The tarantella is a traditional Italian dance done to cure tarantula bites.  Within the context of the play, the tarantella functions as a symbol of Nora's control over Helmer; yet it also shows her lack of control, as her dancing is wild - indeed, later she is observed to "[overstep] the proprieties of the art". Nora first learned to dance the tarantella when she was in Italy, while on the trip she paid for to save Torvald's life - clearly the dance is associated with a time of which she is secretly proud.  The second example of the tarantella, in the scene we have scored, shows Nora using the tarantella as a means of distracting Helmer from the letterbox.  The dance, at this point, shows both her earlier control and her present lack of control - it is now performed so wildly - performed, as Mrs. Linde observes, "as if [her] life were at stake....