Ants are likely highly intelligent, especially for insects, for
1)Ants are highly social and have a hierarchy starting with a queen
2)They are capable of building tiny "cities" complete with primitive ventilation systems
3)Ants communicate with one another by chemical signals.
4)Ants have been known to make rings around ant killer so their buddies won't get in it.
Because of this evidence it is believed that ants are in fact highly intelligent organisms.