Biodiversity

role of Invertebrates in backyard biodiversity

Most people are familiar with invertebrate species such as mites, ants, cockroaches and flies are more commonly know as pests.  Other species such as mosquitoes and ticks can even spread disease and cause death in some animals.
However, not all invertebrates are pests. Most play an essential role in the environment and are directly responsible for many essential ecosystem services such as pollination of flowers and improving soil fertility. Invertebrates themselves are also an important food source for larger animals.
 
To maintain a healthy population of beneficial invertebrates in your backyard you should avoid using dangerous chemical sprays that kill not only the target pest species but all other invertebrates that come in contact with the chemical residue.
When all invertebrates are poisoned in an area (garden) it is generally the introduced pest species that recolonise the garden first.  This can result in another infestation of another pest species.  Instead you should encourage the beneficial insects in your backyard and use organic natural control methods to remove pest species.

Beneficial Invertebrates

Some beneficial invertebrates worth having in your backyard habitat garden and veggie garden include:

Earth Worms
The common earthworm makes the soil more fertile and its borrowing action continually aerates soil, enhances drainage and improves plant growth.  A separate group of very social earth worms do an excellent job of chewing through organic matter and are very useful at converting kitchen scraps into organic compost and fertiliser in specially designed worm farms.

Bees
Honey bees and especially native bees are fantastic pollinators and important for the pollination and production of seed and fruits in home gardens, agriculture and for regeneration in native bushland.  Bees also have the added benefit of producing honey. Australia has ten species of social native stingless bees that pose no threat to humans.  Two of these species, Trigona carbonaria and Austroplebeia australis are often kept in hives in suburban backyards.

Wasps
There are many different varieties of wasps that you may see in your garden.  While some can be quite aggressive with a nasty sting, such as the paper wasp, there are some beneficial wasps.  One such group are the parasitic wasps.  While usually quite small in size, these wasps assist in the control of aphids and caterpillars.  They do this through a parasitic process of laying eggs in a host animal that subsequently dies.

Another species of wasp lays her eggs in the caterpillars of species such as the cabbage white butterfly, where it develops to the pupae stage before emerging from the host. A second wasp species lays its eggs in adult aphids that act as a kind of incubator before the young wasp eats its way out.

Ladybirds and Hoverflies
Ladybirds (six spotted) and hoverflies are both good natural controllers of aphids. Hoverflies will actually lay their eggs on or near a plant that has an aphid problem. After hatching the young hoverflies then feed on the aphids.

Butterflies and Moths
Butterflies are common visitors to backyards. They are very peaceful to watch as they gently flutter between flowers feeding on nectar and inadvertently pollinating plants as they go.  Butterflies are generally more active in the daytime during spring and summer while moths are generally more active in the evenings. 

It is important to provide both flowers for butterflies to feed on and also suitable foliage for the butterflies to lay their eggs on and for hatching larvae to feed on.  While the caterpillars of some butterflies and moths like the introduced cabbage white butterfly (Pieris rapae), can be a pest to garden plants and leafy green vegetables other native species are slowly reducing in numbers and in threat of becoming extinct due to loss of habitat and suitable food plants.

Threatened Butterflies
The Richmond Birdwing Butterfly (Ornithoptera richmondia) is an iconic local native butterfly that is threatened by habitat loss.  In 1870, the Richmond Birdwing Butterfly  was reported as being abundant between Maryborough (Queensland) and the Clarence River (New South Wales).  Today, its rainforest habitat has been extensively cleared with less than one percent of the original area of this type of rainforest still in existence.

The primary plant that the larvae of this species feed on, the Richmond Birdwing Vine (Pararistolochia praevenosa) is listed as rare under the Nature Conservation Act (Qld) 1992.  Unfortunately an introduced plant species, the Dutchman’s Pipe (Aristolochia elegans) is very similar in appearance to the Richmond Birdwing Vine and is toxic to the Richmond Birdwing Butterfly.  This plant is common in gardens and has become a weed in bushland.  Richmond Birdwing Butterflies lay their eggs on the introduced plant, when the larvae hatch they begin feeding on the toxic leaves and die.

The Pink Underwing Moth (Phyllodes imperialis) (southern subsp.– ANIC 3333) is distributed from Nambour to the Queensland – New South Wales border. It is listed as endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.  The Mary Cairncross Scenic Reserve on the Sunshine Coast is one of the only confirmed breeding sites for this moth.

Other butterfly and moth species significant to the region are:

• Bronze Ant-blue
• Illidge’s Ant Blue Butterfly
• Laced Fritillary
• Monarch
• Regent Skipper
• Mangrove Jewel
• Coral Jewel
• Chocolate Argus
• Satin Azure
• Purple Azure
• Bright Forest Blue
• Southern Sedge Darter
• Varied Sword-grass Brown
• Yellow Ochre
   

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