The enemy of my enemy is my friend—that's the strategy ladybugs rely on to protect their offspring and themselves from ants. Ladybugs prefer laying eggs in areas rich in prey, such as the green coffee scale insect (Coccus viridis). However, tree-nesting Azteca instabilis ants, which farm the scale insects to collect their sweet honeydew, routinely assault ladybugs and their eggs (as seen in this picture). To figure out how ladybugs overcome this challenge, scientists collected ladybugs, ants, scale insects, and phorid flies from an organic coffee plantation in Mexico and placed them in an olfactometer, an instrument that measures odors. Ants release a specific alert pheromone when the flies attack that renders the ants motionless for up to 2 hours, since the parasites go after motion. The researchers found that female ladybugs, especially pregnant ones, eavesdrop on these chemical alarms and hunt for areas rich in scale insects during the ensuing lulls in ant activity, findings that will be detailed in a future issue of Ecology and Evolution. This is the first known time a cascade of interactions between multiple species of insects was triggered by ant pheromones, the team reports, a complex web of intrigue that may be common in nature.
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