Metabelba papillipes

van der Hammen, L. & Strenzke, K., 1953, A Partial Revision of the Genus Metabelba Grandjean (Oribatei, Acarina), Zoologische Mededelingen 32, pp. 141-154 : 142-148

Metabelba papillipes (Nicolet, 1855) (figs. 1-4)

Among the species of Belbidae of the " pulverulentus "'-group, only two regularly occur in the forests near Paris, where Nicolet collected his material: one, the commonest, here preliminarily called papillipes , and Porobelba spinosa (Sellnick) . Although Nicolet did not observe the long, curved solenidion on tibia IV, it is not difficult to decide which of the two species is the real papillipes , as the author figured a specimen with long notogastral hairs and with a strongly developed apophysis between the first and the second legs, so that spinosus is excluded. The description of the species based on the topotypes from Paris is here given.

Length 455-515 µ; breadth 310-345 µ (the measurements are sometimes slightly smaller in Dutch and British specimens). Colour reddish brown. The specimens generally bear larval and nymphal skins, and are strongly covered with cerotegument. When observed in air the cerotegument is white and powdery; although it is present nearly everywhere, it is especially thick on the legs, on the sensillus, and at the border between propodosoma and hysterosoma. When observed under a high power microscope the cerotegument looks like a mass of thin threads mixed with numerous small granules.

Propodosoma between I and II with a strong anterior apophysis that is directed to the front; the surface of the apophysis is granulate, and the shape is somewhat variable, sometimes slightly worn off (fig. 1).

The disposition of the hairs on the propodosoma is shown in fig. 2; the hairs are almost completely smooth. The bothridium is cup-shaped, the sensillus flagelliform; the exobothridial hairs are curved to the front, the interlamellar hairs directed upwards and backwards. The length of the sensillus is about 110 µ; the interlamellar hairs are slightly variable, but generally their length is about 70 µ.

At the posterior border of the propodosoma there is a pair of distinet, rounded protuberances opposite to a pair of tooth-shaped protuberances at the anterior border of the notogaster. Generally the posterior pair or even both pairs are covered by the Upper surface of the notogaster (in fig. 2 they are shown as freely visible). In one specimen we observed a distinet, internal, chitinous connection between the two protuberances on the propodosoma.

The disposition of the notogastral hairs is also shown in fig. 2. The notation is as follows: c1 c2, la, lm, lp, h3, h2, h1, ps1, ps2, ps3. The hairs ps are much smaller and are inserted at the posterior border. The length of the dorsal hairs is about 80 µ; when strongly enlarged it is visible that they are slightly thickened just above the place of Insertion. There are no spinae adnatae.

The fissures are best visible in a lateral orientation; they have the same disposition as in M. pulverosa .

The mentotectum is complete, without incision. The labium presents the usual hairs (p.a., p.m., p.h.; cf. fig. 3).

The epimeres show a normal number of hairs (1a, 1b, 1c, 2a, 3a, 3b, 3c, 4a, 4b, 4c, 4a in fig. 3; in the original description of M. cremersi a fourth hair was erroneously drawn on epimere I).

The genital and anal plates are rather widely separate. The genital plates (gen) each bear six hairs, each anal (an) three. There are one pair of aggenital hairs (agg) and three pairs of adanal hairs (ad).

Close to the sejugal stigma are the anterior and the posterior parastigmatic apophyses; they are iarge and pointed, especially the anterior. The discidium is long and curved.

The legs (fig. 4a, b) are moniliform. The measurements of the joints (in ju) are as follows:

The hairs of the legs are partly rough, sometimes beset with distinct hairs. The solenidion of tibia IV is long, and curved backward. The total number of hairs on the joints is as follows:

There are eupathidia on the first tarsus only, viz., the proral pair (p', p") and the unpaired subunguinal hair(s).

The topotypes used for the description of the species originate from Grandjean's collection (15 adults and some nymphs from tube 483, collected near Paris and Versailles ); they are now in the collection of the Rijksmuseum van Natuurlijke Historie, Leiden, and in Dr. K. Strenzke's collection.

It is not easy to establish the synonymy of the species. We studied two slides from the Michael Collection, labelled " Damaeus verticillipes ", one specimen in dorsal view, and one in ventral. The specimen in the dorsal orientation appears to be identical with M. papillipes , although the hairs are darker than in the French and Dutch specimens. The second slide, in ventral orientation, contains a specimen with the genital and anal plates rather close to each other, without anterior apophysis, and with an unpaired poröse area at the posterior border; it is probably a Porobelba , but the specimen has to be remounted for certain identification. In Michael's figure the specimen in dorsal view, although not altogether accurately drawn, indeed corresponds with papillipes , whilst the figure in ventral view, with the genital and anal plates drawn close to eaoh other, probably represents the Porobelba specimen.

Oudemans (1900) proposed the name Oribata michaeli for Damaeus verticillipes Michael non Nicolet ; it appears now certain that the Dutch specimens in the Oudemans Collection bearing the name Belba michaeli , although severely damaged, indeed belong to papillipes . The only other certain record is the description of M. cremersi van der Hammen (1952) from the Netherlands.

From the above mentioned facts it appears that up tili now the species is only known frorri France, England, and the Netherlands. In the last named country M. papillipes is not rare; it was found to occur in woods, especially in birch woods and in thickets of Prunus spinosa and Crataegus ; the species possibly has preference for the lower litter layers.