www.ukbutterflies.co.uk

I have just seen the notification that this butterfly is rapidly spreading north and has been seen in the Netherlands and NE France. If it is heading our way, the question is - how can we distinguish it from the ordinary and ubiquitous Small White? The only pointer I've read is with regard to the black wing tips - in Small Whites, this extends further along the leading edge than down the sides, and in Southern Small Whites, it is the other way round. Not something that would be easy to spot in a species that is not generally that easy to approach.

However, I think the foodplant for the two species is different, so finding caterpillars might be easier.

Are there any other simple distinguishing features to look for?

Dave

Hi Dave,

I think the same larval food plants are used. The following are courtesy of Guy, taken from the Butterflies of Europe iPhone app. I hope that Guy and the other contributors don't mind me posting these!
Cheers,

- Pete

Ooooh, gonna have to keep an eye out for 'unforked apical veins'!

I've only ever seen one SSW and it was immediately obvious that it wasn't rapae. The black markings were far bolder and covered a greater area.

A friend was quite convinced he had seen a Southern Small White a couple of weeks back, at Newhaven. This was before he (or I) was aware of its rise and rise. However, to claim one of these in the UK with confidence will require a few good images. Sadly, he was not carrying his camera!

BWs, Neil

The main foodplant is candytuft (Iberis sp.), though I believe it might have been extending its taste in recent years - I'm not sure about that. That is why it is found predominantly in hot, rocky, grassy places in southern Europe. I don't think you'll find it on your cabbages! But candytufts are widely grown in gardens and yes, the butterfly does seem to be creeping northwards. During my time in Switzerland it has spread from its heartland in the Rhône Valley up into the mountains and I regularly see it in the Villars/Gryon/Huémoz region where I live.

Guy

So I took this photo on the 2nd September on Malling Down, thoughts? This is the most I got of the upperside, she buggered off as soon as the sun came out again and since it was just a Small white I didn't botter to follow.

There's definitely no fork, which leaves mannii in the picture. It's presence is decisive (definitely rapae/napi) but its absence inconclusive. The scaling on the unh is not particularly dense - much more like rapae - but this feature is actually most useful in the spring brood. In the summer brood the scaling is closer in density and pattern to rapae. The wing shape suggests rapae more than mannii (which is typically more rounded), but this again is very variable.

I'd say the percentages are on this being rapae, given all the circumstances. But if I knew the picture were taken in my back field my conclusion would be different ...

Guy

Thanks everyone. These are going to take a bit of finding - we could discover they've been in our midst for a while! The candytuft foodplant is an interesting point, so finding caterpillars on that would help a great deal. Widely grown in gardens - in fact I remember the first flowers I ever grew from seed as a small boy were candytuft.

Anyway - any opinions on this butterfly? I admit the photo quality isn't really good enough, but the dark tips were extensive enough to make me wonder at the time. I think I can make out a faint hint of a forked vein on the first close-up - which would rather answer my own question - but an expert opinion is always welcome!

Dave

Padfield wrote:There's definitely no fork, which leaves mannii in the picture. It's presence is decisive (definitely rapae/napi) but its absence inconclusive. The scaling on the unh is not particularly dense - much more like rapae - but this feature is actually most useful in the spring brood. In the summer brood the scaling is closer in density and pattern to rapae. The wing shape suggests rapae more than mannii (which is typically more rounded), but this again is very variable.

I'd say the percentages are on this being rapae, given all the circumstances. But if I knew the picture were taken in my back field my conclusion would be different ...

Guy

Thank you for your assessment Guy. It was obviously always going to be a long shot but stranger things happen . I shall definately be paying more attention to Small whites in the future!

I believe I've seen a few specimens, while with Guy in Switzerland in 2011. I must admit, the fork on the veins (or, in this case, lack thereof) is almost impossible to see in the field, but the apical markings were much more obvious, looking very much like those of a Large White, but on a Small White (if that makes sense!).
Cheers,

- Pete

It's a good try, but I think I'd fall on the side of rapae, even not considering the fact mannii has never yet been seen in the UK.

