THE SOIL FAUNA: ANTHROPODS - The Soil - page 60

known as oribatid or beetle mites in this country and as moss mites (Moosmilben) in
Germany. In forest litter they may represent 75 percent of the mite fauna. Nearly all
are rather slow moving grazers on bacteria, algae, fungi, spores and dead vegetation.
Compared with earthworms, millipedes and woodlice they probably play only a small
part in the direct decomposition of litter, but they can be significant in some soils, and
more generally important in promoting the distribution of microorganisms which play
a vital role in this process.
Most beetle mites are brown and leathery ( Fig. 19 ) or shiny black or reddish
( Plate 1 ) with a tough chitinous skin. Ridges or flaps are often developed over the
head with projecting spines which must serve for protection from would-be predators.
The oribatid Ceratoppia reminds one of the large herbivorous dinosaur Triceratops
whose horny excrescences presumably played a similar role. Some species carry their
cast nymphal skins about on their backs to provide concealment and protection from
enemies, or cover themselves with white dust or sticky secretions to which particles
of vegetation or dirt adheres. The legs are usually short and stocky and can sometimes
be withdrawn under protective flaps. In a few genera such as Steganacarus ( Fig. 20 )
the whole front part of the body hinges in the vertical plane and can be folded down-
wards like a lid against the hind portion of the body after drawing in the legs. When
closed in this way, these 'armadillo' mites resemble little, hard-coated seeds or eggs.
F IG. 20
An 'armadillo' oribatid mite Steganacarus magnus. (National Museum of Wales.)