I’m crouched in a grassy hollow, chatting to my friend Steve about the ethics of watching a pair of dingy skippers in flagrante, when a visitor arrives out of the blue, distracting us from our moral quandary. Light as blossom, dark as coffee, a minuscule butterfly settles on the strap of Steve’s rucksack, opening dusky brown wings flecked with sky-blue glitter. We’re here to spot butterflies, but we weren’t expecting such a rare treasure to seek us out. It is a male small blue, the UK’s tiniest resident butterfly, with a wingspan barely bigger than my thumbnail. Once known as the Bedford blue on account of a large population near that town, its Latin name – Cupido minimus – is surely the most endearing of binomials. When this littlest love closes its wings, it reveals a frosted underside similar to that of a holly blue, with a freckling of black dots almost too minute to discern with the naked eye. Despite the species’ local abundance in the 19th century in chalky areas where kidney vetch (its sole larval foodplant) grows, numbers declined significantly as a result of habitat loss from agricultural intensification and lack of sympathetic management. By the early 2000s, the small blue was thought to be extinct in Hertfordshire. But contrary to the national trend of diminishing distribution, several populations have been discovered in the county over the last 20 years, and the Hertfordshire and Middlesex branch of Butterfly Conservation has been working with landowners to promote awareness of the species’ importance and support the conservation of known colonies. I spent many happy hours last June in a meadow on the edge of Letchworth Garden City watching small blues congregate in the late afternoon, prior to communal roosting. But this little guy has neither males for company nor females to court. Instead, he alights on our hands, stretching out the thinnest of proboscises to sup our salty sweat. When we are ready to leave, he is still slaking his thirst. We gently dislodge him, but he’s having none of it and attempts to land again. We dodge and run. Two adults hotfooting it out of the chalk pit pursued by an 18mm butterfly.