Type material

Holotype (♂): Cambodia, Battambang Prov., Sampov Lun, cave La Ang Som Nak Poa, N13°21′43.0″ E102°21′56.1″, 24.I.2018, leg. H. Steiner (182/18), SMNS.

Paratypes: Same data as for the holotype, 13 exx., SMNS. – Cambodia, Battambang Prov., Sampov Lun, cave Roung Barang Kleah 1, N13°21′42.6″ E102°21′40.1″, 25.I.2018, leg. H. Steiner (150/18), 1 ex. dry mounted (SMNS), 1 ex. stored in ethanol (SMNS-M379).

Description

Body length 3.8–4.1 mm. Body and appendages dull red-brown. Head as long as wide, widest across anterior margin of eyes. Tempora widest across posterior margin of eyes, parallel, sharply narrowed to cervix. Genae arched from posterior margin of eyes to widest part of genae, genae there arched and directly narrowed to clypeus, margins behind clypeus finely dentate. Clypeus concave, medially with small tooth pointing slightly to the right. Suborbital keel flat, indistinct. Frons and vertex without distinct impressions. Eyes completely divided by genae. Dorsal punctures large, on frons slightly confluent, diminishing towards clypeus, with fine, short, forward-oriented yellow setae. Antennae with golden setae oriented forwards, shape of antennomeres as in Fig. 1, antennomere three 1.5x as long as antennomere two. Pronotum cordiform, only slightly longer than wide, widest across anterior third, lateral margins parallel in anterior half, without distinct crenulation; anterior angles rounded, not protruding; posterior angles rectangular; anterior and posterior margins straight. Disc medially with a feeble longitudinal impression, somewhat deeper before base. Punctures dense, as large as those on head but not confluent, without distinct setae. Elytra oval, widest across middle, 1.8x as long as wide, with ten rows of punctures, size of punctures as on pronotum but more separate, punctures without setae. Alternate intervals 3, 5, 7 and 9 with distinct crenulated keels, interval 7 flattened in anterior quarter; keels with a row of distinct yellow setae pointing backwards. Humeral calli absent. Epipleura with one row of punctures over whole length. Legs covered with fine, light adherent hairs. Posterior tibiae in males slightly curved, all tibiae at inner apical third with distinct dentation (Fig. 3). Ventrites with equisized small punctures and fine setae. Aedeagus as in Fig. 4a, basale broader and about 1.5x as long as apicale, apicale broad with rounded apex. Sternite VIII as in Fig. 4b.

Diagnosis

FouquÈ (2015) established the genus Pseudochillus, included seven species and presented an identification key. In that key, P. steineri sp. n. runs to P. thailandicus Fouquè, 2015. However, that species has vertex with a longitudinal impression, frons next to the eyes with an impression, thicker and longer setae on the head, antennomere three only slightly longer than antennomere two, anterior and posterior margins of pronotum slightly rounded, lateral margins of pronotum finely crenulated, pronotum with distinct setae, posterior tibia in males not curved, all tibiae without dentation in the inner apical third, and a completely different aedeagus [compared with figures in FouquÈ (2015)].

Etymology

Named in honour of Helmut Steiner (Hanau, Germany), collector of the type series.

Remarks

The type locality of P. thailandicus lies in northwestern Thailand (Doi Suthep, Monthathan, 650 m), far away from Cambodia.

Type material

Holotype (♂): Vietnam: Kien Luong: Hon Chong: Nui Bai Voi: grotte-hôpital de Mo So, 19/12/1994, cave, guano, by hand & pitfall trap, Louis Deharveng, Dung & Le Cong kiet leg. (sample n° VIET-045, 10.228138N, 104.616506E, alt. 4 m), SMNS (DNA extraction code SMNS-M440).

