Source: NIWA
2025 Bug of the Year: Yellow Mayfly nomination
Golden elegant enigma seeks ‘2025 Bug of the Year’ crown
A short-lived, strikingly stunning native mayfly known to fly-fishers and aquatic admirers yet seldom seen by the public may have its time in the spotlight this month as a nominee for the 2025 New Zealand Bug of the Year. While the adult yellow mayfly or piriwai only dances on this earth for a short while, the aquatic insect has a prehistoric past, with mayflies one of the oldest surviving winged insect orders on the planet, alongside dragonflies and damselflies.
“The yellow mayfly should be celebrated as perhaps the most beautiful mayfly in Aotearoa New Zealand, if not the world,” says NIWA Freshwater Ecologist Brian Smith, who has put forward the piriwai for the coveted crown for both its looks and rather interesting personality and lifestyle. As one of New Zealand’s leading freshwater invertebrate taxonomists, Smith believes the unheralded yellow mayfly deserves more recognition.
Part of the scientific name for the insect, Ameletopsis perscitus, means ‘very clever’ or ‘exceedingly sharp’, with the yellow mayfly living up to its name. “Draped in vibrant yellow, the sexually immature adult stands out in stunning contrast against the muted greens of its native forest surroundings. But this piriwai’s uniqueness extends beyond its alluring appearance. It is the sole species in its genus, and the only representative of the exclusively Gondwanan family Ameletopsidae in Aotearoa. Piriwai really does represent.”
The life story of the yellow mayfly can only really be understood by appreciating how it overcomes the many challenges to its survival, Smith says. “Adults lead a very short life. They are unable to eat, and the female only has a few days to find a mate and deposit her impressive clutch of up to 8,000 eggs back into the stream.”
He admits that beneath the adult yellow mayfly’s elegant and ephemeral beauty, lies a darker side, a very rare predilection among mayflies. “In its aquatic nymph stage, piriwai is a formidable predator. With lightning speed, the nymph ambushes and devours unsuspecting aquatic insects, employing powerful jaws concealed beneath a comically oversized head.”
Smith is hoping that the enigmatic insect will capture the attention of the public in the 2025 New Zealand Bug of the Year, who have until midnight 17 February to vote for the yellow mayfly at New Zealand Bug of the Year. So far more than 8,000 votes have been cast. “This striking duality between the delicate, transient beauty of the adult and the predatory ferocity of the juvenile presents a fascinating paradox: a creature that is both a fleeting symbol of elegance and yet was a ruthless hunter.”
This rather uncommon mayfly is distributed throughout the country from the Southland and Fiordland streams and up the West Coast and as far as the upper North Island’s rivers.
There is the bigger picture too, about these insects that spent most of their lives as nymphs in freshwater, before emerging in spring and summer for their short adult lives. “Our waterways boast an extraordinary legacy of uniqueness with species of mayfly, stonefly, and caddisfly found nowhere else on earth. These insects are indicators of waterway wellbeing, vital to the health and balance of freshwater ecosystems, and the first to disappear as water quality degrades.”
He says while the increasing pressures of pollution, habitat loss, and deforestation often shift attention to more visible and charismatic species like native freshwater fish, it’s equally crucial to highlight the plight of lesser known yet essential insects like Ameletopsis perscitus. “This nomination aims to shine a light on these overlooked gems, celebrating their beauty and raising awareness about their indispensable role in maintaining ecological health. Let’s champion the tiny, the vital, and the irreplaceable.”
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