A leaf-cutting ant carving a piece of Parafilm. Top left: initiating the cut with nearside hind leg holding the Parafilm edge. Top right: halfway through the cut, both hind legs holding the edge. Bottom left: cut practically total, 2nd hind leg holding the edge. Bottom right: cut complete.
Leaf-cutting ants demonstrate an advanced foraging technique, thoroughly slicing off leaf fragments with their effective mandibles, displaying a precision that rivals human-engineered tools. This remarkable leaf-cutting capability is essential to their survival, as the gathered plant material serves as a substrate for cultivating their cooperative fungi, which works as the colonys primary food source.
New research exposes how leaf-cutting ants carve leaf parts.
While they might not have the capability to jump over high structures in a single leap, leaf-cutting ants are unquestionably superheroes of the insect world. These small powerhouses can haul leaf fragments weighing as much as six times their own body mass, which they utilize to cultivate fungus development in their nests.
However how do thes pests ascertain the size of the leaf pieces they diligently cut utilizing their mandibles?
Do they use their bodies as an easy ruler, or do they use details about the position of their bodies to change how far they cut, adjusting to the density of a leaf while dismembering it?
Understanding that the bugs alter the trajectory of a cut when sculpting Parafilm of various thicknesses, Flavio Roces from the University of Würzburg, Germany, decided to discover how the ants govern the size of the portions they trim.
He and his colleagues, Daniela Römer and Rebecca Exl (likewise from the University of Würzburg), publish their discovery in Journal of Experimental Biology that each ant tracks the position of the leaf edge by grasping it with their rear legs while rotating their bodies as they trim to cut perfect leaf parts.
A leaf-cutting ant sculpting a piece of Parafilm. Top left: starting the cut with nearside hind leg holding the Parafilm edge. Leading right: midway through the cut, both hind legs holding the edge. Bottom left: cut almost total, second hind leg holding the edge. Bottom right: cut complete. Credit: Daniela Römer
Initially, the researchers required to understand how the pests snip out routine leaf pieces. Exl fashioned fake leaves from Parafilm– one layer for thin leaves (0.13 mm), 3 for thick leaves (0.38 mm)– rubbed them with crushed bramble leaves or rose oil to make them more appealing to the ants and installed them in the foraging area of a lab-based Atta sexdens ant nest.
As quickly as an ant climbed up aboard, Exl retrieved the pseudo-leaf and placed it in front of a camera to tape the ants maneuvers.
The ant lay along the edge of the leaf, with the hind and middle leg on the side nearest the edge grasping the Parafilm. It snipped upward, slowly rotating its body up until upright as it cut in an arc, connecting the second hind limb when its body was nearly vertical.
As the ant continued cutting, it turned further, eventually releasing the very first hind limb from the leaf edge while still holding on with the second hind limb, up until it severed the portion by cutting through the leaf edge after rotating the body through 180 deg.
And when Exl compared the ants posture as they cut through thick and thin leaves, she realized that they adapted their method, bending their legs to reduce their reach to cut smaller sized elliptically shaped fragments when offered with thick leaves.
So how were the ants controlling the size of the pieces they incised? Could knowledge about the position of their hind legs grasping the leaf edge assist their cutting trajectory?
This time, Exl waited up until each ant was midway through a cut before carefully inserting a piece of paper in between the ant and the phony leaf to release its grip as it continued snipping. Without understanding of the position of their legs relative to the leaf edge, a few of the ants cut smaller sized elliptical portions.
They were using details offered by their hind legs grasping the leaf edge to direct the trajectory of their cut. Some ants were still able to cut likewise sized pieces.
Were they utilizing some other sensory details to direct their trajectory? Could hairs at the front of the neck, which identify the position of the head, add to their sense of cutting instructions?
Exl cautiously slashed off these hairs and enabled the ants to cut a Parafilm leaf while gently removing the bugs limbs from the edge with the paper guard, and this time the ants entirely lost track of direction, producing randomly shaped fragments that were nothing like the elliptical pieces they had cut previously.
Leaf-cutting ants depend on understanding of the location of the leaf edge provided by their legs and the position of their heads, to keep them cutting on the curve and make sure that they never ever excise pieces that surpass their remarkable strength.
Referral: “Two feedback mechanisms associated with the control of leaf fragment size in leaf-cutting ants” by Daniela Römer, Rebecca Exl and Flavio Roces, 22 June 2023, Journal of Experimental Biology.DOI: 10.1242/ jeb.244246.
The research study was funded by the University of Würzburg.
