Fig. 6. The effect of facial pit size on membrane temperature contrast. The original thermogram (A) used in Fig. 4 has been processed to show membrane temperature contrasts for facial pits both on the optic axis of the pit (B–D) and directly in front of the snake (E–G). The total thickness, including both the outer and inner chambers, is indicated for each row. The membrane is assumed to be 25% of the total diameter from the wall of the posterior chamber. The temperature contrast on the pit membrane is indicated by color steps of 0.0005°C.