Effects of wood ants on weevil community inhabiting oak trees

Ant effects on the community of weevils were studied in a Quercus dentata chaparral of Ishikari Coast, northern Japan, where a supercolony of the red wood ant Formica yessensis expands over the dune. A total of 16 species of weevils were collected in the present survey. The dominant species were Myllocerus griseus, Phyllobius longicornis, Rhynchaenus japonicus and Scythropus japonicus, constituting 94% of 2485 individuals collected. The total number was more remarkably reduced in ant-abundant areas than in ant-rare areas. In particular, 3 of the 4 dominant species were considerably depopulated by ants. Adults of S. japonicus and P. longicornis were aggressively expelled or hunted on the trees. In R. japonicus, the adults were rarely attacked, however, leaf-mining immatures were remarkably predated by ants. In contrast with those 3 species, the population of M. griseus was enhanced by the presence of the ants which were almost indifferent to this species but frequently eliminated its competitors. [The following taxa are also mentioned: Deporaus unicolor, Neocoenorrhyncus interruptus, Meotiorrhynchus querendus, Pseudocneorhinus bifausciatus, R. varigatus, R. takabayashii, Curculio dentipes, C. antennatus, C. minutissimus, Magdalis ruficornis, Cryptorhynchus electus and Caebicryptorrhyncus frontalis].