How To Distinguish Predatory From Plant-Feeding (Herbivorous) StinkbugsĀ 
As a general rule, beaks of predatory stinkbugs are at least twice as thick as their antennae, while beaks of herbivorous stinkbugs are as thin or thinner than their antennae. This characteristic holds for adults and nymphs and can easily be seen with a handlens.
Predator Example:
Spined Soldier Bug (Podisus maculiventris)

Herbivore Example:
Brown Stink Bug (Euschistus servus)

Predator BeakHerbivore Beak