Batriscydmaenus tishechkini Parker and Owens, 2018

Parker, Joseph & Owens, Brittany, 2018, Batriscydmaenus Parker and Owens, New Genus, and Convergent Evolution of a “ Reductive ” Ecomorph in Socially Symbiotic Pselaphinae (Coleoptera: Staphylinidae), The Coleopterists Bulletin 72 (2), pp. 219-229 : 223-224

Batriscydmaenus tishechkini Parker and Owens , new species

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Type Material. Holotype ³: PANAMA: Colón Pr. San Lorenzo Forest 9°17′N 79°58′W. Forest litter, Winkler extraction IBISCA site B1. W 12558 // 10.x.2003. A.Dejean, G.Orivel, B.Cobrara, H.-P. Aberlenc & M.Leponce . Paratypes (5): ³ PANAMA: Colón Prov. San Lorenzo Forest , STRI crane site. 9°17′N 79°58′W FIT-C3-17. 21-24 May 2004 A.K.Tishechkin. AT — 522; ³ PANAMA: Colón Prov. San Lorenzo Forest . 9°17′N 79°58′W. F.I. T., 1.3m 14d FL-C281.3a. 17.x.2003 R. Didham, L. Fagan. IBISCA; ♀ PANAMA: Colón Prov. San Lorenzo Forest , STRI crane site. 9°17′N 79°58′W FIT-I3-15. 15-17 May 2004 A.K. Tishechkin. IBISCA’04; ♀ PANAMA : Colón Prov. San Lorenzo Forest , STRI crane site. 9°17′N 79° 8′W FIT-B3- 14. 20-21 May 2004 A.K. Tishechkin. IBISCA’04; ³ PANAMA : Colón Prov. San Lorenzo Forest. 9°17′N 79°58′W. F.I. T., 1.3m 10d FL-C1A1.3b. 23. x.2003 R. Didham, L.Fagan. IBISCA. The male holotype, two male paratypes, and one female paratype are deposited in Field Museum of Natural History ( FMNH), Chicago, IL, USA . A male and female paratype are held at the Louisiana State Arthropod Museum ( LSAM), Baton Rouge, LA, USA .

Diagnosis. As for the genus, additionally with vestiture of regularly spaced, spatulate setae on dorsal surface, and aedeagus with narrow distal process and patches of erect setae on distal surface.

Description. Holotype male body length 1.57 mm ( Fig. 1A, B ). Upper body surface shiny and glabrous except for sparse but regularly spaced large, suberect, spatulate setae ( Figs. 1A, B , 2A, B, D, D’ ). Body and antenna light reddish brown, appendages and maxillary palpi orange-yellow ( Fig. 1A, B ). Head: Moderately transverse ( Figs 1A ; 2B ). Integument smooth, shiny; dorsal surface with evenly spaced, spatulate setae; ventral surface with dense vestiture of simple, closely spaced setae. Vertex gently convex, smooth, lacking foveae, sulci, or carinae. Eye small, semi-circular, composed of approximately 45 facets ( Fig. 2A ). Postocular margins longer than eye length, gently rounded, narrowing from eyes towards base. Antennomeres 1–3 longer than wide; 3–10 subrectangular, about as long as wide; 11 largest ( Fig. 2A ). Thorax: Pronotum slightly wider than long, widest point at about 1/3 length; lateral margin rounded; disc smoothly shiny with evenly spaced, spatulate setae ( Figs. 1A , 2D ). Mesoventrite with fine lattice microsculpture medially ( Fig. 2E ). Metaventrite smoothly shiny, vestiture of simple, closely spaced setae becoming denser in area between meso- and metacoxae. Abdomen: Wider than long, narrowed posteriorly ( Fig. 1A, B ). Aedeagus with dorsal diaphragm large, centrally positioned within disc; parameres absent; distal process narrow; distal surface with patches of short, erect setae ( Fig. 3D ). Elytra: Subtrapezoidal ( Fig. 1A ), base much narrower than apex; foveae and striae absent; surface smoothly shiny, covered with evenly spaced, spatulate setae ( Fig. 1A, B ). Legs: Simple, elongate, unmodified except protibia with transverse sulcus in apical third.

Female. Externally similar to male. Eye slightly smaller, approximately 25 facets. Lacking transverse sulcus on protibia.

Etymology. The specific name honors our colleague and friend Alexey Tishechkin, histerid expert and myrmecophile enthusiast, who collected several specimens of the type series.

Biological Information. All specimens were collected by either flight intercept traps or a Winkler extractor, so the biology of the species is unknown. However, we think it highly likely that B. tishechkini is a myrmecophile or possibly a termitophile based on a suite of morphological features. The extensive loss of foveae, sulci, and striae to produce a smooth cuticle is a trait common to many inquilinous Pselaphinae ( Chandler 2001) . The spatulate setae closely match the form of known pselaphine myrmecophiles such as the trogastrine Jubogaster Parker and Maruyama ( Parker and Maruyama 2013) and some myrmecophilous aleocharines such as Phyllodinarda Wasmann. The robust, nearly moniliform antennae, composed of compact antennomeres, are also a feature of numerous pselaphine myrmecophiles and termitophiles ( Chandler 2001). Moreover, B. tishechkini is strikingly similar in appearance to Loeblibatrus yunnanus Yin , a myrmecophile of Ectomomyrmex Mayr in China ( Yin 2018). In the absence of molecular data from Loeblibatrus , we presently hypothesize that this close similarity is the outcome of convergent evolution in response to selection inside social insect colonies, rather than from shared ancestry.

Comments. No further specimens of this genus were recovered despite searching in the following museum collections that have extensive holdings of Neotropical pselaphine material: FMNH, American Museum of Natural History, New York , Snow Entomological Museum Collection, Kansas, Natural History Museum, London, UK, and the personal collection of Donald Chandler ( University of New Hampshire) .

Figures

Fig. 1. Batriscydmaenus tishechkini, holotype male. A) Dorsal habitus, B) Lateral habitus.

Fig. 2. Batriscydmaenus tishechkini, confocal images of male paratype. A) Head, lateral view, arrow indicates ocular-mandibular carina, B) Head, dorsal view, with apically notched scape and laterally notched palpomere 4 (arrow) indicated, C) Labrum with four setae (arrow) on epipharynx, D) Prothorax, lateral view, boxed region enlarged in D’ to show spatulate setae; E) Mesoventrite with foveae labeled according to their possible homology to the pselaphine foveation pattern of Chandler (2001): ppf = prepectal fovea; lmvf = lateral mesoventral fovea; mmvf = median mesoventral fovea; MCC = anterior edge of mesocoxal cavity, F) Protarsus (apical tarsomere enlarged in F’ to show tarsal claws) and apical protibial region showing transverse sulcus (arrow).

Fig. 3. Batriscydmaenus tishechkini, male. A) Prosternum showing single, large procoxal cavity (PCC), with circular margin indicated; the intercoxal process (ICP) is recessed inside the procoxal cavity, B) Foreleg with tibial sulcus (arrow); C) Protarsus with projections of bifid anterior tarsal claw (arrows), D) Aedeagus.