The ants, one of the most successful groups of insects,
are of particular interest because they form advanced
colonies. They belong to the order Hymenoptera, and are
close relatives of the sphecid wasps. The first known
ants appeared sometime during the Cretaceous period, and
it is believed that they evolved from the wasps that had
appeared during the Jurassic period. They are physiologically
distinguished mainly by having six legs, sharply elbowed
antennae, and by having a bead-like pedicel formed from
the first few abdominal segments, which in wasps are joined
to the thorax. Ants are mostly wingless, which varies
between individuals in a colony rather than between species.
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