Fatal Metalmark vs Long-Tailed Mayfly

Side-by-side species comparison

Attribute Fatal Metalmark Long-Tailed Mayfly
Scientific Name Calephelis nemesis Palingenia longicauda
Order Lepidoptera Ephemeroptera
Family Riodinidae Palingeniidae
Size 18-25 mm wingspan 30-40 mm body; 60-80 mm cerci
Habitat Rivers & Streams Rivers & Streams
Diet Nectar Feeders Omnivores
Regions Southwestern United States, Mexico Europe
Conservation Least Concern Vulnerable

Fatal Metalmark

A tiny dark brown butterfly with fine metallic silver lines across the wings and minute checkered fringes. Despite its ominous name, it is a harmless nectar feeder.

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Did You Know?

The name 'nemesis' refers to the Greek goddess of retribution, though the reason for this dramatic name is unclear.

Long-Tailed Mayfly

The largest European mayfly with body and cerci reaching over 120 mm. Its spectacular mass hatches on the Tisza River are a famous natural phenomenon.

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Did You Know?

The annual "Tisza bloom" of this mayfly along the Tisza River lasts only a few hours but has been celebrated in Hungarian culture for generations.