Most of us would be familiar with the bright and glossy Christmas beetles. We often see them dazed and confused, crawling around on the ground or in the house in the morning after a big night out (they are attracted to bright lights!).
As their name suggests, the adult beetle is most active during the Christmas season and warmer months. Adult Christmas beetles aren’t much of a pest in most home gardens, although they do feed on eucalypt leaves and can cause severe defoliation in large numbers.
Christmas beetles are about 20 millimetres in length and belong to the Scarab beetle Family (Scarabaeidae) in the Order Celeoptera. The image shown here is courtesy of CSIRO.
Scarab beetles are the second largest family of beetles in Australia. (Weevils are the largest Family).
The life cycle of a Christmas beetle is from one to two years. The larvae of Christmas beetles live and develop in the soil for about a year, eating decaying organic matter and plant roots of mainly native grasses and other vegetation. In agricultural land larvae can feed on the roots of crops and pasture. In urban areas larvae often feed on the roots of turf. This feeding can cause plants to turn yellow and wither.
Toward the end of winter the larvae move closer to the soil surface and pupate. The adults emerge several weeks later and dig their way out of the soil. They then fly to the nearest food plant to feed. And of course their other main duty at this stage is to mate. They then lay eggs in the soil close to their food source.
There are many other Anoplognathus species, in fact there are 35 species of Christmas beetle across Australia, and many are brightly coloured, such as the bright green tropical Christmas beetle shown here, courtesy of www.wildwatch.com.au. Eight species alone occur in Sydney. All are attracted to bright lights at night.
Geoff Monteith, curator of the insect collection at the Queensland Museum says Christmas beetles have a bad reputation for causing dieback of trees, which they don’t entirely deserve.
In the home garden, Christmas beetles are seldom a problem. In fact, they are usually controlled naturally by native animals such as possums, currawongs, magpies and predatory wasps.
However, if they do reach plague proportions they can have a big impact on even healthy trees. Colonies can be disrupted with jets of water. When disturbed during the day adults drop straight to the ground, so laying plastic sheets underneath heavily infested trees and then shaking the tree or disturbing the beetles with jets of water will cause them to drop onto the plastic. They can then be collected and destroyed.
Spraying is not recommended as it is difficult to apply chemicals to large trees and the beetles move when disturbed.
Christmas beetles are an ideal insect to introduce to children as they are quite placid (especially after a big night out).
Glen Johnson from the Department of Sustainability and Environment quipped on ABC Radio back in 2005 that Christmas beetles don’t wear bells but they do emerge at this time of the year without the benefit of a calendar!