When the host species is common and suitable habitat is widespread,
then host-habitat finding is unlikely to be a problem or to require any
special adaptations. Indeed, such appears to be the case for most social
parasites in the temperate region, which include most known social
parasites (Hölldobler and Wilson, 1990). Clearly, socially parasitic
relationships will only evolve among species with overlapping habitat
requirements, and the mechanisms for habitat finding that served the
ancestral species will probably continue to serve the evolving parasite
and might further evolve to more closely match the host species.Host finding
Socially parasitic social insects are generally highly specific to one
or a few host species (see Hölldobler and Wilson, 1990; Heinzeet al.,
1992), and finding colonies of these species is crucial to the formation of
new parasite colonies. For socially parasitic relationships to evolve, the
nesting requirements of the two species must be sufficiently similar to
bring them into close contact and, as the relationship evolves, the parasite
is likely to respond much more strongly to the various cues that facilitate
the appropriate close contact and the ability to locate suitable host nests.
The level of host specificity observed certainly indicates that finding host
nests of the appropriate species is important, but little research has been
conducted on the cues and mechanisms involved.
For many social parasites, the task of locating a host colony
falls exclusively to the newly mated parasite female. However, for slave
makers, the workers must also be able to locate host nests if they are to
conduct effective slave raids. In most cases, parasitic colony foundation is
probably an evolutionary derivative of secondary polygyny, a phenom-
enon in which at least some of the young newly mated queens from a
colony are adopted back into their parental nest after mating and become
active reproductives, together with the other queens in that nest
(Buschinger, 1970, 1986; Wilson, 1971; Alloway, 1980, 1997; Stuartet al.,
1993). Primary polygyny refers to colonies that are initially founded by
multiple, inseminated, fully reproductive queens. Secondary polygyny
occurs in a sizeable minority of ant species and is characteristic of many
free-living species in the particular phylogenetic groups that have given
rise to most social parasites. Independent colony foundation appears to
be extremely hazardous for young queens, with few incipient colonies
surviving long enough to produce a new generation of reproductives
(Pollock and Rissing, 1989). Achieving adoption back into the parental
nest, a conspecific nest or an allospecific nest would protect young
queens from these hazards and could provide an enormous boost to a
queen’s lifetime reproductive success. However, young queens are not
always adopted back into their parental nests, and adoptions into alien
conspecific and allospecific nests can be extremely rare and hazardous as
well (Pollock and Rissing, 1989; Hölldobler and Wilson, 1990). None theSocial Parasitism in Ants 325