PSYCHE 
Vol. 95 
1988 
No. 1-2 
TRAIL PATTERNS AND MOVEMENT OF WORKERS 
AMONG NESTS IN THE ANT FORMICA OBSCURIPES 
(HYMENOPTERA: FORMICIDAE)* 
By Kevin M. O’Neill 
Department of Entomology, 
Montana State University, 
Bozeman, Montana 59717 
Introduction 
In ants of the genus Formica, intraspecific interactions among 
workers from different nest mounds vary from mutual tolerance to 
aggression and territoriality. For example, workers of Formica opa- 
civentris and F. ulkei commonly visited nearby nests without evok- 
ing agonistic responses (Scherba, 1964; Talbot, 1961). On the other 
hand, in a study of a British population of F. rufa, workers engaged 
in aggressive territorial contests with workers from nearby mounds 
(Skinner, 1980). Both aggressive and non-aggressive interactions 
have been observed within populations of F. rufa in Russia (Mari- 
kovsky, 1962) and F. polyctena (Mabelis, 1979a, b). This is not 
surprising, since Formica populations may consist of separate colo- 
nies, some of which have multiple nests (i.e. polydomous colonies; 
Pamilo et al., 1978; Wilson, 1971). The elucidation of patterns of 
interactions among workers from different nest mounds is essential 
for an understanding of the genetic organization of populations 
(Pamilo, 1981, 1982; Pamilo et al, 1978), the social structure and 
spatial dispersion of colonies, and the proximate factors influencing 
the form of intraspecific interactions among ants. Such interactions 
are apparently influenced by the recent history of nest founding and 
* Manuscript received by the editor February 2, 1988. 
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