The Mishna tells us (Taanis 26b) that on the 15th of Av, unmarried girls would borrow clothes, dance in the vinyard, and invite the unmarried men to choose them for marriage.
The Talmud (Taanis 30b) gives a list of historical reasons that make the 15th of Av a holiday on par with Yom Kippur.
Their solution was to have the Benyaminite lie in wait in the vinyards, and when the daughters of Israel would dance in the vinyards, the Benyaminites would take them, without the fathers breaking their vow by giving their daughters to the Binyaminites. (See Shoftim 21:20 and on)
These two things (the unmarried girls dancing in the vinyards every 15th of Av, and the Binyaminites taking dancing girls in the vinyards) seem very similar. Are there any sources that discuss the connection between the two? Was the story with the Binyaminites the start of the yearly custom? Did the custom precede the story with the Binyaminites?
I'm looking for sources that discuss this.