Where there are plants, there are almost certainly aphids feeding on them. These ubiquitous insects are banquets for many predators, and some have evolved incredible defences against them. The cabbage aphid, for example, is a walking bomb.
Its body carries two reactive chemicals that only mix when a predator attacks it. The injured aphid dies. But in the process, the chemicals in its body react and trigger an explosion that delivers lethal amounts of poison to the predator, saving the rest of the colony.
The aphids' chemical weapons are stolen from the plants they eat. Far from being sitting ducks, plants defend themselves from herbivores with a wide range of poisons. Cruciferous vegetables, for example, such as mustard, watercress and wasabi, use a group of chemicals called glucosinolates.
These are harmless on their own, but when they come into contact with an enzyme called myrosinase, the result is a violent ...
