4 
Psyche 
[Vol. 95 
Results 
Trail pattern: Trails of Formica consisted primarily of permanent 
pathways used by ants to travel from nests to foraging areas and to 
other nests. The workers foraged for at least two types of resources. 
They visited plants in the area that had populations of honeydew- 
secreting Homoptera. These included several species of aphids 
(Aphididae) and two species of Membracidae ( Campylenchia latipes 
Say and Publilia modesta (Uhler)). They also foraged on and near 
trails for dead and living arthropods. The major items being carried 
by workers to nests along trails included terrestrial isopods (Crusta- 
cea: Oniscoidea), various species of leafhopper (Homoptera: Cica- 
dellidae), Lepidoptera larvae, and workers of other species of ants, 
especially Formica neoclara Emery. Workers of F. obscuripes were 
observed to prey upon workers of F. neoclara on at least a dozen 
occasions. Nests of the latter species were sometimes within a meter 
of nests of F. obscuripes. 
The major trails (Figure 1) remained active throughout the study 
period. The trails coming from the nests led to 1) concentrations of 
Homoptera on Canada thistle ( Cirsium arvense ), chokecherry ( Pru - 
nus virginiana ), and several other species of plants and 2) other nests 
(Figure 1). Five non-overlapping systems of trails (labelled A 
through D in Figure 1) that intersected 32 of 45 nests were identified 
at the study site. The longest trail system (A), consisting of two long 
parallel trails and branches leading from them, followed an old 
railway bed and served 23 nests (nest group A). The other trail 
systems, within nest groups B through E, served two, three, two, and 
two nests, respectively. Six of the 13 nests for which no trails were 
observed became inactive by the end of the study period; all other 
nests remained active throughout. Only two short sections of trail 
(i.e. one between nests #4 and #6 and another crossing the railway 
bed near nest #6; Figure 1) disappeared during the course of the 
study. Both had been abandoned at least one month before the 
censusing began. 
Worker movement: Workers were marked on eight nests from 
group A. In nine surveys (sampling without replacement) of 29 nests 
in the area made on nine days between 25 August and 1 1 September, 
1986, ants from these eight nests were found to make 88 (39%) of a 
possible 224 different crossovers to other nests. A total of 405 
workers were recaptured on nests other than those on which they 
