A bright yellow to white blob of knots and strands on decaying wood or mulch that rounds up into a pillow shape and turns pinkish and then crusty gray. The crusty gray blob is the reproductive form. It breaks down to release the dark spores inside, which are dispersed by beetles, and presumably wind, rain, and any small animals that walk on them. This structure, called an aethelium, is the largest reproductive structure of any slime mold; most have structures that are tiny to microscopic.

This is a very common slime mold on decaying wood and wood chip mulch, in Wildwood and outside. Most people have seen it on mulch at some time. It often worries gardeners and landscapers, and the internet is full of pages on how to get rid of it. The pages all agree that this is difficult. Why, though? It is harmless to animals, plants, landscaping and people. Just enjoy it.

The early yellow form looks pretty much the same as the vegetative form of many-headed slime (Physarum polycelphalum); however the reproductive structures are very different. Many-headed slime produces sporangia that are much tinier and more complex than the aethelium of dog vomit slime. In the look-alike stages, the best clue is habitat. Dog vomit is the only one of the two found in open sunny areas (although it can occur in the woods), while many-headed slime flees from bright light and would only be found in shady moist woods.

Normally this organism resembles a raw egg white and only comes out at night to feed on bits of decaying matter, spores, bacteria, and protozoa in the mulch. The yellow and pink forms develop when food runs out or conditions change for the worse, and quickly develop spores. In Mexico people go out at night to catch the egg-white form and cook and eat it like eggs.