Two aphidiine species were found to be associated with a thelaxine aphid, Kurisakia querciphila on Quercus serrata and Q. acutissima in Japan. One of them is identified as Papilloma luteum and redescribed, and the other is described as a new species, Praon kurisakiae. Sinoaphidius zhejiangensis is synonymized with P. luteum. Papilloma luteum aestivated within a unique shaped and black “diapausing mummy”. Aestivating adults of P. luteum emerging from “diapausing mummies” in the autumn were darker and smaller than non-aestivating ones. The aphidiine parasitoids of Thelaxinae are reviewed; the systematic position of Papilloma and life cycles of K. querciphila and P. luteum are discussed.