page_title: Fauna of Australia
section_title: Invertebrates
hierarchical_section_title: Fauna of Australia / Invertebrates
caption_attribution_description: English: Wolf Spider with her egg sac en:Commons:Category:Animals of Australia en:Commons:Category:Lycosa godeffroyi
context_page_description: The fauna of Australia consists of a huge variety of animals; some 83% of mammals, 89% of reptiles, 90% of fish and insects and 93% of amphibians that inhabit the continent are endemic to Australia. This high level of endemism can be attributed to the continent's long geographic isolation, tectonic stability, and the effects of an unusual pattern of climate change on the soil and flora over geological time. A unique feature of Australia's fauna is the relative scarcity of native placental mammals. Consequently, the marsupials – a group of mammals that raise their young in a pouch, including the macropods, possums and dasyuromorphs – occupy many of the ecological niches placental animals occupy elsewhere in the world. Australia is home to two of the five known extant species of monotremes and has numerous venomous species, which include the platypus, spiders, scorpions, octopus, jellyfish, molluscs, stonefish, and stingrays. Uniquely, Australia has more venomous than non-venomous species of snakes.
  The settlement of Australia by Indigenous Australians between 48,000 and 70,000 years ago, and by Europeans from 1788, has significantly affected the fauna.
context_section_description: Of the estimated 200,000 animal species in Australia, about 96% are invertebrates. While the full extent of invertebrate diversity is uncertain, 90% of insects and molluscs are considered endemic. Invertebrates occupy many ecological niches and are important in all ecosystems as decomposers, pollinators, and food sources. The largest group of invertebrates is the insects, comprising 75% of Australia's known species of animals. The most diverse insect orders are the Coleoptera, with 28,200 species of beetles and weevils, the Lepidoptera with 20,816 species including butterflies and moths, and around 14,800 species of Hymenoptera, including the ants, bees and wasps. Order Diptera, which includes the flies and mosquitoes, comprises 7,786 species. Order Hemiptera, including bugs, aphids and hoppers, comprises 5,650 species; and there are 2,827 species of order Orthoptera, including grasshoppers, crickets and katydids. Introduced species that pose a significant threat to native species include the European wasp, the red fire ant, the yellow crazy ant and feral honeybees which compete with native bees.
  Australia has a wide variety of arachnids, including 78 spider families with 79 species of spider familiar enough to have common names. There are numerous highly venomous species, including the notorious Sydney funnel-web and allied mygalomorphs, whose bites can be deadly. The redback spider was thought to be deadly but redback bites are no longer thought to be life-threatening, as the lack of deaths since 1956 was thought to be due to the development of an anti-venom which has since been shown to be no better than placebo[126] [127]. There are thousands of species of mites and ticks from the subclass Acari. Australia also has at least 150 species of pseudoscorpion with an estimated 550 more waiting to be described, and at least 17 scorpion genera with 120 species.
  In the Annelida (sub)class Oligochaeta there are many families of aquatic worms, and for native terrestrial worms: the Enchytraeidae (pot worms) and the "true" earthworms in families Acanthodrilidae, Octochaetidae and Megascolecidae. The latter includes the world's largest earthworm, the giant Gippsland earthworm, found only in Gippsland, Victoria. On average they reach 80 cm in length, but specimens up to 3.7 m in length have been found.
  The large family Parastacidae includes 124 species of Australian freshwater crayfish. These include the world's smallest crayfish, the swamp crayfish, which does not exceed 30 mm in length, and the world's largest crayfish, the Tasmanian giant freshwater crayfish, measuring up to 76 cm long and weighing 4.5 kg. The crayfish genus Cherax includes the common yabby, in addition to the farmed species marron and Queensland red claw. Species from the genus Engaeus, commonly known as the land crayfish, are also found in Australia. Engaeus species are not entirely aquatic, because they spend most of their lives living in burrows. Australia has seven species of freshwater crab from the genus Austrothelphusa. These crabs live burrowed into the banks of waterways and can plug their burrows, surviving through several years of drought. The extremely primitive freshwater mountain shrimp, found only in Tasmania, are a unique group, resembling species found in the fossil record from 200 MYA.
  A huge variety of marine invertebrates are found in Australian waters, with the Great Barrier Reef an important source of this diversity. Families include the Porifera or sea sponges, the Cnidaria (includes the jellyfish, corals and sea anemones, comb jellies), the Echinodermata (includes the sea urchins, sea stars, brittle stars, sea cucumbers, the lamp shells) and the Mollusca (includes snails, slugs, limpets, squid, octopus, cockles, oysters, clams, and chitons). Venomous invertebrates include the box jellyfish, the blue-ringed octopus, and ten species of cone snail, which can cause respiratory failure and death in humans. The crown-of-thorns starfish usually inhabits the reef at low densities. However, under conditions that are not yet well understood, they 
caption: The wolf spider, Lycosa godeffroyi, is common in many areas of Australia. In this family of spiders, the female carries her egg-sac.
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