Holly Blues have been flitting across our gardens throughout this month. We have three main blue butterflies in the south of England: holly, common and chalkhill blues. I used to feel unsure about which was which – all were quite small, all dashed about and all looked much the same! Actually, telling if it is a holly blue is quite easy.
For a start, only holly blues have been flying this last month, so if you have seen a blue butterfly it will almost certainly have been a holly blue. Also, only holly blues have light blue underwings. Common and chalkhill blue butterflies’ underwings are a light brown. As holly blue butterflies often rest with their wings folded, this is a really useful feature for ID.
In addition holly blues have a chequered black and white pattern to their wing edge. Common blues’ wing edge is plain white.
Common blues will start flying soon so we will soon be able to have fun spotting which is which. Good luck!