Abstract: Tracheliastes and Pseudotracheliastes are two genera belonging to the subfamily Tracheliastinae of the family Lernaeopodidae.In China four species of Tracheliastes and one species of Pseudotracheliastes are involved.In present paper,Tracheliastes polycolpus,T.brevicorpus and Pseudotracheliastes soldatovi yangtzensis are selected ar representatives of two genera,by using scanning electron microscopy (SEM)for the first time.The result of observation on the structure of labrum and labium is not the same in comparison with the result under the light microscope.The lateral side of labium is single in form and does not divide into two lobes.Consequently the authors revised this structure as above described.As others,no conspicuous difference is observed.