Tau emerald
species of dragonfly
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.
Description
Adult
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.
This brief starts where responsible research should: with the source description of “Tau emerald” as species of dragonfly. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the science & nature register because the source frames it as species of dragonfly. Its deeper value depends on whether names, dates, institutions and citations support that framing.
Datasets, specimens, observations and peer-reviewed methods provide the appropriate test for the technical claims summarized here. The source revision retrieved here is dated May 13, 2026. The linked authority identifier is Q2471088. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1871.
Scientific names, classifications and consensus can change while older terminology persists in catalogues and historical literature. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Tau emerald” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.