Ephydrolithus The Acidocerinae (Coleoptera, Hydrophilidae): taxonomy, classification, and catalog of species Giron, Jennifer C. Short, Andrew Edward Z. ZooKeys 2021 2021-06-18 1045 1 236 8XL82 Giron & Short, 2019 Giron & Short 2019 Insecta Hydrophilidae Ephydrolithus CoL Animalia Ephydrolithus Coleoptera 0 1 Arthropoda genus   Ephydrolithus Giron& Short, 2019: 122.  Gender. Masculine.  Type species.   Ephydrolithus hamadae Giron& 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 xanterior 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 xlength 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.   Figure 31.Habitus of  Ephydrolithusspp. A-C  E. hamadae: Adorsal habitus Blateral habitus Cventral habitus D-F  E. ogmos: Ddorsal habitus Elateral habitus Fventral habitus. Scale bars: 1 mm.  Differential diagnosis.   Ephydrolithuscan be distinguished from most Neotropical acidocerines by their mostly glabrous metafemora. From other genera exhibiting the same condition, such as  Quadriops(  Gironand Short 2017),  Ephydrolithuscan be distinguished by the entire (as opposed to divided; Fig. 11C) eyes; from  Tobochares( Kohlenberg and Short 2017),  Ephydrolithuscan be differentiated by the number of antennomeres (nine in  Ephydrolithus, eight in  Tobochares).  Distribution.  Neotropical: Brazil ( Bahia, Minas Gerais); Fig. 5.  Natural history. All known species are exclusively associated with rock seepages (e.g., Fig. 9;  Gironand Short 2019).  Larvae. Immature stages are not known for the genus.  Taxonomic history.   Ephydrolithuswas only recently described.  Remarks. In the etymology section of the original publication,  Gironand 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  Ephydrolithushave 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.   Gironand Short 2018: original description of the genus and all its known species; Short et al. 2021: phylogenetic placement.