These Caterpillars are an international agricultural pest, particularly on :
- Cabbage ( Brassica oleracea, BRASSICACEAE ).
They are initially grey, and become green with a yellow dorsal stripe. They have a brown head. Initially they feed only on the undersides of the leaves, leaving the upper leaf membrane intact. Later they attack the central shoot, feeding communally in a web. Over their larval period of about three weeks, they grow to a length of about 2 cms.
The pupa is green turning brown with a length of about 1 cm. It is formed in a loose cocoon in the loose soil at the base of the foodplant.
The adult moths are brown with dark markings, and two white spots on each forewing. The wingspan is about 3 cms.
The female is similar to the male but has a less pronounced pattern on the wings.
The eggs are somewhat flat, greenish and are laid in masses of up to 300 at a time. They are arranged in scale-like fashion, one egg overlapping another. They hatch after about four days.
The species is found from South Africa through India to the Pacific including :
Control of the pest is being attempted using :
An interesting observation was made of some moths that had emerged – all female. They were found on their backs on the sand, flapping their wings feebly. Maybe if they get disorientated and overbalance when emerging, before their wings dry and harden, they are not capable of turning themselves over? After turning one the right way up, it got to its feet, flapped its wings, and flipped straight over onto its back again. If disorientation does cause their demise, perhaps turning the soil around the base of their foodplant when they are pupating would greatly cut down on next year’s infestation?