The Disappearance of Butterflies. Josef H. Reichholf
the male releases the ‘clamp’ with which it gripped the tip of the female’s abdomen. She, in turn, crawls and paddles down and looks around, ‘flying’ and ‘paddling’ until she finds a water plant that is suitable for egg deposition. I have found the caterpillars of this aquatic moth on curled pondweed, Potamogeton crispus, water-milfoil, Myriophyllum sp., and, above all, on Canadian waterweed, Elodea canadensis, which in the 1960s and 1970s was still relatively common in lakes and larger lagoons among the reservoirs along the Lower River Inn.
Having said this, those females with wings adapted to paddling are rare in southern Germany, in contrast to, for example, Denmark, southern Scandinavia and Britain. In central Europe, the females usually develop with normal wings. They are significantly larger than the males – and this is essential. This is because it is only the females, travelling on the wing, even if they are borne and blown along by the air currents rather than by actually flying, that are in a position to find bodies of water in which there are perfectly suitable stocks of underwater plants. The pools found near rivers and reservoirs have existed for too short a time to be considered permanent. However, the much more constant shallow lakes around the Baltic Sea have also only been there since the last ice age, that is, for around 10,000 years. If this aquatic moth had produced only females with rudimentary wings that were unable to fly, this species would surely not have survived in the long term. The males need their flight capability in any event, in order to search for females.
At this point I would like to mention a genetic peculiarity. With butterflies and moths, the female sex is genetically marked XY and the male XX; that is, the exact opposite from us. For this reason, it is much easier for females to develop two different forms than it is for males. This characteristic manifests itself with particular clarity in forms of ‘mimicry’, that is, through the imitation of poisonous or foultasting examples by non-poisonous imitators that are not protected by unpleasant flavours. In short: in moth and butterfly circles, it is worthwhile for the females to be more highly diversified. We can see this clearly with the female of the brimstone butterfly, which resembles the poisonous cabbage whites. The females, with the precious cargo of eggs in their bodies, have good reason to keep themselves concealed. Generally speaking, we therefore see considerably more male butterflies and moths in nature than females.
But let us return to the species composition of the aquatic moths. With their ecological placement on the banks of waterbodies and their lives on and in small bodies of water, they not only provide a prime example of how the species are distributed across their specific habitats (each in their own ‘niche’), but also illustrate why the evolution of all the related adaptations in physique and lifestyle are so rewarding. The water edges constitute an environment rich in plants and luxuriant with plant stock, less affected by the vicissitudes of the weather. Plentiful nutrition is always attractive; plants that are not protected by special toxic substances all the more so. Vegetation right at the water’s edge and, above all, under water, is particularly attractive, not only due to its utility but also because it is situated in a place that the main enemy, the parasitic insects, have difficulties in reaching. The life and survival of any type of moth or butterfly almost always depends on the success of its caterpillars. If the caterpillars do not find sufficient food plants, then that species will not do well. If there is enough food, but the caterpillars feeding on it are heavily parasitized, then the species will not become (more) abundant. One such case is found among those butterflies with caterpillars that eat nettles. Since nettle plants are in plentiful supply, these particular butterflies should also be extraordinarily numerous. They are indeed numerous, but not exceptionally so, and their populations fluctuate from year to year. More of this in a separate chapter that will provide an insight into the nature of fluctuations. With regard to the aquatic moths, there is yet another question: what do they teach us about this general trend, the disappearance of butterflies?
The destruction of the biotopes of the little nymphs
The detailed portrayal of their lifestyle set out above could give the impression that aquatic moths only have such a major role in my book because my research into butterflies and moths started with them. However, they serve as an illustration for the precarious situation in which so many butterflies and moths have ended up. As I shall explain in more detail below, the water-filled gravel pits in which they lived when I carried out my doctoral research no longer exist. They have been buried, filled in. Those that were in the open fields have been reincorporated into agricultural land. They belong to the large group of small structures of which farming land has been ‘cleansed’. In this manner, the aquatic moths and many other butterflies and moths lost the biotopes in which they had flourished for many decades. Dozens of moths and butterflies – and, if one includes the smaller species, surely more than a hundred, as well as hundreds of other insects – made these gravel pits into islands of species diversity at the time when the homogenization of the fields was just beginning. In the opinion of certain influential nature conservationists at the time and of those authorities with jurisdiction over the excavation sites, gravel extraction had to be regulated and concentrated in special cultivation areas that should, of course, be as large as possible. When gravel extraction was complete, they could be repurposed as swimming ponds or, if of largely dry construction, could be recultivated as arable land or woods. It was this same trend that moved away from small- and medium-scale enterprises towards large businesses, and which could simultaneously be seen in agriculture.
With my studies of aquatic moths, I was only able to record a narrow spectrum of the insects that lived in gravel pits and small waterbodies. I observed their colony loss through the disappearance of the ponds in which dragonflies and frogs, and in dryer areas also lizards and beetles, had been comfortable. One by one, hedgerows and field copses also disappeared. The riparian woods by the River Inn were almost totally uprooted because of booming maize cultivation: the land was now worthless for growing trees, since firewood was no longer in demand, but had become highly profitable for farmers if they planted maize. The ban on woodland clearance came too late. Large parts of the riverine woods had already been destroyed and were further cleared over the years because the authorities did nothing to prevent it from happening. Perhaps it was only thanks to a series of wet summers that the wetter riparian woods along the River Inn remained untouched. Financial incentives for clearing woodland were eventually stopped.
It is with very mixed feelings that I think back to the 1970s when the fight for these alluvial forests played itself out and nature conservationists like me could only watch helplessly as piece after piece was cleared and converted into maize fields. The media and the general public were not very interested at the time. Such species-rich areas were referred to in the official parlance as ‘wasteland’ or ‘barren land’, descriptions that say everything about the value placed by large-scale agriculture upon animals and plants that have no direct commercial use. Sometimes I doubt whether our attitude to what is truly noteworthy has changed at all, even though one seldom hears talk of wasteland anymore. Words are interchangeable; it is far harder to change their underlying meaning, and there are setbacks time and again. Decades of serious attempts to replace the terms ‘raptor’ and ‘predator’ in Germany with ‘bird of prey’ and ‘carnivore’ (on the basis that ‘prey’ only exists in the eyes of the hunter) were fruitless. For some reason, young journalists in Germany have started using the term ‘raptor’ again quite openly, even though it disappeared from ornithological books long ago. ‘Pest’ is once again used for insects, regardless of whether or not they cause damage intentionally or even whether they cause any damage at all.
My aquatic moths caused no damage in the wild, in the small bodies of water or on lake shores. Unfortunately, the same could not be said of waterlily ponds. Water-lily species with thin leaves, in particular, were devoured by caterpillars, resulting in nothing more than an eyesore. In a garden pond with small, pink-flowering water-lilies most people want flawless floating leaves and, if possible, flowers that have not been spoilt by aphids. But anything that interferes with their look counts as damage, and for many an owner of such garden ponds it would be better if the little moths did not exist at all. Tropical aquatic moths also cause severe harvest losses in rice fields. The opportunity offered to me by the FAO (Food and Agriculture Organization) to carry out my investigations there did not attract me. The moths and butterflies that lived around us were