Dragonflies & DamselfliesDragonfly or Damselfly? Sex Lives and Dragonflies Damselflies Diplacodes haematodes Diplacodes melanopsis (Black-faced Percher) Hemicordulia tau Orthetrum caledonicum Orthetrum migratum Orthetrum villosovittatum
The Tau Emerald Dragonfly (Hemicordulia tau) is a medium-sized, black and yellow dragonfly with long legs. A known vagrant species (in biology, vagrancy describes a creature that appear far from their normal range), the Hemicordulia tau is a wanderer (not usually permanent in any location), although they are common in eastern states, including Tasmania. They are also found in the arid interior of Central Australia and the Nullarbor, around permanent waterholes and temporary bodies of water. They can often be seen skimming swimming pools and ponds.

The Tau Emerald Dragonfly seldom rest, often seen hovering and then suddenly dashing off, sometimes chasing other dragonflies. When they do stop for a second or two, they usually hang vertically with wings extended at right angles.

The genus Hemicordulia have two similar species, Hemicordulia tau (Tau Emerald Dragonfly) and Hemicordulia australiae (Australian Emerald Dragonfly). Distinguishing features between the two species include:
- Hemicordulia tau — from the dorsal view, is mostly black (sometimes black-green) on the 7th abdominal segment.
Hemicordulia australiae — has the yellow lateral markings on the 7th abdominal segment, that extends anteriorly and almost meeting dorsally. - Hemicordulia tau — has a distinctive black inverted T shape on the yellow frons of its face.
Hemicordulia australiae — top of the frons are yellow with a dark T-mark. - Hemicordulia tau — mature Tau Emerald has pale, cream and red-brown eyes.
Hemicordulia australiae — mature Australian Emerald has green eyes. The juevnile Emeralds usually have brownish eyes.



- Scientific classification
- Kingdom: Animalia
- Phylum: Arthropoda
- Subphylum: Hexapoda
- Class: Insecta
- Informal: Pterygotes
- Order: Odonata
- Suborder: Anisoptera
- Superfamily: Libelluloidea
- Family: Corduliidae
- Genus: Hemicordulia
- Species: Hemicordulia tau
Footnote & References
- Many thanks for ID to Jeff Melvaine, member of Australian Dragonflies and Damselflies, Facebook group, https://www.facebook.com/groups/Ozdragonflies/
- Hemicordulia tau (Selys, 1871), Atlas of Living Australia, https://bie.ala.org.au/species/Hemicordulia tau
- Tau Emerald Dragonfly – Hemicordulia tau, Esperance Fauna, http://esperancewildlife.blogspot.com/2010/02/tau-emerald-dragonfly-hemicordulia-tau.html
- Australian Emerald, Family Hemicorduliidea, Dragonflies, http://www.therebedragonflies.com.au/dragonflyPages/hemicorduliaAustraliae.html
Dragonflies & DamselfliesDragonfly or Damselfly? Sex Lives and Dragonflies Damselflies Diplacodes haematodes Diplacodes melanopsis (Black-faced Percher) Hemicordulia tau Orthetrum caledonicum Orthetrum migratum Orthetrum villosovittatum
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