Why does different sexes of cockroaches have different chromosomes

Usually an organism has two kinds of sex chromosomes that determine the sex of that organism, which are X and Y chromosomes. The combination of these chromosomes decide the sex of the organism. Even though there are other chromosome combinations such as  XYZWXOZO, or haplodiploid, XX/XY sex determination system is the well-known sex determination system in most of the mammals, including human beings and in some insects[1][2]
            In the XX/XY sex determination system, two of the same sex chromosomes are present in females like XX and different sex chromosomes are present in  males like XY. Similar to the XX/XY sex determination system, the  ZW sex-determination system determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects (including butterflies and moths), and some reptiles, which has ZZ and ZW chromosome combinations for males and females respectively.
            However some insects such as cockroaches have only one kind of sex chromosome. Males have one chrmosome eg XO, where zero means the absence of the second chromosome and females have two of the same kind eg XX
           In this manner, male and female cockroaches have different number of chromosomes. There are other insects such as crickets and grasshoppers which have different number of chromosomes in males and females. In humans, a female can have XO genotype in which case it results in a chromosomal abnormality, medically termed as Turner’s syndrome.


[1]  Sex-determination system en.wikipedia.org/wiki/Sex_chromosomes
[2]  hindu.com/seta/2006/06/08/stories/2006060801941800.htm