II. A rapid mechanical extraction method suitable for intensive sampling ofCostelytra zealandicaand other scarabaeids

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Abstract
A mechanical method has been developed for the rapid and large-scale extraction of the scarabaeid Costelytra zealandica (White) from soil samples (10 cm diameter × 25 cm). The method gives acceptable recovery rates for the egg, larvae, and teneral beetle stages of between 95 and 99%, without adversely affecting their viability. Cadavers of the species are recovered together with a wide range of soil macro-arthropods. The average extraction rate varies from 77 egg samples to 109 third-instar teneral adult samples per 8 hour man-day. This rapid rate has been accomplished by eliminating oil-water-interface separation and by using various labour-saving devices such as a recirculation system for aqueous magnesium sulphate, a conveyor belt to remove waste soil from the extraction unit, and roller races to move processed samples between operators. The method has been used successfully for two other soil-inhabiting scarabaeids. Herteronychus arator (Fabricius) and Pyronota jestiva (Fabricius).