Stinging Nettle

Stinging nettle uses hypodermic needles made of silicon. Each leaf is covered with hollow hairs that break on contact, injecting a cocktail of formic acid, histamines, and acetylcholine. The sting is memorable enough that most animals learn to avoid nettles after one encounter. This is defense through punishment: make the first bite painful enough that there's never a second.

The strategy is remarkably economical. Unlike chemical defenses that require constant metabolic investment, nettle's stinging hairs are structural - once grown, they cost nothing to maintain. The plant invests upfront in glass-like silicon structures, then derives ongoing protection from their passive presence. Defense as infrastructure rather than operating expense.

Nettle's sting is calibrated for educational impact, not lethality. The pain is significant but rarely dangerous to large animals. This is optimal: dead herbivores don't learn, but injured ones spread the message to their social groups. Nettle's defense is essentially a communication system that teaches herbivores to stay away.

The business insight is that defense through memorable punishment requires only occasional enforcement. Security systems that clearly and reliably punish intruders deter more effectively than those that catch everyone but impose mild consequences. Nettle teaches that the goal isn't catching all violations but making violations memorable enough to prevent repeat offenses.