I'll report my findings about the Plagas here.
The Plagas have 3 distinct characteristics.

1. As mentioned previously, the Plagas have the ability to manipulate the behavioral patterns of their hosts.

2. The Plagas are social organisms. By this I mean that instead of living individually, they live in perfect social harmony. It is believed that they have a collective intelligence.

This type of behavior can be seen among insects such as bees and ants. However this kind of social behavior is rarely seen among parasitic organisms.
Perhaps it was a learned behavior by the Plagas. I'm finding out if this has any relationship with their first characteristic.