Diet and phenology of the carabid beetles Metaglymma monilifer and Hypharpax australis on Canterbury arable farmland : A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Science with Honours at Lincoln University

Abstract

With worsening environmental problems in many current agroecosystems, the search for more sustainable farming techniques has led to interest in biological control, particularly conservation biological control. Before effective conservation biological control can be achieved a clear understanding of the diet, phenology and potential efficacy of already present populations of predatory arthropods is needed. Overseas studies have focused on populations of ground dwelling polyphagous predators. However, in New Zealand very little is known of the phenology, biology and ecology of these predators. In order to determine which predators are potentially valuable to biological control, it is necessary to identify species which may reduce pest populations; predator diet is an important facet of this knowledge. The aims of this study were to increase the knowledge of individual predatory species within New Zealand agroecosystems by investigating the diet of two of the common carabid predators on Canterbury farmland. Individuals of Metaglymma monilifer Bates and Hypharpax australis Dejean were collected by pitfall trapping from the Lincoln University mixed cropping farm. Individuals were dissected and dietary analysis performed with the aid of a microscope. The diets of H. australis and M. monilifer were significantly different (P <0.001). The diet of M. monilifer was more diverse with five identifiable prey orders (Coleoptera, Araneae, Diptera, Hymenoptera and Collembola), while only two prey orders were identified for H. australis (Coleoptera and Diptera). However, dietary analysis was limited for H. australis; this was due to the small size of the beetle and consequent fineness of prey remains, and a significant proportion of dissected individuals had empty guts (P<0.002). Females of both species had a higher incidence of fluid feeding and fewer were found with empty guts compared with males. The importance of soil surface predators, particularly Carabidae in arable farmland is discussed with particular reference to the biological control potential of M. monilifer and H. australis.