A pair of Nectar Scarab Beetles feeding on Kunzea flowers in our garden. Their colours mimic those of an unrelated, very toxic, beetle. Photo: Ian Fraser.
Canberra is experiencing a major outbreak of pasture chafer beetles, harmless little chaps that have emerged from the soil en masse after the recent rains.
The larvae have spent up to two years underground, hatching from eggs laid in the soil. They munched on plant roots, especially grasses, at that time before eventually pupating in a protective case (which, in a butterfly, we call a chrysalis).
A dry spell, such as we’ve been mostly experiencing in Canberra for some months now, traps them in the hard soil, but rains like last week’s soften the soil and trigger them to escape from the pupal case and dig to the surface.
Unlike the larvae, these adult beetles don’t feed, so they must find a mate and lay their eggs in a fairly short time frame. They’re attracted by lights – and we really don’t understand why – so in places that are lit up overnight, the human inhabitants are likely to find a rich carpet of beetles in the morning, perhaps as they arrive for work.
If you’re bothered by them, it might be a good idea to turn off unnecessary overnight lights for a while. These little beetles are currently being widely described on Canberra social media as Christmas beetles; they’re not, though they are related.
I was going to devote this column to beetles in general, but that was an impossible task in the space available. You see, there are at least 400,000 known species of beetles, and no one imagines that that’s anywhere near the real total.
Compare that with less than 70,000 species of vertebrates – all the mammals, birds, reptiles, frogs and fish on earth; at least six species of beetle to every species of bony animals. So, I’m going to limit myself today to the beetle group, which includes the chafers, Christmas beetles, dung beetles and their relatives. That will leave plenty of other beetle stories for another day!
Fiddler Beetle feeding on teatree flowers. You can see half of the ‘fiddle’ on its back. Photo: Ian Fraser.
If we think of scarab beetles at all, we likely think of the scarabs of ancient Egypt. These dung beetles rolled balls of dung across the sand (as food for their larvae), which the Egyptians – or at least their priests – saw as being like the sun god Ra rolling the sun across the sky. Hence, they were revered, and amulets in their honour were widely traded across the Mediterranean world.
Most insects have two pairs of wings. The most obvious characteristic of beetles is that the foremost pair of wings (the elytra) has hardened and acts as a protective cover for the other pair, which does the flying. As a beetle is about to take off, it raises the elytra out of the way before rising into the air.
These elytra are often coloured and sometimes reflectively shiny.
Christmas beetles have been alarmingly scarce for the past couple of years, perhaps due to the tough drought years prior to that, which would have trapped and doomed many emerging beetles underground.
I’ve still not seen one myself this season, but I’ve read about quite a few sightings in Canberra already, which pleases me greatly. Like the chafers, Christmas beetle larvae live under the ground on grass roots, but unlike chafers, the adults are very much feeders when they emerge from the ground. They fly into the canopy of eucalypts and munch on the foliage.
Green Scarab Beetle on a daisy flower in the high Brindabellas. It hasn’t yet noticed the spider! Photo: Ian Fraser.
Many other scarab beetles live on flower pollen (and probably some nectar too). At present, there are huge numbers of glossy coppery brown Nectar Scarabs, with black heads, on flowering shrubs in our yard – kunzea and paperbarks. This colour scheme matches that of an unrelated beetle, the Long-nosed Lycid, which is very toxic and utterly repellent to predators. The Nectar Scarabs – and a range of other insects, not all of them beetles – gain protection from their resemblance.
Up in the Brindabellas, the yellow-flowered pea shrub, Shrubby Bossiaea, is starting to flower and will stain whole mountainsides yellow from a distance. This flowering attracts vast numbers of the lovely glossy Green Scarab Beetle, though there seems to be limited knowledge about its lifestyle.
They feed on the pea flowers and on many daisies, and also eat the foliage.
Another local scarab that does sup on flower nectar is the big, colourful Fiddler Beetle, named for the supposed resemblance of its back pattern to a violin. Its larvae live on rotting wood.
So scarabs are in your backyard and local nature reserves and on your backstep, not just in ancient Egypt.
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