Laccodytes americanus Peschet, 1919

Toledo, Mario, Spangler, Paul J. & Balke, Michael, 2010, Taxonomic revision of the Neotropical diving beetles genus Laccodytes Régimbart, 1895 (Coleoptera: Dytiscidae), Zootaxa 2347, pp. 37-58 : 46-50

Laccodytes americanus Peschet, 1919

Figs (3, 5, 10, 13, 16–21, 30, 46, 56, 62)

Laccodytes americanus Peschet (1919: 145) ; Blackwelder (1944: 74). Laccodytes americana (sic!) Peschet: Nilsson (2001: 239).

Type locality. French Guyana: Charvein, Saint-Laurent de Maroni.

Type material. Syntype 3 ( MNHN, Peschet collection): Guyane francaise, St. Laurent de Maroni // TYPE // Museum Paris // Laccodytes americanus . According to Peschet, there are altogether 2 male and 5 female types in his collection. One male syntype was studied and illustrated by Paul Spangler in 1980, and we base our redescription of L. americanus on his notes and USNM specimens which agree well with the notes on the syntype. Specimens were not available from the MNHN for study any more, due to shortage of staff at that institution.

Other material studied. Guyana: Mazaruni-Potaro District, Takutu Mountains, 6°15'N 59°5'W, Earthwatch research expedition, 6.–18.XII.1983, P.J. Spangler, W.E. Steiner & R.A. Faitoute (20 exs USNM, NMW); same but 6°15'N 58°55'W, 19.XII.1983 (1 ex. USNM).

Suriname: Commewijne, Akintosoela, Celos camp, 39 km SE Suriname river bridge, road to Redi Doti, 40 m, 5°16'17''N, 54°55'15''W, 1.VII.1999, Z.H. Falin, SUR1F99 140 ex: uv light trap (2 exs. KUL) Venezuela: TF Amazonas, Cerro de la Neblina, basecamp, 140 m, 0°50'N 66°10'W, 27.I.1985 & 19.II.1985, P.J. Spangler, P.M. Spangler, R. Faitoute, W.E. Steiner (33 exs CMT, USNM, ZSM); Puerto Ayacucho, 37 km SE Rio Gavilan, 20.II.1986, P.J. Spangler & W. Sanchez (16 exs USNM).

Diagnosis. Habitus ( Fig. 30 ). Body length 2.3–2.4 mm. Body slightly drop-shaped, tip of elytra almost truncate, but still with rounded angles. Hind angle of pronotum rounded.

Color ( Fig. 30 ). Head ferruginous, sometimes slightly darkened laterally along the eyes. Pronotum yellow; base darker, middle of base dark brown to blackish, sometimes medially with dark band extending over disc of pronotum to reach the foremargin; foremargin also sometimes appearing slightly darkened; Venezuelan specimens only with middle of pronotal base blackish. Elytron blackish with contrasting yellow marks: a subbasal transverse band; usually a small to moderately large medio-discal patch; and an apical mark. The subbasal band reaches the margin and the anterior angle of elytron. The medio-discal patch is absent in some Guyana specimens, but usually visible; it is rather large in the Venezuelan individuals studied. Appendages and venter yellowish to ferruginous; metaventrite darker, brownish.

Sculpture. Head with MR consisting of small polygonal meshes; few punctures visible, the diameter of which equals that of the cells. Pronotum with very faint MR and numerous longitudinal lines, or shallow cuts. Elytron with MR as on head; no punctures visible but longitudinal lines which are, however, less distinct than on pronotum. SEM images reveal that the MR consists of networks composed of tiny serial cuticular holes and the lines are made by similar, but smaller holes, densely packed; also setae are surrounded by concentrically arranged tiny holes ( Figs 17, 18 ). Metaventrite rather shiny, with faint MR and few punctures; postcoxal process with MR; metacoxal plates with numerous rather diagonally orientated irregular longish cells (40x), giving the impression of a dense diagonal striation ( Figs 19, 20 ). The SEM (540x) images reveals indeed long lines, which actually consist of tiny holes (1830x); the same is true for the meshes on metaventrite, which are also in fact networks composed of tiny serial cuticular holes ( Fig. 21 ).

