[Irvine Ross]

I was on the upper Don on Saturday and after the thunderstorm had passed I noticed the occasional large dark stonefly on the surface of the water. I think they were hatching but I didn't see one emerge. Once on the surface they were unable to take off so they skated towards the bank, legs going like a clockwork toy. This attracted the attention of the trout. They did not try to suck them down but instead tried splashing to drown them. Sometimes they succeeded and sometimes the stonefly got away. The attacks all came out near the middle of the pool, none that I saw happened close to the bank. I think they were small fish doing the splashing. An otter had gone through the pool shortly before so the bigger fish were probably a bit unsettled.

If I had had a dry fly big enough I would have tried casting upstream and retreiving but I had nothing in my river box that would match the size.

Anyone else see this?

Irvine

[Richard Tong]

Irvine,

The Large Stoneflys seem to hatch over quite a long period-we have seen them on the Don on our last 3 trips from 28th April- 29th May . I think I am right in saying that they tend to crawl up stones,posts etc to emerge and we have seen plenty of shucks and photographed them too(Paul has a shot in his blog on his website taken this season). The ones that we have seen exhibiting the behaviour you mentioned all have long wings covering the bodys (as opposed to short stubby wings = males) and have been females; so we assumed that they have been egg laying.

Have seen the occasional one slurped by Trout but many go unmolested,

Richard

[Irvine Ross]

Richard

I have read that large stoneflies are usually seen crawling up stones etc. to emerge from the water and I didn't see any emerging on Saturday but I have in the past seen large stoneflies emerging onto the surface in the middle of the stillwater fishery pond at Mossat.

The ones I saw on Saturday were all moving in the same direction, from the middle of the pool to the bank as fast as they could go. You would expect them to pause every now and then if they were egg laying.

All the ones that came close to me did have full length wings, therefore were females, so you might be correct.

The next time it happens I will see if I have the willpower to put down my rod and spend more time watching.

Irvine

[Ben Dixon]

Irvine,

Next rime you're out have a good look and see if there is anything subsurface that they could be crawling up, be interested.

[Irvine Ross]

Ben

They were out on the middle of a long pool that is about 10ft deep. No chance of crawling up anything there.  I suppose they might have been dislodged from bank-side stones further upstream by the current but its unlikely they would be swept out into mid-stream. Where I was seeing them was about 50-60 metres downstream from the head of the pool.

Irvine

[Sandy Nelson]

Hi irvine

stonefly's need their skin to dry out before they hatch
just like damsels so they crawl to the edge and up some structure
as previously mentioned.
As Richard says they were most probably egg laying
as only the females can fly. Some of the stones lay their eggs by crawling subsurface, others by dipping their abdomen.
They are not the best fliers so the skittering is quite common as they try to take off
I imagine if they head to shore whilst trying then they hedge their bets on survival

cheers

sandy

[Irvine Ross]

Sandy

OK I accept the theory that all stoneflies need to crawl out of the water to shed their nymphal skin (until proved otherwise ).

One point to note is that the ones I saw made no attempt to fly, the wings remained flat along their backs all the time they were heading for the shore. I have seen stoneflies taking off from water before and they need a long runway. These didn't try it although they had plenty of room.

Irvine

[Richard Tong]

Irvine,

Ditto the ones I have always seen were not attempting to fly,some were heading towards middle of the river,some towards the bank- always the Females,

Richard

[Sandy Nelson]

always the Females,

NO wonder it makes no sense

Sandy

[Irvine Ross]

NO wonder it makes no sense

Sandy

What would your missus say if she saw that comment

On reflection, if the males cannot fly then emerging onto the water surface would be a disadvantage and crawling up a stone to get out of the water would make sense. It's unlikely that any species would have separate emergence strategies for males and females so it's reasonable to assume the females also crawl out. That leads to the conclusion that the stoneflies I saw were most probably egg laying.

I'm still puzzling over why they chose to lay eggs out in the faster water in the middle of the pool where they have more chance of being ambushed by a big trout? Why not near the edge where the escape route is shorter?

Anyway, the day I spot a skittering male we re-write the text book

Irvine

[paavo]

Plecoptera, Stoneflie nymphs crawls at the bottom to the bank, a stone, or a reed straw for hatch.
As Sandy says:

stonefly's need their skin to dry out before they hatch
As Richard says they were most probably egg laying
as only the females can fly. Some of the stones lay their eggs by crawling subsurface, others by dipping their abdomen.
They are not the best fliers so the skittering is quite common as they try to take off
I imagine if they head to shore whilst trying then they hedge their bets on survival

cheers

sandy

Here in Sweden we have 34 species of Stoneflies; the smallest is 5-6mm and the biggest is 40mm, but it´s not common. Stoneflies can booth eat and drink and therefore be able to live for 2-3 weeks.

//Harri