Caterpillar of the Puriri Moth (Aenetus virescens)
Species: A. virescens
Binomial name: Aenetus virescens
Synonym: Hepialus virescens
Common name: Grub of Puriri moth
Aenetus virescens (Puriri moth) is a moth endemic to the North Island of New Zealand. It is New Zealand's largest moth, with a wingspan of up to 150 mm.
A fertilised female moth lays up to 2000 eggs over forest floor litter. After about 14 days caterpillars hatch and live on the underside of fungal fruiting bodies. This stage lasts for 2 to 3 months. At the end of this phase the caterpillars climb and bore through the bark into the wood of the trunk or a branch of a tree. Host plants include native, naturalised, and cultivated species. Its gets it name because one of the main host trees is the Puriri tree (Vitex lucens).
The caterpillars form a distinctive seven-shaped tunnel. The top of the ‘seven’ follows the radius of the trunk/branch and slopes upwards. The longer part of the burrow descends vertically and is where the caterpillar rests. The opening of the burrow and the area used for feeding are not usually visible, as they are covered with a silk covering that mimics the bark.
The tree phase caterpillars grazes on live callus tissue that develops round the opening of the burrow. A mature caterpillar can grow to about 100 mm long and 15 mm in diameter. Caterpillars during this phase can live up to eight months or as long as five years.
When the caterpillar has reached full size it pupates. Pulpation occurs every month from March to November. Pupal duration can be up to 173 days. When the moth is ready to emerge, the pupa wriggles up the shaft helped by 12 abdominal ridges that help it to work its way out of its burrow.
The moths once emerged from the pupa live for only 48 hours.
The large grubs were regarded by Maori as good eating, and were extracted by pouring water down the entrance hole-forcing the grub to evacuate.