The Disappearance of Butterflies

Josef H. Reichholf, Gwen Clayton

• Publisher: Polity
• Year: 2020
• ISBN:
  9781509539819
• Edition: 1
• Topic: Scienze biologiche
• Subtopic: Evoluzione

In the last fifty years our butterfly populations have declined by more than eighty per cent and butterflies are now facing the very real prospect of extinction. It is hard to remember the time when fields and meadows were full of these beautiful, delicate creatures – today we rarely catch a glimpse of the Wild Cherry Sphinx moths, Duke of Burgundy or the even once common Small Tortoiseshell butterflies. The High Brown Fritillary butterfly and the Stout Dart Moth have virtually disappeared. The eminent entomologist and award-winning author Josef H. Reichholf began studying butterflies in the late 1950s. He brings a lifetime of scientific experience and expertise to bear on one of the great environmental catastrophes of our time. He takes us on a journey into the wonderful world of butterflies - from the small nymphs that emerge from lakes in air bubbles to the trusting purple emperors drunk on toad poison - and immerses us in a world that we are in danger of losing forever. Step by step he explains the science behind this impending ecological disaster, and shows how it is linked to pesticides, over-fertilization and the intensive farming practices of the agribusiness. His book is a passionate plea for biodiversity and the protection of butterflies.

Part I
The Biodiversity of Lepidoptera

A Review of 50 Years of Butterfly and Moth Research

My records prevent me from creating rose-tinted memories of past conditions. I started keeping records on nature on 15 December 1958, and I therefore know, for example, that we did not have a ‘white Christmas’ in the Lower Bavarian Inn Valley 60 years ago, but it was, instead, two degrees above zero with light rain. On 2 January 1959, I noted that, outside on the River Inn, on the completely ice-free reservoir, I counted the following numbers of water birds: 800 mallards, 50 tufted ducks, 69 bean geese and 200 coots. Most of the numbers were rounded up, since I was not able to produce more accurate figures using my small binoculars from where I stood, half a kilometre away. I was not given a relatively powerful telescope until a few years later. As I pulled out and glanced through my old records in the course of preparing this book, I also came across a page with four butterflies that I had drawn myself. Astonished, I looked at it and read what I had written about the pictures ‘drawn from my collection’. Next to a swallowtail and a pair of Adonis blues, Polyommatus bellargus, I had drawn a large and striking black and white butterfly, a great banded grayling, and labelled it with the scientific name that was customary at the time, Satyrus circe. This discovery surprised me, since the beautiful ‘Circe’ that flies in such an elegant manner has long vanished from my region. It is largely extinct in Southern Bavaria, just like numerous other species of butterfly that I knew and observed in my youth.

Some of the species that were considered ordinary in those days do still exist, but they have, in the meantime, become rare or very rare. I also found a fitting example of this in my records. A note dated 12 September 1962 contained an observation that would be considered remarkable today. An almost palm-sized moth flew into the local train when we stopped at a station on our early morning journey to school and landed on the red shirt of my classmate. It was a red underwing, Catocala nupta (see Photo 1). When it is resting, the grey-brown, washed bark-coloured forewings of this large noctuid moth cover the bright crimson hindwings that are bordered with an angled black strip, just inside the outer margin. Not yet aware that moths – like all insects – cannot see the colour red, I wrote: ‘The red underwing was thus attracted by the red colour of the shirt.’ In fact, the red shirt would actually have seemed dark to the moth. To its vision in the so-called ‘grey-scale’, it may well have corresponded to a dark tree bark and the grey scales of its forewings. In the wild, the spot would have been suitable as a resting place during the day for this noctuid moth, which is active at twilight. One may therefore assume that red underwings were so common 50 years ago that one of them got lost in a train, presumably startled from its resting place in the station.

If this type of note from my schooldays was a mere anecdote, then these records would offer nothing further. Indeed, one retains what seems unusual, while the ordinary goes unnoticed. And yet, interesting points can be gleaned from unsystematic memos. I can find plenty of examples in my diaries. For example, the nine-spotted moth (or yellow belted burnet), Syntomis phegea, which has long since vanished from the area, sighted on 1 August 1960, or the caterpillar of the wood tiger, Parasemia plantaginis, recorded on 28 July 1960. The latter is only seen very rarely now. However, all of these and the many other records only show that there used to be Lepidoptera^* species that no longer exist there. The true scope of the decline in butterflies and moths and other insects cannot be deduced from the disappearance of individual species. It is quite possible that other species that were not there earlier have appeared during this period. Nature is dynamic: changes can and will always occur. My initial claim that we have lost 80 per cent of the butterflies in the last 50 years refers to their overall frequency and requires much more concrete evidence.

