Circopetes obtusata

Circopetes obtusata (Walker, 1860)
(one synonym is : Monoctenia himeroides)
OENOCHROMINAE, GEOMETRIDAE

Don Herbison-Evans ( donherbisonevans@yahoo.com )
&
Stella Crossley

(updated 20 December 2007)

(Photo: courtesy of Merlin Crossley)

This is a very large Geometrid Caterpillar, growing to a length of 7.5 cms. It looks like a stick. Having only a single pair of ventral prolegs, its usual resting and feeding posture is to grasp a twig with its prolegs and claspers, and a leaf with its mouth and claws. The result is a triangle, with the sides made from the twig, the leaf, and the Caterpillar. The Caterpillar rarely rests lying along a twig. When it does, the body curves between the legs and the prolegs so that there is a space between the body and the twig.

The colour of the Caterpillar is basically green, with brown ventral and dorsal patches. It has three pairs of dorsal horns: the largest is on the first abdominal segment; a slightly smaller pair is found on the fifth abdominal segment, and the smallest pair is on the eighth abdominal segment.

For food, our Caterpillars accepted:

Narrow-leaved Peppermint ( Eucalyptus nicholii, MYRTACEAE ).

The Caterpillar contracts slightly in length prior to pupation, and the skin becomes dull in colour and looks rough. The Caterpillar crawls into the soil where it pupates.

(Photo: courtesy of Merlin Crossley)

The adult moth is grey brown on top.

(Photo: courtesy of Peter Marriott)

The underside is similar, but each hindwing has a small brown spot, and each forewing has three brown spots: one large and two small. The moth rests with the forewings outspread and curled, and the hindwings tucked underneath them. The moth has a wingspan of about 6 cms.

(Photo: courtesy of Bruce Anstee)

The abdomen is often held twisted to one side, even when mating.

pair of adult moths mating
(Photo: courtesy of Anthea Flemming)

This breaks the visual bilateral symmetry charcteristic of most animals, and makes them hard to recognize as being animals. When we first encountered a female of this species at night, beneath a mercury vapour lamp, we repeatedly overlooked the moth thinking it was a dead leaf.

Female laying eggs
(Photo: courtesy of Bruce Anstee)

The moth laid many eggs three days later. The eggs are small green-grey oval discs which are slightly thicker at one end. They were glued by one of their flat sides to the surface of a leaf, and often evenly spaced. The eggs hatched five days after laying.