African Black Beetle

Heteronychus arator

Family: Scarabaeidae

Order: Coleoptera

Description:

Adult

Colour - Brown to shiny black.

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. Usually walk but occasionally fly into paddocks.

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 into a C shape.

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 -

Biology:

Life Cycle:

Eggs usually laid near food source for larva in summer. The larvae are C shaped or curl grubs with a brown head and dark tail. They hatch and initially feed on decaying plant material then feed underground on roots and tubers. In early autumn they pupate in earthen cells. Adults emerge and feed until cold weather forces them to burrow into the soil and hibernate until spring.

Habitats:

Origin and History:

Accidentally introduced from South Africa

Distribution:

Significance:

Pests of cereals, grasses and root crops such as potatoes. Feed on roots making crop unmarketable, killing seedlings or causing lodging of cereals. Adults chew stems at or just below the ground level. Young larvae feed on decaying plant matter and older ones feed on living tissue. In perennial grasses dead patches may appear and plants are easily pulled from the ground.

Management and Control:

Control is difficult.

Cultivation before planting, crop and pasture rotations help reduce the effects.

Insecticides are often ineffective because of the beetle and larva spends much of its time below the ground.

Related Species:

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

Similar Species:

White fringed weevil causes similar damage on potato tubers.

References:

CSIRO. The Insects of Australia. Melbourne University Press. (1991) p562.

WADA. Insects and Allied Pests of Extensive Farming. Department of Agriculture - Western Australia Bulletin No. 4185. p40.

Acknowledgments:

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