Figure 1.

The nocturnal Australian bull ant, Myrmecia pyriformis. (a) Photograph of major and minor worker of M. pyriformis. (b) Scanning electron micrograph of a frontal view of the head of a worker M. pyriformis showing the large compound eyes and three dorsally placed ocelli. (c) Activity schedule of ants on a single day (inset) and throughout the year. The onset of foraging (black circles) was recorded at every 30-min; change in sunset time shows that onset occurs during the evening twilight throughout the year; * indicates no activity. Inset: number of active workers averaged over three nests. (d) Longitudinal section of an ommatidium in the frontal region of the eye in light- and dark-adapted state. CC, crystalline cone; ct, crystalline cone tract; PPC, primary pigment cell; Rh, rhabdom. (a) Photo credit Ajay Narendra; (b) adapted from Reid [24]; (c) adapted from Narendra et al. [25]; inset in (c) adapted from Narendra et al. [9]; (d) adapted from Narendra et al. [26].