Make homes for native bees.

A simple way to make some homes for solitary native bees and other insects is to get a big piece of wood, preferably a chunky post or pillar and drill holes in it about 4-6 mm wide for the bees and some a bit bigger for wasps and spiders.

The holes can be on all sides and be 2-3 cm deep. If you don't have a drill maybe try hitting a fat nail in then pulling it back out.
Some wasps can actually chew through the wood a little bit or may use mud to make a cosy coccoon for its babies.

The bees are good pollinators for your garden. Wasps are predatory on caterpillars and insect eggs and some even eat spiders.
This is a good website for native bees.
http://www.zeta.org.au/~anbrc/bluebandedbees.html
http://www.zeta.org.au/~anbrc/beesinyourarea.html

Natural aphid control.

Unlike most people with gardens I actually don't mind if there is an invasion of aphids. This is because I like a lot of the insects that are going to come along and get rid of the aphids. One of the most interesting ones is the tiny wasp called Aphidius. They lay their eggs inside aphids, thereby paralysing them and providing food for their little larvae. Once the new wasp emerges it can then carry on the cycle by laying more eggs inside other aphids. The aphid 'mummies' are a light brown colour and swollen. When the wasp has emerged you can see a tiny round hole in its back.
It's pretty amazing to see how quickly a group of aphids gets turned into mummies. There's a good chance ladybirds will also discover the aphids too. These little helpers in the garden are most likely to visit if you don't use any poisons in the garden.

Huge flower wasp at Samson Park.

The largest bit of bushland in Fremantle is Frederick Samson Park. There are some magnificent tuart trees, some marri and even jarrah. The wildflowers are pretty good in spring and there are 13 kinds of fungi there. I went for a little wander about the other day and came across a beautiful grass tree (Xanthorrhea preissei) in full flower; its spike was all bent and twisted. I realised there was a large (3 cm) black and white striped flower wasp on it. Not only that but he had his girlfriend with him. The female has no wings of her own, so she needs him to come and collect her and take her to the flowers. She normally hangs about on the ground collecting caterpillers, or digging for beetle larvae and the like. She lays her eggs on the grubs, for the larvae to eat when they hatch.
It's not often you see them together. I felt very honoured to see such an amazing sight. Of course I didn't have my camera! Duh.

http://www.amonline.net.au/factsheets/flower_wasps.htm