted (at times prolonged onto clypeus) or entirely absent; supraorbital stria usually present, sometimes elevated above eyes, occasionally absent; occipital stria usually present. Antennal insertion located on lateral edge of frontal disc between eye and base of mandible. Antennal scape and flagellum differ in chaetotaxy, but generally similar within the subfamily. The most variation is found in the eighth antennomere, which can be saucer-like or cupuliform in some sand-dwelling forms. Antennal club with specialized sensory organ in form of vesicles, sensory areas, slit-like pits or their combination.

Labrum in most cases with two labral pits, each with one (rarely) or two setae, occasionally these pits and setae absent. Mandibles usually punctate, short and stout, sub-apical tooth usually well developed; prostheca very narrow. Mentum with setae, in most cases sub-trapezoid or rectangular, usually with small notch in middle of anterior margin. Terminal labial and maxillary palpomeres in most species with palpal organ. Lacinia of maxilla in most taxa without lacinial hook.

Dorsal surface. Pronotum and elytra usually variously punctate, only rarely smooth; ‘mirrors’ may be present on pronotum and elytra if punctation is extremely coarse and dense (degree of coarseness and density of punctation is expressed by a comparison of puncture diameter with interspaces between punctures; interspaces between punctures sometimes imbricate or substrigulate). Pronotum always, at least in anterior corners, with marginal pronotal stria that can be interrupted anteriorly; lateral pronotal stria rarely also present. Pronotum often with pronotal foveae, rarely with bulges; pre-scutellar depression often present; pronotal hypomeron often setose. Elytral epipleuron usually with punctures, marginal epipleural stria almost always present, sutural elytral stria in most cases present, usually complete.

Elytra usually punctate; inner subhumeral stria almost universally present, outer subhumeral stria often absent, if present then usually very short; humeral stria almost always present, in many cases vague, surface around it often with fine oblique rugae; elytra with four (rarely five) dorsal striae, almost never reaching elytral apex. Dorsal striae can be reduced down to two, often intermittent. Sutural elytral stria almost universally present and usually basally connected with fourth dorsal elytral stria. Propygidium in most cases punctate, short, transverse, often partly covered by elytra. Pygidium well developed, usually punctate, rarely with sulci.

Ventral surface. Anterior lobe of prosternum absent; antennal cavities open, not covered by prosternal ‘alae’, lying next and usually encroaching upon prosternal process, sometimes outer lateral costa of antennal groove distinctly reaching prosternal process. Prosternum usually with two pairs of striae, carinal and lateral, their configuration and/or presence being important in genera determination. Pre-apical foveae of prosternum present in many genera, sometimes united by a transverse sulcus; prosternal process rarely with median fovea.

Mesoventrite usually wider than long, in littoral taxa as long as wide, usually with marginal stria, often covered with punctation. Metaventrite in males often with a longitudinal depression, often punctate, at least laterally, basal area of metaventrite occasionally with two bulges. Pronotal hypomeron, pleura and sterna often with variously long vestiture.

Legs. Protibia usually dilated, outer margin with denticles or teeth topped with denticle; anteri- or margin dorsally in most cases with a distinct apical protibial spur that can be variously long. Posterior surface of protibia smooth or with wrinkles, denticles, punctures or combination of these. Protarsomeres 1–4 of males with one or two leaf-like translucent modified setae.

Mesotibia and metatibia in most cases slender, sometimes expanded, outer margin with denticles, or seldom with teeth topped with denticle; some psammophilous taxa with separately extended ventro-lateral part. Hind legs of some littoral species strongly thickened. Meso- and metatarsi with variously bent and long claws; empodium absent.

Genitalia. Male genitalia with shape and chaetotaxy of the eighth tergite and sternite are greatly variable within subfamily, providing important characters for species identification; the ninth tergite is occasionally divided longitudinally; spiculum gastrale (the ninth sternite) in most cases dilated on both ends; aedeagus usually with fused parameres along the entire length, only sporadically parameres separated from base. Aedeagus tube-like, median lobe little sclerotized; basal piece present, uniform, usually short. Female genitalia as described in ÔHARA (1994) and DE MARZO & VIENNA (1982b).

Biology and distribution. Subfamily Saprininae contains about 620 described species worldwide ( MAZUR 1997), occurring in all geographic regions, except for the Antarctic and Arctic. The Palaearctic Region harbors approximately 270 described species ( MAZUR 1997). The most genus- and species-level diversity, including many endemic genera and species, seems to be found in the desert regions of Central Asia (especially in Turkmenistan and Uzbekistan and to a lesser extent also in Kazakhstan) and Sahara (to a lesser extent also in the Arabian Peninsula). Each continent has its own unique lineages. For example, the genus Euspilotus is particularly species-rich in South America but almost absent from the Palaearctic Region, while the genus Hypocacculus is almost entirely absent from the Nearctic or Neotropical Regions and very species-rich in the Palaearctic or Afrotropical Regions.

The Saprininae are most abundant in arid places, where they are often found on carrion or in dung. Only rarely they inhabit more mesic habitats such as forests. They are most commonly found at lower altitudes up to 1500 m, but some are known to reach high mountains (more than 3500 m) as well. For example, Saprinus (Saprinus) stussineri Reitter, 1909 is often found at elevations above 1500 m; Saprinus (Saprinus) pamiricus Reichardt, 1930 lives at altitudes above 2800 m (KRYZHANOVSKIY & REICHARDT 1976), and several species of Paravolvulus were found at almost 2000 m in the vicinity of Kabul in Afghanistan ( KRYZHANOVSKIJ 1987).

