Megadolomedes australianus
Giant Water Spider Identification in Australia
A large NSW water-edge hunter. Current Megadolomedes australianus is distinct from the Queensland spider now called M. trux.
Usually low risk; avoid handlingAbout Giant water spider
Megadolomedes australianus is a water spider currently placed in Dolomedidae. Older sources often used Pisauridae. The present World Spider Catalog records the species in New South Wales and distinguishes it from Megadolomedes trux. Earlier descriptions and photographs sometimes combined these names, so the familiar giant-water-spider label should not be treated as proof of a single species throughout eastern Australia.
A large, long-legged hunting spider at a creek or river is a useful starting point. Megadolomedes can resemble Dolomedes, and water-side behaviour or a handspan impression alone is insufficient. Use the entire body, leg proportions, locality and adult anatomy together. This page does not apply the Queensland M. trux measurements or photographs to M. australianus. Stay clear of slippery banks and record an already visible animal. An unexpected spider in a pool can belong to an entirely different group, including burrowing spiders washed in by rain.
Identification limit: this guide is a comparison aid. A name match in the identifier does not establish a species record.
Compare similar spiders
Sources and further reading
- World Spider Catalog: Megadolomedes australianus
- Australian specialist field account now labelled Megadolomedes trux
- Healthdirect: spider-bite first aid
Reviewed 21 September 2026. Identification guide; not a confirmed species diagnosis.
Quick identification
- Large long-legged spider at freshwater
- NSW locality for the accepted species
- No prey-catching orb web
- Older M. australianus pictures may actually show M. trux
What to check next
Photograph the whole spider and its surroundings without disturbing it. Use the clues together; a close match is not a confirmed species identification.
When to seek medical help
For a suspected bite, contact the Poisons Information Centre on 13 11 26. Call 000 for breathing difficulty, collapse or other severe symptoms. Do not wait for an online identification.
Where it is usually seen
Freshwater-edge habitat in New South Wales within the current species concept. Queensland records using the old broad name require reassessment.