Nanosaphes, Girón & Short, 2018

Giron, Jennifer C. & Short, Andrew Edward Z., 2018, Three new genera of acidocerine water scavenger beetles from tropical South America (Coleoptera, Hydrophilidae, Acidocerinae), ZooKeys 768, pp. 113-158 : 136-138

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gen. n.

Nanosaphes gen. n. Figs 5C, D View Figure 5 ; 15 View Figure 15 , 16 View Figure 16 , 17 View Figure 17 , 18 View Figure 18 , 19 View Figure 19 , 20 View Figure 20

Type species.

Nanosaphes tricolor

Differential diagnosis.

Very small beetles, total body length 1.15-1.45 mm, width 0.7-0.9 mm. Coloration uniformly brown, to variable along the body (see Figs 15 View Figure 15 - 16 View Figure 16 ). Body shape oval in dorsal view; uniformly, slightly to moderately convex in lateral view (e.g., Figs 15F View Figure 15 , 16F View Figure 16 ). Antennae with eight antennomeres (e.g., Fig. 16G View Figure 16 ). Maxillary palps curved inward, moderately long (e.g., Fig. 16H View Figure 16 ). Each elytron with ground punctures usually only shallowly marked, seemingly forming longitudinal rows (e.g., Fig. 16E View Figure 16 ), with irregularly distributed systematic punctures bearing rather long setae, denser along lateral and posterior regions; elytra without sutural striae. Posterior elevation of mesoventrite, usually only projected as a low and short longitudinal carina between mesocoxae (Figs 5C View Figure 5 , 17A View Figure 17 ; sharply carinated and posteriorly pointed in N. hesperus ). Metaventrite with posterolateral and mesal glabrous patches (Fig. 5C View Figure 5 ). Posterior femora for the most part densely covered by setae. Fifth abdominal ventrite apically emarginated, with stout setae (Figs 5D View Figure 5 , 17C-D View Figure 17 ).

The minute size of Nanosaphes make them smaller than any other Acidocerinae in the New World, and about equal in size as the smallest Agraphydrus species in the Old World. They are among the smallest water scavenger beetles worldwide. The lack of elytral serial or sutural striae and the antennae with eight antennomeres also separate Nanosaphes from all other Neotropical Acidocerinae genera except the co-occurring Globulosis . The genus can be easily separated from Globulosis by its smaller size and narrower, more parallel sided body form (broader and almost rotund in Globulosis , see Short et al. (2017)).


