AWS and auto scaling cassandra

I've setup a AWS instance with cassandra on it and then also setup an auto scaling group to spin up another 4-8 instances depending on alarma. But how does Cassandra know when auto scaling kicks in? How does it know what other nodes to connect to? Do I need to configure something in Cassandra in order for it to sniff the nodes?

when I run node tool, the auto scaling nodes don't show up...

[root@ip-10-205-119-104 bin]# sh nodetool status
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address    Load       Tokens  Owns    Host ID                               Rack
UN  127.0.0.1  107.12 MB  256     ?       a50294ac-2150-4d9e-9dd2-0a56906e9531  rack1

Note: Non-system keyspaces don't have the same replication settings, effective ownership information is meaningless