For reference, here's a female mannii taken on Saturday (the day of Minnie's great adventure!):



Somehow, the jizz is different. The wings are more rounded and the apical spot runs down the outer margin as far as the upper vein of the discal spot.

This said, all my experience of mannii is from Switzerland. Whites do vary across their ranges.

Guy

EDIT: I was referring to Dave Miller's post when I said, 'Good try'. The others hadn't registered when I clicked 'submit'.

Thanks, Guy - as I rather suspected. However, it's another one to look out for along the south and east coast next year if favorable winds may bring an influx of migrating Whites.

Dave

In view of the i/d problems why not call it Cryptic Small White? (cf Wood White i/d difficulties)

Jack

Unfortunately for British butterfly enthusiasts I don't believe the UK is in immediate reach of P. mannii. The northwards expansion of the species involves the subspecies 'alpigena'. First stories of it's expansion started in 2008 in Switserland (only in Valais and very locally in Ticino prior to 2008) and E-France and since then it is moving up the Rhine valley. For these expansion it uses the foodplant Iberis sempervirens, a common garden species and in the village and city gardens it probably finds a similar warm habitat (city effect) as in the rocky south facing valleys in the south of France and in Valais (Switzerland). Occasionally the species also uses Diplotaxis tenuifolia. So the species has now become rather common in the border region of SW-Germany and NE-France. 2015 gave the first sightings in the Köln and Bonn-region. And by pure coincidence I found the first for the Netherlands last week: http://waarneming.nl/waarneming/view/108981149
The subspecies "andegava" from W-France was long believed to be extinct but it was recently rediscovered as well on a location in the original area south of Paris as well as in NE-France in the Meuse valley and on one location in Luxemburg. These populations are however local and no signs of expansion are noted. I haven't heard of any movements of the species from W-France.
So the species is still far from coastal area's with Britain in "reachable" distance.

Thanks for this information, Pieter.

We actually got wind in Switzerland that the butterfly was on the move before 2008 but I think it was that year the first requests went out to keep a special eye on it. Formerly, it was restricted to the Rhône Valley of Valais, east of Martigny (as well as Ticino). Suddenly, it began moving round to the northern leg of the Rhône and up into the mountains. It was a great excitement to find it in my garden in Barboleuse, at 1300m. It hasn't looked back since.

Congratulations on finding the first Dutch individual!

Guy

Thanks for posting, Pieter! Very helpful.

Cheers,

- Pete

Hi All, I'm currently in France and I have been in Spain for a few weeks.
I have a couple of Small White pics(different b/f's) that I have taken this trip, are either of these Southern S/W?
I have been butterflying in France & Spain for 3/4 years now and still not had, as far as I know an "official" one recorded yet.
I know it will not be easy from only 1 pic of each but have a go please.

Russ

It looks good for mannii to me, on all counts as listed (to save repeating them here):
http://www.butterfliesoffrance.com/html ... mannii.htm

The latest Lafranchis work La Vie des Papillons, shows the distribution for mannii to be very much focussed in the far south-eastern corner of France, with a few scattered outposts up to central France, more in eastern France, but very very little in the North, so it is surprising that it has been recorded in the Netherlands (albeit near Maastricht in the far south of the country). It will be interesting to see how its distribution develops.

In the highly unlikely event that it would reach the UK, it would either have to move north through France where this would seem to to require a huge amount of time and not a little global warming, or, more plausibly, via the Netherlands route.

We'll all be looking more closely at boring old Small Whites (P. rapae) in future!

Roger

Well, a feature commonly shared by most books is that they are already outdated when they get published.
Recent distribution maps of P. mannii can be found online for several of the German regions (you should fill in the scientific name in the correct bar).
Baden-Württenberg : http://www.schmetterlinge-bw.de/MapServ ... t/Map.aspx
Rheinland-Pfalz: http://artenfinder.rlp.de/artensuche
I heard that this summer the species was seen also in Bonn and Köln, further down the Rhine valley. From Köln it is only a small step to the south of the Netherlands for the autumn generation(s). We notice it in Belgium with several southern species that the very south of the Netherlands is reached almost as fast (or in this case, faster) as Belgium due to the species following the lower lying Rhine valley instead of trying to pass the higher Ardennes in the south of Belgium.