The Saprininae are typically predators of soft-bodied larvae and eggs of flies or other arthropods. However, according to REICHARDT (1941), some species of the genus Saprinus capture adult flies on dung. CARLTON et al. (1996) reported similar behavior of the South American Euspilotus (Euspilotus) bisignatus ( Erichson, 1834) , which eats heads of living flies after having captured them. Some species of Saprinus are attracted to fetid fragrances emitted by the blooming flowers (for details see THÉROND 1931, REICHARDT 1941, VIENNA 1980 and KOVARIK & CATERINO 2005). The species Chalcionellus hauseri ( Schmidt, 1894) and Paravolvulus syphax ( Reitter, 1904) develop in the drying stalks of Cystanche plants ( REICHARDT 1941, KRYZHANOVSKIJ & REICHARDT 1976, KRYZHANOVSKIJ 1987, KOVARIK & CA- TERINO 2005). Several species of Saprinus prey upon fly larvae that develop in rotting fungi, e.g., S. (Saprinus) lautus Erichson, 1839 (Lackner, pers. observ.).

Specialized littoral species occupy riparian habitats and are found on beaches almost throughout the world. They prey upon insect larvae that develop in the coastal wrack. Here belongs the majority of species in the genus Hypocaccus , all species of the subgenus Baeckmanniolus and Eopachylopus ripae . Several species of the genus Hypocaccus , e.g., H. (Hypocaccus) speculum ( Schmidt, 1884) , H. (Hypocaccus) specularis ( Marseul, 1855) , H. (Hypocaccus) axeli ( Kryzhanovskij, 1976) and H. (Hypocaccus) pelleti ( Marseul, 1862) , are typical inhabitants of shoals of rivers, occasionally occurring at higher altitudes; they presumably prey on fly larvae developing in organic debris ( ÔHARA 1994, KRYZHANOVSKIJ & REICHARDT 1976). However, other species of Hypocaccus and other genera, e.g., H. (Hypocaccus) rugiceps or Exaesiopus grossipes , can be found on the seashores as well as deep inland on landlocked sandy dunes (Lackner, pers. observ.).

The Saprininae also include many specialized psammophilous species, occasionally living deep in the sand (most of the psammophilous Histeridae belong to the Saprininae ). These usually show various degrees of adaptation to the sandy conditions, often having dense vestiture on the ventral surface of the body, shovel-like protibiae and thickened and dilated meso-and metatibiae. The typical representatives of this group include all taxa in the genera Philothis , Ctenophilothis and Xenophilothis (for details on their morphology and biology see OLEXA 1990) and the genera Ammostyphrus , Reichardtiolus , Axelinus , Alienocacculus , Chivaenius and Turanostyphrus ( KRYZHANOVSKIJ & REICHARDT 1976; OLEXA 1980, 1984; TISHECHKIN 2005).

The Saprininae are also regular inhabitants of mammal and birds nests (for more details see KOVARIK & CATERINO 2005). A very thorough survey of species of the genus Gnathoncus and Saprinus (as well as other histerids) frequenting bird nests can be found in HICKS (1959: 52–64). Examples are found within the genera Gnathoncus , Eremosaprinus and Pholioxenus ( REICHARDT 1941, KRYZHANOVSKIJ & REICHARDT 1976, OLEXA 1984). Several species of the genera Gnathoncus or Saprinus are found in the nests of birds and occasionally on carrion, e.g., Gnathoncus nannetensis ( Marseul, 1862) and Saprinus (Saprinus) aeneus ( Fabricius, 1775) ( KRYZHANOVSKIJ & REICHARDT 1976; Lackner, pers. observ.). This behavior can indicate that the ancestral taxon was predominantly free-living and subsequently entered the nests of mammals or birds. Saprinus (Saprinus) rugifer ( Paykull, 1809) has been reported to frequent the nests of Sand Martin ( Riparia riparia Linnaeus, 1758 ), which presumably represent its true habitat, but is also occasionally found on dead birds or even in mole burrows ( Talpa europea Linnaeus, 1758 ) ( KRYZHANOVSKIJ & REICHARDT 1976). The sole Palaearctic representative of the genus Euspilotus , E. (Neosaprinus) perrisi , lives in the nests of the European Bee-Eater ( Merops apiaster Linnaeus, 1758 ) (Olexa, pers. comm. 1995; KRYZHANOVSKIJ & REICHARDT 1976). This species is also seldom collected on carrion (Kanaar, pers. comm. 2008). Almost all species of the genus Pholioxenus , some species of the genus Gnathoncus as well as Eremosaprinus vlasovi live in the burrows of ground squirrels, e.g., Spermophilopsis (Sciuridae) . Myrmetes paykulli is the sole Palaearctic species known to frequent nests of Formica ants, especially those of Formica rufa Linnaeus, 1761 and less frequently those of F. sanguinea Latreille, 1798 . This species is most likely not strictly myrmecophilous, since it has also been found on a dead frog ( KRYZHANOVSKIJ & REICHARDT 1976).

Although most of the known taxa are apparently diurnal, the Saprininae found in the desert regions are sometimes attracted to light, e.g., Saprinus (Saprinus) lucemseductus Kanaar, 2008 recently described from the United Arab Emirates and Alienocacculus vanharteni Kanaar, 2008 ( KANAAR 2008; Pavlíček, pers. comm. 2007).

This permits the conclusion that the Saprininae are very active and appear to be highly adapted to unwelcoming dry habitats. They have also invaded nests of various birds as well as mammal burrows and are even present in ant colonies. This remarkable ecological plasticity is not seen in any other subfamily of the Histeridae .