Silver-washed Fritillary aberration

[xmilehigh]

Hi Pete,

Here are the 2 best shots I got of the SWF aberration, seen today at Bently Wood. Hopefully someone else got a few clearer pics.

Cheers

[Pete Eeles]

Thanks Jerry - nice shots!

Cheers,

- Pete

[eccles]

And here's my two pence worth with another aberration also at Bentley Wood today, a ringlet.

[xmilehigh]

Thanks.
Could the SWF be ab. nigricans Cockayne

No clue about the Ringlet

[Pete Eeles]

Hi Jerry - this is definitely ab. ocellata - based on the 3 butterfly "variation" books I have (Frohawk, Russwurm and Harmer). And as suggested by Piers (Felix) in another thread.

nigricans seems to be reserved for especially-dark individuals. However, there is a point at which the distinction between the two isn't clear-cut. Adrian Hoskins has a photo of another aberration on his excellent website at:

http://www.learnaboutbutterflies.com/pa ... 20001d.jpg

which he has down as nigricans. This individual is right on the "border" for me, between nigricans and occelata and, based on the books I have, would have put down as occelata myself. But it's not an exact science by any means.

Cheers,

- Pete

[xmilehigh]

Cool,

I'll go with the experts on this one then .

Thanks Pete

[eccles]

Deleted entry, wrong thread.

[Jack Harrison]

Pete wrote:

The second is the sheer number of aberrations being seen which are known to occur as a result of extreme temperature as the pupal stage is reached

That undoubtedly is true as has been proved by experimentation.

However, it has also been shown that many aberrations are genetic in origin. I offer the hypothesis that these genetic aberrations could be less robust in the early stages and a only small number each the adult stage. However, in good seasons such as this one, ideal conditions mean that fewer than normal die in the larval or pupal stages.

I well recall another great year, 1976, when valesinas comprised a far greater proportion of females (eg in Bentley Wood, also in north Gloucestershire) than usual. Ideal seasons might mean than the genetically weaker individuals – the aberrations – can succeed when normally they wouldn’t do so.

Just a hypothesis but it would fit the facts.

Jack

[Piers]

Hi Jerry - this is definitely ab. ocellata - based on the 3 butterfly "variation" books I have (Frohawk, Russwurm and Harmer). And as suggested by Piers (Felix) in another thread.

nigricans seems to be reserved for especially-dark individuals. However, there is a point at which the distinction between the two isn't clear-cut. Adrian Hoskins has a photo of another aberration on his excellent website at:

http://www.learnaboutbutterflies.com/pa ... 20001d.jpg

which he has down as nigricans. This individual is right on the "border" for me, between nigricans and occelata and, based on the books I have, would have put down as occelata myself. But it's not an exact science by any means.

Cheers,

- Pete

Pete is spot on with this Silver Washed Fritillary aberration: while this is a particularly extreme example it is certainly an oscellata as the diagnostic features of oscellata (markings extended to form lozenge or 'eye' shapes) are still clearly visible, where as the determining feature for nigricans is an almost entire suffusion of black scales (with the exception of the base of the wings and the fringes), completely obscuring the usual markings. This specimen is an extreme oscellata.

This years aberration 'event' in Silver Washed Fritillary last occurred on this scale in 1976. Prior to that, other 'paphia years' were 1941/42, 1918/19 and 1881, strangely this occurrence seems to happen at 30 year intervals. Could this be linked to a climatic cycle or is it just pure coincidence?

Aberrations are usually caused by one of four factors (or a rarely combination of two or more): Environmental influence, for example extremes of temperature during the early pupal stage; a recessive gene, for example tithonus (the blue female) in the Chalkhill blue; pathological where the insect does not form correctly (the white winged Ringlet being a superb example where an area of the wing lacks pigmentation); and homoeosis, where an area of one wing is 'reproduced' like a curious patchwork on a part of another wing. An example of this could be where an area of upper side pattern and colouration of a Fritillary appears in a 'patch' on the underside of the hind wing. Homoeosis is however very rare in butterflies.

Aberrations are usually named according to the features that make them different from 'type', for example in oscellata where the normal markings are extended into 'eye' shapes, confluens where markings extend and join, radiata where spots extend outwards to form streaks or bars, caeca where the markings are absent (caeca means 'blind') etc.

Aberrations are sometimes named after the individual that first described them (the Chalkhill Blue ab Fowleri being an example) or rarely after the location at which the aberration was first recorded (the Purple Emperor aberration Chattendeni was first recorded from Chattenden).

