Brown Argus and Small Tortoiseshell

[kielder]

I have been reading an article in June's issue of BBC Wildlife Magazine. In case people don't know about this issue, thought I would share the article with you:

"Over the past 30 years, the Brown Argus butterfly has expanded its UK range northwards in repsonse to a warming climate. New research has now revealed that, in doing so, it appears to have given some of its enemies the slip.

Rosa Menendez and colleagues from Lancaster University have discovered that Brown Argus caterpillars in newly-colonised regions of northern England suffer significantly less from parasitoid wasps than their southern counterparts. The ecologists speculate that the northern wasps are not spotting the new arrivals because they are accustomed to targeting the larvae of more established species, such as the common blue."

But while some butterflies seem to be benefitting from milder season, others are losing out. Butterfly Conservation recently announced that the Small Tortoiseshell has mysteriously declined in south-east England by 80% since 1990. Some experts believe this is due to the northward spread of the parasitoid fly Sturmia bella , species more common in Southern Europe. Sturmia lays its eggs on nettle leaves - the caterpillars accidentally eat the eggs, Sturmia larvae hatch and develop inside their hosts, killing them before they can pupate"!

Dan Eatherley BBC Wildlife Magazine

Does anyone else read this by the way?

[ChrisJB]

I'm a bit of a cheapskate and usually have a 'free read' of BBC Wildlife on the shelves of WHS. If there are an abundance of decent articles then I'll buy it.
Certainly in my neck of the woods, the Small Tortoiseshell has seriously declined. When I was a kid it was the commonest species by a country mile.
As for the Brown Argus, I have never seen them up north, though have seen plenty of northern Brown Argus around lovely ol' Silverdale.

Regards, Chris

[Ukwildlifeo]

I read that. Was an interesting story. The parasites wont be far behind though I reckon, and the Small Tortoiseshell will adapt or move further north hopefully

BBC wildlife isn't a bad read. I by it before a long journey if I can, so get most issues

[Swallowtail]

Disappearance baffles scientists - Butterfly Conservation

Butterfly Conservation are working with Oxford University to see if they can find out more about the parasite. Numbers are definately down.

[aeshna5]

Originally Posted by Swallowtail

Disappearance baffles scientists - Butterfly Conservation

Butterfly Conservation are working with Oxford University to see if they can find out more about the parasite. Numbers are definately down.

Numbers of Small Tortoiseshells are more than down here, they've effectively disappeared. To me this is even more serious than the once abundant House Sparrow decline, yet the ST gets a fraction of the publicity, despite it being a colourful, well known species!

[ron1863]

Small Tortoiseshells have not moved up here in any numbers, only seen the odd one this year

[Wild-Woman]

I've not seen one Small Tort in N Kent so far this year-which is indeed a worry. If it is due to the parasitoid, let's hope there's a parasitoid that will parasitise the parasitoid...if you see what I'm getting at. That way the original parasitoid may be held in check and the Small Torts could recover.

[aeshna5]

Originally Posted by Wild-Woman

I've not seen one Small Tort in N Kent so far this year-which is indeed a worry. If it is due to the parasitoid, let's hope there's a parasitoid that will parasitise the parasitoid...if you see what I'm getting at. That way the original parasitoid may be held in check and the Small Torts could recover.

I did see 1 in North Kent today close to Elmley Prison. I also saw a fresh looking one yesterday over a nettle patch in my local country park, that was a real joy to see an old friend again!

[Wild-Woman]

When I think back to my childhood, the Small Tortoiseshell and the 'Cabbage White' as it was called then, were abundant in gardens. Considering I lived on the outskirts of SE London, in an urban area, it really does show how numbers of these lovely butterflies have plummeted.
We raised the caterpillars in sweet jars and waited until the chrysalis was produced. I can remember doing this at school too. Now you would be lucky to find the caterpillar of the ST here.
The whites were seen largely as a 'pest' but even they are low in numbers compared to the dozens I can recall fighting over the vegetable patch.

[aeshna5]

Originally Posted by Wild-Woman

When I think back to my childhood, the Small Tortoiseshell and the 'Cabbage White' as it was called then, were abundant in gardens. Considering I lived on the outskirts of SE London, in an urban area, it really does show how numbers of these lovely butterflies have plummeted.
We raised the caterpillars in sweet jars and waited until the chrysalis was produced. I can remember doing this at school too. Now you would be lucky to find the caterpillar of the ST here.
The whites were seen largely as a 'pest' but even they are low in numbers compared to the dozens I can recall fighting over the vegetable patch.

I was a London kid too + yes Small Tortoiseshells + the whites were in numbers in all the gardens.

Have seen many Small + GV Whites recently, but very few Large Whites. What is going on here?

[Wild-Woman]

Originally Posted by aeshna5

I was a London kid too + yes Small Tortoiseshells + the whites were in numbers in all the gardens.

Have seen many Small + GV Whites recently, but very few Large Whites. What is going on here?

Perhaps too many folk turning their gardens into patioed show-pieces. The traditional vegetable patch is almost a thing of the past, as are allotments.
Shame really, gone are those areas where you could look over your back garden gate to allotments-usually supplied with horse-manure, as the rag and bone man took his cart down the alleyways.
I think 'tidiness' has led to the demise of some wildlife, including the 'traditional' butterflies we used to have in our gardens.

