II. A rapid mechanical extraction method suitable for intensive sampling of <i>Costelytra zealandica</i> and other scarabaeids

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).