Bands, swarms and plagues
Two's company, three's a crowd. It could be a grasshopper's motto. Grasshoppers are solitary inoffensive creatures, that go about their business hopping from here to there nibbling away at grass, seed, leaves, flowers and stems. There are parts of the world, however, when meteorological conditions favour massive reproduction - such as wet weather after a period of drought, and the sudden growth of greenery - and grasshoppers will begin to aggregate, creating at the same time a fertile playground for multiplication. A grasshopper that aggregates is called a locust. There is no taxonomical difference between the two, just a shift in the grasshopper's behaviour and morphology. A band of locusts will grow into a swarm which can become a plague where billions of locusts migrate together landing on crops that they will devour, before moving onto the next. Besides rain after drought, what could prompt a solitary grasshopper to become gregarious? The answer is 4-vinylanisole, or 4VA, a pheromone that is released by locusts and seduces other locusts. 4VA becomes active - although it would be more apt to say attractive - by binding to a protein receptor on the locust's antennae. The olfactory receptor 35, or OR35.
