NITROGEN, LEAF TOUGHNESS AND THE POPULATION DYNAMICS OF PAROPSIS ATOMARIA OLIVIER (COLEOPTERA: CHRYSOMELIDAE)—A HYPOTHESIS

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Abstract

For the annual period of activity of Paropsis atomaria, November to May (2 generations), foliar nitrogen (N) concentrations in a major host, Eucalyptus blakelyi were found to vary between 2.44 and 1.38%. Neither growth nor development of older larvae would be limited by foliar N at most sites but fecundity and early larval survival may have been influenced adversely. In the laboratory all larvae which hatched on foliage with < 1% N died during the first instar. Leaves low in N are very tough and mortality probably resulted from inability of first instar larvae to feed rather than by N starvation. These findings suggest that N is not limiting for P. atomaria in most years since new foliage is normally abundant, soft and high in N. It would be limiting in years when new foliage is scarce and most foliage available is old, tough and low in N.

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