Hypocaccus hirsutus, Lackner, Tomáš, 2015

Lackner, Tomáš, 2015, Hypocaccus (s. l.) hirsutus sp. nov., an atypical new species of the genus Hypocaccus C. Thomson, 1867 from India (Coleoptera: Histeridae: Saprininae), Zootaxa 4040 (5), pp. 589-595 : 590-594

Hypocaccus (sensu lato) hirsutus sp. nov.

Type material examined. Holotype, ♀, side-mounted on a triangular point, left antennal segments 3-11 missing, right protarsus and left mesotarsus broken off, with the following labels: “♀” (printed); followed by: “S India, Kerala, 1994 / SHORANUR 10º46’N 76º16’E / bank of Ponnáni riv. / 31.I., Z. Kejval lgt.” (printed); followed by: “ Hypocaccus (s.str.)? / spec. ?? / det. P. Kanaar 2002” (printed-written); followed by: “Gen. nov. / sp. nov. / P. Vienna det., 2003” (printed); followed by: “ Hypocaccus (s.l.) / hirsutus sp. nov. / HOLOTYPE / Det. T. Lackner 2015 ” (red label, written) ( TLAN).

FIGURE 1. Hypocaccus (sensu lato) hirsutus sp. nov., habitus, dorsal view. FIGURE 2.ditto, ventral view.

Description. Body (Figs. 1–2) PEL: 2.55 mm; APW: 1.25 mm; PPW: 2.10 mm; EW: 2.20 mm; EL: 1.50 mm; cuticle light to rusty brown, pronotum somewhat darker than elytra, legs, antenna and mouthparts similarly colored. Head (Fig. 3): mandibles rather thin, pointed apically, left mandible with a large triangularly shaped subapical tooth; anterior margin of transverse labrum elevated, keel-like, other mouthparts not examined; clypeus transverse, with faint shallow punctures with keel-like median elevation, surface posterior to this elevation depressed, anterior to it clypeal disc even; frontal stria carinate, outwardly arcuate, supraorbital stria erased, absent; occipital stria complete, feebly carinate; frontal disc with scattered microscopic punctation, anteriorly with an almost straight transverse carina, posteriorly with a carinate chevron; between the two a short transverse carina present; frontal disc posterior to chevron with another transverse carina basically delimiting frontal disc from occiput; eyes flattened, well-visible from above. Antennal scape with numerous long amber setae; 8th antennomere shaped like a cupule surrounding antennal club up to one-third (Fig. 3), resembling that of Philothis (Atavinus) atavus (for fig. see Lackner 2010, fig. 6). Antennal club globular, conspicuously small; sensory structures of the antennal club examined only externally, due to the unique available specimen, which lacks one antenna. Although the antennal club has not been chemically cleared, a single stipe-shaped vesicle situated on internal distal side of the club was observable under great magnification. Basal half of antennal club glabrous, apical half with intermingled dense short and sparser longer erect sensilla.

Pronotum sub-trapezoidal, antennal angles acute, pronotal sides narrowing anteriorly; marginal pronotal stria carinate, complete, becoming rather thin and sub-carinate in posterior angles. Entire pronotal disc with punctation, punctures on most of disc forming elongate confluent rugae; only on ante-scutellar area punctures free, separated by their own to several times their diameter. Pronotal base with a double row of dense punctures; ante-scutellar area with a faint depression; pronotal hypomeron with dense long amber setae. Scutellum rather small, triangular.

Elytra: marginal epipleural stria well-impressed; elytral epipleura punctate; marginal elytral stria complete, carinate, continuous with complete apical elytral stria that is continuous with complete and carinate sutural elytral stria. Oblique humeral stria short, double; inner subhumeral stria present as short median fragment; elytral disc with four discal elytral stria 1–4, first stria the longest, surpassing elytral half apically; striae 2–4 somewhat shortened, reaching approximately half of elytral length apically; fourth stria weakly developed, interrupted on its half-length. All striae rather weak and obscured by dense elytral punctation; entire elytral disc densely punctuate, punctures separated by less than their diameter; punctation becomes sparser near elytral flanks and elytral base.

Propygidium transverse, its punctation even denser than that of elytra, punctures almost confluent; pygidium with similar, but sparser punctation, punctures here separated by their own to twice their diameter, becoming sparser apically.

Prosternum (Fig. 4): entire prosternal surface with alutaceous microsculpture, prosternal process with punctures; surface between carinate and complete carinal prosternal striae densely punctate; lateral prosternal striae complete and carinate, convergent anteriorly, united in front of united carinal prosternal striae, passing mesad to small but deep prosternal foveae.

Mesoventrite (Fig. 4): transverse, punctate, punctures separated by about their own to twice their diameter; marginal stria of mesoventrite carinate laterally, anteriorly obsolete, antero-medially absent; meso-metaventral stria undulate, concealing meso-metaventral suture.

Metaventrite (Fig. 4) covered with scattered fine punctures separated by several times their diameter, surface along median longitudinal line slightly depressed; lateral metaventral stria straight, carinate, not reaching metacoxa. Lateral disc of metaventrite with rather deep punctures of various sizes, punctures without setae; metepisternum with similar punctation becoming weaker and sparser on fused metepimeron; lateral metepisternal stria present as a short vague fragment on fused metepimeron.

First visible abdominal ventrite with punctation similar to that of metaventrite, completely striate laterally; punctation becoming microscopic and very sparse apically.

