Onychelmis Hinton, 1941

Linský, Marek, Čiamporová-Zaťovičová, Zuzana & Čiampor, Fedor, 2021, A revision of Onychelmis Hinton, 1941 (Coleoptera: Elmidae), with description of new species, DNA barcoding and notes on the geography of the genus, European Journal of Taxonomy 739 (1), pp. 1-35 : 5-7

Genus Onychelmis Hinton, 1941

Onychelmis Hinton, 1941: 66

(type species: Elmis longicollis Sharp, 1882 ).

Differential diagnosis

The genus Onychelmis is characterized as follows: 1) minute, obovate body with glabrous surface; 2) club-like femora; 3) pronotum shiny, without well-developed microreticulation, with deep and complete transverse depression at apical half; 4) pronotum without well-developed sublateral carinae; 5) elytra with sublateral carina on sixth interval or absent; 6) each tarsal claw with basal and subbasal tooth; 7) aedeagus without parameres; 8) ovipositor with short, noncylindrical styli.

Redescription

Male

BODY. Obovate, 1.01–1.66 mm long, 0.52–0.81 mm wide; dorsum conveX. Surface shiny with sparse, light yellowish setae. Hairy or scale-like tomentum distributed on following areas: genae, sides of prosternum, mesoventrite, metaventrite and abdomen, epipleura, and medial and lateral portions on bases of femora.

COLOUR. Head, pronotum and elytra black; venter, mouthparts, prosternum, coxae, trochanters, femora (except for black apices), tibiae, tarsi, metaventrite and abdomen pale brown to dark brown with reddish tinge; basal segments of antennae and tarsal claws pale brown.

HEAD. Narrower than pronotum, retractile, rounded, dorsally shiny. Labrum wider than long, anterolateral angles broadly arcuate with numerous golden, recumbent hair-like setae. Clypeus shorter and wider than labrum, about 3.5 times as wide as long, anterior margin slightly concave, anterolateral angles rounded. Frontoclypeal suture visible. Mandible short, moderately broad, symmetrical; apex curved with three obtuse teeth, molar part with pores. Prostheca large, entirely membranous. MaXilla with cardo and stipes moderately short. MaXillary palp 4-segmented, segments 1–3 short and wide, terminal segment almost twice as long as segments 1–3 combined. Galea elongate, as wide as maXillary palp. Lacinia about twice as wide as galea, longer than wide, subrectangular. Apex and inner side with dense, long, curved setae. Labium with submentum broad, subpentagonal; mentum transverse, as wide as submentum, very short; prementum elongate, anterior half widened, margin densely setigerous. Labial palp 3-segmented, first segment short and wide; second segment more than twice as long as first, distally widened; third segment suboval, equally wide as segments 1–2, about twice as long as second segment. Antennae filiform, 11-segmented; pedicel about twice as long as scape, remaining segments about 4 times as long as scape and pedicel combined, segments 3–10 subrectangular, subequal in length; terminal segment longest, suboval, with pointed apex. Eyes well developed, hemispherical.

THORAX. Pronotum subparallel, widest behind middle; surface shiny, with narrow reticulation along basal margin and posterolateral angles; sublateral carinae never well-developed (in several species, e.g., O. whiteheadi and O. leleupi , with a very fine raised line in basal ¼ or ½); disc conveX, divided by a broad, deep transverse impression before middle; two prescutellar foveae separated by a raised line extending from base to apical discal half, connecting both halves and merging into them; anterior margin arcuate; posterior margin bisinuate; sides of pronotum convex before and after transverse constriction; lateral margins narrowly rimmed; posterolateral angles orthogonal; anterolateral angles slightly produced. Hypomeron finely microreticulate, widest in middle. Prosternum moderately long in front of procoxae, with anterior margin concave; sides raised around procoxae, forming carinae, not reaching anterior margin, prosternal process long, moderately broad and with posterior margin broadly rounded. Mesoventrite coarse, short and wide, with deep triangular groove for reception of prosternal process; posterior margin around mesocoxae raised. Metaventrite slightly wider than long, shiny with setigerous punctures; disc conveX with medial, triangular depression in posterior half; discrimen in basal ¾; with one prebasal fovea with setal tufts on each side of metaventrite ( Fig. 5 ; foveae or depression indistinct in a few species, e.g., O. onorei sp. nov. and O. minor sp. nov.). Elytra conveX, widest in anterior ¾; sides strongly declivous; surface shiny, with dense tiny punctures; elytral margin narrowly rimmed; humeri indistinctly to broadly produced; epipleuron tapering posteriorly. Prominent sublateral carina on siXth interval reaching ⅘ of elytron length present or absent. Elytra with ten more or less visible rows of punctures, impressed coarsely and deeply to completely absent. Scutellum subovate, flat. Legs moderately long; femora clavate, markedly widened in middle; tibiae longest, apically with cleaning fringe. Tarsi 5-segmented, first four segments each with one fine pale, recumbent seta, fifth segment slightly shorter than remaining segments combined; claws with a large subbasal and smaller basal teeth.

ABDOMEN. With 5 ventrites. First ventrite with basal margin broadly rounded; fifth ventrite longest, apically setose. Aedeagus elongate; parameres absent; phallobase parallel-sided.

Female

Externally similar to male, except metaventrite without distinct medial, triangular depression in posterior half and without two prebasal foveae, fifth ventrite is more elongate ( Fig. 4B ) and eXtension of femoral

tomentum is usually greater. Ovipositor with short, noncylindrical stylus.

