Sampling Rhyparida nitida Clark (Coleoptera : Chrysomelidae) and symptoms of their damage on sugarcane

Sampling statistics were determined for larvae, pupae and adults of the chr ysomelid Rhyarida nitida associated with sugarcane in Australia and for sym ptoms of their damage. Iwao's patchiness regression was inappropriate for m odelling the mean-variance relationships of the insect counts. Taylor's pow er law was used to model these data and relationships were developed for co unts of small, medium and large larvae, all larvae combined, pupae and adul ts. The mean-variance relationships of counts of live shoots and shoots kil led by larvae of R. nitida were modelled using Iwao's patchiness regression ; Taylor's power law was not appropriate to either data set. Relationships to determine sample sizes for fixed levels of precision and fixed-precision -level stop lines for sequential sampling of the different stages and live and dead shoots were also developed. Neither the In(x + 1) transformation n or the Healy and Taylor transformation consistently standardised the mean-v ariance relationships of insect counts and the appropriate transformation s hould be selected on a case-by-case basis. Counts of both live and dead sho ots were adequately transformed by the Iwao and Kuno transformation.