Body oval, uniformly and usually weakly convex (moderately convex in N. punctatus , see Fig. 15F View Figure 15 ), coloration uniformly brown, or variable along the body (e.g., paler pronotum in N. hesperus and N. tricolor , see Fig. 16 View Figure 16 ). Head. Frons and clypeus (e.g., Fig. 16H View Figure 16 ) with shallow ground punctures irregularly distributed over the surface, accompanied by scattered seta-bearing systematic punctures; setae particularly noticeable on frons behind frontoclypeal suture; surface between punctures smooth, at most only finely reticulated along anterior and lateral margins of clypeus; anterior corners of clypeus roundly angulated; anterior margin of clypeus widely roundly emarginate. Eyes oval (e.g., Fig. 16D View Figure 16 ). Labrum rather short and wide, fully exposed and positioned nearly perpendicular to clypeus (e.g., Fig. 16B View Figure 16 ); dorsal surface convex, basally smooth, apically and laterally finely reticulated, with scattered shallow punctures; anterior margin mesally emarginate and bent inwards; anterolateral margins bearing a row of long setae. Temporae densely covered by setae (hydrofuge pubescence), with few longer setae along outer posteroventral margin of eye. Mentum nearly 1.5-1.7-times wider than long, parallel sided, basilaterally flat, with lateral oblique longitudinal ridges; anterior margin with wide, deep, concave median impression. Submentum rather flat, with sparse rather long setae; ocular ridge well-developed (e.g., Fig. 16G View Figure 16 ). Maxilla (e.g., Fig. 15G View Figure 15 ) with ventral surface of cardo and stipes smooth and shiny, with a row of stiff decumbent spiniform setae along outer dorsal margin of palpifer; limit between cardo and stipes oblique; maxillary palps yellowish, longer than antennae; palpomere 1 extending beyond base of cardo, with inner margin straight, only slightly concave at base, and outer margin distally convex; palpomere 2 similar in shape to palpomere 1, 0.7-times as long; palpomere 3 fusiform, slightly longer and wider than palpomere 1, apically widely rounded; apex of palpomere 3 bearing sensilla. Mandibles with apex bifid (examined in N. hesperus ). Labial palps yellowish, nearly as long as mentum, dorsoventrally flattened; palpomere 2 with inner and outer margin convex apicad of midpoint; palpomere 3 digitiform, markedly shorter and narrower than palpomere 2, with a long subapical seta on outer corner. Antennae (e.g., Fig. 16G View Figure 16 ) with eight antennomeres, paler than general coloration of head; antennomere 1 anteriorly swollen near anterior margin of eye, reaching midpoint of ventral surface of eye (reaching cardo-stipes joint), nearly 1.4-times longer than antennomere 2; antennomere 2 slightly longer than antennomeres 3-4 combined; antennomere 5 forming a rather small, but well differentiated cupule; antennomeres 6-8 similar in size (7 shortest, 8 longest), slightly flattened, forming a loosely articulated, pubescent club; setae at apex of antennomere 8 longer than general pubescence of club. Thorax. Pronotum widest at base, narrowed anteriorly, surface evenly convex; ground punctation shallow, uniformly sparse, with surface between punctures smooth and shiny; seta bearing systematic punctures particularly noticeable as transverse anterolateral and mediolateral bands. Scutellar shield of moderate size, triangular, nearly as long as wide, with scarce shallow punctures. Prosternum (e.g., Fig. 16G View Figure 16 ) very short, flat, at most only weakly convex, not carinate; anterior margin of prosternum mesally projected, with a preapical fringe of setae; intercoxal process truncate, aligned with posterior margin of procoxal cavities. Mesoventrite not fused to mesepisterna, with anterior margin nearly as wide as anterior margin of mesepisternum; posterior elevation of mesoventrite either flat (as in N. punctatus ), or longitudinally carinate (weakly as in N. tricolor (Figs 5C View Figure 5 , 17A View Figure 17 ) and N. castaneus or sharply as in N. hesperus ); mesepisternum obliquely widely concave; surface of mesoventrite and mesepisternum reticulated; mesepimeron narrow and trapezoid, with pubescent surface. Mesofurca (examined in N. hesperus ) with short arms, 1.3-times longer than length of mesocoxae; each arm expanding ventrally as a lamina, reaching mesoventrite; apex of arms free (not forming part of lamina), oval and explanate. Metaventrite (Fig. 5 C) posteromesally elevated, with elevation rather flat and metathoracic discrimen well defined; anterior and lateromedian surfaces of metaventrite pubescent, with median and posterolateral glabrous patches. Metepisterna 3-4-times longer than wide, slightly narrowing posteriorly. Metepimeron triangular and acute. Metafurca (Fig. 17B View Figure 17 , examined in N. hesperus ) 1.25-times wider than long, with furcal arms (fa) nearly as long as stalk (s); stalk triangular (wider near the crux (c), gradually narrowing ventrally), with paired longitudinal keels extending along basal two thirds of posterior face, and a well-developed median keel on the anterior face extending to anterior margin of dorsal sheets (ds); outer margins of stalk diverging from ventral third towards midpoint of furcal arms; furcal arms somewhat rectangular, with apex (hemiductus (h)) slightly explanate, perpendicularly positioned; anterior tendons (at) inserted along half third of dorsal edge of furcal arms; dorsal sheaths well-developed, slightly wider than widest point of lateral sheaths (ls). Elytra. Surface even (without elevations or depressions), with serial punctures seemingly longitudinally aligned, usually shallowly marked (e.g., Fig. 16E View Figure 16 ) (except in N. punctatus which has rather coarsely punctate elytra, see Fig. 15 E, F View Figure 15 ), not impressed into striae; seta bearing systematic punctures scattered along interstriae; setae of systematic punctures rather long; elytral margins simple (as opposed to explanate). Epipleura well-developed, nearly glabrous, at most with scarce setae, oblique, anteriorly wide, gradually narrowing posteriorly, extending up to line of first abdominal ventrite; pseudepipleura reduced, limited to margin of elytra. Hind wings well-developed. Legs. All femora with dense pubescence, along basal three fourths, remainder of surface glabrous and shiny; all femora antero-posteriorly flattened; metafemora with rather sharp tibial grooves along apical half. Tibiae moderately slender, rather weakly flattened, with moderately fine and sparse spines. All tarsi with five tarsomeres, bearing few long apical hair-like setae on dorsal face, and two lateral rows of spines on ventral face of tarsomeres 2-4; tarsomeres 1-4 similar in size and shape; tarsomere 5 approximately as long as tarsomeres 3-4 combined, without spines on ventral face; claws rather large, curved; empodium well-developed, bearing a pair of long, curved apical setae. Abdomen. Abdomen with five ventrites, medially longitudinally weakly convex, all ventrites with uniform, fine pubescence, either dense (as in N. tricolor , see Fig. 16C View Figure 16 ) or scanty (as in N. castaneus , N. hesperus and N. punctatus ; e.g., Fig. 16G View Figure 16 ); posterior margin of fifth ventrite mesally weakly emarginated, set with a row of thick, flat spine-like setae (Figs 5D View Figure 5 , 17C, D View Figure 17 ). Aedeagus (Fig. 18 View Figure 18 ) nearly parallel sided, with basal piece between 0.3 and 0.6-times the length of parameres; median lobe with well-developed lateral basal apodemes, wider at base than base of each paramere, usually narrower at apex than preapical width of parameres; apex of median lobe rounded; parameres from slightly shorter to longer than median lobe, and only narrowing at apex; gonopore situated beyond midpoint of median lobe.


