Fly (Sawfly) Pontania promixa) Willow Redgall
Scientific name: Pontania promixa
Common name: Willow Redgall Sawfly
Pontania proxima is a small exptic sawfly, approximately 3.5-5 mm long. They are shiny, black and wasp-like. They cause a gall to form on certain species of willow and this gall is more likely to be seen than the adult sawfly. They are found throughout New Zealand where ever the following willow species are found, Salix alba, Salix ×fragilis, Salix matsudana.
The larvae of the Willow Redgall Sawfly are pale in colour with a dark head. They are small, reaching only 5 mm in length. Adults emerge in late spring, and females seek out suitable willows on which to lay eggs. The female inserts an egg and material that induces galling into leaf tissue where the egg hatches and the larva begin to eat the soft leaf tissue. This stimulates the leaf to produce a gall which is bean-shaped, smooth and emerges equally on both sides of the leaf. The gall may be green, red or yellow. A single larva feeds in the cavity of each gall.
In mid summer the larva leaves the gall to drop to the ground where it pupates. A second brood emerges in late summer, and the fall larvae overwinter as pupae. Generally there are two generations per year.
A gall cut open. The arrow points to the larva.
The galls emerges equally on both sides of the leaf.
The underside of the same leaf as the above photo.