The beetles have as much aesthetic appeal to me as the paintings in a museum - except this is a museum I design and curate to my personal liking

It was a stag beetle that got me started. By European standards, they are pretty large and pretty scary: black and brown beasts a?good two inches long, with (if they are males) two huge mandibles up to a third of their body size to make sure you keep your fingers away. Magnificent!

It was the end of the summer of 1987 and I?had just turned 15. My family was returning from a?few days in the French Alps and had stopped at the house of a friend of my parents for dinner. She had found a pristine dead stag beetle in her garden the week before and, having noticed my interest in wildlife, had saved it for me. I was in awe.

I spent the next several days trying to gather information, identify the animal and look for ways to preserve its dry, brittle form. There was no World Wide Web then, of course, but I?found a?nice little beginner¡¯s guide to entomology at a local bookshop, which answered many of my plethora of questions. I learned how to rehydrate a dry insect, soften it, mount it nicely to museum standards and label it. I?also?learned how to find many more insects and slowly started my own collection ¨C which soon became specifically a beetle collection.

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Collecting is often a pathology. I?had collected all sorts of things before: stamps, stickers, matchboxes and fossils. But beetles became a deeper obsession. There were thousands of different ones all around me, and collecting them satisfied the bond I instinctively felt with nature, my love of organisation and my fascination with shapes and colours. So?I?carried on. I learned the basics of systematics: the science of naming living things based on dividing them into orders, families, genera and species. Long-horned beetles soon became my favourites, and I could name most of the nearly 300 species occurring naturally in France.

I joined several entomological societies, met other insect enthusiasts and developed some very close friendships that are still thriving today. And here I am, 25 years later, with 20,000 beetles that I have either collected myself or obtained from colleagues, including a handful of very rare specimens, nicely organised and labelled in dedicated drawers in my office. And?I am still collecting with unflagging enthusiasm, whether it be specimens from my backyard or the more exotic fauna I?gather on trips abroad.

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So what? Is this just my inability to break out of childish, nerdy collecting habits?

It was only after more than a decade spent collecting beetles that I realised the practice served many different purposes for me. It is, for instance, a?kind of diary. Each insect generally carries two labels: one with its scientific name in Latin, and another that indicates where it was collected, when, by whom and often under what conditions.

As an example, let me pick the minuscule dot, glued on a little piece of cardboard labelled ¡°Bryaxis gallicus; Italy, Cuneo, Limone-Piemonte, Boero, 6?July 2011, N.?Gompel¡±. For me, this dot represents so much more than this cold information. It stands for that summer day when my friend Jean-Philippe Tamisier and I walked up a mass of?fallen rocks in the Alps and reached a mountain ridge towards the end of a beautiful afternoon. We sat there silently contemplating the peaceful landscape for a while; within an hour, we saw an ibex, a mink and a pack of a?dozen chamois. Then we started to sieve the soil at the base of an alpine plant known as Saxifraga and found a dozen very remarkable beetle species, including this tiny speck. It summons up all the images and feelings I?experienced that day, much in the way a?postcard would.

My collection is also a repository of the beauty of nature. The beetles¡¯ forms, colours, patterns and textures have as much aesthetic appeal to me as the paintings in a museum do at first sight ¨C except that this is a museum that I visit almost daily and design and curate to my personal liking.

But first and foremost, my collection has over the years been a major source of scientific inspiration.

My frenzy of mere collecting changed during the late 1990s. I was studying biology at university, majoring in genetics and developmental biology. Developmental biology is the modern name of embryology. Its primary goal is to understand how one cell, the egg, becomes two cells, then several, and ultimately the very sophisticated bunch of specialised cells and structures that constitute the developed animal or plant. The feathers of peacocks, the coloured scale arrays of clownfish, the decorated wings of butterflies, the regularly arranged bristles on flies¡¯ backs: all of these are produced during embryonic development. The instructions to build them are stored in the DNA of each species. Take different species and the instructions will be different: there lies the origin of variation in shape and colour. That statement may sound obvious, but it resonated in my insect collector¡¯s mind as I was becoming a?fully fledged developmental biologist.

I had never even toyed with the idea of?gearing my professional life towards entomology. As much as I liked insects and all insect-related social activities, the professional perspectives felt a bit too dusty for my taste back then. Pinning insects was a 19th-century business, lacking the sci-fi glow of DNA science. Whenever I was asked, I made it clear that entomology would remain a hobby for me?and had nothing to do with my interest in genetics. But DNA¡¯s role in producing the diversity of forms and colours exhibited in my collection was something of a revelation to me. I had never really thought before about how the various species developed or evolved.

