differ from all other ants (see Hölldobler and Wilson, 1990). Some authors
have suggested that inquilines that tolerate the host queen are funda-
mentally different and might often have a very different evolutionary ori-
gin from those that do not tolerate the host queen (Buschinger, 1986, 1990;
Bourke and Franks, 1991, 1995).
Perhaps the most extreme and highly specialized social parasite yet
described is the inquilineTeleutomyrmex schneideri (see Buschinger,
1986, 1987; Hölldobler and Wilson, 1990; and references therein).
Teleutomyrmex, literally ‘final ant’, is a workerless inquiline parasite
of twoTetramoriumspecies,T. caespitumandT. impurum, and occurs
in small, isolated populations in the Swiss Alps, French Alps, French
Pyrenees and Spanish Sierra Nevada. The queens are small compared
with their hosts, generally inactive and spend most of their time riding
around on the backs of their hosts, especially the host queen. The ventral
body surfaces of the parasites are strikingly concave and well adapted to
this ectoparasitic lifestyle, and they have unusually large tarsal claws and
a strong tendency to grasp objects. Large numbers of unicellular glands
under the cuticle appear to be the source of a powerful attractant for the
host workers, which frequently lick the parasites. Older queens are highly
physogastric, their abdomens swollen with fat body and ovarioles.
Several physogastric parasite queens often coexist in the same host nest,
and each can lay an egg every 30 s. TheTetramoriumqueen continues to
lay eggs and produce workers and the colony’s brood is a mixture of the
two species. The bodies ofT. schneiderifemales appear to have under-
gone extensive morphological degeneration. The integument is thin and
shiny, with little pigment or sculpturing. The mandibles, sting and poison
apparatus are reduced. There is degeneration in the exocrine system, with
reduced labial and postpharyngeal glands. The maxillary and metapleural
glands are completely absent. There is even degeneration in the nervous
system, with reduced and fused ganglia. The males are also morpho-
logically degenerate and appear almost pupoid, with a thin, greyish
cuticle, broad petiole and postpetiole and soft abdomen, deflected down
at the tip. As in many inquilines, mating takes place in the nest, and
newly mated females either lose their wings and join the egg layers in
their maternal nest or fly off to found new parasite colonies elsewhere.
Inquilinism has apparently evolved repeatedly and independently
in various ant subfamilies, but the factors responsible for its evolution
remain a matter of debate (see Buschinger, 1986, 1990; Hölldobler and
Wilson, 1990; Bourke and Franks, 1991, 1995; and references therein).
None the less, comparative studies suggest that, once a species has
evolved an inquiline life history, it quickly becomes completely depend-
ent on its host and tends to acquire some or all of an array of characteris-
tics that have been referred to as the ‘inquiline syndrome’ (Wilson, 1971;
Hölldobler and Wilson, 1990). These characteristics include:- Loss of the worker caste.
- Winglessness of queens and males (i.e. ergatomorphism).
Social Parasitism in Ants 323