Those black caterpillars are back

We are having our annual emergence of Pasture Day Moth caterpillar. They come up from under the soil and head off into the pasture to eat broadleaf plants. (Such as capeweed, sometimes called daisies.) We get a lot of these caterpillars emerging from the soil around the hay shed.
WA Agriculture tells us the caterpillar is the lava of the moth and is called Apina callisto. "The caterpillar is a visually striking insect especially when fully grown to 60 mm long. It is dark brown to black with two yellow spots near the posterior end. Large numbers of these caterpillars may be seen on the surface of pasture where they remain and feed until fully grown."
The moth is brown with yellow markings on the wings and orange rings around the body. "Eggs are laid in pasture and hatch at about the onset of rains. When the larvae are fully grown they may be seen burrowing in the soil before becoming pupae," says WA Agriculture. They aren't a real pest. They need autumn rains to emerge and they only become a problem in very bad years.So now we know... Why are they important? Because they are part of the biodiversity - the network of organisms that support each other in ways we don't understand but if we deny or disrupt it, we play dice with the force of nature.