HORDES of little black bugs are descending on Hobart -- and while they may be annoying, the harmless invaders are no cause for alarm.
Local homes and businesses are being inundated by large numbers of the redheaded cockchafer beetle (Adoryphorus couloni), which emerge from their underground pupal cells at this time of year to mate.
Tasmanian Museum entomologist and senior curator of zoology Cathy Young said the 15mm adult beetles, which fly around at dusk and are attracted to light, live only for about a week, after spending more than a year growing underground.
"Then as soon as we get to about this time of year -- late winter or early spring -- they emerge, mate, reproduce and then die," she said.
"They're just in really large numbers [at the moment], and that's why people are noticing them -- they're all over the place.
"They are gradually becoming a lot more common in Hobart. The species was limited to the North of the state until about 10 years ago, seemingly because of the higher rainfalls up there, but they're expanding their range and gradually moving down South, and we're not really sure why."
Dr Young said while the adult beetles were harmless, the juvenile redheaded cockchafer could cause plenty of damage by feeding on grass roots.
And there is no way of treating them with chemicals because, unlike other species of cockchafer, the grubs remain underground to feed and don't come up to the surface.
"The grubs are actually quite a significant pasture pest because they eat grass roots," she said.
"It's possible that we'll see quite a bit of damage to pastures, lawns and other grass areas in autumn next year.
"Because we're getting such large numbers of beetles, there'll be a corresponding large number of grubs that will be attacking grass roots."
http://www.themercury.com.au/art ... 31_todays-news.html
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