Ephydrolithus Giron & Short, 2019

Giron, Jennifer C. & Short, Andrew Edward Z., 2021, The Acidocerinae (Coleoptera, Hydrophilidae): taxonomy, classification, and catalog of species, ZooKeys 1045, pp. 1-236 : 1

Genus Ephydrolithus Giron & Short, 2019 Figs 2 , 5 , 30F-I , 31

Ephydrolithus Girón & Short, 2019: 122.

Gender.

Masculine.

Type species.

Ephydrolithus hamadae Girón & Short, 2019: 130; by original designation.

Diagnosis.

Small beetles, body length 1.8-3.3 mm. Body shape oval in dorsal view, moderate to strongly convex in lateral view (Fig. 31 ); with ground punctation usually moderately marked. Color yellowish brown to dark brown, usually uniform across body regions (Fig. 31 ). Shape of head trapezoid. Eyes relatively small, at most only slightly emarginated anteriorly, usually moderately projected from outline of head. Clypeus trapezoid, with anterior margin from broadly to only slightly emarginate. Labrum fully exposed. Mentum with strong median anterior depression sometimes limited by low transverse carina; surface of mentum mostly smooth and undulated. Antennae with nine antennomeres; cupule slightly asymmetric, with rounded outline. Maxillary palps short, nearly 2/3 width of head, and stout (Fig. 31C ); inner margin of maxillary palpomere 2 nearly straight, outer margin strongly curved along apical half. Elytra without sutural striae, and only rarely with impressed striae; ground punctures moderate to sharply marked, uniformly and rather densely distributed; systematic punctures slightly larger and deeper than remainder punctures; serial punctures usually not clearly differentiated; outer margins of elytra only slightly flared (Fig. 31A, D ). Prosternum flat, sometimes only slightly elevated along longitudinal midline (Fig. 31C ). Posterior elevation of mesoventrite either with transverse ridge, or with well-developed tooth that extends anteriorly as longitudinal carina; anapleural sutures concave, separated at anterior margin by distance nearly 0.3 × anterior margin of mesepisternum. Metaventrite densely pubescent, except for large median teardrop-shaped glabrous patch (Fig. 31C, F ); anteromedian area of metaventrite with a deep and narrow transverse depression before anterior intercoxal process. Protibiae with spines of anterior row hair-like, semi erect, relatively long and thick (Fig. 31C ). All tarsomeres bearing long apical hair-like setae on dorsal face, and two lateral rows of hair-like spines on ventral face of tarsomeres 2-4. Posterior femora mostly glabrous, with few scattered setae along basal half to basal 2/3, with hydrofuge pubescence along anterodorsal margin (Fig. 31C, F ); tibial grooves well-developed, sometimes covered by hydrofuge pubescence. Fifth abdominal ventrite apically truncate, with stout setae. Aedeagus trilobed (Fig. 30F-I ), with outer margins convex, straight or sinuate, with basal piece 0.45-0.9 × length of parameres; median lobe somewhat triangular in shape, with well-developed lateral basal apodemes; apex of median lobe widely to narrowly acute, sometimes “pinched”; parameres nearly as long as median lobe; well-developed gonopore, preapically situated.

Differential diagnosis.

Ephydrolithus can be distinguished from most Neotropical acidocerines by their mostly glabrous metafemora. From other genera exhibiting the same condition, such as Quadriops ( Girón and Short 2017), Ephydrolithus can be distinguished by the entire (as opposed to divided; Fig. 11C ) eyes; from Tobochares ( Kohlenberg and Short 2017), Ephydrolithus can be differentiated by the number of antennomeres (nine in Ephydrolithus , eight in Tobochares ).

Distribution.

Neotropical: Brazil ( Bahía, Minas Gerais); Fig. 5 .

Natural history.

All known species are exclusively associated with rock seepages (e.g., Fig. 9 ; Girón and Short 2019).

Larvae.

Immature stages are not known for the genus.

Taxonomic history.

Ephydrolithus was only recently described.

Remarks.

In the etymology section of the original publication, Girón and Short (2019) indicate that the genus name is neuter, which is erroneous. The name is masculine, which is the gender for the Greek word lithos, the last component of the genus name. Four species of Ephydrolithus have been described until now, all of them from southeastern Brazil.

Species examined.

Holotypes and paratypes of all known species were examined for this study. We have also seen specimens of additional undescribed species.

Selected references.

Girón and Short 2018: original description of the genus and all its known species; Short et al. 2021: phylogenetic placement.

Figures

Figure 2. Phylogeny of the Acidocerinae simplified from Short et al. (2021), indicating the distribution, preferred habitat, and currently described number of species for each genus. For habitat, filled black circles indicate that at least some species of the genus are commonly found in this habitat; light grey circles indicate the genus has been found in this habitat, but is rare or not typical for the group; white circles indicate no species have been recorded for the genus in this habitat.

Figure 5. Known distribution of genera of Acidocerinae: Crucisternum, Ephydrolithus, Globulosis, Helobata, Helochares, Helopeltarium, Katasophistes, and Nanosaphes.

Figure 9. Examples of seepage habitat for Acidocerinae A, B marginal seepage along river (Guyana: GY 14 - 0312 - 01 B) C, D isolated seep on granite inselberg (Venezuela: VZ 10 - 0710 - 01 A) E, F hygropetric zone next to waterfall (Venezuela: VZ 12 - 0122 - 03 A).

Figure 11. Head of miscellaneous Acidocerinae A-D anterolateral view: A Tobochares luteomargo with white arrow pointing to straight anterior margin of eye B Tobochares emarginatus with white arrow pointing to Tobochares canthus emarginating anterior margin of eye C Quadriops politus with white arrow pointing to Tobochares canthus fully dividing the eye in dorsal and ventral faces D Batochares sp. black arrow pointing to transverse carina on labrum E-L dorsal view of head: E Batochares sp. F Helochares tristis G Crephelochares nitescens, H Chasmogenus australis with black arrow pointing to preclypeal membrane I Colossochares ellipticus J Aulonochares tubulus K Peltochares conspicuus L Helobata larvalis.

Figure 30. Aedeagi of Crucisternum, Ephydrolithus, and Globulosis spp. A C. ouboteri B C. toboganensis C C. sinuatus D C. vanessae E C. queneyi F E. teli G E. spiculatus H E. ogmos I E. minor J G. flavus. Scale bars: 0.25 mm.

Figure 31. Habitus of Ephydrolithus spp. A-C E. hamadae: A dorsal habitus B lateral habitus C ventral habitus D-F E. ogmos: D dorsal habitus E lateral habitus F ventral habitus. Scale bars: 1 mm.