Leafcutter ants can be a serious agricultural threat. In extreme cases, leafcutter ants are capable of destroying entire citrus trees in the span of a day and can lead to an annual decrease in crop yield in affected areas. In North and South America, damages caused by leafcutter ants amount to $1 billion in losses.
There are two genera of leafcutter ants. The two genera differ significantly in external appearance: Atta leafcutter ants have three pairs of spines, while Acromyrmex leafcutter ants have four pairs of spines. Both genera have extremely long legs. Workers measure 1.5 to 12 mm, queens can grow larger than 24 mm in length, and male leafcutter ants are approximately 13 to 18 mm long. Some leafcutter ants have brown or black colors, while others may appear to be reddish in color.
Leafcutter ants dwell in warm areas and are unique in that they cultivate and feed on fungus within their nests. Each species of leafcutter ant consumes a different species of fungus, tending the fungi with grass and leaf clippings. These fungi secrete warning chemicals when an ant introduces a leaf to the nest which is toxic.
Within the large nest of an Atta leafcutter ant, air circulation is controlled by natural movements of warm air from the nest’s perimeter to its center. A leafcutter ant nest may descend as deep as six meters.
A mature colony of Texas leafcutter ants could contain 100,000 insects, most of whom are sterile female workers. Depending on their size, these female leafcutter workers are divided into four castes—major, minor, media and minim—which dictate the functions they perform. Major workers are soldiers, minors guard the nests and trails, mediae forage for food and minims tend the fungus gardens.