Cockchafers

Scarabaeidae, Liparetrus species and Colymbomorpha vittata

Family:

Order: Coleoptera

Other names:

Bardi grubs

Whitegrubs

Description:

Adult

Colour - Bronze, brown, orange or dark blue often with a darker head.

Body - Elongated. Cylindrical. 12 mm long, 5 mm wide.

Wings - 2 Pairs. Front wings modified to form hard protective cases (elytra) for rear wings. When at rest they meet in a straight line down the centre of the back. Rear wings membranous and folded both lengthwise and across so they fit under their protective cases. When in flight the elytra are held at an angle and the rear wings beat rapidly. Rear wings may be reduced or absent in some species. Wing-span up to 30 mm. Both pairs attached to the hind body.

Mouthparts - Chewing. Pointing forward.

Antennae - 11 segments. Thread like.

Legs - Rear legs larger than front legs. Feet (Tarsi) simple.

Head - Rigid. Large rounded compound eyes.

Thorax - Front segment associated with head to form distinct fore body. Front segment covered by a hard plate (pronotum). 2 rear segments fused and associated with the abdomen to form hind body.

Abdomen - 10 segments in male, 9 in female. Often only 8 can be counted by eye. Spiracles on segments 1-7 and often on 8 also.

Egg - Usually simple and ovoid.

Habits - Can't fly when cold.

Larva -

Colour - White to cream with darker brown head and dark tail.

Body - Has legs, Long and thin, cylindrical. 25 mm long, 6 mm wide. Tail often swollen and darker due to soil and food contents. Curled or C shaped.

Mouthparts - Chewing. Transverse action.

Antennae - 1 segment.

Legs - 6 legs. 5 segments.

Head - Usually a hard capsule. No ridges on forehead.

Thorax - No functional spiracle on middle segment.

Abdomen - 8-11 segments. No prolegs. Spiracles on segments 1 to 8. Swollen and dark or translucent.

Habits - Feeds underground on roots, tubers or decaying plant material.

Pupa - In soil in earthen cavity.

Biology:

Life Cycle:

Eggs usually laid in pasture paddock or native bush. Larva hatch and initially feed on decaying plant material then feed underground on roots and tubers. In winter they pupate in earthen cells. Adults emerge in spring and may form large swarms that are often seen on calm sunny mornings after rain.

Habitats:

Origin and History:

Distribution:

Significance:

Pests of trees and native wildflowers. Young trees may be severely defoliated and die especially if other stresses are present. Native flower blossoms may be damaged making them unmarketable. Trees on fence lines or windbreaks are most severely affected. In plantations, trees adjacent to native bush are usually most affected. Eucalypts are more susceptible to damage than other species. Old trees are rarely killed. Trees less than 2 years old can be killed.

Management and Control:

Control is difficult because there may be repeated invasions. Damage occurs very quickly so constant monitoring and prompt spraying is essential. Even with spraying, damage can be severe when large numbers are present because the beetle has to eat part of the foliage to receive a dose of insecticide.

Controlling larvae or beetles in adjacent areas has been ineffective.

Related Species:

African Black beetle, Black pasture cockchafer, Cockchafer, Scarab beetle, Spring beetle.

Similar Species:

References:

WADA. Insects and Allied Pests of Extensive Farming. Department of Agriculture - Western Australia Bulletin No. 4185. p91.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.