In C++11 how do I create a map of queues?

How do I create a map of queues and dynamically add queues to it?  Suppose I have

map<string,queue<string>> myQueues;

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 I am doing this from a method in a class so while the following is legal, it doesn't do the job

queue<string> q1;
myQueues["foo"] = q1;

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What I really want to do is something like this (not legal tho)

myQueues["bar"] = new queue<string>;

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What's the legal way to do this?

Just to be clear this is a simplified and contrived example to make the question simple. In the real code, I have a producer thread managed by a class.  The map is an instance variable of the class. The class needs to sometimes dynamically create a new consumer thread and a queue to communicate with it.  The real queues need to be thread-safe queues and the map variable is actually some kind of a handle, but to keep this question simple I'm posing it with standard classes.