Kapala (Hymenoptera: Eucharitidae) are among the most frequently collected chalcidoid wasps from the Neotropics, but general information about their host plants, behavior, and life history is scarce. A new species, Kapala izapa n. sp., parasitizing Ectatomma ruidum Roger (Hymenoptera: Formicidae), is described from Chiapas, Mexico, with a general account of its biology. Field observations on the behavior of adults of Kapala iridicolor (Cameron), which also attack E. ruidum, Gnamptogenys regularis Mayr, Gnamptogenys sulcata (Fr. Smith), Gnamptogenys striatula Mayr, and Pachycondyla stigma (F.) (Hymenoptera: Formicidae), are included. Immature stages of Kapala izapa n. sp. follow the general morphology and behavior described for other eucharitids known to attack Ectatomminae and Ponerinae. More than one parasitoid can complete development on a single host larva. K. iridicolor females were observed laying masses of eggs on undeveloped flower buds of Melampodium divaricatum (L.C. Richard) D.C. (Asteraceae). Extrafloral nectaries of this plant are visited by several insects, including predatory foraging worker ants of E. ruidum. Dissection of recently emerged females of K. iridicolor yielded ≈4,500 fully developed eggs.