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2/14/21

Cromwell Chafer Beetle

The Cromwell Chafer Beetle, also known as Prodontria lewisii, probably evolved from other populations and then became isolated in the Cromwell Basin in New Zealand. Adults eat scabs weeds, while larvae eat the roots of tussocks. They live underground, in sand.

In the 1960s, an entomologist named Charles Watt searched for any other signs of another population of Cromwell Chafer beetles. When he didn’t find any, he started campaigning for its protection. A space was blocked off for the beetle, and in 1993 it became a nature reserve, the first created for the protection of an insect. Watt also got the community involved, and many people caught and transferred these flightless beetles to the safety of the nature reserve.

For more than 15 years, scientists and rangers have gathered each December to count the Cromwell Chafer beetle’s larvae, a much more reliable way to count a population than counting adult beetles. This process has shown an undeniable decline in recent numbers.

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Image by Rod Morris. The redback spider in a nest full of dead Cromwell Chafer beetles.

The reason for this decline in numbers is mostly habitat destruction and, to a lesser extent, predators. Since the Cromwell chafer’s habitat is originally only about 5 square kilometers, habitat destruction is a serious problem. The town of Cromwell can be found in this area, so the expansion of this town threatens the Cromwell Chafer beetle. Other threats include predation and competition from owls, European earwigs and red back spiders, an imported species from Australia. These spider live in abandoned rabbit holes, so many have been filled in to protect this beetle. One redback spider can kill up to 70 beetles. Because dogs and people’s fondness for the area, people had to get creative, using dogs and ferrets to kill the rabbits.

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Image by Bruce McKinley. The Chafer beetle's larvae.

Image by Bruce McKinley

Image by Rod Morris.The redback spider in a nest full of dead Cromwell Chafer beetles.

Image by Rod Morris. Scientists counting larvae.

Works Cited

Written by Ellen Rykers Photographed by Rod Morris, Rykers, W., & Rykers, E. (n.d.). Beetle mania. Retrieved October 18, 2020, from https://www.nzgeo.com/stories/beetle-mania/

Saving the Cromwell chafer beetle. (2017, December 06). Retrieved October 18, 2020, from https://blog.doc.govt.nz/2017/12/07/saving-the-cromwell-chafer-beetle/

Admin. (2014, July 03). Conservation of the Cromwell chafer Prodontria lewisi (Coleoptera: Scarabaeidae). Retrieved October 18, 2020, from https://newzealandecology.org/nzje/1445