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Biol Lett. Jun 23, 2009; 5(3): 306–309.
Published online Mar 4, 2009. doi:  10.1098/rsbl.2008.0764
PMCID: PMC2679915
Behavioural phase polyphenism in the Australian plague locust (Chortoicetes terminifera)
Lindsey J. Gray, Gregory A. Sword,* Michael L. Anstey, Fiona J. Clissold, and Stephen J. Simpson
School of Biological Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia
*Author for correspondence (greg.sword/at/
Received December 11, 2008; Revised February 5, 2009; Accepted February 5, 2009.
Swarming and the expression of phase polyphenism are defining characteristics of locust species. Increases in local population density mediate morphological, physiological and behavioural changes within individuals, which correlate with mass marching of juveniles in migratory bands and flying swarms of adults. The Australian plague locust (Chortoicetes terminifera) regularly forms migratory bands and swarms, but is claimed not to express phase polyphenism and has accordingly been used to argue against a central role for phase change in locust swarming. We demonstrate that juvenile C. terminifera express extreme density-dependent behavioural phase polyphenism. Isolated-reared juveniles are sedentary and repelled by conspecifics, whereas crowd-reared individuals are highly active and are attracted to conspecifics. In contrast to other major locust species, however, behavioural phase change does not accumulate across generations, but shifts completely within an individual's lifetime in response to a change in population density.
Keywords: phenotypic plasticity, behaviour, migration, phase polyphenism, insect
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