Bug FAQMarch Brown Mayfly
Rhithrogena germanica · Order: Ephemeroptera · Family: Heptageniidae
The March brown mayfly (Rhithrogena germanica) is a European species whose aquatic larvae live on river bottoms. Adults have two long tails, visible hind wings, and a dark spot on the femora that separates them from the only other UK Rhithrogena species.
Source: Wikipedia
How to recognize it
A dark spot on the femora distinguishes R. germanica from the related R. semicolorata in the UK.
Source: Wikipedia
Size
Adults and subimagoes have two long tails and clearly visible hind wings.
Source: Wikipedia
Where it lives
The naiads live on the bottoms of rivers.
Source: Wikipedia
Life cycle
Larvae emerge very early in the year, around March to early April, and the subimago appears at the end of winter. Mayflies have two adult stages; the subimago later molts into the imago. R. germanica’s subimago stage can last up to four days, the longest of any mayfly.
Source: Wikipedia
When you see it
The subimago emerges at the end of winter, and the larvae appear from March to early April.
Source: Wikipedia
Where it comes from
It is a European species of mayfly.
Source: Wikipedia
Lookalikes
It can be confused with Ecdyonurus venosus, which is more widespread but emerges later in the year. It is also similar to R. semicolorata, but can be told apart by the dark femoral spot.
Source: Wikipedia
More photos
Questions people ask
When do March brown mayflies appear?
The subimago shows up at the end of winter and the larvae emerge from March to early April.
Source: Wikipedia
How can I tell this mayfly apart from similar species?
Look for a dark spot on the femora; this marks R. germanica and separates it from R. semicolorata, while Ecdyonurus venosus appears later in the season.
Source: Wikipedia
Same family (Heptageniidae)
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Sources
- Wikipedia: https://en.wikipedia.org/wiki/Rhithrogena_germanica
Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia
Text written 2026-10-23 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-23.