an age-old question--sort of

Philosophers have never been able to pin down precisely when sand crosses the threshold from scattered grains to a pile. (In fact, in his later years, Plato was often seen playing on the beaches of Athens, building invisible sandcastles and muttering to himself.)

Now, though, scientists have solved a slightly different problem: how many locusts does it take to make a swarm? The answer:

The experiments showed that at low densities of just 2 to 7 locusts, the insects moved independently, while at slightly higher densities of 10 to 25 locusts they banded together, changing direction in unison, rapidly and spontaneously.

When more than 30 locusts were put together in the enclosed space (equivalent to 74 locusts per square metre), they adopted the aligned movement of a swarm after five minutes, collectively marching around the confined space until the experiment was ended 8 hours later.

No word on when a swarm of locusts becomes a viable political option.