Little is known about the spatial distribution of lianas on emergent trees in tropical rainforests and the factors affecting this distribution. The present study investigated the effects of an arboreal ant species Crematogaster difformis which forms myrmecophytic symbioses with two epiphytic ferns Lecanopteris sp. and Platycerium sp. on the spatial distribution of lianas associated with emergent trees. Living lianas were placed onto trunk surfaces inside and outside the territories of the ants in the canopy to examine their ability to remove them. The number of leaves pruned by the ants was significantly higher on lianas inside than outside their territories. The spatial overlap of the distributions of lianas and the two ferns on emergent trees were then examined. The frequency of liana colonization of tree crowns was found to be significantly lower on trees with than without ferns. Under the natural conditions C. difformis workers were observed biting and pruning the lianas. These results suggest that C. difformis regulates the distribution of lianas on emergent trees.