Conservation of the Cromwell chafer Prodontria lewisi (Coleoptera: Scarabaeidae)
- Entomology Division, DSIR, Auckland, New Zealand
The Cromwell chafer, Prodontria lewisi, is a flightless chafer beetle whose natural range appears not to have been more than 500 hectares and which now, because of habitat destruction and modification, is reduced to about 100 hectares. This inhabited area is situated on the terrace on which the town of Cromwell, Central Otago, is built. The continued existence of the Cromwell chafer is threatened by the expansion of Cromwell township and increasing human activities in the vicinity.
P. lewisi is thought to have evolved from a small founder population which became isolated in the Cromwell basin some time during the Pleistocene. It lives in stabilised dunes of wind-blown sand. Adults come out at night to feed mainly on scabweeds (Raoulia spp.). Larvae feed on the roots of tussocks, especially Poa laevis. Apart from habitat modification, an important limiting factor on P. lewisi may be predation by the little owl, Athene noctua.
The Cromwell Borough Council has fenced an area of 95 hectares of predominantly native vegetation on wind-blown sand, inhabited by P. lewisi, south-west of Cromwell township. It is hoped that this area will soon be declared a reserve. The natural vegetation is threatened by exotic trees and shrubs, especially Pinus radiata. Proposals for control of exotic plants, and other management proposals, are outlined. Vegetation of the proposed reserve is mapped, and described in an appendix by Dr J. C. E. Hubbard and Mr T. Partridge.