The Disappearance of Butterflies. Josef H. Reichholf

hand, are still relatively new. A century of nights illuminated by electric light is not enough. Or so one might think.

      But perhaps we should not take such a pessimistic view. There is actually a rich diversity of species of nocturnal moths living in those big, bright cities. Light pollution in general cannot therefore be the main factor determining their occurrence and abundance. More about this when we discuss the findings of the ‘light catches’ in the cities. But if the spectral composition of the artificial light sources were to be gradually adjusted to become more insect-friendly, this would certainly significantly improve the living conditions for the Lepidoptera in the cities. Then there would not be just ‘small moths’, but also hawk-moths the size of small birds and emperor moths that could be mistaken for small bats, flying ghost-like around the gardens and buildings of the city. Bats have long since fared much better in cities than in the countryside, where almost nothing of interest for them moves across the fields at night. The differences in numbers are enormous; the trends alarming. Thanks to the attraction to light, we know how things are for moths and many other insects of the fields. They will therefore occupy a central place in the second part of this book. Here I would like to continue with another, highly peculiar attraction, one that can be observed out in the forest without any technical assistance at all.

      1 * In German, Sonnenkinder – see also p. 147.

The Strange Behaviour of the Purple Emperor

      The purple emperor, with its tropical blue sheen, is surely among the most impressive of the butterflies that live in our part of the world. There are two species in central Europe, the large purple emperor, Apatura iris, and the lesser purple emperor, Apatura ilia, which is only somewhat smaller than the large one. The males of both species shimmer a magnificent indigo, just as if the upper side of their wings were underlaid with silver. With the females, the indigo is slightly less deep or virtually missing. There is also a special red variant of the lesser purple emperor, whose wings shimmer a dusky pink. It is rare for us, however, to come close enough to these masterpieces of our butterfly world to be able to admire them in all their living beauty, since they fly quickly and usually at quite a height. In Britain, the male purple emperor, A. iris, is referred to as ‘His Majesty’. For the many butterfly lovers there, sighting him represents the highlight of the butterfly year. They drive from near and far to the relatively few places in southern England where this treasure can be found with certainty.

In central Europe, both species of purple emperor can still be found quite regularly in early summer, between the end of June and the middle of August. The lesser purple emperor usually appears slightly earlier than its larger relative, usually from around mid-June. In particularly warm summers, such as 2018, one might even come across them at the beginning of June. Warmth always affects them. The main flying period for the larger purple emperor is the transition from June to July. The smaller species prefers the moister, warmer riparian woods, while the larger species favours logged forests – in southeast Bavaria, even forests dominated by spruce. If you did not know any better, you would be surprised to find the purple emperor in this type of managed woodland, which looks more like a plantation than a natural forest. But they are there, together with their smaller relatives, so that I need to inspect them closely in order to see which species they are when I set out to count the purple emperors along the forestry tracks. Often, I can already recognize the males of the larger purple emperor at quite a distance based on their distribution along the track. They sit right in the middle, at quite regular intervals of 20–30 metres – or every half kilometre, depending on how common or scarce they are in that particular year. From time to time, they fly up and perform an elongated oval over the forestry track, first in the direction of their neighbour on one side, then towards the other, which can sometimes lead to short aerial battles. Then the regular distribution pattern of the males is reproduced for a time. In other words, they claim a section of track as a territory that they defend against other members of their own species as well as against the lesser purple emperor, although less forcefully. If they are not close enough, they seem to be just as bad at differentiating these from their own species as we humans are. There is a marked, tooth-shaped point in the white stripe on the underside of the wing of the larger purple emperor, which disappears when the wings are closed, and which one can only make out when one is quite close. Similarly, the lesser purple emperor has another small ochre-coloured ‘eye’ on the lower outer edge of its forewing, and not just on the hindwing like the purple emperor.

I have always struggled to get close enough to this jewel of a butterfly to attempt a photograph: whenever I looked through the viewfinder of the camera and had the impression that I was close enough, had chosen the right section of the view and found the proper angle to capture the heavenly sheen, it would disappear with a barely perceptible wingbeat. Annoyed, and also ashamed of my slowness, I would later ascertain that on many such supposed butterfly pictures there would be nothing but the bare surface of the forestry track. Anyone who wants to take good photographs of such flighty beauties will need a lot of patience. Even then, it will barely suffice if you are not familiar with the behaviour of the butterfly and have no idea how it is influenced by the prevailing air temperatures or by the interplay of light and shadow in the forest. Early morning is the best time for photographs, when the sun is quite high and the butterflies are still numb from the cool and damp of the night. That said, at that time of day our purple emperors are usually still sitting in the unreachable heights of the treetops. Sometimes, one is simply lucky, and a photo comes out well. At other times, there might be special circumstances, such as those I once came across on a perfectly ordinary summer day in early July.

Butterflies on drugs

That morning, my wife and I were taking the dog for a walk in the forest. It was still cool enough for him under the trees. As usual, he walked a couple of metres ahead of us and sniffed his way carefully along the edges of the forestry track. When a few large butterflies flew up into the air, disturbed by the tip of his snout, he stopped short and sniffed the spot, but it appeared to hold nothing of great interest for his nose. He turned instead to trees where other dogs were accustomed to leaving their scent marks. We had not yet moved far from the parking area by the edge of the forest, and were therefore in the zone in which dogs that are taken to the woods mark most thoroughly. I would not have paid any further attention if the butterflies had not immediately flown back to the same place. Only then did it occur to me that our dog must have poked them directly with his nose. That was certainly highly unusual, since the group consisted of different butterfly species, namely two red admirals, a large purple emperor and two lesser purple emperors – that is, butterflies that were usually especially elusive. At 25°C in the shade, it was definitely warm enough for them, but what struck me was the peculiar flight pattern of these butterflies. Barely had they been roused than they settled down again on the same spot with their wings closed, that is, brought together vertically, so that when seen from above they looked like nothing more than five straight lines. Photographing lines is not particularly interesting, even when the lines are actually butterflies. But recording the camouflage effect of the folded wings piqued my scientific interest. When else does one get such an opportunity, and, what is more, with three different species?

      I also photographed a side view of the butterflies, so that they would be more recognizable. The fact that I did not need to slither up to them commando-style across the dusty forestry track, given that they were undisturbed by my approach, astonished me even more. One does not let such rare opportunities slip through one’s fingers. I photographed them from increasing proximity and hoped that they would do me the additional favour of opening their wings. But this they did not do, or at least, if they did, it was so instantaneous and so incomplete that I had no chance to capture the moment. Then, suddenly, one of them, a lesser purple emperor, put me in a most awkward situation. I must have got too close to it with my camera lens, wanting to see exactly how and where it was poking its unfurled proboscis. It flitted onto the camera and from there onto the back of my hand. There it sat and unfolded its wings so that they were perfectly flat, and their brightness shone right into my eyes.

      For seconds I simply stared, enjoying this unparalleled view of the magnificent butterfly on my