Onychelmis whiteheadi Spangler & Santiago, 1991,

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: 9-11

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Onychelmis whiteheadi Spangler & Santiago, 1991


Onychelmis whiteheadi Spangler & Santiago, 1991 

Figs 2View Fig C–D, 6H, 7A–B, 12B

Onychelmis whiteheadi Spangler & Santiago, 1991: 495  , figs 1–2.

Differential diagnosis

Onychelmis whiteheadi  can be distinguished from other species of the genus by the combination of the following characters: 1) larger size (CL: 1.65–1.66 mm); 2) pro- and mesofemora with tomentum at base ( Fig. 6HView Fig); 3) humeri produced; 4) prominent carina on sixth interval present; 5) elytral punctures shallowly impressed; 6) apeX of aedeagus trilobate ( Fig. 7View Fig A–B).

Material examined

Holotype COLOMBIA • ♂; “ COLOMBIA: [CUND.]: Río Cachéta near Bogota, 26 Feb 1984, Maria T. Szauer // [red] HOLOTYPE Onychelmis whiteheadi Spangler  & Santiago.”; NMNH. 

Paratype COLOMBIA • 1 ♂; “ COLOMBIA: [CUND.]: Río Cachéta near Bogota, 26 Feb 1984, Maria T. Szauer // [blue] PARATYPE Onychelmis whiteheadi Spangler  & Santiago.”; NMNH  .



BODY. Obovate, black ( Fig. 2View Fig C–D); length 1.65–1.66 mm; width 0.79–0.81 mm; dorsum conveX, glabrous, 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 dark brown to black; coxae, femora and tarsi dark brown with reddish tinge; trochanters and tibiae brown; basal segments of antennae and tarsal claws pale brown.

HEAD. Partly retractable into prothoraX, dorsally shiny. 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. Labrum with anterior margin very slightly emarginate medially; 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 almost straight. Eyes well developed, HW: 0.31–0.32 mm, ID: 0.15–0.16 mm, suboval in lateral view, protruding from head outline in dorsal view, circumocular surface raised. Frons convex between eyes.

THORAX. Pronotum widest behind middle, PW: 0.47–0.48 mm, PL: 0.51–0.54 mm; surface shiny, with narrow reticulation along basal margin and posterolateral angles, with dense tiny punctures; sublateral carinae never well-developed, but a short, very fine raised line in basal ¼ present; 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, wrinkled, more or less shiny with setigerous punctures; disc convex with deep, medial, triangular depression in posterior half; discrimen in basal ¾; in males with one prebasal fovea on each side. Elytra (EL: 0.12–0.15 mm, EW: 0.79–0.81 mm) conveX, widest in anterior ¾; sides strongly declivous; surface shiny, with dense tiny punctures; elytral margin narrowly rimmed; humeri protruding from outline; epipleuron tapering posteriorly. Prominent carina on siXth interval in ⅘ of elytron. Elytra with ten rows of small, shallowly impressed punctures, separated by 2–4 times puncture diameter, diminishing toward lateral margins and elytral apeX. Scutellum subovate, flat. Legs moderately long; femora clavate; tibiae longest. Protibiae with anterior cleaning fringe on apical ⅓; mesotibiae with two cleaning fringes – anterior on apical ⅕ and posterior on apical ⅓; metatibiae with posterior cleaning fringe on apical ⅓. 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, with posterior margin broadly arcuate. Aedeagus ( Fig. 7View Fig A–B) elongate. Penis without fibula; corona below apeX, well developed; in ventral view concave, from apical half widening toward laterally projected, apically nearly acute sides, apical margin medially with wide arcuate projection; in lateral view thick, evenly narrowed from base to curved apex, with apical sides pointing backwards. Parameres absent. Phallobase about 1.5 times as long as penis, subparallel, distal portion markedly narrowed, in ventral view straight, curved in lateral view.




Known only from the type locality in Cundinamarca, Colombia ( Fig. 12BView Fig).


USA, Washington D.C., National Museum of Natural History, [formerly, United States National Museum]


Smithsonian Institution, National Museum of Natural History














Onychelmis whiteheadi Spangler & Santiago, 1991

Linský, Marek, Čiamporová-Zaťovičová, Zuzana & Čiampor, Fedor 2021

Onychelmis whiteheadi

Spangler P. & Santiago S. 1991: 495