Hydrodessus keithi, Miller, Kelly B., 2016

Miller, Kelly B., 2016, Revision of the Neotropical diving beetle genus Hydrodessus J. Balfour-Browne, 1953 (Coleoptera, Dytiscidae, Hydroporinae, Bidessini), ZooKeys 580, pp. 45-124 : 79-81

Taxon classification Animalia Coleoptera Dytiscidae

Hydrodessus keithi sp. n. Figs 1, 5, 19, 37, 50

Type locality.

Ecuador, Pastaza, Provinica Tzapino, 32km NE Tigueno, 1.183°N, 77.233°W.

Diagnosis.

Hydrodessus keithi has very characteristic coloration with the pronotum redi with testaceous margins and the elytra dark testaceous with distinctive maculae (Fig. 19A). There is a large subrectangular yellow macula at the humeral angle and a large subtriangular yellow macula at about 3/4 length of the elytron (Fig. 19A). The ventral surfaces are black. The lateral elytral carina is short and present only at the humeral angle (Fig. 19B). The prosternal process is relatively slender with moderately well-developed lateral lobes anteriorly (Fig. 19C). The metaventrite carinae are distinctive and strongly divergent posteriorly (Fig. 19C). The male median lobe in lateral aspect is slender and broadly curved with the apex subapically constricted on the ventral margin and apically sharply pointed (Fig. 19D). In ventral aspect, the apex is bilaterally symmetrical, broadly expanded and broadly rounded (Fig. 19E). The lateral lobe is large, broad and broadly sinuate with the apex broadly rounded (Fig. 19F). Males and females are dimorphic with the female apicolateral margin of the elytron distinctly flanged (Figs 5B, 19A1).

Description.

Measurements. TL = 2.6-2.9 mm, GW = 1.2-1.3 mm, PW = 1.0-1.1 mm, HW = 0.8 mm, EW = 0.5 mm, TL/GW = 2.1-2.2, HW/EW = 1.6. Body elongate, lateral margin conspicuously discontinuous between pronotum and elytron (Fig. 19A).

Coloration (Fig. 19A). Head yellow to yellow-brown, darker anterolateraly. Pronotum medially broadly yellow, laterally and posteriorly dark red. Elytron medially with broad, longitudinal black region subtending suture, medially with black or red-black region connecting to lateral margin of elytron, otherwise yellow, elytral coloration appearing as four, large, yellow maculae. Antennae and palpi yellow. Legs yellow except coxae, including metacoxae, black. Venter black except abdominal ventrites V and VI lighter, red-yellow and elytral epipleuron lighter yellowish apically.

Sculpture and structure. Head apically broadly subtrunctate, clypeus somewhat swollen laterally near eyes; surface covered with fine punctures; eyes large, conspicuous. Pronotum cordate, broadest near anterior margin (Fig. 19A), lateral bead slender; surface covered with fine punctures, somewhat rugulose anterolateraly. Elytra together elongate, apically slightly pointed (Fig. 19A); lateral carina inconspicuous, rounded, extending about ¼ length of elytron (Fig. 19B); elytral surface evenly covered with fine punctures. Prosternum medially carinate, with fine, long setae on each side of carina; prosternal process broad, lateral margins somewhat sinuate, broadest anteriorly with prominent lateral lobes, apex trunctate, longitudinally excavated (Fig. 19C). Metaventrite with anterior process prominent, parallel-sided, long; metasternal carinae inconspicuous, low, represented posteriorly by impunctate line, extending to near anterior ends of metacoxal lines (Fig. 19C); other surfaces covered with fine punctures. Legs with surfaces covered with fine punctures; metatibia with distinctive brush of dense, elongate setae on postero-apical surface; pro- and mesotibiae conspicuously broad; metatrochanter moderately offset, apex angulate; metacoxa evenly covered with fine punctures; metacoxal lines moderately broadly separated, subparallel and anteriorly slightly divergent (Fig. 19C). Abdomen evenly covered with fine punctures.

Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect broadly curved, with basal portion short and subtriangular, apical portion elongate slender and broadly curved, apically with ventral margin broadly sinuate, subapically expanded, and with apex slender and pointed (Fig. 19D); in ventral aspect slender, medially constricted, apically expanded and apex broadly rounded (Fig. 19E). Lateral lobe broadly sinuate, broad basally, apical portion more slender and evenly curved ventrad, apex narrowly rounded and with a small cluster of setae (Fig. 19F).

Female genitalia. Gonocoxosternite triangular, medial margin straight, apical portion small (Fig. 37). Gonocoxa with apical portion slender, elongate triangular, anterior apodeme short (Fig. 37). Bursa short and broad; spermathecal duct slender, moderately short; receptacle semispherical; spermatheca undifferentiated from fertilization duct, without spermathecal spine, this combined structure extremely long and coiled, tapering to apex of fertilization duct (Fig. 37).

Sexual dimorphism. Male pro- and mesotarsi I–III more broadly expanded than female and ventrally with several large adhesive setae; female with elytron prominently expanded and lobate subapically (Figs 5B, 19A2), male evenly curved (Figs 5A, 19A1); male abdominal seternite VI evenly rounded across surface, apex with minute pointed lobe apically, female with prominent lateral depression on each side of VI.

Variation. Specimens are somewhat variable in coloration with some relatively lighter and others relatively darker.

Etymology.

This species is named keithi in honor of the author’s brother, Keith B. Miller.

Distribution.

Hydrodessus keithi has been found in Ecuador, Colombia and central Brazil (Fig. 50).

Habitat.

This species has been collected from blacklight traps. Nothing else is known about their habitat.

Specimens.

The holotype is in USNM labeled, "ECUADOR,Past. Prov.,Tzapino, 22May76ele.400m Jeffrey Cohen blacklight trap/ 1°11' S– 77°14'W 32KmNE Tigueno/ ECUADOR-PEACE CORPS. SMITHSONIAN INSTITUTE AQUATIC INSECT SURVEY/ HOLOTYPE Hydrodessus keithi Miller, 2016 [red label with black line border]."

Paratypes, 24 total. Brazil, Para, Rio Gurupi, 12-15km E Caninde Igarape Coraci, 19 Dec 1965, B. Malkin (1, FSCA). Colombia, Meta, Villavicencio, National University Biological Station, 4.15°N, 73.633°W, 8 Jan 1973, blacklight trap, C.R. Gilbert (1, USNM). Ecuador, Napo, Limocha on Rio Napo, 0.737°S 78.111°W, 10 Nov 1974, BLT, B.A. Drummond (4, FSCA); Provincia Tzapino, Pastaza, 32km NE Tigueno, 1.183°N, 77.233°W, 22 May 1976, blacklight trap, Ecuador Peace Corps Smithsonian Institute Aquatic Insect Survey, 400m, J. Cohen (18, USNM).