Up a small track above Caussou, you pass through damp streamside woodland, rocky limestone grassland and then drier woodlands. There are also pastures edged by miles of electric fencing; the farmer and his family have been moving the herd regularly in the past few weeks as these are quickly grazed off and trampled; turned from flower rich meadows into an untidy short grass sward although they are quick to recover. Many of the woodlands are grazed too. Finally, the herd moves from the exhausted lowland pastures to the steep limestone grasslands on the mountain slopes. Some fields are ungrazed and cut for hay. Late June is the time when spring turns to summer in the these Pyrenean foothills.

The plants are changing too; the Ophrys orchids are fading and bug orchid Anacamptis coriophora appears all over the dry grasslands in mid June and is going over by the end of the month. The limestone grasslands are now a vivid picture of purple thyme and yellow rock rose and stonecrop. Up the track red Cephalanthera rubra and marsh helleborines Epipactis palustris appear, the former part-concealed under bracken and the latter alongside a wet ditch. Just up the road at Col du Marmare there are also a few spikes of dark red helleborine in a long abandoned quarry.

The most notable find is a few Cross Gentian Gentiana cruciata, or in French the more elegant sounding Gentiane croisette, that appear on a small patch of limestone grassland that is being invaded by blackthorn scrub. Almost too late, I realise this is the foodplant of the mountain form of the Alcon Blue Phengaris alcon rebeli. I miss the males which fly earlier, but for one day only (21st June) I find the females laying on the gentian. A few days later all there is to prove their existence are the white eggs on the, now flowering, gentians. There are perhaps a dozen plants across this patch of grassland that are sustaining the colony of this rare butterfly. This is one of the ‘large blues’, all of which have the most remarkable life cycle; after hatching the larvae feed on the gentian leaves until the 3rd instar drops to the ground where it is found by a species of Myrmica ant and carried into the nest. Here it lives for the next 23 months where it is cared for and at the same time feeds on ant larvae before pupating and emerging as an adult. The sophisticated mimicry it elicits to fool the ants into being the perfect hosts is both chemical and acoustic and is beautifully summarised here.

There are other butterflies here too, the many heath fritillaries are joined by a few dark-green fritillaries that charge up and down the track. Sloe hairstreaks feed on the thyme. The species that are common in England such as red admiral and small tortoiseshell are joined in late June by peacock, comma and ringlet. But there are also white admirals and large tortoiseshells here too. The diversity of plants and butterflies in these Pyrenean foothills is simply stunning.