Abstract: The morphology，musculature，and ultrastructure of legs of Bittacus planus Cheng and B. implicates Huang et Hua adults were described and illustrated based on observations with optical microscopy and scanning electron microscopy. Adult hangingflies have three pairs of legs with similar structure，all being raptorial with grasping structure formed from the fourth and fifth tarsomeres，unique in Insecta. It has been found for the first time that the femoro-tibial extensor b is composed of an elongate thin tendon arising proximally from a small triangular femoral muscle. The tendon of pretarsal flexor is modified into a strong flexor muscle in a shuttle-shaped swollen area，bearing distally a process which is blocked by a Y-shaped pedestal in a notch. The relationships between the predating habits of adults and the structure of raptorial legs were analyzed，and the characteristics of the raptorial legs of hangingflies and mantids are tentatively compared.

Key words: Mecoptera, Bittacidae, Bittacus, raptorial leg, morphology, musculature, ultrastructure