This is the initial study on the fine structure of labipalp and ventral spine of periplaneta americana. Each Labipalpus consists of 4 segments where many receptor hairs adhere. From the basal segment to the distal one the sensilla increase gradually. They may be divided into 5 types: Cheatic sensillum A

Cheatic sensillum B

Grooved sensillum. Perforated sensillum and Campaniform sensillum. Only Cheatic s. B can be seen on the basal segment

while the perfoated s. and grooved s. are distributed on the distal one specially. Ventral spines are not segmented. Many Cheatic sensillum B makes an even distribution on the surface of cylindrical spines.