The study on the nerve cells in the subesophageal ganglion of 5-day-old cabbage butterfly, Pieris rapae L., was performed to observe their ultrastructures and classify them on the basis of the differences in size, shape and relative distribution of cell organelles. 1. Type I neurons: These cells are neurosecretory granules ranging 100 to 300 nm in size. 2. Type II neurons: As giant neurons averaging 25 to $30{mu}m$ in size, such as mitochondria and Golgi apparatus. 3. Type III neurons: These spindle-shaped cells range 9 to $15{mu}m$ in width. 4. Type IV neurons: These cells have a range of diameter from 12 to $16 {mu}m$. The cells are abundantly observed in the subesophageal ganglion. 5. Type V neurons: These cells are very small nerve cells with 4.5 to $8.0{mu}m$ in size and have a prominent nucleus.