Tritoxidium, Leschen, Richard A. B. & Löbl, Ivan, 2005

Leschen, Richard A. B. & Löbl, Ivan, 2005, Phylogeny And Classification Of Scaphisomatini Staphylinidae: Scaphidiinae With Notes On Mycophagy, Termitophily, And Functional Morphology, The Coleopterists Bulletin (mo 3) 59, pp. 1-63 : 30-31

Tritoxidium new genus

( Figs. 28–33 ) Type species: Toxidium indicum Achard

Diagnosis. Body laterally compressed. Dorsal setae reduced. Mandible with apex bifid. Galea wide and radulate. Apex of submentum trilobed. Antennomeres 3 and 4 elongate. Corbiculum absent. Pronotal and elytral carinae hidden in dorsal view. Mesepimeron present. Elytron with basal stria absent. Hind coxae separate. Profemora without ctenidium. Pro- and mesotibiae without 2 basal spines.

Description. Body. Body form somewhat laterally compressed and narrow, about 2 3 longer than wide. Dorsal setae reduced. Pronotal and elytral carinae hidden in dorsal view.

Head. Labral setae present and apically notched or frayed. Mandible with apex bifid, subapical serrations present. Maxillary palp normal, palpomere 3 with apical setae. Galea wide and radulate, with brush apical. Lateral setae of lacinia absent. Hypopharyngeal setae present and setose. Labial palps normal, palpomere 2 with 1 subapical seta; terminal palpomere inserted apically, strongly angulate. Edge of mentum straight, surface setose. Apex of submentum trilobed, surface with setae modified into spines. Maxillary ducts absent; gular pores present. Gular suture not reaching submentum. Frontoclypeal suture present. Eye notched; interocular distance small. Antennal insertion hidden; level below midline of eye. Antenna filiform; antennomeres 3 and 4 elongate; antennomeres VII–X asymmetrical. Tentorial spine present.

Prothorax. Corbiculum absent. Prosternum with anterior portion of procoxal cavity asetose; prosternal process anteriorly spinate. Anterior bead of pronotum reduced, present only laterally. Hypomeron completely visible in lateral view; apex not extended beyond hind margin of pronotum. Pronotal carina prominent and beaded. Prothoracic angle acute, extending below epipleural line and extending to anapleural suture.

Mesoventrite. Mesoventral space (prepectus) present. Mesoventral lines present and impunctate; connecting with mesocoxal cavity and parallel with mesoventral rests. Secondary lines present. Mesoventral process paxillate. Median lines absent. Mesepimeron present; length about one-third or less than full length of anapleural suture. Width of intercoxal process less than that of coxa.

Metaventrite. Metaventrite fused to mesoventrite; sulcus present externally and transverse ridge present internally. Mesocoxae round. Mesocoxal lines arcuate and impunctate; connected at middle. Setiferous patch absent; primary setae present and discal. Premetacoxal lines, descrimen, and intercoxal plate absent. Metepimeral suture punctate. Metepimeron mostly exposed. Metepimeron with longitudinal line. Metendosternal stem present. Metacoxal process digitate.

Pterothorax. Scutellum visible between elytral bases; width about one third length of pteronotum; scutellar lines type III. Hind wing present. Elytron with basal stria absent and lateral stria present; serrations present.

Abdomen. Hind coxae separate. Submetacoxal space present; submetacoxal lines parallel and punctate. Four primary setae present on disc of ventrite 1. Abdominal ventrites slightly setose. Brickwall membranes between segements 1–4 present. Paratergites of segments 4 and 6 absent. Spiracle 8 absent. Aedeagal sclerites not tripartite.

Legs. Profemora without ctenidium. Pro- and mesotibiae without 2 basal spines. Mesofemora rounded in cross-section; subapical seta not sclerotised. Tibiae smooth; length of mesotibia not less than the tarsus; outer mesotibial spines absent; two inner mesotibial spines present, subequal with largest one 2 greater than the other. Length of mesotarsomere 1 greater than 2. Metatarsi smooth. Empodium asetose.

Comments. This genus is described for Toxidium indicum Achard which is consistently placed outside the genus Toxidium in all of the phylogenetic trees. Unlike other species presently placed in Toxidium , Tritoxidium has many characters separating it from these groups, and it can be distinguished from all members of Toxidium by the presence of a trilobed submentum and a well developed mesepimeron.

We decided not to erect genera for the other two groups of Toxidium included in the data matrix, mainly because this group of laterally compressed genera deserve further study (see discussion above). The taxonomy of T. indicum was discussed by Löbl (1971, 1979). Specimens examined of Tritoxidium indicum are maintained in the MHNG.

Distribution. India (Kerala, Tamil Nadu).

Included Species. Tritoxidium indicum (Achard, 1915) , new combination.

Etymology. The genus name (gender neuter) is a combination of the genus name Toxidium and the Latin prefix tres -referring to the trilobed structure of the submentum.

Figures

Figs. 28–33. Tritoxidium indicum. 28) Dorsal and lateral habitus (scale bar ¼ 1 mm); 29) right mandible, ventral view; 30) right maxilla, ventral view; 31) labium, ventral view; 32) mentum, ventral view; 33) submentum, ventral view.