Larval phototaxis test. (A) Schematic representation of the testing plate. The light and dark halves of the testing plate are colored light and dark gray, respectively. See Materials and methods for details of the 11-min phototaxis test. (B) Dynamics of w1118 3rd-instar larval distribution in the light and dark halves of the testing plate during the 11-min phototaxis test. Twenty larvae were placed on the light side of the LD boundary at the beginning of the test. The number of larvae in the light half was counted every 0.5 min. The testing time of 11 min was used to demonstrate the final larval distribution. Light intensity was 550 lux.