Hemicordulia tau
In 3 days ~60% in a week ~90%
The tau emerald (Hemicordulia tau) is a species of dragonfly in the family Corduliidae. The species was first described by Edmond de Sélys Longchamps in 1871. The tau emerald is a medium-sized, black and yellow dragonfly with long legs,
reaching a body length of about 50 mm. As is unique to dragonfly and mayfly species, H. tau has flight muscles attached directly to the wings, and in both the males and females the inboard edge of the hindwing is rounded. The 7th abdominal tergum is extensively black above and yellowish at the sides. The top of the frons are yellow with a dark T-mark. The species exhibits a linear relationship between head width and body length.
Nearly all of the dragonfly's head is eye, allowing incredible vision that encompasses almost every angle except right behind them. H. tau has a particularly large and well developed compound eye with two principal regions, the dorsal eye and the ventral eye. The dorsal eye is principally sensitive to short wavelength light, while the ventral eye has 3 or more spectral types of photoreceptors.
The length of time each larval stage of H. tau requires can decrease as the temperature... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Grampians National Park | 🇦🇺 Australia | |
| 2 | Hattah-Kulkyne National Park | 🇦🇺 Australia | |
| 3 | Great Otway National Park | 🇦🇺 Australia | |
| 4 | Flinders Ranges National Park | 🇦🇺 Australia | |
| 5 | Booderee National Park | 🇦🇺 Australia | |
| 6 | Kosciuszko National Park | 🇦🇺 Australia | |
| 7 | Wilsons Promontory National Park | 🇦🇺 Australia | |
| 8 | Blue Mountains National Park | 🇦🇺 Australia | |
| 9 | Royal National Park | 🇦🇺 Australia |
Possible
About 30% of wildlife watchers report a Tau Emerald sighting in Grampians National Park on a given day, based on 62 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 10th most-seen of the 148 insects we can rate there. Over three days the chance rises to about 60%, and over a week to about 90%, if each day is a fresh chance.
December
In that month about 50% of wildlife watchers report a Tau Emerald in Grampians National Park on a given day, against under 5% in February and May–August, the lowest months.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Tau Emerald sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Yes
Of the 9 parks where we can rate Tau Emerald sightings, Grampians National Park has the highest daily chance: about 30%. Next come Hattah-Kulkyne National Park (Australia, about 30%) and Great Otway National Park (Australia, about 20%).
GBIF citizen-science records
It is estimated from how often the Tau Emerald is recorded against all the insects logged in Grampians National Park (62 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
