The male of Xystromutilla bucki Suárez, 1960 is described and associated with the female based on couples reared from trap-nests occupied by Auplopus subaurarius Dreisbach, 1963 (Hymenoptera: Pompilidae). Information on the diapause of X. bucki and Pseudomethoca nr. chontalensis (Cameron, 1895) (Hymenoptera: Mutillidae) is presented. Seasonal and annual variation in the abundance of X. turrialba Casal, 1969 are also given.