Mayfly nymph (Ameletopsis perscitus) Yellow dun

Kingdom: Animalia
Phylum: Arthropods
Class: Insecta
Order: Ephemeroptera
Family: Ameletopsidae
Genus: Ameletopsis
Species: A. perscitus
Binominal name: Ameletopsis perscitus
Common adult names: Yellow dun, Sulphur dun.

The larva of Ameletopsis perscitus has a body length of 16 millimetres and cerci around five millimetres. It is New Zealand only carnivorous mayfly larva and one of very few in the world. This predatory nymph lives in stony streams and rivers. It has an enlarged large skull-like head.

Ameletopsis perscitus is New Zealand’s only yellow mayfly. This rather uncommon mayfly is distributed throughout the country from the Southland hill streams to Fiordland’s mountain streams and up the West Coast and as far as the upper North Island’s rivers.
This mayfly imago (the last stage an insect attains during its metamorphosis) is 18 mm in length. The head is yellow; the thorax is a light yellow with brown areas dorsally and ventrally. The abdomen is a bright yellow except for its top surface which is a fawn colour. The wings, legs and wings are yellow. This winged stage appears from the end of December to March. The adults are short-lived.

Photo of an Ameletopsis perscitus nymph Ameletopsis perscitus nymph by David Wilson.jpg 

1-mayfly is an adult Ameletopsis perscitus .jpg

[[uploads/images/Te Henui/Fauna/Mayfly (Ameletopsis perscitus) Yellow dun.jpg-original.jpg|Mayfly (Ameletopsis perscitus) Yellow dun.jpg-original.jpg
]]This photo of adult fly is courtesy of Dean Bell a New Zealand fly fishing guide. 

Thanks to Wikipedia for text and information: