Calathus (Certocalathus), Schmidt & Will, 2020

Schmidt, Joachim & Will, Kipling, 2020, A new subgenus for “ Acalathus ” advena (LeConte, 1846) and the challenge of defining Calathina based on morphological characters (Coleoptera, Carabidae Sphodrini), Zootaxa 4722 (4), pp. 326-338 : 329-331

Certocalathus subgen. n.

Type species: Pristodactyla advena LeConte, 1846 , Fig. 1 . Syntypes, Museum of Comparative Zoology, Harvard. Image of single male examined. MCZ #35336. Type locality northeast Maine ( Bousquet 2012).

Diagnostic characters. Taxon with characteristics of Calathina and Calathus , respectively, as defined by Lindroth (1956) and Ball & Nègre (1972). Combination of following characters defines the subgenus: Colour of body brown to dark brown, dull. Patterns of microsculpture isodiametric on head and most parts of pronotum, very slightly transverse paramedially, scale-like on elytra. Head and mandibles typical, not thickened, eye size typical for Calathus , antennae pubescent from fourth antennomere, mentum tooth bifid. Pronotum discoidal, markedly constricted towards base, with basal margin only slightly broader than or subequal to apical margin; basolateral lobes rounded, not or very slightly protruded posteriorly, not or very vague and incompletely beaded, basolateral seta situated near side margin. Prosternal process not marginally beaded. Elytra slender, without humeral tooth; basal bead moderately concave, much shallower than typical form in most Calathina , the medial end near base of parascutellar stria moderately protruded anteriorly and situated distinctly behind level of tip of humeral angle ( Fig. 1 ); latter obtuse (110-120°); parascutellar seta present, third interval in apical 2/3 with 2-3 discal setae adjoining second stria (sometimes with an additional seta at the end of the anterior elytral quarter, situated in mid of interval), surrounding region of setigerous punctures not depressed; fifth and seventh intervals without setae; elytral intervals with very short, fine pubescence that varies in extent from pubescence across all intervals or restricted to the lateral two or three intervals and across the apical third. In old, dirty, or rubbed specimens elytral pubescence is difficult to see, but always at least apparent at the elytral apices. Metepisternum elongated, with lateral margin> 1.5 times longer than anterior margin. Legs of average relative length for Calathus , neither markedly slender nor particularly robust; mesocoxa with one ridge seta, metatrochanter with seta present, hind tibia in male not densely pubescent, tarsi without pubescence or wrinkles on dorsal surface, male protarsomeres dilated, meso- and metatarsomeres I-IV with lateral grooves distinct internally and externally, fifth tarsomeres with a single pair of dorsal setae, claws pectinate. Basal gonocoxite markedly short, only slightly longer than apical gonocoxite, latter markedly robust, with one ensiform seta at dorsal and two ensiform setae at external margin, with sensory pit well-developed ( Fig. 3 ); bursa copulatrix not markedly sclerotized ( Fig. 2 ). Aedeagus left side superior in repose, with right paramere styloid and very slender towards apex, terminating in a distinct apical hook; left paramere ovoid with membranous lobe developed; median lobe in dorsal view straight, with apical portion markedly short, beak-shaped, without apical disc; endophallus without sclerites ( Fig. 4 ).

Recognition. Absence of the lateral bead on prosternal process is a character state that Certocalathus subgen. n. shares with the Palearctic subtribe Dolichina sensu Hovorka (2017b, and other authors cited above). All species of the respective genera and subgenera of Dolichina ( Acalathus , Procalathus , Dolichus , Xestopus , Morphodactyla Semenov, 1889 , Doliodactyla Sciaky & Wrase, 1998 , Anchomenidius Heyden, 1880 , Casaleius Sciaky & Wrase, 1998 ) are distinguished by markedly reduced sensory pit of the apical gonocoxite. Absence of lateral bead on prosternal process differentiate Certocalathus subgen. n. from most Calathina except Tachalus Ball & Nègre, 1972 , and some species of Lindrothius . Species of the Caucasian Calathus subgenus Lindrothius differs from the new taxon by having the body and legs much more robust, pronotal laterobasal setae removed from side margin, metepisternum shortened, meso- and metatarsomeres I-IV with lateral grooves reduced, basal gonocoxites larger, and apical portion of aedeagal median lobe much longer. The Mexican Calathus subgenus Tachalus differs from Certocalathus subgen. n. by the longer pronotum, elytra without discal setae, shortened metepisternum, slenderer gonocoxites, and aedeagus right side superior in repose, with longer paramere without apical hook and shorter paramere without membranous apical lobe.

