Tritrophic interactions on a sticky plant: Indirect defense and hostplant farming by predators

Sticky plants - those producing adhesive glandular exudates - are typically thought to exclude predators. The sticky exudates are considered a direct defense that carry a cost of also inhibiting indirect defense. In common madia (Madia elegans), plant stickiness actually enhances indirect defense by entrapping insects which provision food for predators. Even generalist predators are able to control herbivores on sticky tarweed plants. Furthermore, the volatiles released by the rupturing of tarweed's glandular trichomes (which occurs via insect contact) attract a key specialist predator in the system, the assassin bug Pselliopus spinicollis, which appears to use the volatiles as a direct signal of prey availability. Another predator in the system, the tree cricket Oecanthus quadripunctatus, induces tarweed to become stickier through feeding and oviposition damage. This induced increase in stickiness translates into a 60% increase in the amount of carrion that is entrapped on tarweed, and is then fed upon by the tree cricket.