Helvetobelba dichotoma, Mahunka, S., 1999

Mahunka, S., 1999, Oribatid mites from Switzerland, IV (Acari: Oribatida: Suctobelbidae), Acta Zoologica Academiae Scientiarum Hungaricae 45, pp. 375-381 : 376-377

Helvetobelba dichotoma sp. n.

(Figs 1-4)

Material examined - Holotype: " TI-11: Tessin: Rancate , foret de chataigniers, tamisages; 7.IX. 1965; leg. C. Besuchet." Two paratypes from the same sample , 2 paratypes: "SG-4: St. Gallen: Quinten , feuilles mortes; 17. VIII. 1999; leg. C. Besuchet." Holotype and 1 paratype in the Muséum d'Histoire naturelle, Geneva ( MHNG), 2 paratypes (1640-PO-99) deposited in the Hungarian Natural History Museum ( HNHM), Budapest, with identification number of the specimens in the Collection of Arachnida.

Measurements - Length of body: 236-260 µm, maximum width of body: 134-142 µm.

Prodorsum: Rostrum very wide, rostral setae arising medially, curved inwards, ciliate. Lateral teeth long. Margin concave behind the rostral teeth a triangular plate present under the margin (Fig. 4, marked with an arrow). Shape of tectopedial fields normal. Between them a well divided lamellar knob present, both tubercles bearing lamellar setae. A pair of weakly sclerotised costulae present in the interbothridial region. Bothridia large, also well sclerotised, with a relatively small, roundish basal apophysis. Behind each bothridium a separate, large tubercle present. Sensillus long (Fig. 1), its distal part asymmetrically incrassate, with some minute cilia.

Notogaster: Dorsosejugal margin distinct medially. Ten pairs of mostly straight notogastral setae present. All setae finely roughened.

Lateral part of podosoma (Fig. 3): Exobothridial and acetabular region well sclerotised and granulated. Exobothridial tubercles form a characteristic, longitudinal lath. Pedotecta I small, with some alveoli and a transverse line.

Ventral parts: Median part of the mental tectum well protruding anteriorly (Fig. 2). Epimeral borders and apodemes normally developed, a wide sternal field present between the epimeral plates medially. Epimeres IV normal in shape, with serrated posterior border. Setae 1c located laterally, on the surface of pedotecta I. Setae 4c arising on basal part of discidium. Anogenital setal formula: 6-1-2-3. Anterior pairs of genital setae longer than the others. Position of adanal setae normal, setae ad1 in postanal position. All setae in this region mostly smooth.

Legs: Form and chaetotaxy of legs I and IV as for the family. Setae p of tarsi II-IV spiniform. Two ventral setae of tarsus IV plumose.

Remarks: The new species is well distinguishable from all members of the Suctobelba , Suctobelbella-group by its divided lamellar knob.

Etymology: Named after the divided interlamellar knob.

Figs 1-4. Helvetobelba dichotoma gen. et sp. n. 1 = body in dorsal view, 2 = body in ventral view, 3 = podosoma in lateral view, 4 = prodorsum in dorsal v,ew. Legs not illustrated