Locust Phase Polyphenism: An Update

This chapter updates former reviews on locust polyphenism and also discusses recent findings. Over 200 articles were published in scientific journals on various aspects of locust phase polyphenism, markedly advancing the knowledge of the subject. However, the chapter refers to the older literature when background information is necessary for complementary and better treatment, or because of historical importance. Some of the recent publications report contradictory findings, and such contradictions have been emphasized in the chapter. Substantial progress has been made in the study of locust phase polyphenism over the past several years. The topic has well and truly emerged from the realms of applied entomology to assume a prominent position in the modern study of phenotypic plasticity, whereby adaptive phenotypes arise during development as a result of plastic interactions between genes and the environment. The study of behavioral gregarization has seen some of the most far-reaching progress. The involvement of locust-emitted volatiles in aspects of phase biology has generated substantial research and its fair share of productive controversy. It has been especially heartening to see that some of the major areas of controversy, such as the role of phenylacetonitrile, appear to have been at least partially resolved during the past year. New genetic resources also offer a solution to a more prosaic problem in locust research. There has been a growing realization that some of the differences reported between laboratories in aspects of phase polyphenism most likely reflect effects of rearing locusts in long-term culture in the laboratory.