Balkan Clouded Yellow | Colias caucasica balcanica (Mike Watson)
The weather had other ideas for us this morning. Back in Serbia, rain swept across Kopaonik National Park, washing out any hope of productive butterflying, so we decided we might as well put the time to good use. Rather than waiting for the weather to improve, we drove towards another, much more remote mountain, hoping the skies would clear by the time we arrived.
Our target was one of Europe's most localised butterflies: the Balkan Clouded Yellow Colias caucasica balcanica, confined to isolated mountain populations stretching from Bosnia and Herzegovina through Serbia and North Macedonia to Greece.
As we approached our destination the rain began to ease and, encouragingly, patches of blue appeared between the clouds. Unfortunately, a far more serious obstacle awaited us.
The forest track that Janó had identified as our route to the high-altitude meadows was exactly as he had feared—unsuitable for an ordinary four-wheel-drive SUV. Looking uphill through binoculars, we could see sections where rain had washed part of the road away. This was unfamiliar territory and we didn’t want to become stranded several kilometres from the nearest village, unable to turn around on a muddy mountainside—or worse, slide into the forest below.
Our waypoint lay around five kilometres further up the mountain. Hiking that distance in uncertain weather, with no guarantee the rain would hold off, simply wasn't worth the effort. Reluctantly, we admitted defeat and turned back towards the nearest village.
Then fortune intervened.
As we rolled away we heard the roar of a large engine approaching. Around the bend came an enormous Jeep with oversized tyres, raised suspension and, reassuringly, an "Off-Road Club" sticker on the side.
The driver introduced himself as Almas, a young migrant worker (as a crane operator in Berlin). He was heading up the mountain to visit his aunt, who lived on a remote farm high above the forest, exactly where we wanted to go.
"I can take you, and bring you back down, I’ll be there for a couple of hours."
We could hardly believe our luck. Sometimes our adventures produce moments that seem almost too perfectly timed to be coincidence.
The journey uphill was memorable. Almas clearly regarded the climb as an extension of his off-roading fun afternoon and drove the deeply rutted forest tracks with remarkable speed. His Jeep, however, was every bit as impressive as its appearance suggested. Obstacles that would have bounced our own vehicle into the trees were overcome effortlessly by its enormous suspension. I didn’t enjoy hurtling through the forest at full speed, expecting a disk to bulge at any moment, but I certainly appreciated the time saving.
It was a considerable relief to climb out beside his aunt's delightful little farmstead, surrounded by colourful flower meadows, accompanied by the smell of a burning clutch.
With just two hours, we had to walk around a kilometre to our waypoint. Fortunately, the remaining track was almost level and along the way we passed an angry pair of nutcrackers, before the forest gave way to one of the most beautiful alpine meadows I have seen.
Balkan Clouded Yellow habitat
The meadow stretched away towards the distant ridges in a riot of wildflowers beneath a clearing sky. Sunshine now flooded the mountains, transforming what had begun as a gloomy morning into a glorious summer afternoon. Now, where was balcanica?
Janó followed the woodland edge towards the waypoint while I walked parallel across the centre of the meadow. Between us we hoped to intercept any Colias butterflies flying across the open grassland.
As we approached a dry valley—more of a broad depression than a valley—I caught sight of movement.
One.
Then two.
Then three unmistakably orange male Clouded Yellow-type butterflies patrolling the meadow.
"Janó!" I shouted… lots of times, so he could follow my voice as I chased after the butterflies.
Janó had disappeared briefly while following another interesting butterfly, before reappearing moments later. "They're very orange!" he said.
Balkan Clouded Yellow | Colias caucasica balcanica (Mike Watson)
The butterflies patrolled tirelessly up and down the slopes in search of females, rarely pausing for more than a second. Photographing them proved demanding as usual with this genus. They flew with purpose, forcing us into sustained power-walking pace across the hillside. The intensity of the richly coloured alpine flowers gave the camera's autofocus no end of trouble, making flight photography challenging.
Eventually persistence paid off. I managed a few flight images before the butterflies finally began settling briefly to nectar.
