Factors Influencing the Cycles of Foraging Activity and Inactivity in Colonies of the Leaf‐Cutting Ant Atta sexdens (Linnaeus) in Eucalyptus Plantations

ABSTRACT Foraging in leafcutter ants alternates between periods of inactivity and activity that extend over several days or weeks. Many factors could influence this alternation, with a preponderance of environmental factors, such as temperature, humidity, and rain. Moreover, ant colony size and the management practices used for their control could also modify the cycles of activity/inactivity. We surveyed the foraging activity of the nests of the leaf‐cutting ant Atta sexdens (Linnaeus) in Eucalyptus plantations and evaluated the relative importance on foraging activity of temperature, past possible immediate experience in foraging, and use of machinery. Twenty transects with an average of 6 colonies in each were selected. Each nest was checked for foraging activity once in different months of the year and we investigated whether foraging inactivity was influenced by nest size, temperature, number of favourable hours for foraging on the day preceding the evaluation, and the use of agricultural machinery. The management practices of A. sexdens nests in Eucalyptus plantations had no influence on the occurrence of foraging inactivity, contrary to nest size and possible past immediate experience in foraging. The probability of foraging inactivity decreased by about 23% for each 10 m 2 increment in the nest size. A nest was also more likely to be active on a certain day if the conditions for foraging activity had been favourable on the preceding day. Leaf‐cutting ants are one of the main herbivores in Brazil, often reaching pest status in several crops. Our results indicate that the efficiency of their control in Eucalyptus plantations could be increased by implementing control strategies several times a year and by increasing the number of bait applications in areas with a high density of small nests (less than 20 m 2 ), as these areas are more prone to inactivity and thus may lead to increased control failures.