The puzzle of locust density-dependent phase polyphenism

Locust density-dependent phase polyphenism presents a quintessential example of environmentally induced plasticity. Almost a century of research has yielded ample knowledge regarding the multitude of ecological, physiological, and molecular phase-dependent characteristics. This short review highlights the considerable advances that have been made in our understanding of the locust's extreme plasticity and the highly complex nature of the phase phenomenon. Several challenges in locust research resulting from this unique complexity are also presented. It is concluded that the joint, interdisciplinary collaborative efforts, already underway, hold the promise of translating our ample knowledge into a complete solution to untangling the locust phase puzzle.