Underground Grass Grub

Oncopera fasciculata

Family: Hepialidae

Order: Lepidoptera


Attracted to lights.
Colour - Brown or grey.
Body - Large size. Stout. Long hair scales.
Wings - 2 Pairs. Membranous. Hairy. Slender. Patterned. Wing-span 40 mm
Mouthparts -
Antennae - 3 segments.
Legs - Broad overlapping scales. Feet (Tarsi) have 5 segments.
Head - Broad overlapping scales. Large rounded compound eyes.
Thorax - Broad overlapping scales. 3 segments. Front segment much smaller. Hairy
Abdomen - Broad overlapping scales. 7-11 segments. Spiracles on segments 1-7. Hairy
Egg -
Habits - Can't fly when cold. Rapid flyers from the "Swift moth" family. Fly at night in spring. Large flights of moths may be associated with rain.
Attracted to fire. Cooked moths eaten by aborigines.
Caterpillar -
Colour - Young - Dark with black head. Mature - Dark green brown or bluish. Prepupal - Pale greyish yellow.
Body - Summer stage-25 mm long, 4 mm wide. Autumn mature stage-up to 75 mm long, 5-8 mm wide.
Mouthparts - Chewing.
Antennae - Short. 3 segments.
Legs - 5 segments.
Head - Hard. Black.
Thorax - 10-11 segments. Spiracles on segments 1 to 8. Prolegs on segments 3-6 and 10.
Abdomen -
Habits - Herbivorous. Dig into soil to eat roots and emerge at night to eat shoots of grasses. Live under litter in summer and in silk lined vertical tunnels in autumn-winter.
Pupa -
One of the 'witchetty grubs' eaten by aborigines.


Life Cycle:

Moth fly at night in spring and lay eggs on long grass. Eggs hatch and young caterpillars live under litter, feeding on roots over summer. At this stage they are long, thin and dark with black heads. In autumn they make vertical silk lined tunnels 100 - 200 mm deep, grow quickly and feed voraciously. By August a non-feeding, pale greyish yellow prepupal stage is reached which turns into the yellow and brown pupa. Moths emerge in September.


Origin and History:



Caterpillar is a major pest of grasses. Tussocky grasses are worst affected. These are often chewed off at ground level.

Management and Control:

Inspect pastures carefully in summer by digging up the top 75 mm of soil. Insecticides can be applied if caterpillars are present.

Related Species:

Oxycanus Grass Grub.

Similar Species:


CSIRO. The Insects of Australia. Melbourne University Press. (1991) p818 (f41.2Thorax), 820(f41.4Wing scales), 829, 839(f41.20wings), 841.

Goode, J. Insects of Australia. Angus and Robertson. p166 (Larva photo).

Victorian Department of Agriculture. Insect Bulletins. p2.


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