Elachistelmis, Maier, Crystal A., 2012

Maier, Crystal A., 2012, Elachistelmis gen. n. (Coleoptera: Elmidae: Elminae) from Suriname, with description of two new species, Zootaxa 3500, pp. 61-69 : 62-63

Elachistelmis gen. n.

( Figs. 1 –26)

Type species: Elachistelmis tetramera , sp. n.

Diagnosis. This genus can be distinguished from all other elmid genera by the following combination of characters: 1) small size (ca. 1.0– 1.2 mm), 2) pronotum with sublateral carinae and lacking depressions ( Figs. 10 & 13 ), and 3) the presence of a narrow band of plastron setae on the lateral edge of each elytron ( Fig. 21 ).

This new genus keys to couplet number 14 in Manzo (2005). Elachistelmis resembles Neolimnius in that it has a very long lacinia and galea ( Fig. 1 ), but differs in the degree of pronotal sculpturing, size, and overall body shape and sculpturing. Elachistelmis also has a thin band of plastron setae laterally on the elytron ( Fig. 21 ), which Neolimnius lacks. Additionally, members of this genus were found in samples with numerous specimens of Neoelmis spp. The two genera are rather similar in body size and shape, but they can quickly be separated by the presence of a transverse pronotal depression with lateral foveae in Neoelmis spp., and the absence of this character in Elachistelmis spp.

Description. Body elongate, moderately convex ( Figs. 10 & 13 ). Integument with sparse setae; color testaceous, rufo-testaceous, or rufus, often with lighter testaceous patches at elytral humeri, embracing umbone ( Figs. 9 & 12 ). Plastron distributed dorsally between lateral border and carina; body ventrally with plastron setae laterally on all abdominal ventrites, meso- and metaventrites.

Head prognathus, capable of being partly retracted into prothorax but not beyond the basal portion of the submentum ( Figs. 11 & 14 ) microreticulate. Eye hemispherical, separated by a distance three times the radius of eye.. Antenna with eleven antennomeres, with apical antennomere spindle-shaped, three times as long as penultimate antennomere (Fig. 24). Maxillary palpus with four palpomeres, distal palpomere turbinate, with patch of sensilla apically ( Fig. 1 ). Lacinia elongate, with row of stout, curved spines medially ( Fig. 1 ). Galea elongate, three segmented ( Fig. 1 ). Labial palpus with three palpomeres, apical palpomere spindle shaped, with two parallel elongate sensory patches ( Fig. 2 ). Labium ovate, sparsely clothed with setae ( Fig. 2 ). Labrum broadly rounded; anterior margin without distinct emargination, sparsely clothed with stout setae ( Fig. 4 ). Frontoclypeal suture absent.

Pronotum quadrate, with two strong longitudinal sublateral carinae diverging anteriad; lateral edges broadly rounded, with distinct carinae; base broadly sinuate on each side of scutellum; anterolateral angles acute; posterolateral angles acute ( Figs. 10 & 13 ). Disc of pronotum lightly sculptured, lacking depressions. Hypomeron without plastron (Fig. 23). Scutellum flat, wider than long, rounded trapezoidal in shape. Elytron with sparse long setae; with seven longitudinal rows of weak punctures; without accessory row of punctures; with two strong longitudinal carinae overlapping the fourth and sixth puncture rows, area between carina and lateral margin with dense plastron ( Fig. 21 ). Elytral apex truncate, explanate ( Figs. 10 & 13 ). Prosternum long in front of procoxae, about two times as long as prosternal process ( Figs. 19 & 23); lateral margins microreticulate; prosternal process expanded behind procoxae. Disc of prosternum smooth. Mesoventrite microreticulate, short, ending just behind mesocoxae. Metaventrite long, clothed with setae of plastron; with deep longitudinal groove medially. Legs with visible portion of procoxae globular and trochantin not visible. Tibiae of all legs with apical cleaning fringe of tomentum. All tarsi with four or five tarsomeres. Claws prominent and without teeth.

Abdomen with five ventrites; ventrites covered by setae of plastron, glabrous medially. First ventrite with paired, broad carinae behind metacoxae extending halfway to posterior border of first ventrite (Fig. 22). Second ventrite of male with paired median putative sensilla (Fig. 22). Apical ventrite with two short, curved hooks laterally.

Female. Externally similar to male (tend to be larger in size), lacking two ventrally produced tubercles (sensilla) medially on second abdominal ventrite.

Etymology. Elachistelmis from the Greek “elachisto” meaning “smallest”, from its diminutive size, and “elmis”, from the family name, Elmidae . The gender is feminine.

Remarks. All known specimens were collected at a blacklight in Suriname.

Figures

FIGURES 1 – 4. Elachistelmis tetramera, n. sp.: 1. Maxilla; 2. Labium; 3. Mandible; 4. Labrum. Scale bar = 0.05 mm.

FIGURES 9 – 14. Elachistelmis tetramera, n. sp.: 9. Habitus, dorsal view, showing coloration; 10. Habitus, dorsal view, SEM; 11. Habitus, ventral view. Scale bar = 0.5 mm. Elachistelmis tetramera, n. sp.: 12. Habitus, dorsal view, showing coloration; 13. Habitus, dorsal view SEM; 14. Habitus, ventral view. Scale bar = 0.6 mm.

FIGURES 15 – 21. Elachistelmis tetramera, n. sp.: 15. Mesotarsus; 16. Interior of elytron, showing spines; 17. Metatarsus; 18. Head, vental view; 19. Prosternum; 20. Lateral border of elytron; 21. Elytron, showing long tuberculate setae of dorsal plastron.