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A question of identity …

Some years ago I inherited several collections of British Lepidoptera, which have now been donated in their entirety to the Hope Department of Entomology at the Oxford University Museum of Natural History (OUMNH). The collections came from two respected English entomologists, now sadly both deceased. The combined collection contained a number of very interesting items, one of which is pictured below. I know what I think it is but I’m interested to know what you think it is?

Over to the experts …

I have a feeling I may get more than one answer on this …
Image copyright OUMNH. Photographed by Katherine Child, Hope Department of Entomology.

The only thing that comes to mind is P. bellargus ... so what I am missing?

Is it some isolated race of adonis blue, now extinct?

My guess would be bellargus X corydon as it seems to have features of both, though a flight time of early June seems odd.

Mike

MikeOxon wrote:My guess would be bellargus X corydon as it seems to have features of both, though a flight time of early June seems odd.

I've heard of this but have never seen a photograph of one. I'd expect any such hybrid to show some characteristics of chalkhill blue though. The one above looks purely adonis to me (though what do I know?)

JKT wrote:The only thing that comes to mind is P. bellargus ... so what I am missing?

The colour is completely wrong. It's the same colour as I can see on my screen

Cheers,

- Pete

I'll not comment on the identification, as I've already discussed the matter with Mark, but here's an image of bellargus x coridon, otherwise known as ab. polonus. It was taken on Mill Hill on 19th May 2010 and remains the rarest butterfly I have ever seen ... and probably the rarest I will ever see.
Neil

David M wrote:I've heard of this but have never seen a photograph of one.

Kipper found one (19-May-2010): gallery/images/upload/2f8e8be4455f386d1 ... 54cb14.jpg

And here's one on the web: http://www.lepiforum.de/cgi-bin/2_forum ... d;id=94108

Cheers,

- Pete

Thanks for that, Pete.

What a stunner. How rare is this hybridisation between the two?

Hi David,
One of the leading authorities on aberrant butterflies told me that only about a dozen specimens have ever been recorded (UK and Continent), although another expert in the field reckoned on at least twice this number. Either way, it's extremely rare. I spotted it from c.30 metres away (it stood out clearly amongst the many Adonis) and scrambled up the steep slope rather quickly, suspecting it must be polonus. By the time I closed in on it my hands were shaking with excitement, so I was very relieved when some of the images came back sharp. Larger files show it to be scale-perfect.
BWs, Neil

If we're still guessing, I'd speculate on an aberrant Adonis blue rather than a hybrid. In the Cockayne Collection there is an ab. argentea that seems to have the deep blue replaced with a silvery tone, though it's difficult to judge colour from the pictures there.

Coincidentally, the Cockayne argentea was also taken at Folkestone, eight years previously.

Guy

I'm sorry if I'm being completely thick here (which to be fair, is highly likely!), but can someone explain the differences between Kipper's "Adonis" and the standard model? I know Adonis Blues can vary a great deal in colour according to wear and the angle of the light, so wondered if there is something else from the coridon side that distinguishes this one.

Is it right that the cross only occurs at the same time as the first generation of Adonis? Is this because the Adonis genes dominate? Are these butterflies crosses between male Chalkhills and female Adonis or vice versa?

I have a few pale-looking specimens of Adonis photographed (though none all that well). You can't help wondering...

Dave

If it IS aberrant, then there's nothing jumping out at me other than the less intense colour (which you would naturally expect in a many decades old specimen).

Put us out of our misery, Mark.

Hi Dave,
In the image below I've marked the left forewing in red with the features that scream coridon. However, the biggest giveaway is the ground colour, which is literally a mix of bellargus and coridon. Your images of typical Adonis illustrate the difference well.
Hi David,
The colour of old butterfly specimens remains almost undiminished IF they are shielded from ultraviolet. Well-preserved collections, protected from museum beetle etc and kept in cabinet drawers, can look amazingly fresh even after 100 years. Have a look at some of the images of Oxford specimens currently being transferred to the galleries. Mark's specimen is in excellent condition and the colour is probably pretty 'true'. Abnormal ground colouration is the basis upon which many aberrations are named.

BWs, Neil

Thanks, Neil. I can see now the broader black borders around the forewing which are straight from a Chalkhill!

Considering how similar the females of the two species are, I imagine any female crosses would be almost impossible to detect.

Dave

Hi Dave,

I forgot to answer your other question, "Is it right that the cross only occurs at the same time as the first generation of Adonis? ". Of course the actual act of hybridisation occurs during the second generation of Adonis, as this is the only time when both bellargus and coridon are on the wing. But yes, the hybrid only occurs in the adult stage at the back-end of the subsequent year's first brood of Adonis. Mine was an unusually early specimen (not that the sample is very large!), given that most polonus occur in June.

Will a female polonus ever be recognised? That must be a "no"!

BWs, Neil

Sussex Kipper wrote: Hi David,
The colour of old butterfly specimens remains almost undiminished IF they are shielded from ultraviolet. Well-preserved collections, protected from museum beetle etc and kept in cabinet drawers, can look amazingly fresh even after 100 years. Have a look at some of the images of Oxford specimens currently being transferred to the galleries. Mark's specimen is in excellent condition and the colour is probably pretty 'true'. Abnormal ground colouration is the basis upon which many aberrations are named.

Is it an aberrant based on its ground colour then?

Must admit, the hue resembles that of Common, rather than Adonis, Blue.

Please don't tell me those hybridise as well.

Hi David,

David M wrote:Must admit, the hue resembles that of Common, rather than Adonis Blue. Please don't tell me those hybridise as well.

Just to add to any confusion ab. pallida, Austin (1890), = pallida, Mosley (1896), is a form often referred to as a hybrid between icarus and bellargus.

Sorry ...

Kind regards. Mark

Mark Colvin wrote:Hi David,

David M wrote:Must admit, the hue resembles that of Common, rather than Adonis Blue. Please don't tell me those hybridise as well.

Just to add to any confusion ab. pallida, Austin (1890), = pallida, Mosley (1896), is a form often referred to as a hybrid between icarus and bellargus.

Sorry ...

Kind regards. Mark

You're a real tease, Mark.

Can these two genuinely hybridise? I know icarus is genus polyommatus but I had always thought bellargus was lysandra until I read this thread.

Sussex Kipper wrote:Hi Dave,

...Of course the actual act of hybridisation occurs during the second generation of Adonis, as this is the only time when both bellargus and coridon are on the wing. But yes, the hybrid only occurs in the adult stage at the back-end of the subsequent year's first brood of Adonis. Mine was an unusually early specimen (not that the sample is very large!), given that most polonus occur in June.

BWs, Neil

I suspect you probably can't answer this, but does polonus spend the winter as a caterpillar (like bellargus) or as an egg (like coridon)? It must be one or the other. As a hybrid couldn't it exhibit the trait inherited from either parent, and not necessarily appear with the spring bellargus brood? Is it at the back-end of that brood because it overwinters as an egg, but hatches earlier than coridon and so emerges as an adult earlier? Could its rarity be something to do with the vulnerability of its caterpillars appearing at the "wrong" time?

We'll probably never know!

Dave