The role of arthropods in forest ecosystems is poorly understood. Yet such knowledge may be critical in order to explain fully the fundamental forces that shape the structure and regulate the functioning of such ecosys tems. There are numerous hypotheses about the roles of various arthropods, but few, if any, of these hypotheses have been rigorously tested. Some, however, have been repeated so often and so widely that they are now accept ed by many as unequivocal fact. Nothing could be further from the truth. Forest arthropods which derive most of their sustenance from plants are usually...