Silver Studded Blue sizes

[Trev Sawyer]

I think it was Gibster and Felix who were discussing the size differences of Silver Studded Blues a few days ago...
I went to Kelling Heath in Norfolk on Thursday and whilst watching Common Blues, noticed a worn and far smaller brown butterfly which I originally put down as an old Brown Argus. I then saw a tiny blue butterfly (from above it looked like a very small Common Blue). I managed a few (absolutely rubbish, sorry!) record shots before I had to move on, but later started to think they were both Silver Studded Blues (especially now I have downloaded the pics). I did find a few "normal" sized Silver Studded Blues (see last photo), but the first three snaps show butterflies which were literally as small as Small Blues ie not much more than 1.5cm wingspan. I was amazed at just how ridiculously small they appeared. I spoke to a local photographer I met there, who told me that the Silver Studded Blues had supposedly just started to appear, but I wonder whether these smaller insects had hatched a while ago and become worn already.
Is it possible/likely that the small versions pupated first when there was potentially less food for them and the larvae had not been able to grow very large - hence the size of the adult? If they pupated earlier, they may well hatch out earlier too. Is it common for there to be such a variation in size at the same site? My fellow enthusiast mentioned that the Silver Studs at both Kelling Heath and Buxton Heath were re-introductions. Does anyone know where the original source was from for these sites?

small female?

absolutely TINY blue

the same insect (showing how small it was against a bramble flower)

a "normal" Silver Studded Blue at the same venue

Trev

[PhiliB]

Trev
I was at Kelling Heath on the 21st June and the SSB were on the wing then - although not in large numbers.
Phil

[Gibster]

Hi Trev,

my local Silver-studded Blues, argus are at Fairmile Heath, Surrey - takes me under 20mins to get there. The ones at Fairmile always seem pretty large to my mind, although I have seen very small 'runt-type' males on occasion. I also see them at Thursley and in the New Forest where they appear smaller (more regular-sized, in fact!) I recently saw the Prees Heath colony in Shropshire, close to masseyi, and noted several very small males (one was about as small as a Small Blue!) Later that same day I was on The Orme in north Wales where ALL of the Silver-studded Blues caernensis are positively smaller than is normal, both sexes. Last week I trundled down to Portland in Dorset for the isolated populations there, close to cretaceus, and they were normal-sized and distinctly larger than a female Small Blue in the same area.

Felix is the chap to chat to, I'm pretty amateur at this. But he says that Silver-studded Blues are VERY variable and I guess that genetically/geographically isolated colonies will naturally vary in size/patterning/extent of blue scaling from one another as well as some degree of intra-colony variation (is that even a phrase?? )

"Is it possible/likely that the small versions pupated first when there was potentially less food for them and the larvae had not been able to grow very large - hence the size of the adult? "

Not too sure about this theory, but it doesn't seem likely. Felix to the rescue............???