Every visit was to the vivid crimson blooms of Dianthus sanguineus, Blood Pink, a species I knew from last year’s trip to Stara Planina in southeastern Serbia.
We were delighted—or at least we were until I studied the images on the back of my camera.
"Oh dear..."
Had we made a terrible mistake?
The butterflies showed yellow veins crossing the black apical border of the forewing—a feature usually associated with the common Clouded Yellow Colias croceus. Worse still, they didn't appear quite as intensely orange as many of the illustrations in the field guides.
Fortunately, the scientific literature tells a more complicated story.
A 2015 paper by Ana Nahirnić, Predrag Jakšić and Arne Lykke Viborg, Colias caucasica balcanica (Pieridae) rediscovered in Montenegro, with additional new records for Serbia, reported that this feature is far more variable than identification guides suggest. Although most references state that male C. caucasica balcanica lacks prominent yellow veins in the black forewing border, the authors found that this is far from absolute.
One specimen collected at Borje in southwestern Serbia had initially been identified as Colias croceus because of its conspicuous yellow veins. Closer examination revealed that around 30% of the Serbian males examined displayed yellow veining to some degree. A similar proportion—23%—was found among Greek specimens. In other words, the feature widely presented as a reliable field character is quite variable.
That finding contradicts the impression given by both the 2008 Collins Butterfly Guide and the 2026 Princeton Field Guide, both of which continue to present the absence of yellow veins as a key identification feature.
Janó wasn't remotely concerned.
"Don't worry," he said. "They are balcanica, I've seen thousands of Clouded Yellows, and none of them has ever looked as orange as this. It's exactly the same with myrmidae."
He was right.
The field guides need a small revision on this point. The butterflies illustrated in many books also resemble the deeper orange individuals found further south in Greece, where the Balkan Clouded Yellow reaches its richest coloration. That striking southern form has become something of the 'standard' illustration, making more northerly Serbian butterflies appear unexpectedly pale by comparison. The specimen plate published in the 2015 study shows just how much variation exists.
Even so, our butterflies still looked distinctly different from the common Clouded Yellow.
Balkan Clouded Yellow | Colias caucasica balcanica (Mike Watson)
The habitat itself also provided an important clue. We were standing at 1,630 metres above sea level in flower-rich alpine meadow—exactly the sort of environment expected for Colias caucasica balcanica. Although Colias croceus occasionally wanders to over 2,200 metres in the Alps, it generally breeds below about 1,600 metres and is primarily a butterfly of lower elevations. Everything about the location pointed towards balcanica.
What appears a subtle distinction to us represents a much deeper evolutionary history. DNA studies suggest that Balkan Clouded Yellow diverged from the Danube Clouded Yellow, Colias myrmidae (from which it was originally described as a mountain subspecies) around 1.2 million years ago.
In keeping with the Balkan name theme, a pristine male Balkan Copper Lycaena candens appeared by the track on our return to the farmstead. Its brilliant, purple-edged orange upperwings glowed in the afternoon sunshine, providing the perfect finale to an unforgettable afternoon. Almas’s aunt gave us some delicious homemade cheese served with Turkish coffee. Fabulous stuff! Looking at her friendly, Turkish Kangal guard dog, which was the size of a small horse, we asked “Do you get wolves here?”. “Yes, and bears too”. Gulp.
Balkan Copper | Lycaena candens (Mike Watson)
Now, I find myself looking at the 1996 North Macedonian first day cover depicting both Balkan Clouded Yellow and the Macedonian Grayling Pseudochazara cingovskii. This time it means far more than just an attractive stamp issue, bringing back vivid memories of alpine meadows, a remote mountain farm, the generosity of strangers, and an extraordinary afternoon when everything somehow came together. One of the best!
Mike and Janó at Almas’s aunt’s farm, 22 June 2026 (János Oláh)
1996 North Macedonian first day covers even show the variation!… and the yellow veins across the apical border! Pure coincidence owing to print run timing - see how the graylings also vary but how apt nevertheless? (Mike Watson)