The moth is reddish-brown and measures 23-25 mm across the extended wings. The male is smaller than the female, which has a large dark triangular blotch two thirds of the way along the hind margin of each forewing.
Damage: Macadamia nutborer is a major pest of lychee and longan fruit, and significant infestations occur in most seasons.
On hatching, larvae bore through the skin and into fruit in search of the seed. When this occurs in green fruit, the fruit will drop, however the larva will most likely still develop to maturity in the fallen fruit, if ground predators don't discover it. Ripening fruit generally does not fall, and the larva often drowns in the juice if the skin is penetrated in the equatorial region where the flesh is thickest.
The rind tissue around the entry hole may appear to be scalded, and such damage is sometimes wrongly attributed to fruit fly, which rarely attacks lychees and longans. Entry on the shoulder or near the peduncle is more likely to ensure survival of the larva enabling it to reach the seed. Mature fruit damaged by macadamia nutborer may weep and stain other fruit in the cluster or those hanging below. One larva can cause perhaps 10% more damage through this secondary staining effect.