46 Pa. Stat. § 145.7
Whenever the General Assembly may convene following an attack, it shall be the duty of the Speaker of the House of Representatives and the President pro tempore of the Senate, or their elected emergency interim successors, promptly to take steps to determine which, if any, members of their respective bodies may then be unavailable. In the event any legislator or legislators may be determined to be unavailable, it shall further be the duty of the Speaker and President pro tempore or their elected emergency interim successors, to appoint, in consultation with the county chairman or chairmen of the political party or parties of which the unavailable legislator or legislators may be affiliated or should the said chairman or chairman be unavailable with other appropriate representatives of the political party or parties concerned, a person or persons for temporary emergency succession to the powers and duties but not the office of the unavailable legislator or legislators within their respective Houses of the General Assembly.
46 P.S. § 145.7