It is not necessary to aver the capacity of a party to sue or be sued or the authority of a party to sue or be sued in a representative capacity or the legal existence of a partnership or an organized association of persons that is made a party. When a party desires to raise an issue as to the legal existence of any party or the capacity of any party to sue or be sued or the authority of a party to sue or be sued in a representative capacity, he shall do so by specific negative averment, which shall include such supporting particulars as are peculiarly within the pleader's knowledge.