HERBIVOROUS INSECT SPECIES IN THE TREE CANOPY OF A RELICT SOUTH-AFRICAN FOREST

1. The herbivorous insects on twelve species of evergreen broadleafed trees were repeatedly sampled over a period of 11 months in a small re lict forest on the east coast of South Africa. This extraordinarily sp eciose forest patch has an unusually high proportion of endemic tree s pecies, some of which are extremely rare. 2. The insect herbivore faun a (number of species) seems to be markedly depauperate compared to tha t reported on native, broadleafed trees from other parts of the world. Some possible reasons for this are discussed. 3. The total number of herbivorous insect species on each tree species was strongly correlate d with the local relative abundance of the host plant species. 4. Ther e was no relationship between the total number of insect herbivore spe cies on each tree species and the relative taxonomic isolation of the trees. The proportion of seemingly unique (=specialist) herbivorous in sect species (i. e. those that occurred on one tree species only) was greatest on taxonomically isolated trees. 5. A fundamental deficiency in the interpretation of the data in this study, and of many other sim ilar studies that report on the number of insect species on plants, is discussed, namely the lack of clarity on the closeness of the associa tion between individual insect herbivore species and their respective host plants.