USAThe latest chapter in the long story of panda diplomacy was written at Washington’s National Zoo, where the Chinese government agreed to lengthen the “loan” of popular panda pair Mei Xiang and Tian Tian for another five years. Actually, the loan is conditioned on whether they produce a new heir or heiress to the cuteness of panda-dom in the next two years; ¬†one or both could be exchanged for more fecund substitutes.