[aopirose]

Iota Alpha Pi - This is the only group, as a whole, that voted to close rahter than affiliate with another group. That was ~1972.

The rest affliated with other NPC groups.

Alpha Delta Theta m. Phi Mu, 1939.

Alpha Sigma Delta m. Lambda Omega, 1932; Lambda Omega m. Theta Upsilon, 1933; Theta Upsilon m. Delta Zeta, 5/6/62.

Beta Phi Alpha m. Delta Zeta, 6/22/41

Beta Sigma Omicron m. Zeta Tau Alpha, 8/64

Delta Sigma Epsilon m. Pi Delta Theta, 1940;
then DSE m. Delta Zeta, 1956

Sigma Phi Beta m. Phi Alpha Chi, 1/7/28;
Sigma Phi Beta m. Phi Omega Pi, 10/1/33;
Sigma Sigma Omicron m. Sigma Phi Beta, 1972.

Phi Omega Pi m. Delta Zeta, 8/10/46

Pi Kappa Sigma m. Sigma Kappa, 5/15/59

Pi Lambda Sigma m. Theta Phi Alpha, 6/28/52

Theta Sigma Upsilon m. Alpha Gamma Delta, 6/29/59

Theta Upsilon m. Delta Zeta, 5/6/62