I have lived in Houston for 40 years, and have only seen them swarm once.
Pretty disgusting.
We also call them Palmetto Bugs, which doesn’t sound quite as bad.
One night I was standing inside the door of an apartment building waiting for someone. As I opened the door to look to see if they were coming, ‘something’ hit me smack in the forehead and landed there for a brief moment. With a bright light right outside the door I was sure it was a large moth. Nope. Turned out it was a huge water bug. A giant cockroach! I never even knew the SOBs could fly.