Metabelba

van der Hammen, L. & Strenzke, K., 1953, A Partial Revision of the Genus Metabelba Grandjean (Oribatei, Acarina), Zoologische Mededelingen 32, pp. 141-154 : 152-153

THE OTHER SPECIES OF THE GENUS METABELBA

The greater part of the Belbidae have originally been described as Belba , Damaeus , or Oribata species, and because most authors did not pay attention to the chaetotaxy of the legs, especially to the presence of protective hairs near the solenidion of tibia IV, it is not easy to decide to what genus the species in reality belong. As late as 1952, Hammer described five new Belbidae from arctic Canada as species of Belba ; although it is evident that none of these is a real Belba , her descriptions do not allow of definite conclusions concerning the real generic position.

In 1902 Kulczynski described as Oribata comptus a species that in its general appearance shows a close resemblance to representatives of the genus Metabelba . Nevertheless the presence of a protective hair near phi IV points to the genus Belba , as already stated by Forsslund (1945) and Strenzke (1952). A detailed investigation of the specimens shows some more characters that correspond with the genus Belba , such as the very short distance between the genital and anal plates; a detailed redescription of B. compta might prove interesting, as there are also striking differences from B. corynopus (Hermann) , the type of the genus Belba . We draw, for instance, attention to the normal number of hairs on the epimeres, and to the Metabelba-like shape of phi IV.

The species of Metabelba , known up till now, can be arranged in groups. The first group, possessing a distinct anterior apophysis, contains papillipes (Nicolet, 1855), pulverosa Strenzke nov. spec., and propexus (Kulczynski, 1902). The remaining groups have no anterior apophysis, and at first it seemed necessary to create a new subgenus for these; after studying Metabelba montana , however, we concluded that such a subgenus would be too heterogeneous. For the moment we prefer to distinguish three groups beside the first: a second group containing sphagni Strenzke (1950) and italica (Sellnick, 1931), a third group containing lanceolata van der Hammen (1952), and a fourth group containing montana (Kulczynski, 1902).

The last named species has some special characters that give it a peculiar Position; we mention the rough notogastral hairs and the presence of a particular, very coarsely granulate cerotegument.

The species of the genus can be identified with the following key. In this key Damaeus romandiolae and D. propinquus Sellnick (1943), species that probably belong to Metabelba , are not included. Oribata ursina , insufficiently described by Sig Thor (1930), may be related to Metabelba montana ; it differs from the latter species by its yellow colour and by the presence of four small protuberances on the propodosoma.

Key to the species of Metabelba

1. Between the first and the second legs a distinct apophysis .......... 2

- Propodosoma between I and II rounded .......... 4

2. No distinct protuberances at the posterior border of the propodosoma, and no protuberances under the anterior border af the notogaster .......... pulverosa Strenzke .

- Propodosoma posteriorly and notogaster anteriorly with protuberances .......... 3

3. One pair of protuberances at the posterior border of the propodosoma .......... papillipes (Nicolet).

- Two pairs of posterior protuberances on the propodosoma .......... propexus (Kulczynski) .

4. Notogastral hairs very broad and lanceolate, inserted on distinct elevations .......... lanceolata v. d. Hammen.

- Notogastral hairs not strikingly broadened .......... 5

5. Notogastral hairs dark, stiff, radiating bristles .......... 6

- Notogastral hairs lighter; the first pair directed to the front, the remaining pairs strongly curved and directed backward .......... montana (Kulczynski) (cf. also ursina Sig Thor).

6. Opposite to the pair of posterior protuberances on the propodosoma there is a corresponding pair under the anterior border of the notogaster; trochanter IV longer than femur IV .......... sphagni Strenzke .

- No corresponding protuberances under the anterior border of the notogaster; trochanter IV shorter than femur IV .......... italica (Sellnick) .