Broxhead - 10th June 2016
Silver-studded Blue numbers continue to increase gradually. This afternoon there were 16 males in the lek and for the first time there were females with them, I counted 4. There were 11 males on the bank facing the lek and I know there are two females there too. Also three others dotted around the reserve but I could not find the two I found the other day near the pond. In any case the total is now 38. I met a guy who was doing a transect and he had counted 45 but he had ranged a bit further than I did.
Today I thought I would start my report on observations I have made about this species at Broxhead to date. I have only been studying them properly from last year even though I have seen them here for a few consecutive years. As for the Small Coppers I shall break it down into parts but unlike them, my starting point is the variation in the brood.
Variation of the Silver-studded Blue at Broxhead
There is a slightly aberrant subspecies known as “ab caernensis”, the female of which has a blue sheen. The books I have read suggest it only exists on the Great Orme in North Wales, but this example I found at Broxhead may be a female.
One of my books shows the male of this subspecies. It typically has much thinner black wing bands and the bands on the hind-wing are interrupted so they appear more like discrete blobs. My study of the colony at Broxhead shows there may be a few like this. They are also noticeably smaller than the standard species. I wonder if someone at sometime has introduced them from the other known locations without telling anyone but it is very hard to tell because there is a fair deal of natural variation in the main species and this is a fact at Broxhead.
I followed one male which appeared to be of this subspecies for about 20 minutes and unlike the main species it seemed to reach much further. It travelled in a wide arc from the lek and around it - I estimate at least 40 metres, twice the normal range.
I once saw a standard male giving this smaller male the attention it might give a female. The smaller size and reduction in black markings is not just confusing to humans it would seem; and the blue flush on a female won't help matters for them either.
I must say though that I am not entirely convinced. These differences in size, colour and habit may all just be natural variation or other aberrations of the main species or in some cases even due to the age of the butterfly. Given that ab caernensis inhabits a limestone grassland environment on the Great Orme and Broxhead is a sandy heath also adds suspicion that natural variation is really the cause.
Here are some of the variations I have seen at Broxhead. Starting with the darkest. The borders are thick white and black. The blobs on the rear-wings are almost unnoticeable as they join up so much. The butterfly when fresh is quite a deep blue.
Next a variation has thinner black forewing bands and the rear band is starting to break up so you can see blobs of black. It is not quite as deep blue overall.
The variation shows even thinner forewing bands and now the hind-wing bands are completely broken up. This is the one that look most like the ab caernensis male I think.
Finally this variation has the thinnest forewing bands, almost no white edge and has brownish patina, although this might be an aged specimen.
Another aberrant can also be found at Broxhead. This is a micro-sized version of the standard species type (ab minor). Its wings are half the normal size while the body is normal. Here is a picture of a female. The wing size makes the body look very cumbersome and club-like but the fact that the body is normal sized means it is capable of mating.
There are 33 recorded aberrants for this species of butterfly nationally so I have read.
Well that's it for my short sojourn into the variation of this species at Broxhead. I shall keep looking this season to see if I can find any more.
Does anyone else have any odd-looking SSB’s? I would love to see them. If you have already posted any in the past could you give me a reference? Thanks.
Non-butterfly snapshot of the day
A Beautiful Yellow Underwing caterpillar being taken by a Sand Wasp – Ammophila sabulosa for his dinner.