Two new light attracted rove beetle species of Astenus Dejean, 1833 (Coleoptera: Staphylinidae: Paederinae) from Kerala, India

: Two new light attracted species of rove beetles of the genus Astenus Dejean, 1833 ( Astenus keralensis sp. nov. and Astenus rougemonti sp. nov.) from Malabar coastal plains of northern Kerala in southern India are described, illustrated, and compared to closely related species. First report of Astenus kraatzi Bernhauer, 1902 from Indian mainland and a checklist and key to all 41 species of Astenus recorded from the Indian mainland are provided.


INTRODUCTION
Genus Astenus belongs to the subtribe Astenina Hatch, 1957, of tribe Lathrobiini Laporte, 1835 (Staphylinidae: Paederinae). The genus Astenus Dejean, 1833 is cosmopolitan (Cameron 1931) with 468 extant species described across the world (Newton 2020). It is easily recognizable from related genera by having head more or less expanded before eyes. Other diagnostic features being, rather small and slender habitus; reticulate-umbilicate sculpture of the integument; head comparatively large with respect to pronotum; narrow neck; labrum emarginate with two small teeth; long, slender, curved and pointed mandibles; and the bilobed penultimate tarsomere (Cameron 1931).
Thirty-nine species of Astenus are recorded from the Indian Mainland, with 19 of them being described by Cameron (1914Cameron ( , 1919Cameron ( , 1920Cameron ( , 1931Cameron ( , 1943. Cameron (1931) gave brief descriptions and keys to 25 species of Astenus from the Indian Mainland. After Cameron (1931), only 11 new species of Astenus were added to the Indian species list; three by Cameron (1943) himself, three by Coiffait (1982), four by Biswas & Sen Gupta (1983), and one by Biswas (2003) -with all records from northern India. There is very little work on Astenus species from southern India with only 14 species recorded with 13 of them being reported by Cameron (1931) and one by Fauvel (1904).
Two new species of Astenus (A. keralensis sp. nov. and A. rougemonti sp. nov.) are described from the Malabar coastal plains of northern Kerala in southern India. A revised and modified taxonomic key and checklist to Astenus of Indian mainland is provided along with first records from Indian mainland and from southern India. Notes on endemism, biogeographical affinities and remarks on taxonomy of Astenus are also discussed.

Specimen collection and treatment
The specimens mentioned in this paper were collected as part of a three year (2017-2019) survey on Staphylinidae conducted in the entire northern Kerala region, specifically in the Western Ghats forest regions and scattered and isolated ranges of Malabar coastal plain moist deciduous forest. The rove beetle specimens, which were later identified as new species, were collected using low intensity UV light traps (SAFS) from isolated patches of forests in Chelari (11°06'40.6"N 75°54'14.1"E ) and University of Calicut campus (11°13'40"N, 75°89'52"E ) located in Malabar coastal plains of Malappuram District in Northern Kerala. Collected specimens were transferred to 75% ethyl alcohol, were cleared using 10% KOH and were dissected to study the male genitalia. Species level identification was performed using new taxonomic key prepared based on type descriptions and key to species in Cameron (1931). Specimens and dissected genitalia were examined and measured under a Leica M205C stereozoom microscope. Images were taken using a Leica MC 170 HD microscope camera and enhanced using the Leica Application Suite V4.12.
The type specimens are deposited in Zoological Survey of India, Western Ghats Regional Center, Kozhikode, Kerala, India (ZSIK).

Abbreviations
The following abbreviations were used for measurements (in mm): Length of antenna (AL), head length from anterior margin of clypeus to posterior margin of head (HL), head width (excluding eyes) (HW), length of pronotum (PL), maximum width of pronotum (PW), maximum length of elytra from base to apex (EL), maximum width of elytra (EW), length of aedeagus from apex of ventral process to base of median lobe (ML), total body length (TL). Colour: Head brownish-black, antennomeres I-IV dark brown and rest pale reddish-yellow; mouth parts infuscate; pronotum reddish-brown; elytra black with posterior margin in sharp contrast with distinct broad yellowish band, wider at the middle of each elytron and narrowed medially and laterally; scutellum reddishbrown; abdominal tergites III-V reddish, VI and VII dark brown, VIII dark brown with reddish posterior margin, apex of the femora dark brownish-black, fore and middle tibiae dark brownish-black, tarsi entirely yellowish; setae entirely black.

Taxonomy
Head: Elongate, rugose, closely punctate and reticulate, disc bulged at the middle, posterior angles widely rounded, tempora with several black setae, head in front of the eyes more or less parallel, eyes prominent; antennae long, all joints longer than wide, antennomeres III-X sub equal, XI longer.
Neck: 1/5 th width of head. Pronotum: Shield like, furnished with longitudinal rugae, narrower than head, gradually expanded until about 2/3 from base, then narrowed toward neck; anterior half of pronotum on each side with five black setae; posterior margin rounded. Elytra: Glossy, wider but shorter than pronotum, narrowed at apex and base, strongly and closely punctate, having regular pubescence and several large setae.

