Laetiporus portentosus (White Punk)

The fruit body is a polypore that grows out from wood. In shape it is often somewhat like a horse’s hoof (roughly triangular in cross-section with the lower surface horizontal, the upper sloping) and the vertical third side flush against the woody substrate), but sometimes a little flatter. It may grow to 40 centimetres in its longest dimension. When fresh, the smooth upper surface is a pale brown and the whitish to faintly yellowish underside is densely packed with tiny pores. However, often you don’t see those fresh features, since the fruit bodies are usually attacked by invertebrates fairly quickly and then numerous chew holes show themselves.

An old fruit body, if it escapes the ravages of invertebrates, is likely to develop irregular, polygonal cracking, both on the upper surface and on the underside. You then see that there is only a thin, brownish skin on the upper surface, the underlying flesh being white. In this photo (https://www.anbg.gov.au/fungi/images-captions/laetiporus-portentosus-0049.html), taken in Black Mountain ACT, the upper surface has started cracking and you can see some streaks of exposed, white flesh.   

Fallen, chewed-out fruit bodies may lose all evidence of the initial form and then look like odd lumps of polystyrene, especially as this is a very low-density polypore.

This fungus is fairly common in our region, on live trees of various species but is also found on dead wood. Often it is found singly, but two or more fruit bodies may appear close together.

Look-alikes

There is probably no species with the same combination of chunkiness, size, density and chew holes. Ryvardenia cretacea, not yet recorded from out region, is somewhat similar but has a brittle, chalky texture and appears to escape being chewed and looking like polystyrene. G. Gates and D. Ratkowsky (A Field Guide to Tasmanian Fungi, 2nd. ed, 2016, page 193) say that “When overmature, it falls off the wood and becomes chalk-like lumps on the forest floor”.