The defensive secretion of Parectatosoma mocquerysi, a walkingstick insect from Madagascar, was determined to contain glucose, water, and a new monoterpene, parectadial, (4S)-(3-oxoprop-1-en-2-yl)cyclohex-1-enecarbaldehyde. Here, we describe the elucidation of parectadial's molecular structure and absolute configuration via microsample NMR technology, GC-MS, CD, chiral GC-FID, and synthesis from enantiomerically pure (S)- and (R)-perillaldehyde. This work demonstrates the value of walkingstick insects as sources of new bioactive compounds and provides an analytical framework for identifying such substances.