Ytu hypnos, Sampaio & Ferreira-Jr, 2018

Sampaio, Brunno Henrique Lanzellotti & Ferreira-Jr, Nelson, 2018, Five new species of Ytu Reichardt (Coleoptera: Myxophaga: Torridincolidae) and new records from Brazil, Zootaxa 4402 (3), pp. 508-524 : 512-514

Ytu hypnos sp. nov.

( Fig. 2 )

Diagnosis. Pronotum with sublateral carinae complete; first third of pronotum with an impression near sublateral carinae and a pair of oval impressions medially; posterior two thirds of pronotum with a heart-shaped impression near each lateral impression; medial carina on posterior two thirds. Elytral formula 12d(I-II,III-IV,V-VI,VII- VIII,XI-XII) + 2a(IXa,aX) + 1sl / 5d(III,V,VII,IX,XI) + 1sl(XIII); striae formed by a row of foveolate punctures and grouped in pairs, except for striae IX, X and their accessory striae. Male genitalia with parameres slightly longer than phallobase; phallus widened on apical half, in dorsal view; ventral face sinuous, apex curved toward ventral side.

Description: Holotype. Antennae black; head dark and shiny dorsally; gena light brown; pronotum dark and shiny brown; hypomeron laterally light brown ( Fig. 2a ); elytron dark brown medially; carinae shiny; ventrally light brown; legs light brown, except for the tibiofemoral joint and tarsi, which are dark brown ( Fig. 2b ). Measurements: total length: 1.85 mm; maximum head width: 0.41 mm; pronotal length: 0.35 mm; maximum pronotal width: 0.65 mm; elytral length: 1.12 mm; maximum elytral width: 0.41 mm.

Labrum subtrapezoidal ( Fig. 2c ); anterior margin bearing denticles and filiform setae; medial region of anterior margin slightly emarginate; lateral margin oblique; surface with sparse punctures on anterior half, bearing setae. Anterior margin of clypeus slightly arcuate ( Fig. 2d ); anterolateral angles and lateral margin oblique; posterior margin sinuate, feebly emarginate on lateral parts, medially projected. Head with conspicuous supra-orbital carinae, from clypeus to near the posterior margin of eyes; medial carina extending from the posterior margin of eyes, fading before the margin of clypeus; surface with a microrugose area behind the eyes. Antenna with nine antennomeres; last antennomere with a pair of apical setae. Mandibles asymmetrical ( Figs. 2e–f ); left mandible with two incisive teeth—one immobile (distal), one movable (proximal); distal incisor without denticles on inner margin; outer margin of mandible with rounded projection; in dorsal view, depressed from distal incisor to basal third, where it presents a raised V-shaped area from the projection on outer margin to the region where the movable tooth is inserted; right mandible similar to left one, but bearing only an immobile incisor. Maxilla ( Fig. 2g ) with galea and lacinia fused; with apical cuticular teeth; maxillary palp with four articles; second article three times as long as first one; third article slightly longer than second one; fourth article bearing an apical tuft of setae.

Anterior margin of pronotum sinuate ( Fig. 2a ); lateral margin oblique on first third and slightly convex on posterior two thirds; posterior margin sinuate, with a median incision; sublateral carinae extending from anterior to posterior margin; first third of pronotum with an impression near each sublateral carinae and a pair of oval impressions medially; posterior two thirds of pronotum with a heart-shaped impression near each lateral impression; medial carina more conspicuous on posterior two thirds; region between sublateral carinae and lateral margin depressed. Scutellar shield very small and diamond-shaped. Elytron with anterior margin bisinuate ( Fig. 2a ), slightly pronounced on humeral callus; lateral margin arcuate, converging to an acute apex; elytral formula 12d(I-II,III-IV,V-VI,VII-VIII,XI-XII) + 2a(IXa,aX) + 1sl / 5d(III,V,VII,IX,XI) + 1sl(XIII); striae formed by a row of foveolate punctures; complete striae are grouped in pairs except for striae IX and X, which are separated by the two accessory striae (IXa and aX); odd intervals carinate, except for first interval; carinae less conspicuous on second fourth of elytron, especially the carina on the 9th and 11th intervals, the last between accessory striae; sublateral carina strongly raised on 13th interval, beginning on second fourth of elytron, extending to the apex; epipleuron broader on anterior third, with a constriction near the hind coxae. Hind wings developed ( Fig. 2h ); margin fringed from radial hinge to anterior region of anal lobe; ScP e RA1+2 extending to radial hinge; RA3+4 beginning near radial hinge, extending toward anterior margin, just after a feeble sinuosity on anterior margin; RA3+4 delimits a pigmented area; RA4 feebly marked, fading without reaching the margin; RP feebly marked, extending shortly; r1 short, not connecting to any vein; r4 oblique; MP1+2 well marked, angulated on medial hinge, crossing rp-mp1 and rp-mp2, forming oblong cell; Cu vein parallel to MP1+2 toward posterior margin, reaching AA3, which extends to posterior margin; AA3+4 restricted to base; AP3+4 well marked, following the margin of anal lobe. Anterior margin of prosternum feebly emarginate ( Fig. 2b ); lateral margin subparallel, diverging on prosternal process; posterior margin of prosternal process slightly arcuate, with acute lateral angles; anterior margin of mesoventrite sinuate, with a medial gibbosity, which fits into an internal concavity of prothorax; lateral margin oblique; posterior margin truncate. Metaventrite with shallow depression at the discrimen, extending from anterior to posterior margin; metaventral carina complete, extending from anterior to posterior margin; metaventral tubercle absent. Procoxae with a pronounced trochantin; profemur with a shallow concavity on anterior face to fit the tibia, and a row of fine setae on posterior face; mesofemur with a row of fine setae on anterior face and a shallow concavity on posterior face to fit tibia; metacoxa with a shallow concavity on posterior face to fit femur; metafemur with shallow concavity on posterior face to fit metatibia; metatarsus 4-segmented; first and second tarsomeres with some setae on ventral side; third tarsomere longer than twice the first and second together; third tarsomere with three apical setae on ventral side; the middle setae much longer than the other two; last tarsomere longer than the third (less than 1.5× length of third tarsomere).