Description
Measurements ( Colour: Head and pronotum dark reddish-yellow; elytra bicoloured with anterior half black and posterior half with pale reddish-yellow transverse band slightly extended anteriorly along the suture, sutural line yellowish posteriorly and black in anterior 1/3 rd ; abdominal tergites dark reddish-yellow, VI th abdominal tergite with intersegmental membrane yellow, VII th abdominal tergite mostly brownish-black with posterior margin pale reddish-yellow; antennae, legs and mouthparts pale reddish-yellow; setae black.
Head: Elongate and somewhat rectangular, quite umbilicate reticulate sculpture, head in front of the eyes parallel, two pairs of anterolateral punctures with black, short and stout setae, post ocular region moderately rounded bearing three black, short and stout setae and several long slender decumbent setae, posterior margin more or less straight; labrum short and wide with two distinct teeth and two very long yellow setae, eyes bulged, antennae long, almost reaching the base of pronotum, scape broader at the apex, second antennomere shortest, III-X sub equal, XI slightly longer.
Neck: 1/3 rd width of head. Pronotum: Convex, shorter and narrower than head, distinctly narrowed anteriorly and posteriorly, widest at 1/3 rd ; sculpture almost similar to head but broader, space between is more "s" like; antero-lateral margin of pronotum with long erect setae.
Elytra: Glossy, finely pubescent, longer and wider than pronotum, as wide as long. Lateral margins with seven long oblique setae and numerous small setae. Anterior half more densely punctate than posterior half. Elytra narrowed apically.
Abdomen: Pubescence fine and dark, base of abdomen narrower than elytra.
Aedeagus: Median lobe narrowed from basal half to the apex, apical region pointed and curved.
Female: Unknown Etymology: The species is named in memory and honour of late Guillaume de Rougemont, a very charming personality and a man who loved rove beetles, who guided us with the taxonomy of the genus Astenus.
Differential diagnosis: Astenus rougemonti is close to A. leptocerus (Eppelsheim, 1895) based on the colour pattern of elytra, but differs in having only the V th visible abdominal tergite (VII th tergite) black (in A. leptocerus all the abdominal tergites are black). It is also close to Astenus horridus Rougemont, 2018, an endemic of Borneo but differs from it in following characters; slightly smaller (TL 4.80 mm in A. horridus) VI th abdominal tergite (IV th visible tergite) not dark (VI th abdominal tergite dark in A. horridus), yellow fascia of elytral apex widening towards the suture (yellow fascia of elytral apex not widening towards the suture in A. horridus). Sculptures on the pronotum broader than on head and the space between is more's' like (sculptures on pronotum as on head in A. horridus).
Twenty-three species (including the two new species described; seven species endemic to the eastern Himalaya; five of the seven species (except A. hindostanus Cameron, 1919;A. kraatzi Bernhauer, 1902) endemic to the Western Ghats and Sri Lanka hot spot of biodiversity; four species endemic to the Kashmir Himalaya; and five other species (A. gratus Cameron, 1931;A. marginalis Cameron, 1931;A. pulchripennis Cameron, 1931;A. semibrunneus Cameron, 1931;A. tanicus Biswas & Sen Gupta, 1983)) are endemic to the Indian mainland (Table 1).

First Reports
Astenus kraatzi Bernhauer, 1902, which had distribution records only from Sri Lanka, is recorded for the first time from the Indian mainland (India: Kerala: Chelari, 11.1112778N, 75.9039166E) and two species, A. flavus (Kraatz, 1859) and A. indicus (Kraatz, 1859) are recorded for the first time from southern India.
Taxonomic status of Astenus subnotatus Fauvel, 1904: Fauvel described Astenus subnotatus as a variation of A. melanurus (Küster, 1853) and it was considered as a variation by Cameron (1931) also. Later the paratype of A. subnotatus (with locality given as Bedford Cape, South Africa) was wrongly re-described as A. itremo Lecoq, 1996 (a species with distribution only in Madagascar), which is evident from the paratype label (Royal Belgian Institute of natural Sciences). As per the current classification A. subnotatus is having

23.
Astenus setiferidus Newton, 2017 Endemic to the Indian mainland (WG)*     Cameron, 1931 13 (Fauvel, 1879) verified species status with Oriental, Palaearctic, and Afrotropical distribution (Newton 2020). Distribution of Astenus flavus (Kraatz, 1859): Kraatz (1859) described A. flavus as Sunius flavus with data on distribution given only as "Oriental India (Ind. Or.)" which could be anywhere in British India. Later Newton (2020) gave its distribution as confined to eastern India and Nepal. This work reports A. flavus form southern India with recorded distribution from the Western Ghats.