Legs: protibia: outer margin apically with two rather approximate low teeth topped by large round denticle; this double-tooth rather widely separated from the following 6 proximal low teeth each topped by round denticle diminishing size in proximal direction. Protarsal groove shallow, protibial spur large, bent, growing out from apical protibial margin; posterior face of protibia rugulose-lacunose; apical margin ventrally with two tiny denticles, posterior protibial stria carinate and complete, separating rugulose-lacunose outer part of protibia from smooth median part of prosternal surface; inner row of setae sparse; inner posterior denticles absent. Mesotibia and metatibia similar, outer margin of both with dense row of long thick denticles supplemented by another, sparser row of shorter denticles on anterior face; both meso-and metatibial spurs well developed and rather long, straight; each meso-and metatarsomere with two long strongly sclerotized setae; tarsal claws in both cases approximately as long as half-length of their respective apical-most tarsomeres, slightly bent apically.

Male unknown.

Differential diagnosis. Hypocaccus hirsutus sp. nov. differs markedly from all species of the genus Hypocaccus from India by densely ciliate pronotal hypomeron as well as by strongly elevated anterior margin of clypeus.

Biology. Unknown, the type specimen was collected on the bank of Ponnáni River.

Distribution. Known only from the type locality, village of Shoranur in the Indian province of Kerala (Fig. 5).

Discussion. The genus Hypocaccus C. Thomson, 1867 contains currently three subgenera: Hypocaccus , Baeckmanniolus Reichardt, 1926 and Nessus Reichardt, 1932 . The primarily Holarctic nominotypical subgenus FIGURE 3. Hypocaccus (sensu lato) hirsutus sp. nov., head, dorsal view.

FIGURE 4. Hypocaccus (sensu lato) hirsutus sp. nov., prosternum, meso+metaventrite.

FIGURE 5. Type locality of Hypocaccus (sensu lato) hirsutus sp. nov. in India.

Hypocaccus is normally found on sandy soils, banks of rivers, and seashores, and includes 44 described species ( Lackner 2014d). The pronotal hypomeron of Hypocaccus s. str. is normally asetose; however, several Nearctic psammophilous representatives (e.g., H. texaco Mazur, 1991 ) do possess ciliate pronotal hypomeron. From India, three species have been recorded so far: H. brahminius (Marseul, 1864) , H. brasiliensis (Paykull, 1811) and H. sinae (Marseul, 1862) .

Another subgenus, the strictly beach-dwelling Baeckmanniolus , with 11 described species ( Lackner 2014d), occurs mainly on seashores of all continents (except Antarctica) but has not yet been recorded from India, although one species, H. (B.) varians (Schmidt, 1890) is widely spread in Indo-Malayan as well as Australian regions. Mazur (2011) reports it from neighboring Sri Lanka. Species of Baeckmanniolus do not have a ciliate pronotal hypomeron. The two subgenera, Hypocaccus and Baeckmaniolus are separated based on their pronotal punctation (species in the subgenus Baeckmanniolus possess impunctate pronotum vs. punctate in the subgenus Hypocaccus ) and number of rows of denticles on the metatibia (two in Hypocaccus vs. three in Baeckmanniolus ) ( Lackner 2010, Bousquet & Laplante 2006).

The third subgenus is the species-rich Nessus containing 53 species distributed almost exclusively in the Old World and occurring chiefly on carcasses, mammal excrement, and in rodent nests, with some specialized Middle- Asian psammophilous forms ( Lackner 2014d). Four species: H. (N.) fugax (Marseul, 1857) , H. (N.) fugitivus (Desbordes, 1925) , H. (N.) malabaricus (Reichardt, 1932) and H. (N.) rubripes (Erichson, 1834) are known from India ( Mazur 2011). Nessus was historically treated as a subgenus of the genus Hypocacculus Bickhardt, 1914 but was moved into Hypocaccus by Mazur (2011) without explanation. Although Mazur (2011) did not give any reasons for inclusion of Nessus in Hypocaccus , he apparently did so based on few differences between the two taxa (the densely punctate-variolate structure of frons, occasionally with transverse rugae is often shared between the two taxa), with the exception of perhaps the body size, that is normally much smaller in Nessus than in Hypocaccus (Mazur pers. comm.). There are, however, also rather ‘small’ Hypocaccus species, e.g., an undescribed species from Mongolia, which only reaches 2.00 mm, a length ‘normal’ for species of Nessus (Lackner unpublished). There are also ‘large’ species of Nessus , e.g., the psammophilous H. (N.) vlasovi Kryzhanovskij, 1966 from Turkmenistan, that reaches up to 3.00 mm, a body length ‘normal’ for most species of Hypocaccus s. str. (Kryzhnovskij & Reichardt 1976).

The newly described species H. hirsutus does not fit neatly into any current subgenus of Old World Hypocaccus based on the setose pronotal hypomeron, as well as strongly elevated anterior clypeal margin. It is morphologically most similar to members of Hypocaccus s. str. On the other hand, the elevated anterior clypeal margin resembles the monotypic African genus Parahypocaccus Vienna, 1995 , but differs from it by the presence of prosternal foveae. Apparently, the external morphological characters (body size, pronotal pilosity, etc.) vary between species of both Hypocaccus s. str. and Nessus , most likely convergent adaptations to the environment. Recent phylogenetic analysis of the Saprininae genera and subgenera ( Lackner 2014d) based on morphological characters failed to clarify the relationships between the taxa Nessus, Hypocaccus or Baeckmanniolus , recovering them in a large unresolved clade of taxa sharing a single synapomorphy of single pear or stipe-shaped vesicle inside their antennal club. The newly-described species lacks numerous characters (e.g. male genitalia, mouthparts) that would be needed for inclusion in a cladistic analysis for proper (sub)generic placement. A subsequent phylogenetic study based on molecular characters is in progress.