1. (1) Megaloblatta blaberoides nymphs stridulate in response to disturbance. Sounds are produced by rubbing a pair of bilateral ventral files on the sixth sternum across opposing stationary scrapers located laterodorsally on the fifth sternum. The forward-moving file on one side and the backward-moving contralateral file generate sound simultaneously. 2. (2) Intact nymphs produce a broad frequency band noise (5–35 kHz). Due to superposition of signals and silent pauses produced by the bilateral organs, no regular pattern of amplitude modulation is measurable. The sound produced by unilaterally muted nymphs contains regular pulse-train groups (forward and back cycle) each of which is divided into a short forward motion and a longer backward motion. These are interrupted by a short pause. A longer pause occurs prior to the anteriorly directed motion of the intact file. 3. (3) Megaloblatta's proteinaceous tergal secretion is chemically and physically similar to that of Blatta orientalis. Coupling of acoustic warning, bright colour patterns, and chemical defence constitutes a multi-modal aposematic display which may be effective both nocturnally and diurnally against potential predators.