Global heating, pesticides and habitat loss are devastating insect populations – but in Australia we’re already seeing summer bug eruptions, both wanted and unwanted.
The Bureau of Meteorology’s long-range forecast is for a warmer and wetter than usual summer for most of the country, an ideal environment for many insect species.
Already there’s been the annual intrusion of cockroaches in Sydney, the migration of flies from the bush, and swarms of butterflies, shiny Christmas beetles and ladybirds.
Cockroaches
Australia has about 400 native species of cockroach, but none are considered pests.
Associate prof Tanya Latty, from the University of Sydney’s life and environmental sciences school, says a few “mostly exotic” cockroaches make their way into homes and businesses.
These are the ones that will be scuttling around in summer, tootling from crack to crevice.
Sydney is their “perfect place”, because of its warmth and humidity, Latty says. She says while they are attracted to food debris around the home, the roaches are not unclean.
“If you ever watch a cockroach, they spend a huge amount of time cleaning themselves,” she says. The problem is they can move bacteria around, if they crawl over things in the bin, then the kitchen, she says.
And people can be allergic to their exoskeletons or excrement, if there’s a lot of it around.
But, she says, spraying is rarely an effective answer. Her advice is clean up any crumbs, seal up any cracks, and if that doesn’t work – call a professional.
One of the most common in Sydney is the so-called German cockroach – they’re very sociable and like to clump around in large groups, and the female can produce up to 20,000 young annually. Researchers recently used DNA sequencing to show that this “German” actually came from east India and Bangladesh.
Christmas beetles
People worry Christmas beetles are disappearing but Latty says it’s hard to know for sure what’s going on.
“It’s pretty much anecdotal but it comes even from people who’ve been entomologists for a while,” she says.
“But we can’t demonstrate a decline because we don’t have the data.”
She runs an annual citizen science project counting the Christmas beetles.
Dr Adam Ślipiński, a CSIRO entomologist agrees and adds that people’s memories can be very fickle.
“People will say ‘when I was younger I saw them a lot’, but we don’t have data for that,” he says.
Latty says the beetles can be susceptible to drought, but also to waterlogged soil.
“They’re beautiful. They arrive in the holiday season. They’re harmless,” she says.
Flies
There are about 30,000 fly species in Australia. The CSIRO says just 6,400 have been described. There are fruit flies, house flies, march flies, bush flies and blow flies, to start with. And don’t forget mosquitoes, part of the big fly family.
Ślipiński says there are definitely fewer bush flies – the annoying ones that hang around your face, drinking your sweat and tears – than there used to be.
“The bush fly was the common thing, but it’s being controlled better,” he says.
“We introduced the dung beetle to Australia to manage the dung of the cows and the horses – that has been an extremely successful story.”
As Australia’s climate heats up, more species of dung beetles are being brought in, he says, to keep dung down.
The blow flies, the carrion eaters, he says, will “multiply very quickly” if there are corpses around. They’re helpful, he says, in helping things decompose.
Mosquitoes are set to have an excellent breeding season with the warmth and the wet, and will be out in numbers at dawn and dusk, especially where water has pooled. They’re both annoying, and disease carriers.
Data from the health department shows Ross river virus is the most common, with more than 3,260 cases so far this year. Dengue is the second, with more than 2,000.
There are cases of malaria, Barmah forest, Chikungunya, Japanese encephalitis, Murray Valley encephalitis, and West Nile/Kunjin virus all listed although some, such as malaria, have been caught overseas.
Spiders
The warmer season means more spiders, and outdoor activities mean more opportunity to run into them.
Potentially deadly funnel webs are out and about starting their breeding season. The Australian Reptile park has asked people to collect them and their egg sacs for their venom, to create antivenom.
ARP spider keeper, Emma Teni, said this year’s rainy weather and rising temperatures had created “perfect conditions” for males to leave their burrows in search of mates.
The funnel web is one of the deadliest spiders in the world, along with the redback, but there have been no confirmed deaths from either for decades.
Happily, the much-maligned white tailed spider is unlikely to cause a flesh-eating infection.
Ladybirds
Ślipiński says ladybird populations fluctuate so much it’s hard to tell how they’re going. But they generally follow the aphid population, he says. Aphids build up in hot weather, and about 30 or 40 days later the ladybirds catch up.
They also make some mysterious moves.
“They start gathering on higher elevations, in towers, on top of mountains,” he says.
“They seem to be gathering there, then they sit for a week or longer, then they disperse. We don’t understand why. They don’t copulate, they hang around, then they disperse.”
They’re also known to fly out to sea then drown, with thousands washing up on beaches, and to gather together to hang out over winter.
There are more than 200,000 insect species in Australia, with many of them interacting more with humans over summer.
There have been reports of plagues of cabbage white butterflies, and South Australia has seen a large migration of caper butterflies.
The cicadas on the east coast have been deafening, and beekeepers are bracing for the national invasion of the varroa mite, while scientists are worried about Australia’s native bees.
Latty says humans only notice a small proportion of what’s out there, and lump them together even if there are hundreds if not thousands of species in a group. And it worries her that people often only notice things are disappearing once they’ve gone.
Latty says while bugs face many challenges, she’s optimistic they can turn things around.
“The hopeful thing for insects to me is they have short reproductive cycles, she says.
“You can see them rebounding particularly quickly.”
