Lachnodacnum Orchymont, 1937

Clarkson, Bruno, Albertoni, Fabiano Fabian & FIKÁýEK, Martin, 2014, Taxonomy and biology of the bromeliad-inhabiting genus Lachnodacnum (Coleoptera: Hydrophilidae: Sphaeridiinae), Acta Entomologica Musei Nationalis Pragae 54 (1), pp. 157-194 : 160-167

Lachnodacnum Orchymont, 1937

Lachnodacnum Orchymont, 1937: 134 .

Type species. Lachnodacnum saundersi Orchymont, 1937 , by original designation.

Diagnosis. Eyes small, rounded in dorsal view (Fig. 3); labial palpomere 2 bearing dense brush of long setae on inner face and distal margin; pronotum weakly convex, anterior corners rounded, posterior corners weakly angulate; hypomeron with large pubescent inner portion and moderately wide marginal glabrous portion (Fig. 26); mesoventrite well-divided from anepisternum 2 except sublaterally, anepisternal suture distinct medially and laterally (Figs 27, 34); preepisternal plate widely attaching and as high as anterior portion of metaventral process, forming a mesometaventral keel, constricted at the area where meso- and metaventrite join each other ( Figs 24 , 33 í36); anteromedian pit-like groove large, well developed (Fig. 27); grooves for reception of procoxae not de¿ned (Figs 27, 34); elytron weakly convex, sutural stria very ¿ne but distinct, developed only on elytral apex (Fig. 30); mesofemur pubescent on ventral surface ( Fig. 29 ); metatarsus slightly compressed laterally, metatarsomere 1 about twice as long as metatarsomere 2; aedeagus with rather long and well developed symmetrical phallobase ( Figs 15 í16); parameres wide throughout; median lobe wide basally, with a pair of short basal projections, more or less gradually narrowing apicad; gonopore distinct, subapical.

Redescription. Body widely oval, weakly convex in lateral view; pronotal and elytral outline continuous in dorsal and lateral views ( Figs 1 í2, 9í10).

Head. Clypeus wide even anteriorly, only slightly narrowing before eyes, with anteromedian margin truncate (Fig. 3). Frontoclypeal suture conspicuous; lateral portions of frons between anterior margin of eye and frontoclypeal suture lacking punctuation. Eyes small (Fig. 3), not protruding laterad, rounded in dorsal view, surrounded by micropunctures, separated by 7× the width of one eye, distinctly emarginated anteriorly in lateral view. Clypeus and frons with scattered trichobothria. Labrum small, membranous, concealed under clypeus. Maxillary palps with four palpomeres, short and rather stout. Mentum (Fig. 25) 1.4× as wide as long; lateral margins nearly parallel-sided, each side bearing a row of setae [examined in L. luederwaldti only, poorly preserved in available specimens of L. saundersi ]; anterior margin deeply bisinuate; surface of mentum bearing sparsely distributed long setae. Labial palps with three palpomeres: palpomere 2 longest, strongly widened distally, bearing dense brush of long setae on its inner face and distal margin; palpomere 3 much narrower and about 0.6× as long as palpomere 2. Submentum pubescent. Gula slightly constricted between tentorial pits, bearing low longitudinal carina in posterior half [examined only for L. luederwaldti ] (Fig. 25). Antenna with nine antennomeres (Fig. 28); scapus rather long and thick, its basal portion bent dorsally; pedicel cylindrical; antennomere 3 twice the length of antennomere 4, antennomeres 3í5 narrower than pedicel proximally, slightly widened distally; cupula long and wide, bare, concealing basal portion of antennomere 7; antennal club loosely segmented, depressed dorsoventrally, densely pubescent with few longer and thicker setae on sides and on distal margins of antennomeres.

Prothorax. Pronotum weakly convex, with a bead on anterior and lateral margins including antero- and posterolateral corners; anterior corners rounded, posterior corners weakly angulate; posterior margin slightly arcuate; pronotal trichobothria present sublaterally. Prosternum not carinate medially, weakly convex (Fig. 26). Procoxal cavities large, open posteriorly, anterolateral aperture of procoxal cavity open (Fig. 26). Hypomeron with large pubescent inner portion and moderately wide marginal glabrous portion.

Mesothorax. Mesoventrite fused with anepisternum 2 sublaterally, anepisternal suture deeply concave, distinct medially and laterally (Figs 27, 34); epimeron 2 well delimited, divided from anepisternum 2 by a suture, pubescent; anterior collar of mesothorax broad, well demarcated. Mesoventrite highly elevated medially into preepisternal plate; widely attaching metaventral process ( Figs 24 , 33 í36); mesoventral process as high as metaventral one in lateral view; anteromedian pit-like groove large, well developed. Grooves for reception of procoxae not de¿ned. Elytron weakly convex, without longitudinal series of larger punctures ( Figs 1 , 9); elytral trichobothria present (Fig. 32); sutural stria very ¿ne but distinct, developed only on elytral apex (Fig. 30). Epipleuron ( Fig. 24 ) wide and strongly inclined throughout, reaching elytral apex; inner pubescent portion (= ‘epipleuron’) very wide anteriorly, strongly narrowing towards the level of posterior coxae. Mesocoxal cavities transverse, narrowly divided medially by meso-metaventral plate.

