Spotting moths in France, in all their superb variety

I had a friend who lives in the UK come to stay who is an entomologist, specifically a butterfly and moth expert. He knows this area but has never been here in spring when there are possibilities of finding species that he cannot find in Sussex, where he lives and works.

We decided to set up a moth trap. There are very many more species of moths (papillon de nuit) in France than there are butterflies – approximately 5,000, while there are about 253 species of butterflies.

The difference between moths and butterflies depends on several criteria, and there is no straightforward definition, but there are a couple of characteristics that are broadly true, although there will be exceptions. It should be noted that the common ideas – that it is to do with the time of flying (there are many day-flying moths), that butterflies are more colourful, and that hairiness is indicative – are all misconceptions.

The first general characteristic is to be found in the shape of the antennae (organs of smell that are to be found on the heads of the insects). A butterfly has clubbed ends, while moths tend to have broader, feathered antennae. Butterflies tend to fold their wings vertically over their backs, while moths tend to hold their wings horizontally when at rest.

However, in reality there is not much difference between the two groups, though there are some precise scientific definitions, but not for the layman. They both belong to the group Lepidoptera (from the Latin for “scale wing”), a very diverse insect order, comprising some 150,000 species worldwide, of which only 18,000 are butterflies.

It is not quite clear why moths are attracted to (or disorientated by) a light source. There are various theories which make for interesting reading. Nevertheless, it is an easy method to use a light/net trap such as the one we used.

In the base of the trap, old egg boxes are placed as hiding places for the insects caught. Early in the morning, it is necessary to identify and then release them as quickly as possible. They can be gently eased into small transparent tubes and kept in a cool place if there are too many to identify at once.

The ‘star’ of our night’s trapping was an enormous moth (Europe’s largest), over 15 centimetres across. It was the final form of the Giant Peacock moth, and has only a limited lifespan of about a week, during which the only aim is to find a partner, mate and lay eggs. 

The majority of adult, i.e. winged, Lepidoptera only live for a short while, although some do hibernate – for instance, the peacock butterfly (paon du jour), which can live for up to a year. 

This Giant Peacock specimen was near the end of its life, the tattered, worn-away edge of the white border on the wings indicative. It was reluctant to fly away from the rose where we placed it, and rested there the whole day before disappearing the next night. Hopefully it went on to find a mate and complete its life aim of passing on its genes.

Moths and butterflies have a similar life cycle, generally in four successive stages, leading to a complete metamorphosis. Once the eggs are laid, often on a particular ‘host’ plant that is specific to that species, the caterpillars (chenilles) will hatch and begin to eat voraciously. 

They will in time form a chrysalis (chrysalide) and finally transform into a winged insect, the adult that is known as an ‘imago’.

Hatching takes place in spring, but is spread out over several months depending on the species. This is why you find many of the same species at the same time. This, of course, has to be synchronised with the growth of the ‘host’ plant.

Altogether, we caught 30 moths and three micro-moths, which, as the name implies, are relatively tiny, having wingspans of not more than 20mm. They come from families that evolved early, from about 200 to about 250million years ago. 

The larger moths – macro-moths – evolved more recently, from about 125million years ago, at about the same time as flowering plants evolved.

Of course, this hints at the role that moths (and butterflies) play in nature. They are powerful pollinators. 

Recent research has shown that they are more efficient pollinators at night than bees are during the day. They are also an important part of the food chain, being prey for a wide range of birds, bats and other insectivorous animals.

Mike’s time here happened to coincide with the migration of a rather wonderful butterfly, the Painted Lady (Belle dame). This butterfly completes a rather extraordinary migration every year, a little like the monarch butterfly of the Americas, but even longer.

It has taken an incredible amount of work by one expert, Constanti Stefanescu, and his team, who studied the species for over 40 years, to work out the migration strategy.

The starting point is the Atlas Mountains of Morocco. To escape the attentions of a parasitic wasp that lays its egg in the body of the caterpillar (as a food supply), eventually killing it, the species has evolved to migrate north. Stopping in Catalonia and the south of France, they mate and lay their eggs there, then die. After some time, the next generation continues to the Parisian region. The cycle is repeated and a third generation continues north: to the United Kingdom and even the Arctic Circle in northern Norway.

The knowledge of this amazing migratory baton is passed on from generation to generation. Using highly sensitive radar that can detect even an aphid at more than one kilometre in height, and as a result of citizen science in the records of amateur observers submitting their sightings, it is now known that it can take up to six generations to complete the total journey back and forth – a journey of nearly 14,500kilometres – choosing the moment of favourable winds to fly in a given direction. All that comes from a creature that weighs less than a gram and has a brain one-sixth the size of a pinhead.

To my mind, this is miraculous.