and pulls the fixed jaw behind it by closing them together until the fragment detaches. Which jaw is fixed and which is motile varies depending on the direction in which the ant chooses to cut a fragment. The sizes of leaf fragments have been found in some studies to vary based on the size of ants due to the ants' anchoring of their hind legs while cutting, though other studies have not found correlations. This is likely because many factors affect how ants cut leaves, including neck flexibility, body axis location, and leg length. Load sizes that do not impact the running speed of the collecting ants are favored. Often, ants stridulate while cutting vegetation by raising and lowering their gasters in a way that makes a cuticular file on the first gastric tergite and a scraper on the postpetiole rub together. This makes a noise, audible by people with great hearing sitting very close to them and visible using laser-Doppler vibrometry. It also causes the mandibles to move like a vibratome and cut through tender leaf tissue more smoothly. The metabolic rate of the ants while and after cutting vegetation is above standard. Their aerobic scope is in the range of flying insects, which are among the most metabolically active animals. The behavior of the foragers that bring the material back to the nest varies greatly among species. In some species, especially those that harvest close to their nests, the harvesters bring the litter back to their colony themselves. Species such as A. colombica have one or more cache sites along a trail for foragers to grab litter. Other species, such as A. vollenweideri, that carry leaves as far as , have two to five carriers per leaf. The first carrier takes the segment a short distance toward the nest and then drops it. Another picks it up and drops it, and this repeats until the last carrier brings it the greatest distance until reaching the nest. Data does not show that this behavior maximizes load transportation, so scientists have explained this behavior in other ways, though the data are still inconclusive. One theory is that this type of task partitioning increases the efficiency of individual workers as they become specialists. Another is that the chains accelerate communication between ants about the quality and species of the plants being cut, recruits more workers, and reinforces territorial claims by reinforcing