Mitosis and male meiosis were studied inMyrmedobia coleoptrata(Fn.), (Heteroptera,Microphysidae). Spermatogonial metaphase revealed 14 chromosomes(2n=12 + XY).The nucleolar organizing region was found on the X chromosome. No m-chromosomes were present in the complement. Male meiotic prophase was characterized by a prominent condensation stage. At this stage, the sex chromosomes were positively heteropycnotic and appeared as separate univalents, while in autosomal bivalents homologous chromosomes werealigned side by side along their entire length, i.e. meiosis is achiasmatic. Meiosis was prereductional for the autosomes and post-reductional for the X and Y chromosomes. Meiosis was further characterized by non-radial arrangement of chromosomes in metaphase I plate and radial arrangement in metaphase II. Cytological characteristics of achiasmatic meioses and their distribution within Heteroptera are discussed