It was difficult to imagine that the hard winter, with weeks of lying snow and freezing temperatures, was not going to have an adverse effect on the emergence of the Small Blue, especially as it overwinters at ground level in the larval stage. Would the prolonged cold produce more aberrations or drastically reduce their numbers?

A very warm dry Spring followed with temperatures exceeding 20C and plants flowered early bringing the season 'forward' by a couple of weeks and butterflies were no exception. In the UTB region the first Small Blue was seen on April 30th (Pitstone in Bucks), two weeks earlier than 2010, when it was May 15th.

A year on from the 2010 emergence date numbers were peaking at Pitstone and Brian Jessop's transect produced an astonishing 894 (416 last year) despite hazy sun and breezy conditions. He speculated that there had to be thousands throughout the area. Helen Hyre found an unprecedented 50+ in Pitstone churchyard and people living close by saw them in their gardens.

Probably because of the very dry conditions, many were found seeking minerals or moisture from the ground and it was noticeable that some were very small indeed. It may well be that although the numbers didn’t seem to be affected by the prolonged low temperatures it may have caused a larger number of these small individuals.

Small Blues seeking minerals or moisture
Photo © Dave Turnbull

Sightings from the Upper Thames region were up on last year with good numbers from Swyncombe, Yoesden, Aston Upthorpe, Bradenham and Crog Hill. Mick Jones was pleased to report two from Dancersend and one was recorded at the Blue Lagoon in Bletchley.

Where there are good colonies, two broods seem to be normal now in our region. At Pitstone the first brood finished towards the end of June with the second starting mid July. Second brood numbers were small and this year were down on last year despite the huge first brood numbers.

Sightings are usually sparse in August and last year I commented on how unusual it was to see one as late as August 24th. This year at Pitstone sightings stopped on August 22nd and following regular visits none were seen and I thought their season was over. But our strange weather this year produced another hot dry spell and after a three week gap in sightings, I found a single newly emerged male on September 15th. Then on September 28th Richard Soulsby saw one at Swyncombe. Both of these dates are exceptionally late and are some of the latest ever recorded in the Upper Thames region and I speculate that these could be from a, previously undocumented, third brood.

With global warming could this be a trend of the future? Certainly these late records, coupled with the early emergence, have given us the longest flight period for this butterfly in the Upper Thames region and without doubt in spite of my apprehension during the winter the Small Blue has had an exceptionally good year.

My thanks to everyone who sent in their sightings to the website or to me.


Dave Turnbull
January 2012

Small Blue larva
Photo © Dave Turnbull