Key to species of the genus Sigmaboilus based on tegmen

1. Whole tegmen fuscous.................................................................................................................................................. 2

-. The coloration of tegmen formed irregular bands ........................................................................................................ 3

2. Second anterior branch of CuA+CuP1a forked and CuP1b straight ............ S. gorochovi Fang, Zhang & Wang, 2007

-. Second anterior branch of CuA+CuP1a pectinate and CuP1b curved. .............................................. S. fuscus sp. nov.

3. First and second anterior branch of CuA+CuP1a forked, the ‘handle’ forming a distinct angle with crossvein between the ‘handle’ and CuP1a ....................................................................... S. sinensis Fang, Zhang & Wang, 2007

-. Second anterior branch of CuA+CuP1a dichotomously ramified, the ‘handle’ subparallel to each crossvein between the ‘handle’ and CuP1a ................................................................................................................ S. peregrinus sp. nov.