Biology Reference
In-Depth Information
(a)
(i)
(ii)
(b)
(c)
0.8
2
1
3
0.6
0.4
0.2
0
-3
-2
-1
0
1
2
3
Distance from trail centre (cm)
(d)
0
10
20
30
40
50
60
cm
Fig. 6.21
(a) (i) A colony of army ants
Eciton burchelli
on the trail. Photo © Stefanie
Berghoff. (ii) Some are taking a large insect prey back to the nest. Photo © Nigel Franks.
(b) Ants returning to the nest with food (red curve) tend to occupy the centre of the trail
with outbound foragers (blue curve) on the periphery, either side. (c) Individual ants
detect the pheromone gradient (shown as a normal distribution about the centre of the
trail) with the tips of their two antennae, moving towards the side with the strongest
concentration. (d) The result is a straight line movement along the trail or, with some
error in detection of pheromone concentration, a sinusoidal trail around the centre.
From Couzin and Franks (2003).
Ian Couzin and Nigel Franks (2003) have studied similar traffic lanes in New World
army ants
Eciton burchelli
. Colonies of this species have up to 200 000 foragers and form
spectacular trails up to 20 m wide and 100 m long, with ants leaving the nest predominantly
using both margins of the trail, and ants returning to the nest with arthropod prey using
the centre (Fig. 6.21a,b). Couzin and Franks showed that this remarkable group
organization arises from three simple movement rules followed by individuals:
