Never put your G. portentosa with your Tiger hissers Gromphadorhina grandidieri (listed in Europe as "Princisia vanwaerbeki black and white", etc.)
Unfortunately it would appear that they can cross.
(It should not be that great a surprise as they have the same male genitalia.)
Unfortunately it would appear that they can cross.
(It should not be that great a surprise as they have the same male genitalia.)