The eggs of the South American palm borer (Paysandisia archon) are fusiform (tapering off at both ends), resembling rice grains. They have a light creamy or creamy pink colour when freshly laid, with six to seven ridges. Most eggs are found within the fibre webs closest to or within the palm crowns.
Immediately after hatching, the larva is pink. After the first moult, mobility diminishes considerably and the larva turns ivory white. There are nine larval instars. The larvae start feeding immediately after hatching and bore into the host plant.
The pupae are about 5.5 cm long and are pale yellowish immediately after pupation, then turn reddish brown within about two days. Most of the abdominal segments are furnished dorsally with transversal rows of short spines pointing backwards. The pupae are protected by a palm-fibre cocoon, which makes them very cryptic. The pupa exits the cocoon using its spines and the mobility of its abdomen. Pupal exuviae can be found anchored in the cocoon.
The adult is a large moth with a wingspan of 6 to 10 cm and has greenish-brown forewings. The hindwings are orange, with a wide transverse black band containing five or six white cells. The antennae are clubbed with a typical apical hook. Females bear a long, telescopic ovipositor and are generally larger than the males.