Fig. 13. Structure of the abdominal paddle and thoracic bristle tufts of the final-stage larva. (A) Abdominal tip showing details of the fan-like paddle. The inset shows an individual tuft of 12 bristles from the fan. (B) Details of thoracic bristle tufts. Each of the four tufts consists of 13 bristles: the inset shows two bristles at higher magnification. (C) Drawings from a video sequence showing three stages in the right-to-left swing of the abdomen of a swimming larva viewed from above. During the rapid flexural stage of the stroke (middle profile), the thoracic bristle tufts on the concave side of the body are bent forward in the direction of flow (dashed line). Open-headed arrows indicate the scissor-like motion of the anterior and posterior halves of the body. The filled circle at the junction of the thorax and abdomen indicates the position of the presumed centre of gravity of the larva.
