Not so long ago, if you saw a blue butterfly in the countryside you would have to think "Why is that NOT a common blue?" Living up to its name it was certainly the most common of the blues but that seems to have changed in the last couple of years with its numbers seemingly much lower now; in places Adonis blue and silver-studded blue seem to outnumber the common blue. The common blue can be found in a wide range of habitat types from flower-strewn grassland and meadows, hedgerows, woodland glades, heathland, parks and occasionally gardens. Generally double brooded down here in Dorset in good years they are known to have three broods meaning they can be seen from May into October and sometimes even later; there is a gap in June between the first and second broods.
We have fifty eight records for 2017 and 2018 in the Nature of Dorset database and there are records for almost every week from week 16 in late April to week 44 at the end of October. In June 2017 there was the inter-brood gap with just one record that month but in 2018 it seems July was the gap month with far less records than the previous July. With far more seen in May 2017 than May 2018 it seems that emergence was later in 2018 meanuing the second brood was later too.
Seventy four sites have reports of common blue and whilst chalk grassland sites feature well in the list there are also heathland sites as well as woodland. Durlston, Badbury Rings and Ballard Down all have several reports of common blue and these all have a calcareous rock base.