Oulimnius echinatus Berthélemy

Jr, Fedor Č Iampor, Ová, Zuzana Č Iamporová-Za Ť Ovi Č & Kodada, Ján, 2009, Description of the larva of Oulimnius echinatus Berthélemy (Coleoptera: Elmidae: Elminae), Zootaxa 1984, pp. 57-60 : 57-59

Oulimnius echinatus Berthélemy

( Figs 1–11 )

Description of the larva. Habitus ( Fig. 1 ). Length 2.80–2.90 mm, greatest width 0.70 mm. Dorsal side dark gray, ventral side paler; areas around eyes, antennae and legs except coxae pale yellow, mouth parts and apex of ninth abdominal segment darkened to brown. Body elongate, tapering posteriorly; moderately convex dorsally, almost flat ventrally, subtriangular in cross-section. Biforous spiracles present laterally on mesothorax and abdominal segments 2–8. Integument with dense setose granules and sparse longer pale hairs ( Figs 8 , 14).

Head ( Fig. 2 ) dorsoventrally flattened, sides subparallel in posterior portion, prognathous, partially retracted into prothorax; frontoclypeal plate without granules, epicranial plates and genae granulated, granules with small scales.

Epicranial and frontoclypeal sutures present. Stemmata small, clustered laterally, exposed cuticular capsula. Gula short. Antenna three-segmented ( Fig. 3 ); scape widest, subapically with short tufted setae; pedicel slender, elongate, about three times as long as scape, with sparse elongate scales and apical setae; flagellum setiform, apex with central elongate sensilum surrounded by short scale-like sensilla; sensorium subacute, almost three times as long as flagellum. Labrum about 1.6 times wider than long, glabrous, with longer sensory hairs and tufted scales ( Fig. 5 ); anterior margin shallowly emarginate in the middle. Clypeus wide. Mandible ( Figs 6, 7 ) subtriangular, palmate, with apex tridentate; incisor area with long straight articulated setose process; mola absent; penicillus well developed; outer margin smooth, with two moderately long setae; ventral condyle rounded. Maxilla ( Fig. 4 ) slender; cardo small subtriangular, with moderately long branched seta; stipes elongate, smooth, slightly narrowed anteriad, with one long sublateral seta and few short, forked scales; galea shorter than lacinia, both lobes apically with acuminate setae; palpifer oblique, maxillary palpus shorter than galea. Labium elongate ( Fig. 4 ). Prementum narrow, short, subtriangular between palpi; ligula setose. Postmentum undivided, glabrous, with few scales and two pairs of sublateral sensilla, apical angles slightly excavate with elongate pegs; labial palpi short, last segment globular. apex excavated with sensory field.

Thorax. Protergum ( Fig. 8 ) ca 1.5 times wider than long, widest before base, depressed mediolaterally, mesal longitudinal carina tuberculate; disc with dense setiferous tubercles and few long hairs; anterior margin feebly convex; posterior margin almost straight, rimmed with elongate, apically excavated setiferous tubercles; sides convex with setiferous tubercles. Meso- and metatergum about 3 times as wide as long, about half as long as protergum. Venter of thoracic segments (Fig. 12, 13) with: basisternum and sternellum subtriangular; episternum and epimeron moderately wide; pleural suture well impressed; laterotergites narrow. Legs well developed, with serrate setae and several long sensory hairs. Fore-legs shortest and robust ( Fig. 9 ), mid- and hind-legs slender, similar in shape ( Figs 10, 11 ). Coxae large, partly microgranulate. Trochanter (shortest segment) subtriangular. Femur elongate, slightly widened distad. Tibia slightly longer than femur, feebly narrowed distad. Tarsungulus long, slender, acuminate, about half as long as tibia, moderately curved, with long, baso-ventral seta.

Abdomen with nine segments; tergites microgranulate on anterior portion (Fig. 14), sternites scaled on anterior portion (Fig. 15); exposed portion of tergites 1–8 with dense setiferous granules, pairs of which form distinct longitudinal mesal carina, posterior margin rimmed by elongated apically excised tubercles with tufted setae (Fig. 14); lateral margins slightly convex, with setiferous granules; segments 1–8 simple, wide and short in dorsal view, similar in shape, subequal in length; segments 1–7 with distinct pleura (Fig. 15) and subquadrate sternum; segments 8–9 with sclerites fused. Segment 9 trapezoidal, elongate, about 1.9 times as long as wide; apex feebly emarginate, with numerous robust hairs (Fig. 16). Ventral operculum subpentagonal, almost 1.5 times as long as wide, tapering in posterior third, depressed along midline, sides rimmed by setae, anterior margin rounded; apical opercular claws well developed, long and slender (Fig. 17).

Differential diagnosis. The most important diagnostic feature of O. echinatus is its geographical distribution, as it is endemic to the Balearic Islands. Morphologically it resembles more O. jaechi and O. fuscipes than O. tuberculatus or O. troglodytes . From O. jaechi and O. fuscipes it differs in the denser dorsal granulation, the less prominent setiferous tubercle on the posterior angles of tergites, and the absence of mesal setiferous tubercle on tergites and/or ventrites.

Figures

FIGURES 1 – 11. Oulimnius echinatus larva, 1) habitus; 2) head, dorsal view; 3) antenna, dorsal view; 4) labium and maxillae, ventral view; 5) labrum, dorsal view; 6) right maxilla, ventral view; 7) right maxilla, dorsal view; 8) protergum; 9) left fore-leg, dorsal view; 10) right mid-leg, ventral view; 11) right hind-leg, ventral view; 12) ventral side of thorax (legs removed); 13) detail of lateral margin of prosternum; 14) detail of abdominal tergites; 15) detail of abdominal sternites and pleura; 16) abdominal segment 9, dorsal view; 17) apex of abdominal segment 9 with operculum, ventral view.