A second species of Cheleion from Johor, Malaysia (Coleoptera, Scarabaeidae, Aphodiinae, Stereomerini)

Abstract A new species of the genus Cheleion Vårdal & Forshage, 2010, Cheleion jendeki sp. n., from Johor, Malaysia is described, illustrated and compared with the type species of the genus, Cheleion malayanum Vårdal & Forshage, 2010. Photographs of the two species are presented. The adaptation to inquilinous lifestyle of Cheleion is compared with those in other beetle groups and briefly discussed.


Material and methods
The specimens were examined with an Olympus SZ61 stereomicroscope. Measurements were taken with an ocular graticule. The habitus photographs were taken using a Canon MP-E 65mm f/2.8 macro lens with 5:1 optical magnification on bellows attached to a Canon EOS 550D camera. Partially focused images of specimen were combined using Helicon Focus 3.20.2Pro software. External morphology of both species was also examined with a Hitachi S-3700N environmental electron microscope in the Department of Paleontology, National Museum in Prague (in both cases using uncoated specimens). Exact label data are cited for the type material. Our remarks and addenda are found in brackets, separate label lines are indicated by a slash (/), separate labels by a double slash (//). The holotype of the newly described species is deposited in the collection of National Museum, Prague, Czech Republic (NMPC). For comparison, the holotype of Cheleion malayanum (deposited in Swedish Museum of Natural History, Stockholm, Sweden) was studied. For morphological terms used in the description we largely follow Howden and Storey (1992) and Vårdal and Forshage (2010).
Type Description of female holotype. Slightly convex, integument chestnut brown; head appendages and tarsi amber coloured; whole dorsal surface more or less covered with appressed lanceolate scales ( Fig. 1).
Head (Figs 1, 3, 7) remarkably transverse, subrectangular in dorsal view, clypeus shiny, impunctate, apically pointed and reflexed under head, frons slightly convex with five straight, anteriorly divergent furrows; posterior transverse furrow across head between posterolateral corners of eyes; occiput with numerous small, longitudinal pits. Surface covered with dense appressed, lanceolate, approximately regularly spaced scales, individual scales separated from each other by less than their diameter (Fig. 7). Antennae long, length equal to width of head, with long macrosetae. Maxillary palpi length equal to length of head, with securiform ultimate palpomere. Labial palpi with long macrosetae apically. Eyes small but visible in dorsal view (Fig. 7).
Pronotum (Figs 3,9,13) large and transverse, anterior edge shallowly bisinuate, sides regularly, broadly rounded, posterior edge with broad medial protrusion. Pronotal disc with seven furrows medially, converging towards middle in hourglass  pattern, mid furrow shallower than lateral furrows (Figs 3,9). Anteromedial disc with distinctly raised knob, posteromedial disc and posterolateral sides with slightly lower, bulbous areas; anterolaterally of the furrows with large, flat elliptical depressions, de- lineated by furrows. Knob posteriorly and bulbous areas anteriorly with tufts of long dense microtrichiae (= trichomes) (Fig. 13); surface covered with dense apressed, lanceolate, approximately regularly spaced scales, individual scales separated by less their diameter from each other anterolaterally and laterally; scales on knob and bulbous areas smaller and sparser; flat lateral areas with several sparse rather irregularly spaced scales only (Fig. 13).
Elytra approximately as broad as pronotum and only slightly longer than pronotum and head combined; tapering posteriad, rounded apically. Each elytron with five longitudinal ridges before the lateral edge (Figs 1, 3, 11); ridges of approximately same height, elevated and almost continuous, consisting of longitudinal rows of almost confluent tubercles (Fig. 11); intervals (between ridges) flat, rugose, with irregularly circular pads, each pad bearing lanceolate scale on posterior edge, individual pads sepa- rated by less their diameter from each other discally, becoming confluent into small rows or groups laterally, especially in humeral area (Figs 11, 14). Epipleura broadly inflexed; posterior two thirds of lateral edge slightly recurved (to allow free movement of metathoracic legs).
In spite of clear differences mentioned above, we are aware that only single specimens are known for each Cheleion species. In addition, both type localities are placed only about 200 km apart, without any distinct barrier between them. Thus, we cannot exclude the possibility that morphological differences of C. jendeki sp. n. represent only an intraspecific variability of C. malayanum, but we consider it quite improbable.
Etymology. Patronymic; named in honour of our colleague and friend Eduard Jendek (Ottawa, Canada), excellent student in Buprestidae and collector of the holotype.
Distribution. So far known only from the type locality in the Johor Province of continental Malaysia.

Discussion
Virtually nothing is known about the biology of Stereomerini. Beetles were repeatedly supposed to be termitophilous, based on single finding of Termitaxis holmgreni  Krikken, 1970 with termites in Peru (Krikken 1970). However this genus no longer belongs to the tribe Stereomerini as it was excluded by Bordat and Howden (1995). All other members of the Stereomerini were usually collected by flight intercept traps (FIT) in primary forests, more rarely they were also sifted or attracted at UV light (Storey and Howden 1996), collected with window trunk traps, or with yellow pan traps (Howden and Storey 2000).
We have not been able to trace any "typical characters" distinguishing myrmecophilous and termitophilous beetles. For example, Crowson (1981) noted that "termitophilous beetles tend to show rather less extreme structural modifications than comparable myrmecophilous ones", and that "termitophilous beetles do not as a rule develop the elaborate trichomes seen in some of the more specialized myrmecophiles". It is far beyond the scope of this paper to solve this problem, but we would like to point out several facts that may suggest myrmecophilous association of Cheleion and other Stereomerini.
1) There exist numerous well known myrmecophilous aphodiines, especially of the tribe Eupariini (see, e.g., Stebnicka 2009;Maruyama 2010). Those beetles usually live in debris in ant nests, fly well and are frequently collected with FIT or attracted at light.
2) In rather rare cases of presence of trichomes in termitophilous scarabaeids, those structures are not recorded from the pronotum and have a quite different appearance from Cheleion (see, e.g., Maruyama 2012a,b).
institutional support from resources of the Ministry of Education, Youth and Sports of the Czech Republic. The work of J. Hájek was partly supported by the Ministry of Culture of the Czech Republic (DKRVO 2015/14, National Museum, 0002327201).