#beech scale insect

One of the features of the Antarctic Beech forests of New Zealand, particularly on the South Island, is the thick layer of what looks like black moss covering many of the trees. And the ground. And most of the plants in the understory.

The black moss is actually sooty mold, a complex combination of fungi from a variety of different Orders, thriving on the ludicrous amounts of honeydew pumped out by the Sooty Beech Scale Ultracoelostoma assimile. The white filaments sticking out of the mold in the first photo is the anal tube of the scale insects, the longest such tube of any insect. The insect is most abundant on Black Beech Nothofagus solandri (the black in the name is from the mold) and middle-aged trees may lose 80% of the sugars they make to them. Younger trees have smooth bark that doesn't offer safe nooks and crannies for the crawlers, and in mature trees the bark is too thick for the scale insects to drill through.

The honeydew is a keystone feature of the Nothofagus forests - birds, bats, reptiles and insects all feed on the honeydew. Some rely on it. There's at least two species of caterpillar that prey on the scale insects. And a beetle - the only one in its family - that feeds only on the sooty mold.

And then the wasps arrived.

Two species are the problem - Vespula vulgaris (see photo) and Vespula germanica. Both are now more common in the Nothofagus forests then they are anywhere else in the world, and by a horrifying degree. Not only are they getting a diet of pure rocket fuel for much of the year, they then denude the forest of invertebrate life to feed their larvae. By monopolising the honeydew supply they're starving the birds and other animals that need that food supply, especially since introduced mice, rats, and stoats are eating the fruit and seeds of the forest, or turning on the birds when they run out of mice.