Distant (1910) while transferring Caystrus nigriventris Germar for the first time in its appropriate genus Caystrus Stål synonymized
marginiventris Stål with it and Linnavuori (1982) speculated that another species C. trivalis might only be a race of S. marginiventris.
Presently not only C. nigriventris is redescribed but the above three species/forms are compared in table I and the genitalial characters of C.
marginiventris and C. trivalis are compared in table II (in the male holotype of nigriventris the pygophore is missing).
