Here we describe the immature stages and seed-carrying and feeding behaviors of Melanaethus crenatus (Signoret) (Hemiptera: Heteroptera: Cydnidae: Cydninae: Geotomini), based on 4 sampling dates from 2009 through 2011. Adult females of this species move seeds of its host plant, Richardia scabra L. (Rubiales: Rubiaceae), to small cavities under small rocks for feeding; these cavities in some cases correspond to oviposition sites where nymphs also feed on the seeds. All instars of Melanaethus crenatus are described and illustrated for the first time. This species is associated with dry oak forest and lives under rocks. This record probably represents an intermediate behavior between nonparental and parental care.