In several families of scale insects (coccids), the sex of an embryo is determined by the number of genetically active genomes present (one = males, two = females). In mealybugs (Pseudococcidae), both males and females develop from fertilized eggs but, in the embryos that develop into males, the set of chromosomes (genome) of paternal origin (PG) becomes heterochromatic (H) and genetically inac...
