The Elements of Evolution (51-1-12) Locusts


Desert locusts transform between two extreme phases, solitary and gregarious, depending upon their local population density. ~ Brazilian biologist Patrício Simões et al

Locusts are nominally solitary grasshoppers that abruptly switch lifestyle to swarm as a ravenous horde after food becomes abundant and population size soars. It is a Jekyll-and-Hyde transformation.

When in their solitary phase, locusts are unassuming: their brown-green bodies ideal camouflage to blend into the foliage as they saunter with a low, creeping gait. Solitary locusts generally avoid one another unless they are mating.

Lifestyle dramatically changes after it rains and enough food becomes available to spur population multiplication. Then, as their numbers skyrocket, food exhaustion and physical contact with other locusts from overcrowding triggers a cascade of metabolic, mental, and behavioral changes.

The solitary and gregarious forms are so distinct in physiology and aspect that they were once thought to be distinct species. Instead, the extravagant show of adaptability is an ecologically induced fervor.

Gregarious locusts are colorful, move faster, and are attracted to other locusts. In this phase locusts form oppressive swarms that can blacken the skies and decimate vast fields of vegetation.

As a solitary insect, a locust is quite picky about what it eats. In swarm mode, locusts have no aversion to the bitter tastes which plants present to avoid being eaten alive.