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 ofthe 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.

Overlooked side effects of organic farming inputs attract soil insect crop pests

“…Furthermore, the discrepancy in larval survival found in our study could be explained by the higher moisture sensitivity of first‐instar larvae than of eggs (King et al. ), but very wet soil also hosted few eggs. Although the later observation contrasts a report by Logan , a similar finding obviously demonstrated that decomposing plant residues are associated with lower number of eggs than decomposing cow manure (Fig.…”

Quantifying the economic cost of invertebrate pests to New Zealand’s pastoral industry

“…Both temperature and moisture are critical factors governing population change, with early larval instars being the most sensitive of the life stages to these factors. Cumulative thermal units above 15°C in spring are directly related to summer larval survival, while high soil moisture in spring and early summer adversely affect early stage larval survival (King et al 1981a(King et al , 1981b. Warm temperatures also accelerate larval development leading to early adult emergence which allows the beetles a longer period for accumulating fat before winter.…”

Colonisation of renovated pastures in Waikato by four coleopteran species

“…In the northern half of the North Island these four pest species are often sympatric. Costelytra zealandica and H. arator are univoltine species (Henzell et al 1980;King et al 1981), S. lepidus is bivoltine (Gerard et al 1999) while N. lecoloma takes 8-24 months to complete a generation (Hardwick 1999). Heteronychus arator, C. zealandica and S. lepidus disperse away from previously occupied areas by flights occurring in autumn, spring and summer respectively (Henzell et al 1980;Watson 1980;Addison & Hardwick, unpubl.…”