constellation energy corps stock rose 12 in afterhours trading and gap incs fell 4 after sp dow jones indices said constellation energy would replaced the retailer in the sp 500 index before trading begins on feb 3 shares of companies that join the sp 500 often rise as portfolio managers who track the index buy shares gap will instead move to the take sp midcap 400 taking over jack in the box incs spot meanwhile jack in the box will replace spectrum pharmaceuticals inc in the sp smallcap 600 sp dow jones said sp 500 constituent exelon corp is spinning off constellation energy in a transaction expected to close feb 2 meanwhile watts water technologies inc will replace sterling bancorp in the sp midcap 400 and hostess brands inc will take over watts spot in the sp smallcap 600 those changes will take effect before trading begins feb 1 and euronet worldwide inc will replace compass minerals international inc in the sp midcap 400 while compass minerals international will take over great western bancorp incs spot in the sp smallcap 600 with changes also slated to take effect before trading begins on feb 1 first interstate bancsystem inc is acquiring great western bancorp