The Scarce Swallowtail is an oddly-named species of butterfly because, well, it’s not very scarce. Or at least, not when you consider Europe as a whole. It seems that the Scarce Swallowtail got its name from the fact that it is so rarely seen in the UK, whilst in other parts of Europe it is positively common.
Just consider France, where I spent last summer. Here the Scarce Swallowtail is decidedly abundant, and on sunny days it was not unusual to find at least one specimen and sometimes many more flitting across the garden. They can be even more common in the countryside, where half a dozen specimens may be seen feeding on a single clump of wild flowers.
The Scarce Swallowtail does at first glance resemble the better-known Swallowtail. They are both quite large butterflies with yellowish wings. They also both enjoy the unusual projections from the hind wings that give them their “swallow tail”. Look just a little bit closer, however, the differences become quite noticeable.
For one thing, the Scarce Swallowtail is much paler in colour – a gentler and more subtle shade of yellow than the bright primrose yellow of more traditional Swallowtails. The wing shape is also quite different, with the Scarce Swallowtail having more “delta-shaped” wings – a shape that is quite unique among other common European butterflies. These features – the size, colour and wing shape – make these commonly-seen butterflies very easy to identify – even from some distance away.
Scarce swallowtails are most frequently seen on warm summer days where they seem to “glide” as much as flutter. They are often to be found feeding on nectar, though in colder or wetter weather they tend to hide away in bushes and hedges to stay safe. It is here that they can become victim to predators, who pick them off while they are at a disadvantage.
Indeed, the photos of the Scarce Swallowtail resting on my hand were not taken with the butterfly’s permission. It didn’t flutter down to land on me, or agree to be gently picked up off a flower. Instead, I happened to see it struggling to fly through heavy rain, pursued at lightning speed by two house sparrows. It seems they were trying to take chunks out of the poor thing as it struggled to escape. Eventually it crash-landed on the lawn and I dashed out to save it.
Only on a cold, wet day after a long tussle did the Scarce Swallowtail let me pick it up gently, placing it well out of the rain to recover. Some hours later the rain stopped and the sun came out. I then noticed that “my”swallowtail had gone. I do hope he flew off to enjoy life, rather than becoming someone’s dinner.
The Scarce Swallowtail undergoes a standard butterfly-style lifecycle. Eggs are laid, typically on blackthorn, though other plants have sometimes been used in the past. Here the eggs hatch, and begin feeding at speed. Within a couple of months they then turn into a chrysalsis, before emerging as adult butterflies. It is believed that the species may have two or even three broods per year before the cold winter weather sweeps in.
It may be that one reason for this butterfly’s scarceness in the UK is the lack of blackthorn. As mechanisation has been introduced, and farmer’s fields have increased in size, so hedgerows have been destroyed – the most common place to find wild blackthorn. Alternatively, or additionally, it may be that the average summer temperatures in Britain are simply too low for this species, which only occasionally manages to make it’s way across the Channel.
Whatever the case may be, as the climate continues to warm we might just find this stunning butterfly cropping up rather more often. And what a joy that will be for us nature lovers!