Figure 1.
The study species, Myrmecia pyriformis and its daily activity rhythm.
(a) The nocturnal bull ant, Myrmecia pyriformis. Graduations are in mm. (b) Activity rhythm of M. pyriformis on one summer day. Bars indicate the proportion of outbound (red) and inbound (blue) workers in 10-minute bins. Modified from Narendra [34].
Figure 2.
Effect of ambient light intensity on walking speed and pause duration and frequency in the nocturnal ant, Myrmecia pyriformis.
(a) Example trajectories of 9 ants and pauses they made (blue dots) on their foraging route at (i) 0–30 minutes after sunset, (ii) 30–60 minutes after sunset and (iii) 60–90 minutes after sunset. Time taken to travel from the nest to tree is shown as means±SD. (b) Pause duration and (c) walking speed of animals plotted against light levels. Two nests were studied and are indicated as red and black. Regression lines for each dataset are shown.
Figure 3.
Homing success and navigational efficiency of the nocturnal bull ant, Myrmecia pyriformis.
Top row: Homing paths of ants released at the base of their foraging tree (R, blue circle) to the nest (N, black circle) in three one-hour slots: (a) Dark: 60–120 minutes before sunrise, (b) Dim: 30 minutes on either side of sunrise, (c) Bright: 60–120 minutes after sunrise. Red: ants that successfully returned to the nest; grey: ants that did not return to the nest within 50 minutes of tracking. Bottom row: (d) Sinuosity of all paths: the larger the Emax value the straighter are the paths; (e) homing duration of successful ants (difference between the times of release and nest entry); (f) travel speed of all ants including pauses. Sector graphs show the proportion of ants that reached the nest within the recording duration of 50 minutes. Significance codes: *p<0.05; **p<0.01; ***p<0.001.
Figure 4.
Visually mediated homing in bright and dark conditions.
Responses to displacement (a) before sunset, and (b) after sunset. Blue: outbound paths of 15 individual ants from nest (N) to tree (T). Ants were captured at the tree (T), fed and transferred in the dark to R (12 m in a direction perpendicular to the normal foraging direction). Red: ants that successfully returned to the nest; grey: ants that did not return to the nest. Circular plots indicate initial bearing of ants at 0.5 m from release. Black arrow: true nest direction; blue arrow: fictive nest direction based on a path integrator (blue arrow) is shown. Sector graphs show the proportion of ants that reached the nest within the recording duration of 50 minutes.