Aberrations are fairly finite. Although new aberrations that are as yet undescribed do at times occur, the majority have been described and named. Some species are more variable than others: in Britain the Chalkhill Blue has 446 named aberrations, the Silver washed Fritillary 47, the Painted Lady 32, and the White Letter Hairstreak a humble 7.

When identifying an aberration it is worth looking for what is different about the specimen and what remains the same; what features have altered and how. That way it is possible to narrow down the possibilities. This is how Pete was able to determine that the Silver Washed Fritillary aberration photographed by Adrian Hoskins was oscellata and not nigricans.

I could waffle on for hours and in great detail about this subject but I am not very quick at writing or typing (at least not in a way that makes any sense!), and (for those that are still reading) I have probably gone on and on and on enough!!

Felix.

[Piers]

Pete wrote:

The second is the sheer number of aberrations being seen which are known to occur as a result of extreme temperature as the pupal stage is reached

That undoubtedly is true as has been proved by experimentation.

However, it has also been shown that many aberrations are genetic in origin. I offer the hypothesis that these genetic aberrations could be less robust in the early stages and a only small number each the adult stage. However, in good seasons such as this one, ideal conditions mean that fewer than normal die in the larval or pupal stages.

I well recall another great year, 1976, when valesinas comprised a far greater proportion of females (eg in Bentley Wood, also in north Gloucestershire) than usual. Ideal seasons might mean than the genetically weaker individuals – the aberrations – can succeed when normally they wouldn’t do so.

Just a hypothesis but it would fit the facts.

Jack

Valesina is a different kettle of fish. It is a dominant gene that produces the valesina form of the Silver Washed Fritillary, and when breeding in captivity from a valesina female the female offspring are predominently of this type.

So why is valesina not the dominant form in the wild? there are no problems with the viability of ova or larvae from valesina females so why does valesina only make up a small percentage of the total female population? well there are theories for this: It could be that valesina is simply not as attractive to males than the type females. Or (and this is more likely IMHO) the valesina females do not have as much opportunity to mate successfully. Valesina (because of her dark colouration) prefers the shadier areas of a woodland, presumably due to her ability to absorb heat faster. Because of this behavioural adaptation valesina females are not going to be spotted as easily by patrolling males. It is also due to this behaviour that valesina are easy to overlook; even when basking valesina (if the ambient air temperature is warm enough) will often choose to bask wings open on a shaded area of bramble rather than on a flower exposed to the sun.

This behaviour was also very evident in the extreme oscillata aberration in Alice Holt: when feeding and basking the butterfly was more often than not to be found on the shaded or partially shaded bramble flowers rather than with her kindred on those flowers in full sun. It is fairly safe to assume that due to this individuals greatly increased area of dark scaling the butterfly absorbed heat far faster and therefore chose to keep out of the direct sunlight when the ambient temperature rose above a specific point.

Interestingly, while in many southern woodlands valesina makes up only a tenth of the female population, there are some woodlands (a couple in South Wilts in particular) where valesina accounts for up to a quarter of all females in 'good' years. There is clearly room for further research into this.

Jack is spot-on about the viability of extreme aberrations though - captive breeding has shown that many extreme aberrations (genetically inherited or environmentally stimulated) are inherently weak and often fail to hatch from the pupae successfully if at all; many emerging crippled or expiring just prior to emergence.

Felix.

[Piers]

Sorry - it's spelt OSCELLATA.

Spellin' int me strong point and despite re-reading everything over and over something always slips through...!

[Gruditch]

Fascinating Felix, am I right in thinking this is a Argynnis paphia ab. confluens Spuler

Gruditch

[Pete Eeles]

Sure looks like it to me:

http://www.nhm.ac.uk/jdsml/research-cur ... scientific

Nice shot!

Cheers,

- Pete

[Pete Eeles]

Sorry - it's spelt OSCELLATA.

I think it's "ocellata"

Cheers,

- Pete

[Gruditch]

Cheers Pete, this is the best I could get.

Gruditch

[Pete Eeles]

Cheers Pete, this is the best I could get.

Rest assured - I'll be using these on the main species pages when I get round to it

I assume this was the "dust pump" in action?

Cheers,

- Pete

[Gruditch]

It was, good job I took it. This was in Radio active corner again BTW

Gruditch

[eccles]

An amazing corner. Have you begun to glow green yet, Gary?

[Gruditch]

It's funny you should say that

Gruditch

[xmilehigh]

Makes you wonder what will come out of there next

Any bets