What do mayflies look like?
- 4 mm - 35 mm in length with an average wingspan of 15 mm across.
- Widest at wing attachment (wide shoulders), abdomen long and column-like.
- Body appears soft and fragile.
- Very short, bristle-like or thread-like.
- Large, covering most of the head, and are very close together or actually touch.
- Reduced in adult.
- One or two pairs but usually two.
- Hindwings much smaller than forewings.
- Both wings are membranous, clear and have numerous cross-veins forming many cells.
- At rest wings are held upright above abdomen often pressed together.
- Six slender legs.
- Usually three tails (two cerci, one middle filament) rarely two with middle tail reduced or absent; all tails longer than body, thread-like and similar in size.
Where are mayflies found?
- Near water on vegetation, rocks or in the air.
What do mayflies do?
- They group together in large numbers to form mating swarms. The swarms are often over a particular object such as a rock, tree, or bridge. This object can be indicative of a particular species.
- When disturbed they fly away.
- Many hold their front legs out in front when perched.
- They are weak flapping fliers.
- Adult mayflies do not feed.
- Adults are short-lived, on average survive for 1-2 days, but can live for only minutes.
- They are active night and day. Some are attracted to light.
What looks similar?
- Stoneflies can be distinguished from Mayflies by their wings. Their wings are similar in size and folded around the body at rest. Stoneflies also never have more than two tails.
- Caddisflies can be distinguished from Mayflies by their wings, antennae and a lack of tails. Their wings are hairy, similar in size and held tent-like at rest. While their antennae tend to be more than half their body length.
- Alderflies and dobsonflies can be distinguished from Mayflies by a number of features. Their wings are similar in size and held tent-like at rest. They also have chewing mouthparts, long antennae and very short tails.
- Flies can be distinguished from Mayflies by their wings and a lack of tails. The forewings of flies have few cells, while their hindwings are replaced by a club-like structure called halteres.
- Male scale insects are occasionally confused as Mayflies. Wings of scale insects have few cells and their tails, if present, are never multi-segmented.