MATE AVAILABILITY AND MALE DISPERSAL IN THE ARGENTINE ANT LINEPITHEMAHUMILE (MAYR) (=IRIDOMYRMEX HUMILIS)

In the Argentine ant Linepithema humile (=Iridomyrmex humilis) only ma les disperse whereas female sexuals (unmated winged queens) stay in th eir mother nest where they mate. This study investigated (1) whether d ispersing males are accepted into foreign colonies, (2) whether they c an mate with resident female sexuals, and (3) whether the propensity o f males to disperse is affected by the expectation of mating in their mother nest. Field experiments demonstrated that males were accepted i nto foreign colonies only when these colonies contained female sexuals or queen pupae. Before and after the time of (sic) female sexuals, wo rkers attacked and killed most of the foreign males. Laboratory experi ments snowed that males that successfully enter foreign colonies can m ate with resident female sexuals. The propensity of males to disperse was significantly influenced by the presence of female sexuals in thei r nest. Males were more likely to fly out from colonies containing no female sexuals than from those with them. These results are consistent with males preferentially dispersing when there is little or no oppor tunity to mate in their mother nest. Thus there are two mating strateg ies available for males: staying in their mother nest when an opportun ity to mate arises or dispersing and attempting to mate in a foreign n est when there are no female sexuals in their mother nest. This latter behaviour could mediate gene flow between colonies and account for th e lack of significant inbreeding previously documented in this species .