Lebertia (Pilolebertia) vigintimaculata Thor 1900

Lebertia (Pilolebertia) vigintimaculata Thor, 1900

Lebertia (Pilolebertia) 20maculata Thor, 1900: 272, pl. 10 figs 1–2.

Nomen dubium, probably identical with L. obscura Thor, 1900.

Missing. Type locality: Norway, “Storvandetz (Hammerfest); Hannesvand (Senjen)”; no date, no information on number of specimens, at least one female.

NORWAY • 1 ♀, 1 dn; “ 10-7-1897 Dam i Bergselv paa Hindö. Sig Thor Lebertia 20-maculata Sig Thor + NB nymfe”; slide mounted; NHMO • 4 ♂♂, 11 ♀♀; “6-7-97 Svartelv [??] Sollivand naer Bodö. Sig Thor Lebertia 20maculata Sig Thor”; of these, 2 ♂♂ and 2 ♀♀ slide mounted; NHMO • 1 ♀; “ Lebertia vigintimaculata, ♀, Hamersdengen (?) Dr. Sig Thor ges. 3.7.1897 ”; slide mounted; MNHB 1762 (see Gerecke 2009) • 1 ♀; “ K. Viets 45262; Lebertia vigintimaculata Thor / Cotype. Norwegen. Svartelv ved Bodö. 6.7.1897 S. Thor leg. 2000”; slide mounted; SMF.

Characters considered as species-diagnostic in the original description concern exclusively body colouration (Thor 1900). It was described as dark brown “with a narrow, dark dorsal line” (in Thor 1900: fig. 1, a Y-shaped line is visible; such a line, representing the excretory organ, is typically whitish in species of Lebertia). Furthermore, Thor observed dorsally a pattern of ca 20 darker dots (“strongly resembling L. oudemansi, but the latter with 12 such dots only”). The description includes the following additional details: idiosoma L/W 1500/1300–1400; integument rather thick and punctate. Shape of coxal and genital fields “as in L. insignis and L. porosa ”; palps and legs very strong (palps as thick as I-L); III- and IV-L-5/6 each with 6–12 long swimming setae “in a bundle”. His two figures (Thor 1900: pl. 10 figs 1–2) show a dorsal view of a specimen of uncertain sex and the partial venter of a female. From his fig. 2, a mL ratio Cx-I/II of about 2.0 can be calculated.

The arrangement of the name-giving twenty dots in Thor’s fig. 1 makes it clear that they represent glandular sacs which are present in all water mites in a stable number of 16 pairs. In specimens of Lebertia of minor size (and lower age), only 12 of these sacs may be visible in dorsal view (as stated by Thor for L. oudemansi Koenike, 1898; see above). With increasing age and larger size, sacs of lateral glandularia move to a position that they become better visible in dorsal view, resulting in an increased number of dorsally visible “dots”. Thor himself discussed the significance of glandularia for the coloration and stated that he had doubts about this taxon (Thor 1926).

The information provided in the original description does not allow any attribution to one of the clades defined in our study. From a morphological analysis of specimens identified by Sig Thor (Material examined above; the indication “Cotype” for SMF 45262 is incorrect) we conclude that they agree with our redescription of Lebertia obscura.

This species was proposed as a junior synonym of Lebertia porosa by K. Viets (1956) without acknowledging that L. porosa and L. porosa obscura would be junior synonyms of Lebertia vigintimaculata, since the latter species was described by Thor 1900 on page 272, while L. porosa and porosa obscura were described on page 273 (page priority). Due to the lack of type material, no taxonomic stability can be attained for L. vigintimaculata, and we regard it as a nomen dubium. Records of L. vigintimaculata from outside Norway are of questionable identity.