You have a horrible design actually that is wasting more CPU cycles than you ever will with a polling solution. Thread creation and destruction is expensive. Besides, a quick look at the documentation shows that you can have pcap_next() block until it receives a packet or times out.
So no, this isn't really a good use of threading. The program should only have two threads, the first thread would be for the user-interface (This may not be required if you are using a console application). The second thread captures and processes all the packets and sends whatever important information back to the main thread to display. There is no need to add further threads for the pcap stuff.