A member of the Orthezia praelonga species group has 16 chromosomes in the germ line of both the male and female, and shows no apparent differential behavior between the two haploid complements in the male. In not showing a chromosomal difference between the sexes, it is unlike any other bisexual species of coccid yet studied cytologically. In most respects, spermatogenesis appears to conform to the primitive coccid pattern. Various possible modes of sex determination, derivable from the basic coccid XO system, are considered in the discussion.