Psilogramma casuarinae

Psilogramma casuarinae (Walker, 1856)
Southern Privet Hawk Moth
(formerly known as Macrosila casuarinae)
SPHINGINAE, SPHINGIDAE, BOMBYCOIDEA

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

Psilogramma casuarinae
early instar
(Photo: courtesy of Tom and David Sleep, Brisbane, Queensland)

Initially this caterpillar is green with a nearly straight horn on its tail pointing backwards.

later instar
(Photo: courtesy of Joanne Edelman, Albury, New South Wales)

Later instars develop a series of diagonal white stripes on its sides, and pale tubercles on the thorax, tail spike, and claspers. As well as the green form, there is also a brown form of the caterpillar which may still has areas of green on it.

Brown form of the caterpillar
(Photo: courtesy of Tom and David Sleep, Brisbane, Queensland)

The coloration of both forms of the caterpillar look very striking, but when the caterpillar is on a foodplant, the spacing of the stripes is often about the same as that of the leaves, and the caterpillar becomes very hard to see. This use of colour to hide is a form of camouflage. The caterpillar is most easily located by observing the black fecal pellets under the bush where it is feeding.

close-up of head and thorax in threat posture
(Photo: courtesy of Trevor Jinks, Upper Burnett, Queensland)

When disturbed, the caterpillar lifts the front of its body, and bends its head underneath, exposing the tubercles on its thorax.

The caterpillar is an agricultural pest on

Olive trees ( Olea europaea, OLEACEAE ),

but is perhaps most often found in suburbia on

Privet ( Ligustrum sinense, OLEACEAE ), and

Trumpet Creeper ( Campsis radicans, BIGNONIACEAE ).

It has also been found on common garden plants of other families, such as :

Japanese Honeysuckle ( Lonicera japonica, CAPRIFOLIACEAE ),

Pagoda Plant ( Clerodendrum paniculatum, LAMIACEAE ),

Snapdragon ( Antirrhinum majus, PLANTAGINIACEAE ), and

Golden Dewdrop ( Duranta repens, VERBENACEAE ).

As it matures, it becomes voracious, being observed to eat at least 28 leaves from the small-leaved privet tree a day. The caterpillar grows to a length of about 8 cms.

(Photo: courtesy of the Macleay Museum, University of Sydney)

When the caterpillar is fully grown, it leaves the food plant and walks up to 20 metres to pupate under the soil to a depth of up to 15 cms. The pupa is brown with a separate compartment loop under the head, in which the haustellum develops. The pupa can have a length up to 5 cms.

(Photo: courtesy of Ted Cadwallader, Swan Hill, Victoria)

The adult moth has long narrow forewings which are a boring grey colour, with a variable darker grey pattern. Unlike other Psilogramma species, there is no obvious white dot near the middle of each forewing. The hindwings are dark grey, each with a pale area containing a wavy black line at the tornus. The thorax is grey outlined in black. The abdomen is pale grey with dark sides, and a dark dorsal line. The wingspan is can be over 10 cms.

(Photo: courtesy of Andrew Mitchell, Australian Museum)

The underside is brown with a series of with dark submarginal bands. The moth typically rests with the tip of the abdomen curled under the body. The male can make a hissing sound by rubbing parts of its body together.

underside
(Photo: courtesy of Eileen Collins, Chiltern, Victoria)

The eggs are spherical and initially pale green, and laid singly on the underside of a leaf of a foodplant. They have a diameter of about 2 mm.

(Photo: courtesy of Tom and David Sleep, Brisbane, Queensland)

The species occurs in

New Guinea,

as well as in Australia in

Queensland,

New South Wales,

Australian Capital Territory, and

Victoria.

This species is difficult to distinguish from Psilogramma menephron.