Apart from their aesthetic qualities, my chief interest in form and colour had previously derived from the critical information they conveyed for naming species.

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For instance, the long-horned beetles Anastrangalia sanguinolenta and Anastrangalia dubia are identical at first sight. But under a stereoscope you can tell them apart because their heads are shaped slightly differently. This difference is constant and provides a reliable criterion of identification. My biology degree taught me that this is probably because some of their genes are different. And what is true for the heads of these two beetles holds true across the tree of life.

Take cats. You can tell a feline is a feline at?a glance. The various species differ mostly according to subtle features such as their size or ornaments such as hair and colour patterns. Some, like the tiger, are striped; some, like the cheetah, have dots; and yet others, like the panther, are uniformly coloured.

Strongly influenced by countless discussions on the subject with my PhD supervisor, Alain?Ghysen (currently INSERM director of research at the University of Montpellier?2), I?started to look at wildlife with a new eye. Beetles provided unique raw material with which to do so.

I discovered that other scientists were actively revisiting 19th-century-style natural history from the angle of modern developmental biology. They wanted to understand how animal life in particular had diversified (through which genetic means, that is). This field was championed by scientists such as Michael Akam, currently head of the department of zoology at the University of?Cambridge, and Sean Carroll, Howard Hughes Medical Institute investigator and Allan Wilson professor of molecular biology, genetics and medical genetics at the University of Wisconsin-Madison. Very soon, as I was revisiting my insect collection in a thought experiment, I decided that I wanted to join the endeavour.

In 2002, I was fortunate enough to join the Carroll lab in the midst of the harsh Wisconsin winter. His research group had a strong interest in exploring how shapes and colours are formed ¨C and, most importantly, how they change between species. Despite their diversity of shape, I was disappointed to discover that beetles were not immediately amenable to genetic research because, unlike animals known as ¡°model systems¡±, such analysis would not have a century of previous genetic work to draw on.

The star of insect genetics is not a beetle but a fly: Drosophila melanogaster, generally known as the vinegar fly or common fruit fly. I knew nothing about the systematics of flies, but I had a net and a backyard, and I started to catch flies and bring them to?the lab. I had enough experience with systematics in general to determine that the fly?specimens I collected fell into different camps, including many distinct Drosophila species.

The most striking element of diversity was?their pigmentation. The Carroll lab had started to decipher the genetics of pigmentation in Drosophila; melanogaster is Latin for ¡°dark bellied¡± and is a reference to the darkly coloured tips of male vinegar flies¡¯ abdomens. Some of the flies I collected had dark abdomens, but others had patterns, such as stripes and dots: similar subtle variations to?those I?dealt with as a beetle enthusiast. However, with fruit flies I had some hope of uncovering the genetic causes of the variation. So began my long-standing collaboration with fellow French scientist Benjamin Prud¡¯homme, my lab mate at the time.

The flies have not disappointed us. We were?lucky to start identifying how the genes involved in painting them with different patterns have changed between species. Discovering why a?fly has a dark butt or black spots on its wings sounds like a mundane question ¨C the kind of question that can capture the fascination of a few scientists for a?lifetime while boring everyone else. But it is?not about pigmentation: it is about the diversity of life. That is a much bigger question, of course, and it seems almost arrogant to hope to address it, but as is so?often the case in biology, solving big questions starts with modest answers.

Four decades of research in molecular biology has taught us that the expression of DNA is governed by similar rules across all species, so what we learn from flies can be extrapolated conceptually to other animal groups. Accordingly, as our work on fly pigmentation unfolded, other scientists tackling the same question of variation using other model systems achieved similar results. From maggots to sticklebacks, beach mice, even plant leaves, the emerging picture explaining the genetics of variation in patterns and shapes is consistent and growing.

So that first stag beetle my parents¡¯ friend gave me can be seen, retrospectively, as the starting point of my journey towards understanding the nature of diversity in living things. And my beetle collection remains a?wonderful playground for scientific inspiration.

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A big scientific question is rarely solved in?one shot: a more typical path is to break it down into smaller, more approachable ones. These smaller questions are then refined, polished, rephrased over time, like a hunter who points his gun at his target and refines the shooting angle again and again before actually pulling the trigger. People who meet me for the first time are usually startled when, in the midst of a conversation, I spring out of my chair, catch some minute six-legged UFO, dig out a?small tube from my pocket and shove the small insect into it while expressing my amazement aloud. But this has been my way of polishing these questions all my adult life.