Proximity of the colonies of the tending ant species as a factor determining the occurrence of aphids.
Aphis craccivora Koch is common in the Indian State of Kerala and is periodically found infesting the new shoots of Gliricidia sepium (maculata) in Calicut soon after the first rains; it is tended almost exclusively by the ant Anoplolepis longipes (Jerd.), which nests in bare soil. In the compound of the Malabar Christian College, two sides had been flooded with rain water and ants could not nest there, and Gliricidia plants on these sides were completely free of aphids; on the other sides, where soil drainage was better, there were 15 Anoplolepis nests and the plants were heavily infested with aphids. It is concluded that the occurrence or at least the continued survival of Aphis craccivora in a given locality depends on the proximity of nests of its attendant ant.