Scanning Microscopy


The present study describes the fibers occurring in the space extending behind the frons plate, or the region between the ocelli and the clypeal plate of the Oriental hornet. These fibers connect to the brain in the anterior part of the head in a zone which is demarcated by an imaginary line traversing the upper part of the two omrnatidia. Static fibers are present in the upper part and in the center of the space. These static fibers do not move with acceleration of the structures attached to the head. They are perpendicular to the frons plate, are relatively numerous and usually short. In contrast, the fibers in the lower part are directed toward the organ with which they connect, are few in number, have triangular fastenings and are longer. All of the fibers are branched, especially near their point of attachment to the substrate. On the surface of these fibers, there are occasionally coin or bob-like protuberances or other dilations. As seen in serial sections, proceeding from the top down to the base of the space, the fibers are longer at the center of the frons and gradually shorten toward its margins. We propose that the interaction between the fibers and the various structures in the head to which they are attached, having a harp-like appearance, is responsible for the proprioceptive sensing in hornets including the detection of gravity in the course of comb building.

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