Serratella ignita (Poda, 1761)

= Ephemerella ignita (Poda, 1761)

  = Ephemera ignita Poda, 1761

Blue Winged Olive

Nymphs: Nymphs with four pairs of plate like gills visible.  Gills are held above the body and when viewed from above they do not extend beyond the sides of the body.  Nymphs swim poorly with a characteristic 'S' shaped rocking motion.

Adults: Small to medium sized flies with three tails and large hind wings.  The sub-imago has dark blue grey wings and the tails are pale grey and are ringed with brown.  Females have dark green eyes and the body is a greenish olive.  As the flight period progresses the body darkens to a rusty brownish olive.  The male has red eyes and the body varies between orange-brown and olive brown.  The last segment is often a much lighter shade.

The imago has transparent wings with pale brown venation.  In the female the eyes are greenish brown while the male has bright red eyes.  The body varies between olive brown and a deep sherry red, however in the male the body is generally lighter.

Nymphs: The nymphs of Serratella ignita have a distinctive rocking swimming style and have a marked black and white pattern to the legs and tails.  The nymphs are generally dark, however this tends to vary with the colour of the substrate.  They can be separated from the closely related Ephemerella notata by the alternating pattern on the legs and tails.  Some workers suggest that the presence of distinctive marks on the underside of E. notata can be used to separate these species however this is unreliable as the marks are often present, albeit faintly, in S. ignita.  A definitive feature is the profile of the body.  In S. ignita there are a pair of small spines on the upper surface of each body segments (a).  These spines are absent in E. notata.

Adults: Serratella ignita is superficially similar to Habrophlebia fusca however in S. ignita there are small detached single veins at the edge of the forewings, between each of the major veins.  H. fusca never has detached veins at the edges of the forewing.

Many workers use the presence of distinctive marks on the underside of E. notata to separate it from S. ignita, however this may prove unreliable as the marks are often present, albeit faintly, in S. ignita. 

Nymphs of this species live in fast flowing streams and rivers, especially where aquatic vegetation is present.  Occasionally it has been found on the stony shores of upland lakes.  They are usually found clinging to, or crawling amongst submerged plants and stones, although they may swim in short bursts if disturbed.  The nymphs feed by collecting or gathering fine particulate organic detritus from the sediment. 

There is one generation a year, which usually overwinters in the egg stage and emerges between April and September.  There may be separate winter and summer generations in warmer water, such as those of southern England, and this would result in a longer flight period.

Emergence of the adults takes place at the surface of the water during daylight hours and at dusk.  The males of this species can be found swarming throughout the day, and swarming continues until dusk.  The mated female produces an egg mass which she holds under her tail.  The eggs are usually laid in areas of fast flowing and turbulent water, where moss is present.  The female flies over the water and releases the egg mass.

Serratella ignita is one of the most common Ephemeroptera species in the British Isles.