This book is dominantly about chemical defences of terrestrial arthropods, though other types of defences (camouflage, catapulting, sticky traps) are also mentioned. Chapters are short, and typically feature the defences of one organism, or at most a small group of related organisms. One or more colour photos, in themselves almost worth the cost of the book, enhance both the aesthetics of the book and the ability to drive home each chapter’s message. Chemical formulae are illustrated in those chapters focusing on chemical defences. As the subtitle alludes, an array of terrestrial arthropods is dealt with, but by far, the majority of this book is about insect defences. However, scorpions, centipedes and other non-insects together account for about 15% of the book’s material. Examples include the well-known spray of the Bombardier Beetles, the less well-known vomit attacks of noctuid moth caterpillars and immobilizing wax of oleander aphids. This book will appeal to a wide array of readers, the caveat being that those with no (or little) training in chemistry (like me) will miss out on some of the nuances of the chemicals themselves; this did not give rise to any problems at all for my enjoyment of this book. The other caveat being that those not liking those long, tongue-tripping scientific names of organisms will have to gloss over them periodically as they read; even where common names exist for the organism of the chapter’s focus, the scientific name is typically used throughout the text. Grade-school children will be able to use this book though clearly not as completely as older folk; entomology instructors could easily incorporate this material into lectures. Truly, this book can meet the needs of many. There is an abundant amount of fascinating material that simply makes this well-written book a joy to read; I have been equally satisfied after having read Waldbauer’s books, including What Good are Bugs? (also from Harvard Press). Unlike the latter book, the chapter bibliographies of Secret Weapons are replete with papers of the book’s authors, particularly the Eisners. Their work in chemical ecology, translated by them from their papers to this book, is a grand example of making science more consumable by the nonspecialist. RANDY LAUFF