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News — When you need to cut a thin piece of paper, do you grab a knife or a pair of scissors? This seemingly simple decision mirrors the daily challenges faced by leaf-cutter ants (Atta cephalotes). A new study from Imperial College, UK, sheds light on the remarkable cutting strategies of these adept ants. Based on current literature, we know that leaf-cutter ants typically use a “knife-like” method to cut through leaves: one mandible anchors the leaf while the other slices through it like a knife (Figure i). However, during an unexpected observation in the lab, Dr. Frederik Puffel and his team noticed the ants switching to a “scissors-like” strategy (Figure ii) involving both mandibles when dealing with leaves that had either straight edges or wide notches (Figure iii). Intrigued, they conducted a series of experiments to investigate this scissor-like cutting behavior.

First, they ran a behavioral assay with live ants, providing leaves that varied in shape and thickness. The results were clear: the ants overwhelmingly preferred knife-cutting when the leaf edges had narrow or irregular notches but switched to scissor-cutting when the edges were straight or had wide notches. This observation is particularly exciting because most research had focused on their knife-cutting behavior, with little attention given to scissor-cutting.

To explore whether this behavioral choice was based on mechanics, the researchers then simulated leaf knife-cutting using mandibles in the heads of dead ants. They discovered that cutting straight edge leaves was nearly impossible without causing excessive bending. This would make cutting less efficient for foragers, requiring more force. The team concluded that scissor-cutting likely evolved as an adaptation to overcome these mechanical constraints, especially when dealing with objects like thin leaves or flower petals.

This study revealed something fundamental about leaf-cutter ants: the flexibility of their cutting strategies. Understanding these behaviors could help with management of agricultural areas where leaf-cutter ants are significant pests. With climate warming expected to increase insect activity, future research could dive deeper into the mechanical constraints these ants face with their mandibles. If we can pinpoint what limits their ability to cut leaves, we might develop new ways to mitigate crop damage, potentially turning this knowledge into effective pest control strategies.

Looking ahead, Dr. Puffel is eager to explore new questions: What happens when leaf-cutter ants are exposed to abrasive materials? How does the potential wear on mandibules affect the forager's behavior during cutting? These intriguing possibilities could open up exciting avenues for future research into the adaptability and ingenuity of these extraordinary insects.