Minimising mortality in field and pot experiments using Heteronyx piceus Blanchard (Coleoptera : Scarabaeidae) eggs and larvae

The establishment of experimental populations of scarab larvae using eggs a nd early instar larvae has proven to be difficult for many researchers. Des pite this, little work has been published examining ways to optimise establ ishment under artificial conditions. In this experiment, we examined the ef fect of shade and irrigation on the establishment of Heteronyx piceus Blanc hard larvae introduced into pots as eggs and first-, second- and third-inst ar larvae to optimise artificial infestation techniques. The most important factor affecting larval establishment was the life stage introduced. Estab lishment of eggs and first instars was very low, with only 21% of eggs and 11% of first-instar larvae establishing. In contrast, 82% of second-instar larvae and 84% of third-instar larvae established successfully. The additio n of shade marginally improved overall survival from 45% in the unshaded po ts to 53% in the shaded pots. However, most of this increase was in the egg s and first instars. Irrigation did not improve survival. These results sug gest that when introducing scarab larvae to field or pot experiments, secon d- or third-instar larvae should be used to maximise establishment. The pro vision of shade and supplementary irrigation is optional.