Description

Body length 4.2 mm. Body and appendages dull red-brown. Head as long as wide, widest across anterior margin of eyes. Tempora widest across posterior margin of eyes, parallel, sharply narrowed to cervix. Genae arched from posterior margin of eyes to widest part of genae, genae there arched and directly narrowed to clypeus, margins behind clypeus finely dentate. Clypeus concave, medially with a small tooth pointing slightly to the right. Suborbital keel prominent. Frons without, vertex with a feeble longitudinal impression. Eyes completely divided by genae. Dorsal punctures large, slightly confluent on frons, diminishing towards clypeus, with fine, short, forward-oriented yellow setae. Antennae with golden setae oriented forwards, shape of antennomeres as in Fig. 5, antennomere three 1.5x as long as antennomere two. Pronotum cordiform, 1.15 longer than wide, widest across the middle, lateral margins constricted in anterior half, without distinct crenulation; anterior angles rectangular, not protruding; posterior angles rectangular; anterior margin finely convex, posterior margin straight. Disc medially with a feeble longitudinal impression, somewhat deeper anterior to base. Punctures dense, of same size as those on head, partly confluent, without distinct setae. Elytra oval, widest across middle, 2.0x as long as wide, with ten rows of punctures, size of punctures as those on pronotum but more separate, punctures without setae. Alternate intervals 3, 5, 7 and 9 with distinct crenulated keels, interval 7 flattened in anterior quarter; keels with a row of short yellow setae pointing backwards. Humeral calli absent. Epipleura with one row of punctures on whole length. Legs covered with fine, light adherent hairs. Posterior tibiae curved in males, without distinct dentation on inner surface. Ventrites with equisized small punctures and fine setae. Aedeagus as in Fig. 6, basale narrow and only slightly longer than apicale, apicale narrow, parallel, finger-like, with rounded apex. Sternite VIII and spiculum gastrale as in Fig. 7.

Diagnosis

Pseudochillus honchongensis sp. n. is very similar to the only other known species from Vietnam, P. indochinensis Fouquè, 2015. However, in the latter the pronotum is slightly shorter, the anterior angles of the pronotum are rounded and the aedeagus is different in having the apicale not parallel-sided but distinctly broader across the middle and with an acute apex [compared with figures in FouquÈ (2015)].

Etymology

Named after the Hon Chong Karst in Vietnam, where the holotype was collected.

Remarks

The Hon Chong limestone hills are known to host a remarkable subterranean biodiversity (Deharveng & Bedos 1996). The type locality is already the only known collection locality of other cave invertebrates, such as the ground beetle Eustra honchongensis Deuve or the pseudoscorpion Lagynochthonius fragilis Judson (Deuve 1996; Judson 2007). Regarding Tenebrionidae only, the area hosts remarkable monospecific genera, such as Harvengia Ferrer, 2004, the only representative of the tribe Harvengiini, of uncertain affinities, or Microblattelus Ferrer, 2006, one of the three monospecific genera of the tribe Falsocossyphini Ferrer, 2006 [see Bremer (2014) for a discussion regarding this tribe].

The new species had already been reported from the cave under the name “Dichillus sp.”, in a previous work dealing with the diversity of the Hon Chong area (Deharveng et al. 2009). The area is under threat due to destruction of the hills for cement exploitation (Deharveng et al. 2009).

Remarks

A further species of Pseudochillus was collected in a cave in Thailand. This species, according to unpublished photographs (YUNCHUN LI, pers. comm.), differs distinctly from P. steineri sp. n. and P. thailandicus Fouquè, 2015.