Metathorax. Metaventrite with pubescent surface, slightly elevated into narrow, longitudinal bare plate medially; median plate projecting anteriorly into long and narrow metaventral process joining mesoventral plate to form a meso-metaventral keel ( Fig. 24 ), the keel constricted at the area where meso- and metaventrite join each other. Median bare portion of metaventrite with scattered punctures, punctures densely arranged in anterior half and on posterior margin; punctation of posterior half of the keel sparser than on anterior half, posterior half with weak longitudinal groove. Metepimeron rather large with long posterior projection. Hind wigs ( Fig. 11 ) with R-M loop distally the maximum width of the wing; RA 3+4 not attached to RA basally, forming a opened radial cell; radial cell large, subtrapezoidal, pigmented on anteroapical half; r3 absent; r4 developed, connecting RA 3+4 to R-M loop; apical ¿eld with RA 3 well de¿ned, short, not reaching the margin of the wing apically; RA 4 fused with RP 1, together forming a pigmented area almost reaching wing margin apically; base of RP 1 far of R-M loop; RP 2 forming a pigmented area wide on base, almost reaching R-M loop basally but not reaching edge of the wing apically; RP 3+4 well de¿ned, narrow and long, arising from R-M loop basally, curved posteriad and reaching wing margin apically; medial ¿eld with medial spur rather long, narrow and sharp; MP3+4 present, weakly developed, nearly connected with MP 1+2, not attached to MP 3 and MP 4 +CuA 1; MP 3 and MP 4 +CuA 1 well de¿ned, not connected to basal portions of the veins proximally, reaching wing margin posteriorly; CuA 1 strongly reduced, without connection with MP 3+4, MP 3 and MP 4 +CuA 1; CuA 2 present and well de¿ned, reaching the posterior edge of the wing apically; CuA 3+4 absent and hence wedge cell missing; AA 3 and AA 4 strongly de¿ned and long, nearly reaching posterior margin of the wing; anal ¿eld with venation strongly reduced, composed of a short AP

3+4

and nearly inconspicuous AP

1+2

.

Legs. Procoxa globular, pubescent; profemur with deep tibial groove delimited by low ventral and high dorsal ridges, ventral surface pubescent except for small bare distal area; protibia cylindrical, bearing series of stout spines and irregularly arranged small spines, distal portion bearing “crown” of smaller stout spines and two large spurs. Mesotrochanter slightly sinuate on posterior margin; ventral surface of mesofemur pubescent in basal 0.75 ( Fig. 29 ), reticulate; tibial groove deep, developed throughout, delimited by high ventral and low dorsal ridges; mesotibia flattened, sparsely covered by short and stout spines, bearing longitudinal series of larger spines and a subapical transverse series of larger spines; distal apex with series of short spines and two long spurs on inner margin. Metatrochanter slightly sinuate on posterior margin, pubescent; metafemur large and wide, ventral surface bare except of sparsely arranged setae on extreme anteroproximal portion, surface reticulate with scattered setiferous punctures; tibial groove well developed, deep, delimited by high ventral and low dorsal ridges. Metatibia flattened, bearing scattered short spines and two series of larger spines on outer margin, and a series of larger spines on inner margin on ventral surface; distal portion with transverse series of moderately long spines and two long spurs on inner margin. Tarsi much shorter than tibiae, each tarsomere bearing a dense brush of long setae ventrally, with longer setae sideward and with a single to few long setae dorsally. Metatarsus slightly compressed laterally, metatarsomere 1 about twice as long as metatarsomere 2; claws small, simply arcuate.

Abdomen. With ¿ve ventrites, all ventrites flat, without any longitudinal carina; posterior margin of ventrite 5 without apical notch nor the median group of stout setae.

Male genitalia. Aedeagus ( Figs 15 í16) with rather long and well developed symmetrical phallobase; parameres wide throughout; median lobe wide basally, with a pair of short basal projections, more or less gradually narrowing apicad, gonopore distinct, subapical. Sternite 9 wide basally, bearing rather narrow tongue-shaped median projection, lateral struts arcuate, slightly shorter than median portion.

Figures

Figs 1í10. General habitus of adults and larvae of Lachnodacnum Orchymont, 1937. 1í3 – adults of L. luederwaldti Orchymont, 1937 (1 – dorsal view, 2 – lateral view, 3 – dorsal view of the head). 4í8 – larva of L. luederwaldti (4 – third instar larva in dorsal view; 5 – same in ventral view; 6 – ¿rst instar in dorsal view; 7 – detail of head and thorax of third instar, dorsal view; 8 – same, ventral view). 9í10 – adults of L. saundersi Orchymont, 1937 (9 – dorsal view, 10 – lateral view).

Figs 11í14. Morphological details of Lachnodacnum Orchymont, 1937 and Phaenostoma Orchymont, 1937. 11í12 – hind wings (11 – Lachnodacnum luederwaldti Orchymont, 1937; 12 – Phaenostoma urichi (Scott, 1912)). 13í14 – detail of spiracular atrium of the third instar larva of L. luederwaldti.

Figs 15í17. Aedeagus. 15 – Lachnodacnum luederwaldti Orchymont, 1937; 16 – L. saundersi Orchymont, 1937; 17 – Phaenostoma urichi (Scott, 1912).

Figs 24í28. Adult morphology of Lachnodacnum luederwaldti Orchymont, 1937, SEM micrographs. 24 – whole beetle, ventral view; 25 – head, ventral view; 26 – prothorax in ventral view (prosternum and hypomeron); 27 – lateral portion of mesoventrite (arrow indicates the anepisternal suture); 28 – antenna.

Figs 29í32.Adult morphology of Lachnodacnum luederwaldti Orchymont, 1937,SEM micrographs.29 – mesofemur; 30 – apical portion of elytra; 31 – microsculpture of the clypeus; 32 – trichobothrium on the elytron.

Figs 33í36. Mesoventral elevation of Lachnodacnum Orchymont, 1937, SEM micrographs. In ventral (33í34) and lateral (35í36) views. 33, 35 – L. luederwaldti Orchymont, 1937; 34, 36 – L. saundersi Orchymont, 1937 (arrow indicates the anepisternal suture).