Structures. Pronotum with narrow lateral bead. Prosternum and base of prosternal process with small ridge; prosternal process broadly carinate and with a short, needle-shaped, acute tip ( Fig. 5 ). Elytra apically rounded. Epipleuron broad up to level of sternite 6 or 7. Hind margin of sternite 7 different in male and female (see below). Metatarsomeres 1–4 with apicolateral angle distinctly lobed ( Fig. 13 ). Hind lobes of metacoxal process straight, truncate, with only a slight medial incision ( Fig. 10 ).

Male. Pro- and mesotarsi not dilated. Hind margin of sternite 7 slightly concave in the middle ( Fig. 56 ). Aedeagus ( Fig. 46 ): median lobe apically with a slender, flat process, as long as about 1/3 of its length. Parameres visibly different in sizes, both club-shaped, apparently without apical setae.

Female. Sternite 7 ( Fig. 56 ) normally rounded on both sides, hind margin with a narrow, deep U-shaped emargination in the middle.

Distribution ( Fig. 62). French Guyana, Guyana, Suriname, Venezuela.

Biology. In Guyana, the species was collected at blacklight in a forest clearing, close to a stream, and in a stream. Venezuelan specimens were seined from rocks in the rapids of Rio Baria, some 30 specimens from Cerro de la Neblina were picked by hand from leaf packs taken from a stream.

Figures

FIGURES 28 – 39. Subschematic body shape and colour patterns: 28) Laccodytes apalodes; 29) L. rondonia; 30) L. americanus; 31) L. phalacroides; 32) L. takutuanus; 33 a – 33 b) L. neblinae (variation of elytral patterns); 34) L. bassignanii; 35) L. obscuratus; 36) L. olibroides; 37) L. androginus; 38) Laccodytes sp. 1.; 39) Laccodytes sp. 2.

FIGURES 17 – 25. SEMs of MR in some Laccodytes species: 17) detail of elytron of L. americanus (magn. 2100 x); 18) idem, (magn. 2600 x); 19) metacoxa (MTX) and metaventrite (MTS) of L. americanus; 20) idem, detail at higher magnification; 21) idem, detail of metaventrite (MTX) at higher magnification; 22) detail of elytron of L. apalodes; 23) detail of metacoxa of L. apalodes; 24) idem, detail at higher magnification; 25) detail of metacoxa of L. neblinae.

FIGURES 3 – 16. SEMs of some Laccodytes species structures: 3) segments 1 - 3 in male protarsus of L. americanus; 4) prosternal process of L. apalodes; 5) idem, L. americanus; 6) idem, L. neblinae; 7) metaventrite of L. apalodes, the arrow indicates the groove in which the tip of prosternal process fits; 8) idem, L. neblinae; 9) metacoxal process of L. apalodes; 10) idem, L. americanus; 11) idem, L. neblinae; 12) hind tarsus of L. apalodes (male); 13) idem, L. americanus (male); 14) idem, L. neblinae (female); 15) ovipositor of L. apalodes; 16) idem, L. americanus.

FIGURES 54 – 61. Last abdominal segment (left male; right female) in Laccodytes species: 54) L. apalodes; 55) L. rondonia; 56) L. americanus; 57) L. phalacroides; 58) L. takutuanus; 59) L. neblinae; 60) L. bassignanii; 61) Laccodytes sp. 1 female.

FIGURES 44 – 47. Male genitals in Laccodytes species: 44) L. apalodes: a) median lobe of aedeagus in lateral view, b – c) right and left parameres; 45) L. rondonia: idem; 46) L. americanus: idem; 47) L. phalacroides: a) apical half of median lobe of aedeagus in dorsal view, b) median lobe in lateral view, c – d) right and left parameres;