I have already achieved that with birds: my counts of the water birds on the reservoirs of the lower River Inn, which I carried out every two to three days for six years, resulted in my first specialist ornithological publication in 1966. However, a quantitative survey of butterflies and moths was a very different challenge from counting birds that were resting on the banks or swimming on the water. My attempts gradually took form during my zoology studies at the University of Munich. A scientific approach was required for my doctoral thesis on aquatic moths, so I quickly familiarized myself with the five different species of moth that make up the Crambidae family and learnt how to reliably distinguish them by recognizing their flight patterns in the field.

However, given their number, moth and butterfly species require far greater knowledge if one wants to record all of them. The training is far more difficult and time-consuming than getting to know bird life. In southeast Bavaria alone, there are more than 1,100 species of butterfly and moth; for the whole of Bavaria, 3,243 have been reported (as of 2016). Many of these are very small and can only be identified with the help of specialist literature. For birds, there were already very good identification guides in the 1960s, which were not prohibitively expensive. Consequently, my initial engagement was with the bird world rather than with the butterflies. The reason was proximity, in the literal sense of the word: the reservoirs and riparian woods along the lower River Inn, which I could reach on foot or by bicycle, are a bird paradise. They are among the wetlands with the largest numbers of species in inland central Europe. When I started my zoology studies in Munich in 1965, I had already gained professional recognition as an ornithologist, thanks to my native surroundings, and I was familiar with various methods that are employed in field research.

Insects fly towards UV light

During my studies, I became familiar with a method that is more suitable than any other to establishing the abundance of moths. It consists of attracting species that are active at night using UV light. This is no longer done with large mercury-vapour lamps of 1,000 watts, which are used to light up white sheets that have been stretched behind them, as was common practice in the past and as I have attempted myself, but instead by means of an ingenious construction using UV neon tubes of only 15 watts. The moths and other insects are drawn in by this UV light. When they approach, they enter a funnel under the light tubes, leading to a large sack, in which the insects land. In order to offer them a place to hide until the following morning, empty egg cartons or similar are placed in the sack. This collection method does not harm the moths in any way. In the sack they quickly settle down, since the stimulus of the light has been removed. Together with the other insects, the moths are counted the following morning, and identified species by species, to the extent that their species identification is possible. At that point, all the insects are released immediately. In this manner, readily analysable and statistically useable results are achieved, which can be compared, depending on the problem in question, with a similar assembly of the apparatus in another location. This method can even be used to establish frequency and species composition of moths in quite different habitats. This is exactly what I did, starting from 1969. Dr Hermann Petersen perfected the method. I am greatly indebted both to him, and also to Elsbeth Werner for allowing me to use her pesticide-free farm for research.

Unfortunately, this type of light attraction does not work with butterflies. In order to establish changes in frequency for them in a comparable manner, I started to count them in the 1970s, along specific, fixed routes that would not be changed over the years. For example, along forest tracks or dirt tracks across fields, or along embankments already specified as transects. With their signs indicating river kilometres, placed at intervals of exactly 200 metres, these riverside routes are perfectly suited to such transect counts. In the 1980s, I primarily used the findings that I had obtained in this way for my lectures on ecology and nature conservation at the Technical University of Munich and on ecological biogeography at the University of Munich. Over the years, it became clear that the light traps and the route counts (or ‘transects’) yielded fewer and fewer butterflies. As for the ‘by-catch’, as I referred to the other insects that flew into my lights, even the cockchafers disappeared, despite previously having been so numerous. On more than one occasion, their mass flight to the UV light caused the sack to become detached from the funnel and fall to the ground, since up to 1,000 cockchafers had crept in there in the gloaming. Since there were often hardly any moths in the cockchafer season at the beginning of May, such a mishap did not compromise the annual totals. But the rather sudden decrease in the cockchafers perplexed me. This was the first signal that my investigations were providing important data about the changes to nature. Yet in the 1980s, I still had no inkling of how sharply downhill things would go for the moths and the other insects, nor that my findings would result in an eco-nutritional basis for the decline of the birds in the meadows and the fields.

Urban Lepidoptera: more common than expected

In the early 1980s, I also started to research butterfly and moth frequency in the city. Munich, the place where I had been a scientist at the Bavarian State Collection of Zoology (ZSM), offered ideal conditions for this. There were enough suitable locations from the centre to the city margins to provide a kind of cross-section of the occurrence and frequency of nocturnal insects. Moreover, the large collections present in this research museum, together with the assistance of my specialist colleagues, stood at my disposal during my endeavours to identify precisely all the insects. The fact that I would need their help became evident as soon as I started work on my first findings. They were so much more species-rich than expected that I could never have coped on my own. Furthermore, the catches turned out to be extraordinarily rich in terms of quantity, too. The widely held idea that there would only be a pitiful fraction of the species diversity found in the countryside was not only called into question by my findings, but immediately exposed as mere prejudice.