The phylogeny based on molecular data provided by Ruiz et al. (2010) places Certocalathus subgen. n. (= “ Acalathus ” advena ) as sister taxon to the monotypic Calathus subgenus Iberocalathus from the Iberian Peninsula. The latter is characterized by the presence of a well-developed lateral bead on prosternal process. Iberocalathus additionally differs by the pronotal basolateral lobes markedly protruded posteriorly, pronotal laterobasal setae removed from side margin, elytral basal bead much more concave with medial end markedly protruded anteriorly, elytral discal setae adjoined to the third stria, metepisternum shortened, meso- and metatarsomeres I-IV with lateral grooves reduced, basal gonocoxites larger, apical gonocoxites much shorter with a single ensiform seta at external margin, apical portion of aedeagal median lobe much longer, markedly turned to the left, with endophallus extensively sclerotized, and with right paramere stouter than left, not hooked at apex.

Certocalathus subgen. n. is most similar to the Calathus subgenus Indocalathus from Kashmir Himalaya in that these taxa share the following character states: i) the shape of the pronotum with basally markedly constricted side margins, ii) basolateral lobes rounded and not or incompletely beaded, iii) basolateral seta situated just beside side margin, iv) slender elytra with moderately concave basal bead, v) hind wings developed, vi) laterally furrowed meso- and metatarsomeres I-IV, and vii) the short beak-shaped aedeagal median lobe with unarmed endophallus. Remarkably, one Indocalathus kirschenhoferi Battoni, 1982 specimen was found to possess a reduced prosternal lateral margin. Consequently, this species seems to be polymorphic for this character. However, Indocalathus differs from the new subgenus by having the elytra with 4-5 discal setae all adjoined to the third stria and set in small fossae, mesocoxa with two ridge setae, fifth tarsomeres with two pairs of setae on dorsal surface, and aedeagal median lobe markedly sclerotized ( Schmidt 2018).

Etymology. The name is derived from the Latin adverb “certo” (certainly) and the name of the ground beetle genus Calathus , and thus refers to the taxonomic position of the new taxon within Calathus sensu auctorum.

Geographical distribution. Distribution information is from Bousquet (2012), Ball & Nègre (1972), Lindroth (1955) and collections noted in the materials above. Specimens are known from as far north in eastern North America as Newfoundland and in the west to the western Aleutian Islands, Alaska. The range extends south to New York and the Great Lakes region in the east and south coastal California, Utah, and Arizona in the west. California specimens we collected and examined (see materials above) confirm the doubtful record reported by Bousquet (2012).

Figures

FIG. 1. Calathus (Certocalathus) advena (LeConte, 1848), habitus, dorsal view; male specimen from Alaska: Afognak Is.

FIGS 2–4. Calathus (Certocalathus) advena (LeConte, 1848). Fig. 2: female genital tract, ventral view; Fig. 3: gonocoxites, ventral view; Fig. 4: aedeagus, dorsal view. Abbreviations: bc: bursa copulatrix; co: common oviduct; ds: dorsal ensiform seta; es: external ensiform setae; gc 1: basal gonocoxite; gc 2: apical gonocoxite; sp: spermatheca; sp-gl: spermathecal gland; spit: sensory pit; pm-l: left aedeagal paramere; pm-r: left paramere; vg: vagina.