MECHANISMS AFFECTING LOAD SIZE DETERMINATION IN ATTA-CEPHALOTES L (HYMENOPTERA, FORMICIDAE)

The size of leaf-cutting ant foragers correlates more closely with the weight than the area of the leaf fragments they cut. This implies tha t the mechanism of load size determination is not a simple function of body geometry. Ants were found not to adjust the radius of cut to com pensate for experimental changes in leaf weight during the process of cutting. However, ants changed their cutting behaviour according to th e thickness of the region of the fragment being cut. Ants decreased th eir cut radius when cutting through leaf veins. Similarly, when cuttin g artificial laminae of varying thicknesses, ants reduced the cut arc radius when traversing thicker regions. Cut radius was not principally controlled by the position of the rear legs nor the overall body leng th but by mechanisms associated with the head and thorax of the ant.