Over the years and decades, the extensive research results that I shall report in this book thus came into being. They represent the results of half a century of quantitative entomology.

Over the past half-century, nature has changed to an extent and at a speed that are simply unprecedented in such a short period. The findings are staggering and the prospects that they imply are exceptionally grim. This is because we cannot expect the main agent of this loss of species diversity – agriculture – to undergo any substantial change. Anyone who delves into the ‘agricultural problem’ in any depth will find that it has less to do with the farmers themselves than with agricultural politics. The billions of subsidies they have received over the last 50 years have resulted in a highly competitive displacement of the small-scale farms by the large ones. Traditional farmers more or less disappeared, until only a tenth of their former numbers now remain, and yet the victor in this situation, international agrobusiness – in particular, the producers of crop protection products – managed to keep a low public profile, while the decline of insects and birds proceeded in shocking parallel to the death of small-scale farm-based agriculture.

The much-maligned city life has long since become better than life in the country, where the slurry stinks to high heaven and poison is used in unprecedented quantities, and where the birds have been silenced and the groundwater is no longer fit to drink. How can things go on like this? Is it not possible to curb the spirits we once called upon in good faith to lighten the work of farmers and improve their lives? Can we even imagine a ‘butterfly effect’ that might lead to a reversal in the state of industrialized agriculture? Although it may surprise you, my outlook at the end of this book is cautiously optimistic. And yet perhaps this hesitantly expressed optimism is nothing but a dream, for future generations won’t appreciate what they haven’t come to know or experience themselves: the biodiversity of nature and our moths and butterflies.

Death’s head hawk-moth: a guest that can barely live with us anymore

Right now, species that could have had a lasting impact on our children, if only they had got to know them, are disappearing. I am thinking of the great wonder that seized me one evening in early October, when a death’s head hawk-moth emerged from its pupa in a glass on my windowsill (see Photo 2). I had found it during the potato harvest. In the early 1960s, the potato fields in Lower Bavaria were predominantly harvested in the old-fashioned way. A horse pulled a plough with its share set at such an angle that, with the correct spacing, it created a deep furrow on one side, while a line of earth about two hand-widths higher than required was tipped over with the potato haulms. Some potatoes would thus escape harvest. We would look for these and then find others that were still encased in earth, which we would grub out by hand. In our Lower Bavarian dialect, we called this ‘Kartoffelklauben’ (‘potato grubbing’). The caterpillars of the death’s head hawk-moth, however, also now feed on potato plants in summer, since they are adapted to eating plants of the nightshade (Solanaceae) family. The potato plant, which originally came from South America, belongs to this poisonous plant family.

The distant origins of the death’s head hawk-moth are not a disadvantage; they actually work in its favour. This is because there is nowhere in the wild where the females of these massive moths will find any nightshade plants in such abundance and so conveniently grown, with open ground around the bushes, as in a potato field. Accordingly, soon after its large-scale introduction into Europe in the early seventeenth century, the American potato plant became a preferred alternative for this large African hawk-moth. We can assume that, prior to this, it flew here from the edge of tropical Africa only seldom, due to the lack of suitable forage plants. The bittersweet nightshade, Solanum dulcamara, did not offer much nutrition and grows so sparsely that even today the caterpillar of the death’s head hawk-moth is rarely found on it.

When these caterpillars are fully grown, they dig an elongated hollow slightly below the surface of the ground, in which they pupate. After several weeks of pupation, the mature moths emerge, and must try to fly south, across the Alps. They will not survive the winter to the north of them. My specimen was just such a fully grown caterpillar. I had housed him in a clean jam jar on a bed of garden soil and loosely covered him. From time to time I would spray the soil a little, so that the pupa would not dry out. With success: the newly emerged death’s head hawk-moth, whose wings were not yet fully unfurled, not quite covering the yellow and black-ringed plump abdomen, appeared massive to me. More so, when I let it crawl onto my index finger so that I could place it on the curtains. This way of holding it would allow it to fully stretch out its wings, so that they could become fit for flying. My goal was, after all, to release it at dusk, so that it could return to Africa. The mere thought that this plan might be successful and that I might contribute to it excited me tremendously.

However, the pale-yellow design on the back of its thorax that was supposed to remind me of a skull made little impression on me. No matter which way I looked, it did not ...

Table of contents

• Cover
• Title Page
• Copyright
• Foreword
• Acknowledgements
• Introduction
• Part I: The Biodiversity of Lepidoptera
• Part II: The Disappearance of Lepidoptera
• Two Findings in Place of an Epilogue
• Select Bibliography
• Index
• Ebook plates
• End User License Agreement