XO type (XX-XO type): It is observed in large number of insects, grasshopper. Numbers of chromosomes are different in male and female individuals. Here, female shows homogameity (XX) while male shows hetrogameity (XO). It is clear that, all eggs (ova) bear an additional X-chromosome besides the autosomes while only 50% of the sperms bear X-chromosomes. In grasshopper, eggs fertilized by (A+X) type sperm become females while those fertilized by (A+O) type sperm become males. Therefore, sperm determines the sex of the offsprings.