My Tyranid Hive Fleet is based off a certain type of ant.
A species of biting red ants, known as "Siafu" in Kiswahili, hunt at night in droves, consuming all things in their path like a gigantic tidal wave. They form highways where protection ants, waiting for any intrusive attack, stand guard above and around an undercurrent of travelling masses. Siafu ants, much like mosquitoes I believe, hunt by sensing the carbon dioxide given off by insects, small rodents, large rodents...erg...and humans.