Graphic: Jamie Brown Graphic: Jamie Brown
Local cockroaches are parched but for leaf-eating bugs it’s an orgy of eating and breeding, as Melbourne’s drying conditions are a boon for some creatures and dire for others.
Rainfall in Melbourne has been well below average for five of the past six months, down by about one-third in every month but June, which is bad news for native cockroaches.
Dry conditions are both the reason why we have some cockroaches in urban areas and the reason we see them inside homes, Melbourne Museum’s manager of live exhibits Patrick Honan says.
About five years ago the local shy variety were hardly known. These creepy crawlies ate bush leaf litter, quietly churning soil nutrients, breaking down mulch and being part of the native eco system. But when gardeners – worried about water restrictions and drought – started introducing mulch to their gardens many were inadvertently transporting native cockroaches to their gardens inside bags of mulch.
As the gardens continued to dry out during the drought, desperate local cockroaches, like the common shining cockroach, started to venture into bathrooms seeking moisture, Mr Honan says.
“They only tend to be inside temporarily because there is nothing for them to eat inside. They are transient visitors,” he said.
These locals are around all year but it is only the dry conditions that bring them to notice, he says. There are about 500 native species but only four introduced varieties which are the ones seen scurrying in pantries or wardrobes.
Mr Honan knows most people either fear or loathe cockroaches no matter where they come from.
“People don’t like them but they are neutral as far as humans are concerned, they are neither good nor bad,” he said.
In theory, he says, Melburnians with cockroaches in their bathrooms should be looking for a garden hose to water their garden rather than a shoe to splat them with.
“That would make the garden outside more attractive than the inside of the house, but it might not work in all circumstances,” he said.
In dry weather leaf-eating bugs such as aphids, lerps (which attach themselves to leaves) and common butterflies are also likely to thrive.
“Leaf chewers do well during the dry weather,” Mr Honan said.
Distressed plants concentrate their nutrients in an effort to survive making leaves and sap richer and a feast for leaf chewers.
“Every year there will be a massive increase in one particular insect,” Mr Honan said.
“The environmental factors and sequence seem to make it perfect for that particular insect. There could be seven or eight factors that make it perfect for them to breed in numbers. We never really know what those factors are until it’s happened – it might be dry, then two weeks of rain and then very dry conditions. You just don’t know.”
There is one weather factor that brings an universally dreaded bug, and that is the hot northerly wind from the top end of Australia. The foul bush fly travels on those winds.
“Once they start being blown down on the hot northerly they start to breed here, but they can’t survive Melbourne’s winter so that’s something,” Mr Honan said.
This story Administrator ready to work first appeared on Nanjing Night Net.