New material

Cambodia, Battambang Prov., Sampov Lun, cave Roung Nou 2, N13°20′55.8″ E102°30′13.5″, 3.II.2018, leg. H. Steiner (039/18), 1 ex., SMNS. – Cambodia, Battambang Prov., Sampov Lun, cave La Ang Touch, N13°22′09.9″ E102°22′18.4″, 27.I.2018, leg. H. Steiner (090/18), 7 exx., SMNS (1 ex. with DNA extraction code SMNS-M374). – Cambodia, Battambang Prov., Sampov Lun, cave Roung Nou 1, N13°20′57.6″ E102°30′15.7″, 3.II.2018, leg. H. Steiner (101/18), 1 ex. dry mounted, SMNS, 1 ex. stored in ethanol, SMNS-M380. – Cambodia, Battambang Prov., Sampov Lun, cave Roung Barang Kleah 1, N13°21′42.6″ E102°21′40.1″, 25.I.2018, leg. H. Steiner (149/18), 2 exx. dry mounted, SMNS, 1 ex. stored in ethanol, SMNS-M382. – Cambodia, Battambang Prov., Sampov Lun, cave La Ang Barang Kleah 2, N13°20′41.1″ E102°21′36.4″, 8.II.2018, leg. H. Steiner (164/18), 4 exx., SMNS, 1 ex. with DNA extraction code SMNSM375. – Cambodia, Battambang Prov., Sampov Lun, cave La Ang Som Nak Poa, N13°21′43.0″ E102°21′56.1″, 24.I.2018, leg. H. Steiner (181/18), 7 exx. dry mounted, SMNS, 1 ex. stored in ethanol, SMNS-M381. – Cambodia, Battambang Prov., Sampov Lun, cave Roung Heyndan 1, N13°21′57.4″ E102°27′44.6″, 31.I.2018, leg. H. Steiner (195/18), 1 ex. SMNS. – Cambodia, Angkor Wat West, under stone outside cave, N13°24′43″ E103°51′47″, 27.III.2015, leg. J. Schönfeld, 1 ex., SMNS. – [All specimens from Thailand listed hereafter were identified by R. GRIMM.] N Thailand, Chang Mai, NNE Chang Mai, Mae Ngad Dam, 20.VIII.1995, leg. R. Grimm, 4 exx., SMNS. – Thailand, Old Sukhothai, 26.V.1999, leg. R. Grimm, 7 exx., SMNS. – N Thailand, NE San Kamphaeng Roong, Aroon Hot Springs, 28.V.1999, leg. R. Grimm, 3 exx., SMNS. – N Thailand, NE Mae Malai Mae Ngad Dam, 14.V.1999, leg. R. Grimm, 2 exx., SMNS. – N Thailand, N Chiang Mai, 8 km NE Mae Malai, W Cho Lae, 14.V.1999, leg. R. Grimm, 8 exx., SMNS. – NW Thailand, Mae Hong Son Pai, Thapai Hot Springs, 6.V.2004, leg. R. Grimm, 3 exx., SMNS.

Remarks

Ferrer & Lemaire (2019) described Gebieniella fouquei on the basis of a single female from Angkor Wat in Cambodia, illustrated the differences in external characters to G. stenosides and added an identification key to the species of the genus. Unfortunately, the aedeagi were not studied. The above-listed specimen from Angkor Wat fully coincides with G. stenosides.

Distribution

Widespread in Indochina, in and outside caves: Burma, Thailand, Cambodia (new country record), Vietnam.

Foranotum Nabozhenko & Sadeghi, 2017: Iran (Nabozhenko & Sadeghi 2017).

Eschatoporis Blaisdell, 1906: USA: California (Aalbu et al. 2017a).

Terametus Motschulsky, 1869: South Africa (Schawaller 2007).

Dichillus Jaquelin du Val, 1861: Thailand (Kaszab 1980).

Discopleurus Lacordaire: Brazil (Aloquio et al. 2019).

Gebienella Koch, 1940: Cambodia (present work).

Harvengia Ferrer, 2004: Vietnam (Ferrer 2004).

Pseudochillus Fouquè, 2015: Cambodia, Vietnam (present work).

Typhlosechus Linell, 1897: North America (Aalbu & Andrews 1985).

Leptodes Dejean, 1834: Iran, Afghanistan (Tahami et al. 2016; Kaszab 1959).

Trimytantron Ardoin, 1977: Cuba (Garrido & GutiÉRrez 1997; Peck et al. 1998).

