Chrysomya rufifacies(Diptera: Calliphoridae)is a species of blow fly invasive to the New World,but native to parts of the world like China and Australia.Unlike other flies which have heteromorphic sex chromosomes and a sex determination system based on embryonic genotype,C.rufifacies has homomorphic sex chromosomes and a monogenic system of sex determination in which the sex of her offspring is a phenotype of the mother.Based on QTL mapping,tissue exchange,and proteomics studies,female-producing(thylegenic)females are heterozygote-dominant for a protein produced in the germ-line and incorporated into the soma of the eggs that predetermines the sex of the offspring.At present,hybridization studies suggest the presence of sex-lethal and daughterless homologues in this species.In other species,a transformer homologue is also an important part of the sex-determination cascade.Temporal patterns of gene expression throughout immature development in arthropods,such as Diptera,have been described,and there has been a plethora of research highlighting sex-specific patterns of gene expression.In addition to differences in temporal patterns of gene expression,the different sexes may also develop at different rates.