ARTHROPOD FALLOUT ON HIGH ALPINE SNOW PATCHES OF THE CENTRAL PYRENEES, NORTHEASTERN SPAIN

Arthropod fallout on summer snow patches of Central Pyrenees (northeastern Spain), was studied. Small winged insects, especially aphids, are the main component of the fallout. Composition differences between native alpine fauna (sampled by emergence and pitfall traps) and snow samples suggest that fallout mainly consists of lowland taxonomic groups. Densities and daily rates of fallout on the crest snow patches are among the highest ever reported (up to about 1500 and 1100 individuals m-2, respectively). The results suggest that the lee side of crests is a very efficient trap for windblown arthropods, and that arthropod fallout must be higher on crest snowdrifts than in other snow or nonsnow alpine areas. These noticeable allochthonous inputs may have an important significance as a food source for high alpine communities.