It’s a New Year and time to plan mayfly-related activities for the next 12 months.
First off will be the continuation of our work on Ameletus inopinatus in the Cairngorms. Visits to the sample sites in January and February will be a great way to start the year. I’m hoping this mild spell won’t last too long and that we get some snow so we can see the effects on the watercourses up there.
February will also see the first tentative hatches of Large dark olives (Baetis rhodani). During crisp spring days the weak winter sun has just enough warmth to stimulate a hatch of these tenacious little insects.
In late March the place to be is the Scottish Borders where you can see the fantastic spectacle of thousands upon thousands of March browns (Rhithrogena germanica) hatching en-masse from the River Tweed.
April is the start of the field season and the opportunity to sample a wider range of waterbodies. It’s a great time to see two stillwater species, the Sepia dun (Leptophlebia marginata) and the Claret dun (Leptophlebia vespertina). Both of these species migrate from deeper water to the shallows of lakes in preparation for their emergence.
May is a busy month. It’s the month when we see large hatches of true Mayflies (Ephemera danica) hatching from the chalkstreams of southern England, however I’ll be in Perthshire at the FSC field centre at Kindrogan. I’ll be delivering two workshops ‘Entomology for Anglers’ and ‘An introduction to freshwater invertebrates’. It’s also an opportunity to visit the Loch of the Lowes, a great stillwater managed by the Scottish Wildlife Trust.
I’m spoiled for choice in June as there will be hatches of a wide range of species throughout the month. If I get the chance I’ll be looking for the Northern summer dun (Siphlonurus alternatus). This species was first recorded in UK from the River Tummel by Martin Mosely way back in 1913. There are less than five modern records and it would be great to find it on the Tummel again.
I’m not going to manage it this year, but July would be a great time to visit the River Wye in Herefordshire, home to the largest population of the Yellow mayfly (Potamanthus luteus) in the UK. If I get the chance I’ll try and find the Dusky yellowstreak (Electrogena lateralis). This species has a relatively widespread distribution but doesn’t occur in huge numbers and is always a joy to find.
As August approaches the focus turns to the less obvious species such as the Autumn dun (Ecdyonurus dispar). Due to the difficulties with identification of larvae I don’t get many records of this species. The appearance of adults in late summer gives a great opportunity to positively record this species.
The terrestrial field season finishes in September but aquatic invertebrates can be collected throughout the year (weather permitting). September is a month of change in freshwater. Stoneflies, absent from samples during the summer, begin to appear in samples once more. The eggs laid by mayflies during the summer have hatched, but the nymphs are still tiny. There are still identifiable mayflies to be found though. Species with two generation a year such as the iron blues (Baetis muticus and B. niger) are gearing up for their last hatches of the year. You can also still find first year nymphs of Ephemera danica, although not all populations of this species have a two year life-cycle (but that’s a different story!).
Things will have really quitened down by October. Most of the big hatches have finished but there’s still a chance of some mayflies emerging on warmer days. The Pond olive (Cloeon dipterum) is one you can usually rely on for hatches in October. It’s an incredibly successful species and be found in most ponds.
With the clocks going back on October 27th it’s time to start identifying the bulk of the material collected during the year. I’ll still try and get down to the river whenever I can. I’ve found nymphs of Blue-winged olives (Serratella ignita) as late as 6th December in the north of Scotland – I wonder if I can beat this record?