The immature stages are unknown.


Noun in apposition. Named after the small size of the beetles (the smallest known acidocerines), with the Greek word nanos meaning little and the Greek word saphes meaning distinct, in reference to the relative ease of recognizing the species of the genus. Genus is to be treated as neutral.


Brazil ( Pará), Guyana, Suriname. See Fig. 19 View Figure 19 .


Species are associated with stream margins, particularly where there are banks for margins of sand and roots.

Characters of taxonomic importance for Nanosaphes .

In contrast to some to of the other acidocerines treated here, the known species of Nanosaphes are diagnosable by external characters alone.

Punctation. The well-marked ground and serial elytral punctures differentiate N. punctatus from the remaining species, in which the punctation is only shallowly marked.

Coloration. The most common and widespread species of Nanosaphes ( N. tricolor and N. hesperus ) have a distinctive yellow coloration on the pronotum, and can be distinguished from each other by the coloration of the head. The entire body of N. castaneus is uniform in coloration.

Posterior elevation of mesoventrite. In Nanosaphes the overall shape and sharpness of the carina formed in the posterior elevation of the mesoventrite aids species identification, where only N. hesperus has a sharp carina.

Density of abdominal pubescence. It is uncommon in the Acidocerinae that this character varies. Only Nanosaphes tricolor has densely pubescent abdominal ventrites, whereas the remainder species of the genus the pubescence is sparser.

Key to the species of Nanosaphes

1 Elytra with well-marked punctures (Fig. 15E, F View Figure 15 ); posterior elevation of mesoventrite flat N. punctatus
- Elytra with shallowly marked punctures (e.g., Fig. 15A, B View Figure 15 ); posterior elevation of mesoventrite weakly to sharply carinate 2
2 Coloration of the body rather uniformly brown (Fig. 15A-D View Figure 15 ) N. castaneus
- Coloration of pronotum yellow (see Fig. 16 View Figure 16 ) 3
3 Coloration of the head and clypeus uniformly dark brown (Fig. 16D View Figure 16 ); posterior elevation of mesoventrite weakly carinate; ventral surface densely pubescent (Fig. 16C View Figure 16 ) N. tricolor
- Coloration of the head brown, with orange clypeus (Fig. 16H View Figure 16 ); posterior elevation of mesoventrite sharply carinate; ventral surface scantily pubescent (Fig. 16G View Figure 16 ) N. hesperus