Activity patterns and population characteristics of the New Zealand endemic Cromwell chafer, Prodontria lewisii (Scarabaeidae; Melolonthinae)

Abstract

The sole remaining population of Cromwell chafer beetles was investigated by pitfall trapping during the spring and summer months of 1986, 1989, 1993, 1994, 1996 and 1997 as part of an ongoing management programme. Sampling by pitfall trapping proved to be a major source of variation in the database. Within this constraint, no marked weekly differences in activity during the spring and summer months were recorded. Males appeared to emerge slightly earlier than, and were active longer than, females. Variation in activity during spring and summer months was related to temperature and humidity, but these explained only 27% of the variation. Variation in density was most marked between quadrats within the study area, with little temporal variation. We conclude that, so far as we can tell from present sampling techniques, the chafer population is relatively stable.

Keywords:

• Cromwell chafer beetles
• Prodontria lewisii
• activity patterns
• population densities
• sex ratios
• sampling techniques