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Leafcutter Ants

Leafcutter ants can be serious agricultural threats. In extreme cases, leafcutter ants are capable of destroying entire citrus trees in the span of a day and can lead to a 10 to 15 per cent annual decrease in crop yield in affected areas. In the United States, damages caused by leafcutter ants amount to billions of dollars in annual losses.

There are 39 species and two genera of leafcutter ants. The two genera differ significantly in external appearance: atta leafcutter ants have three pairs of spines with a smooth upper body, while acromyrmex leafcutter ants have four pairs of spines with a textured body. Both genera have extremely long legs. Workers measure three to 12 millimeters, queens can grow larger than 25 millimeters in length and male leafcutter ants are approximately 13 millimeters 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 from the Lepiotaceae family, 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, 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 leafcutter ants could contain over eight million 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 during predator attacks, mediae forage for food and minims tend the fungus gardens. Major leafcutter ants are strong enough to cut through leather.