[aeshna5]

Originally Posted by Wild-Woman

Perhaps too many folk turning their gardens into patioed show-pieces. The traditional vegetable patch is almost a thing of the past, as are allotments.
Shame really, gone are those areas where you could look over your back garden gate to allotments-usually supplied with horse-manure, as the rag and bone man took his cart down the alleyways.
I think 'tidiness' has led to the demise of some wildlife, including the 'traditional' butterflies we used to have in our gardens.

I agree these are all valid points + I'm sure have contributed to some degree, yet my garden at the moment is designed for wildlife, is bursting with flowers- both native + exotic (but nothing overbred with fancy doubles, etc) + this is normally heaving with insects at this time of year. My next door neighbour does next to nothing so there is a lot of long grass with brambles, others have more cultivated gardens, but there's a good mosaic.

With ecology it's difficult to isolate individual factors, but I think last year's weather combined with the cold early spring after a mild winter this year have had a big impact.

I also wonder whether this new (to UK) parasitic fly, Sturmia bella, is affecting Red Admirals. Apparently the fly lays its eggs on nettles + is ingested by caterpillars which then develop inside the larvae. It is reputedly the main reason (research being done by Oxford Uni this summer) for the rapid decline of Small Tortoiseshell + I believe it isn't host specific, so may have some effects on other vanessids, such as the Red Admiral. However, despite some successful overwintering in recent years, this species is fairly dependent on immigration + given the general paucity of migrant insects, this may also be the reason?

[Gill Catton]

I grew up (some would argue that I haven't yet finished growing up but still...) in the countryside and too remember lots of Small Tortoiseshells and have noticed a real decline.

And you're right I don't know why its hasn't been shouted about??! and the thing is, presumably this parasitic wasp has always been around? If it is the wasp that's causing the problem, there must be another factor contributing to why suddenly this wasp is more successful - could this be a vicitm of tidy britain? less scrub and tall ruderal patches?

[ChrisJB]

If the parasite is host specific then one would expect 'boom and bust' years of Small Tortoiseshells. As the butterflies decline, then so would the parasite, as the butterfly recovers, same for the parasite. Akin to to the nematode causing Strongylosis in red grouse, which leads to a similar scenario.
It does seem though that we are in a period of 'bust' with Small Tortoiseshells at the moment.

Regards, Chris

[aeshna5]

Originally Posted by Gill Catton

I grew up (some would argue that I haven't yet finished growing up but still...) in the countryside and too remember lots of Small Tortoiseshells and have noticed a real decline.

And you're right I don't know why its hasn't been shouted about??! and the thing is, presumably this parasitic wasp has always been around? If it is the wasp that's causing the problem, there must be another factor contributing to why suddenly this wasp is more successful - could this be a vicitm of tidy britain? less scrub and tall ruderal patches?

This parasite is a fly, not a wasp + is a recent arrival to our shores from the continent, so will only recently have affected our butterflies. I haven't heard how it fares in Europe.

[Susie]

I wonder if the drop in butterfly numbers is partly down to the weather. We had a very rainy period for about ten days earlier in the year and after that all the orange tip larval on garlic mustard and Red Admiral larval on nettles in my garden died in just a couple of days. The whole lot wiped out. It seems as if they just could not take the dampness and were attacked by a fungus or something similar.

[Jez]

Got a bad feeling Butterflies in the UK will be hit badly by climate change! We're starting to see it now!!!

[aeshna5]

Originally Posted by Susie

I wonder if the drop in butterfly numbers is partly down to the weather. We had a very rainy period for about ten days earlier in the year and after that all the orange tip larval on garlic mustard and Red Admiral larval on nettles in my garden died in just a couple of days. The whole lot wiped out. It seems as if they just could not take the dampness and were attacked by a fungus or something similar.

I'm pretty sure you're right there Susie!

[Cheryl]

I've not seen a Tortoiseshell Butterfly - small or large - for a very long time. It was definitefly the "common" butterfly when I was a child.

We've had no butterflies as such in the garden at all this year apart from a few Holly Blues and a Peacock earlier in the year. However, I have now spotted 8 or 9 diferent varieties when walking in the local park which on the whole is a natural park and the grass and flowers are allowed to grow.

My buddleia is in flower and I've not seen a single butterfly and only the occasional bee

[Wild-Woman]

Large Tortoiseshell is regarded as extinct in Britain. We only have the odd migrant one gracing our shores now.

[Gill Catton]

Originally Posted by aeshna5

This parasite is a fly, not a wasp + is a recent arrival to our shores from the continent, so will only recently have affected our butterflies. I haven't heard how it fares in Europe.

Oh right that is interesting, as it definately arrived of its own accord? As in it is a native European fly perhaps with an expanding range?

[aeshna5]

Originally Posted by Gill Catton

Oh right that is interesting, as it definately arrived of its own accord? As in it is a native European fly perhaps with an expanding range?

As far as I know- that's what is implied each time I read about this insect; maybe one of the dipterists on WAB can give more info on this fly?

[keirnen]

This is a very interesting forum. I live on a small island off the west coast of scotland and for years I had masses of butterflies in my garden feeding on buddleia, marjoram etc - Peacocks, Small Tortoiseshells, Red Admirals, Painted ladies etc. But during the 2007 and 2008 summers - hardly a one. This year I have only seen 2 Peacocks, 1 Small Tortoiseshell and 1 Red Admiral on my buddleia so far and it is the end of August. Looks like a major crash in their populations? Only hope they recover over time - it isn't a real summer without the butterflies.