Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 36 - Leptophlebiidae (Ephemeroptera) - Popular Summary

Towns, DR; Peters, WL 1996. Leptophlebiidae (Insecta: Ephemeroptera). Fauna of New Zealand 36, 144 pages.
( ISSN 0111-5383 (print), ; no. 36. ISBN 0-478-09303-9 (print) ). Published 19 Aug 1996


The Leptophlebiidae are the largest group of mayflies in New Zealand, comprising 30 species in 12 genera, all unique to New Zealand. Closely related genera occur in New Caledonia, southern South America, Australia, and Madagascar.

Juvenile mayflies (nymphs) inhabit relatively unpolluted running and standing waters. New Zealand species are generally found only in flowing water. A few species inhabit ponds, lakes, or deep, slow-flowing rivers. Most nymphs feed on detritus and algae, which they sweep from rocks, wood, and leaves with brush-like mouthparts.

The nymphs grow and moult for up to a year, then transform into two winged stages: a subimago, which has incompletely developed reproductive structures and usually lasts for 24 hours, and finally an imago with functional reproductive structures. Neither the subimago nor the imago has a functioning digestive system or mouthparts. The imago too usually lives for 24 hours, during which time it mates, often in swarms that gather over water or landmarks such as small trees. Eggs are then deposited in streams.

Nymphs that live in fast-flowing water are often flattened, with adaptations such as sucker-like gills for firm anchorage. Other species have gills that are fringed, thread-like, or flattened. Nymphs living on plants that trail in the water often have large claws or modified legs to help them maintain a firm grip. Few nymphs are brightly coloured, but the imagos may have wings tinted yellow or red. Imagos of different species vary from 5 mm to 15 mm in length.

Mayflies of the family Leptophlebiidae are often the most abundant organisms living in clean, flowing streams in New Zealand. They are important food for trout, as is well known to anglers, but also for a wide range of native insects, birds, and fishes. In the eastern South Island they are important in the diet of birds that nest on braided rivers, including wrybill, black-fronted tern, and black stilt. Because of their abundance in clean water with a high oxygen content, and their sensitivity to pollution, mayflies are often used to assess changes in the quality of water in New Zealand streams and rivers.

The rarest New Zealand mayflies are Leptophlebiidae, and up to one-third of the species are known only from restricted areas. Some of the species may only appear to be rare because there have been few reliable guides to the identification of even the most common forms. Our work (Fauna of New Zealand no. 36) provides the first comprehensive guide to identification of all life stages of New Zealand Leptophlebiidae.

A few mayflies can be identified with the naked eye, but for most species identification will need to be checked using either a stereoscopic microscope for structures on the body and wings, or a compound microscope for structures on the mouthparts of nymphs.