Insects breathe through tracheae opening at spiracles along the body wall, and airflow through them is normally near-silent. In Gromphadorhina, a pair of enlarged spiracles on the fourth abdominal segment can be constricted while the abdomen contracts sharply, driving air through the narrowed opening and producing an audible hiss.
The animal uses more than one hiss. A disturbance hiss is given when the roach is handled or threatened, and males also produce hisses during aggressive encounters and courtship, with fighting males hissing as they push at each other with the thoracic horns. Playback and observation indicate that individuals respond to the sounds of others, so the signals function socially rather than only as a startle response.
The species is also ovoviviparous: eggs are retained inside the female in an ootheca held internally, and she gives birth to live nymphs. That reproductive mode, and the animal's size and docility, are why it is one of the most widely kept insects in classrooms, but the trade-off is that captive populations often carry mite associates that alarm new keepers unnecessarily.