First abdominal ventrite with a conspicuous medial carina fading near the posterior margin; ventrites 2–5 with lateral margin raised with a fine pubescence. Male genitalia ( Figs. 2i –j ) with short parameres, slightly longer than phallobase; each paramere with a pair of apical setae, shorter than parameres; phallus widened in apical half, in dorsal view; ventral face sinuous, curved apex pointing toward ventral side.

Female: unknown.

Variation. Total length: 1.63¯ 1.85 mm; maximum head width: 0.32¯ 0.41 mm; pronotal length: 0.33¯ 0.37 mm; maximum pronotal width: 0.57¯ 0.65 mm; elytral length: 1.00¯ 1.12 mm; maximum elytral width: 0.37¯ 0.41 mm.

Comparative notes. Ytu hypnos sp. nov. is very similar to Ytu thanatos sp. nov., differing slightly in the pronotum sculpture and conspicuously in male genitalia. Ytu hypnos sp. nov. presents the skull-like raised area on pronotum, as in Ytu thanatos sp. nov., but the impressions near sublateral carinae are more conspicuously marked in Ytu thanatos sp. nov.. The phallus of Ytu hypnos sp. nov. is sinuous in lateral view and widened on distal half, dorsal view, while on Ytu thanatos sp. nov. it is arcuate in lateral view and does not present a widened area in dorsal view.

Etymology. This species is named after the Greek mythological entity Hypnos, personification of sleep and twin brother of Thanatos, in reference to a similar surface of its pronotum.

Type material: Holotype. Male. Brasil, Rio de Janeiro, São Fidelis, Serra Bela Joana, Filme d’água em pedra, 22°05’03.8”S; 41°26’05.3”W, 25.X.2009, Col.: Clarkson, B.; Cardoso-Costa, G.; Ferreira-Jr, N. [ DZRJ 5641 ] ; paratype: 1 male— Brasil, Rio de Janeiro, Guapimirim, Parque Nacional da Serra dos Órgãos, BR-116, Km 92.5 (aprox.), parede com água escorrendo, 22°28’16.8”S; 43°00’04.4”W, 15.V.2011, Col.: Ferreira-Jr, N.; Sampaio, B.H.L. [ DZRJ 5642 ] ; 1 male— Brasil, São Paulo, Ubatuba, BR-101, Km 1, 300m antes da cachoeira da escada (sentido RJ-SP), Riacho de segunda ordem, 23° 21’14.5”S; 44°46’12.1”W , 221m alt., 09.IX.2011 Col.: Sampaio, B.H.L. [DZRJ 5643].

Figures

FIGURE2. Ytu hypnos sp. nov.: a̅b: habitus, a) dorsal view, b) ventral view; c) labrum,dorsal view; d) clypeus, dorsal view; e̅f: mandibles, dorsal view, e) left mandible, f) right mandible; g) right maxilla, dorsal view; h) right hind wing, dorsal view; i̅j: aedeagus, i) dorsal view, j) lateral view.(Scale bars:a̅b:0.5 mm; c̅g: 0.1mm; h: 1 mm; i̅j: 0.5 mm).