Distribution

Known from Central and South America; presence of Onychelmis specimens is reported in at least eight countries: Colombia, Costa Rica, Ecuador, Guatemala, Honduras, Panama, Peru and Venezuela ( Fig. 12B ).

Key to the species of Onychelmis

1. Carina on sixth elytral interval absent .............................................................. O. splendida sp. nov.

– Carina on sixth elytral interval present ............................................................................................. 2

2. Body size larger than 1.30 mm ......................................................................................................... 3

– Body size smaller than 1.30 mm ....................................................................................................... 5

3. Males with profemoral tomentum reaching around half ( Fig. 6A ) .............. O. leleupi Delève, 1968

– Males with profemoral tomentum at base ( Fig. 6C, H ) .................................................................... 4

4. Smaller size (CL: 1.35–1.37 mm); apex of penis broadly rounded with medial projection ( Fig. 8C ) ................................................................................................................................. O. lobata sp. nov.

– Larger size (CL: 1.65–1.66 mm); apex of penis trilobate ( Fig. 7A ) ................................................... .......................................................................................... O. whiteheadi Spangler & Santiago, 1991

5. Humeri produced ( Fig. 3C, E ) .......................................................................................................... 6

– Humeri feebly developed ( Figs 2A , 3F ) ........................................................................................... 7

6. Elytral punctures absent; penis lanceolate ( Fig. 10A ) ........................................... O. lenkae sp. nov.

– Elytral punctures shallowly impressed; penis with rounded, medially projected apex ( Fig. 9A ) ...... ................................................................................................................................. O. onorei sp. nov.

7. Smaller size (CL: 1.01–1.07 mm); elytral punctures reduced; males with mesofemoral tomentum reaching below apex ( Fig. 6E ); apex of penis rounded with medial projection ( Fig. 10C ) ............... ................................................................................................................................. O. minor sp. nov.

– Larger size (CL: 1.27 mm); elytral punctures moderately impressed; males with mesofemoral tomentum reaching around middle ( Fig. 6D ); penis lanceolate ( Fig. 7C ) .......................................... ................................................................................................................ O. longicollis ( Sharp, 1882)

Figures

Fig. 5. Venter and metaventrites of male Onychelmis spp. A, C. O. lenkae sp. nov., paratype, ♂ (PUCE). B. O. splendida sp. nov., paratype, ♂ (PUCE). Arrows show setal tufts. Scale bars: A = 0.5 mm; B–C = 0.3 mm.

Fig. 4. Fifth ventrite of O. lobata sp. nov. A. Male. B. Female. Scale bar = 0.1 mm.

Fig. 12. Distribution map of Onychelmis Hinton, 1941. A. New species described within this study. B. Published records of Onychelmis and potential distribution of the genus.

Fig. 6. Tomentum on pro- and mesofemora of Onychelmis spp. A. O. leleupi Delève, 1968. B. O. lenkae sp. nov. C. O. lobata sp. nov. D. O. longicollis (Sharp, 1882). E. O. minor sp. nov. F. O. onorei sp. nov. G. O. splendida sp. nov. H. O. whiteheadi Spangler & Santiago, 1991. Drawings are schematic, bodies are divided to identical halves: left = male, right = female (note: females unknown for D and H).

Fig. 8. Aedeagi of Onychelmis spp. A. O. leleupi Delève, 1968, ventral view. B. O. leleupi, lateral view. C. O. lobata sp. nov., ventral view. D. O. lobata sp. nov., lateral view. Scale bar = 0.1 mm.

Fig. 7. Aedeagi of Onychelmis spp. A. O. whiteheadi Spangler & Santiago, 1991, ventral view. B. O. whiteheadi, lateral view. C. O. longicollis (Sharp, 1882), ventral view. D. O. longicollis, lateral view. Scale bar = 0.1 mm.

Fig. 3. Habitus of Onychelmis spp. A. O. leleupi Delève, 1968, ♂ (PUCE). B. O. lobata sp. nov., holotype, ♂ (PUCE). C. O. onorei sp. nov., holotype, ♂ (PUCE). D. O. splendida sp. nov., holotype, ♂ (PUCE). E. O. lenkae sp. nov., paratype, ♂ (PUCE). F. O. minor sp. nov., holotype, ♂ (PUCE). Scale bar = 0.5 mm.

Fig. 2. Habitus of Onychelmis spp. A–B. O. longicollis (Sharp, 1882), holotype, ♂ (NHM). A. Dorsal view. B. Ventral view. C–D. O. whiteheadi Spangler & Santiago, 1991, holotype, ♂ (NMNH). C. Dorsal view. D. Ventral view. Scale bar = 0.5 mm.

Fig. 10. Aedeagi (A–D) and ovipositor (E) of Onychelmis spp. A. O. lenkae sp. nov., ventral view. B. O. lenkae sp. nov., lateral view. C. O. minor sp. nov., ventral view. D. O. minor sp. nov., lateral view. E. O. leleupi Delève, 1968, ovipositor, ventral view. Scale bars = 0.1 mm.

Fig. 9. Aedeagi of Onychelmis spp. A. O. onorei sp. nov., ventral view. B. O. onorei sp. nov., lateral view. C. O. splendida sp. nov., ventral view. D. O. splendida sp. nov., lateral view. Scale bar = 0.1 mm.