Adults of Periplaneta americana, P. australasiae, P. brunnea, P. fuliginosa, and P. japonica are well known and have been well described. However, little systematic work has been conducted on the immature stages. There are very few descriptions of the nymphs of any Periplaneta species, and those that are available are rather brief and not completely accurate. This paper presents detailed descriptions and keys to the first-stage nymphs of the above species. Five types of setae, including unique mechanoreceptive setae, were found on the thoracic segments. P. australasiae, P. fuliginosa, and P. brunnea have very setose thoracic nota·and a banded color pattern, while thoracic nota of P. americana and P. japonica are less setose and solid in color. Great variability of setal number and color pattern probably exists among all the species in the genus. / Master of Science