I also wonder if the Visitors operate like an insect hive, with Anna as the queen and Lisa as the future queen. From the conversation in the restaurant kitchen between Nichols and the traitor, it sounds like they're all drones plugged into some sort of web, and you suffer withdrawl if you get disconnected. Some, like Nichols, overcome the withdrawl and value their independence. Others, like the traitor, are apparently never able to overcome their cravings.