Coeloecetes Blair, 1929: W Malaysia (Blair 1929).

Guanobius Grimm, 2008: Malaysia, Sabah (Grimm 2008).

Phayllus Champion, 1886: Venezuela (Peck & Kukalova-Peck 1989).

Eleodes (Caverneleodes Triplehorn, 1975): Mexico; USA: New Mexico, Arizona, Utah, California (Triplehorn 1975; Aalbu et al. 2012).

SpelaebiosisBousquet&Bouchard,2018(=ArdoiniaÖzdikmen, 2004): Cuba (Ardoin 1977; Peck et al. 1998).

Brises Pascoe, 1869: Australia (Matthews 1986)

Either all species or at least one species of each of the listed genera seem to have a cavernicolous mode of life. The subfamilies Diaperinae and Alleculinae are missing completely from this list, whereas the tribe Stenosini is the most diverse in caves. Although some adults are known exclusively from caves, it has not been observed whether they really live and feed in caves, including in their immature stages, or if they shelter in caves only during certain periods due to the more stable humidity conditions and, less probably, temperature conditions there. Cave tenebrionids are morphologically not highly adapted to that environment, although sometimes the eyes are reduced or completely missing. However, this condition is not found uniquely in cave-adapted species but also in species from other habitats.

Besides the listed genera, many species of the genera Megagenius Solier, 1835, Akis Herbst, 1799 and Scaurus Fabricius, 1775 have been mentioned as frequent in caves in Spain and Morocco, with some species being only known from caves (Kocher 1965; EspaÑol 1972; Labrique 1995; Decu et al. 1998). Many species have been recorded from guano in tropical caves in Cuba (see Peck et al. 1998), the genera Zophobas Dejean, 1834, Blapstinus Sturm, 1826 and Alphitobius Stephens, 1829 have been recorded in caves in Jamaica, Puerto Rico, Mexico, Australia and Venezuela (Decu et al. 1998). All these taxa are regarded as first-level troglophiles sensu Peck et al. (1998), i.e., species living also outside of caves.

The following species mentioned in Decu et al. (1998) are occasional visitors of caves, and can be found also outside caves, have their life cycle outside of caves and should not be considered troglophilic or troglobitic:

Mesostenopa cavatica Andres, 1926 (= Mesostenopa longicornis cavatica Andres, 1926) from Egypt.

Troglogeneion zapoteca Aalbu, 1985 from Mexico.

Menimopsis (= Caecomenimopsis) leleupi Kaszab, 1970 from the Galapagos Is. (Ecuador), in cave and soil.

Pterohelaeus Brême, 1842 from Australia (Johannsen's cave).

Timosmithus basilewskyi Ardoin, 1974 from Botswana (Drotsky cave).

Perdicus anthrophilus Fairmaire, 1899 from a cave in Madagascar.

Palorus cerylonoides Pascoe, 1863 [syn. P. exilis (Marseul, 1876)] from Assam (Siju cave).

Diaclina rufocincta Fairmaire, 1893 from Assam (Siju cave).

Eurychora Thunberg, 1889 from a guano cave in Angola (Furina Grande).

Praogena splendens Mäklin, 1864 and Peristeptus marginalis Gebien, 1910 from lava tubes on Mt. Suswa, Kenya.

Tenebrio guineensis Imhoff, 1843 from caves in Ivory Coast and Congo.

Cave habitats are mainly characterised by stable ecological conditions throughout the year and by extremely poor food resources. A food resource that might be suitable for tenebrionids are the fungi growing on bat guano and on washed-in rotten wood. But only the subfamily Diaperinae, which contains mainly arboreal fungus-feeding taxa, is so far unknown from caves.

It is striking that tenebrionids have only been found in caves in regions with higher average temperatures. In more temperate regions (e.g., Europe, Japan) other Coleoptera families, such as the particularly abundant and highly adapted Carabidae and Cholevidae, occur in caves.