Ecology of black beetle, Heteronychus arator (Coleoptera: Scarabaeidae)—Population studies

Abstract

The dynamics of populations of black beetle, Heteronychus arator (F.), in plots of paspalum (Paspalum dilatatum Poir), ryegrass (Lolium perenne L.), and ryegrass/white clover (Trifolium repens L.) pastures were studied. Life tables were constructed which quantified individual and generation mortalities and identified the key factors causing population change. The important components were variation in natality, summer mortality, and winter-spring disappearance. Investigation of the density relationships of the mortalities revealed possible density dependence in the variation in natality. Two very different types of population dynamics were evident. Populations in paspalum pastures were relatively stable, but in ryegrass pastures large population decreases between autumn and spring suggested that these pastures are favourable habitats during spring and summer only. Examination of the possible components of population mortalities revealed significant relationships between key mortalities and the level of population development. Evidence for the role of soil temperature and moisture levels, disease, adult migration, and combat mortality in influencing population change is presented.

Keywords:

• Coleoptera
• Scarabaeidae
• Heteronychus arator
• population dynamics
• Paspalum dilatatum
• Lolium perenne
• Trifolium repens
• life tables
• mortality factors
• population change
• population regulation
• key factor analysis