Search patterns of Myrmecia midas on different substrates at twilight and day

Australian night active bull ants, Myrmecia midas (subfamily: Myrmeciinae) were collected during their foraging trip in the twilight and displaced to a distant unfamiliar gridded (8m/8m) place. Their search paths were recorded under 3 different substrates at twilight and day: 1. on natural substrate (grass mixed with small wooden pieces), 2. on a uniform tarp surface, and 3. on a quasi-fractal substrate of two different substrates. On the natural substrate at twilight the smaller loops of the forager ants made bigger turn angles, smaller segment lengths, and a shorter distance from the start compared with searches by day. On the uniform (tarp) and quasi-fractal surfaces at twilight and day, the absolute turn angles and the average segment lengths did not differ significantly. But the average distances from the start were bigger on the fractal substrate than on the uniform tarp and distances from the start were bigger in day-light than in twilight on natural substrate. The data pattern replicated other data where the ants showed the expanding search pattern of travelling further and further from their starting point in the course of the search in all conditions. The exponential function (for the distribution of lengths of straight segments) best fitted the uniform tarp substrate and the stretched exponential best fitted the quasi-fractal substrate at twilight, while a bi-exponential provided the best fit for the natural substrate at twilight and day, as well as uniform tarp and quasi-fractal substrates by day. The bi-exponential may be common in search patterns of forager ants in unfamiliar natural and artificial environments.