that were present in the parasite colony where they eclosed could be an
important aspect of host specificity (Topoff, 1997). Moreover, the learning
of colony-specific nest-mate-recognition cues by newly eclosed workers
helps to explain how new slaves can be continually incorporated into
slave-maker colonies, whereas the acceptance of these new slaves by
older adult colony members clearly indicates that learning of nest-mate-
recognition cues is not confined exclusively to the early adult stage, at
least in these species (Stuart, 1988a,b). Thus, paradoxically, the learning
of nest-mate recognition cues forms the basis for much of colony defence
in social insects, but it is also one of the primary factors that appears to
make them vulnerable to exploitation by social parasites.Host suitability
Once a young queen of a socially parasitic ant species finds and accepts
a host colony, it must penetrate the host society, overcome the host’s
defences, gain acceptance and reproduce; and the parasite’s brood and
eclosing offspring must also be accepted and nurtured by the host colony.
Much of the literature on socially parasitic social insects is devoted to
detailed descriptions of the broad range of diverse mechanisms used by
social parasites to penetrate host colonies. As referred to above, social
insect colonies are typically highly aggressive in the defence of their
nests, with well-developed nest-mate-recognition systems, which enable
them to discriminate between legitimate nest mates and various kinds of
intruders (Hölldobler and Michener, 1980; Stuart, 1988b). To be success-
ful, socially parasitic social insects must have mechanisms to breech
these defences, and various tactics have apparently evolved in this
context.
Obligatory slave makers are highly aggressive in their attacks on
host nests and exhibit various fighting and recruitment adaptations for
conducting slave raids, which enable them to defeat their hosts in direct
frontal assaults (see Buschinger, 1986; Hölldobler and Wilson, 1990; and
references therein). Workers of obligatory slave-making ants are often
quite literally highly evolved fighting machines, with an array of adapt-
ations for successful slave raiding. In many species, the workers have
specialized, clipper-shaped or sickle-shaped toothless mandibles, which
they use for dismembering their opponents or piercing their exoskeletons
during slave raids. In some cases, the workers have enlarged poison
glands and the propensity to sting their opponents to death, whereas
others have apparent chemical weapons, so-called ‘propaganda
substances’, which they use to confuse and disperse their opponents or
induce them to attack one another during raids (e.g. Regnier and Wilson,
1971; Allieset al., 1986). Moreover, all known slave makers actively
recruit nest mates for coordinated assaults on target nests, often using
chemical trails. Once a slave-maker colony launches a raid on a target
nest, the outcome is seldom in doubt.Social Parasitism in Ants 327