René Antoine Ferchault de Réaumur (; ; 28 February 1683 – 17 October 1757) was a French
entomologist
Entomology (from Ancient Greek ἔντομον (''éntomon''), meaning "insect", and -logy from λόγος (''lógos''), meaning "study") is the branch of zoology that focuses on insects. Those who study entomology are known as entomologists. In ...
and writer who contributed to many different fields, especially the
study of insects. He introduced the
Réaumur temperature scale.
Life
Réaumur was born in a prominent
La Rochelle
La Rochelle (, , ; Poitevin-Saintongeais: ''La Rochéle'') is a city on the west coast of France and a seaport on the Bay of Biscay, a part of the Atlantic Ocean. It is the capital of the Charente-Maritime Departments of France, department. Wi ...
family and educated in Paris. He learned philosophy in the
Jesuits' college at
Poitiers
Poitiers is a city on the river Clain in west-central France. It is a commune in France, commune, the capital of the Vienne (department), Vienne department and the historical center of Poitou, Poitou Province. In 2021, it had a population of 9 ...
, and in 1699 went to
Bourges
Bourges ( ; ; ''Borges'' in Berrichon) is a commune in central France on the river Yèvre (Cher), Yèvre. It is the capital of the Departments of France, department of Cher (department), Cher, and also was the capital city of the former provin ...
to study
civil law and
mathematics
Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...
under the charge of an uncle, canon of
La Sainte-Chapelle. In 1703 he went to
Paris
Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
, where he continued the study of
mathematics
Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...
and
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
. In 1708, at the age of 24, he was nominated by
Pierre Varignon
Pierre Varignon (; 1654 – 23 December 1722) was a French mathematician. He was educated at the Society of Jesus, Jesuit College and the University of Caen, where he received his Magister Artium, M.A. in 1682. He took Holy Orders the following ...
(who taught him mathematics) and elected a member of the
Académie des Sciences
The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefron ...
.
[Egerton, F. N. 2006]
A History of the Ecological Sciences, Part 21: Réaumur and His History of Insects
Bulletin of the Ecological Society of America 87(3):212–224. From this time onwards for nearly half a century hardly a year passed in which the did not contain at least one paper by Réaumur.
At first, his attention was occupied by mathematical studies, especially in
geometry
Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...
. In 1710, he was named the chief editor of the ''
Descriptions of the Arts and Trades'', a major government project which resulted in the establishment of manufactures new to France and the revival of neglected industries. For discoveries regarding iron and steel he was awarded a pension of 12,000
livres. Content with his ample private income, he requested that the money should go to the Académie des Sciences for the furtherance of experiments on improved industrial processes. In 1731 he became interested in
meteorology
Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agricultur ...
, and invented the
thermometer
A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...
scale which bears his name: the
Réaumur. In 1735, for family reasons, he accepted the post of commander and
intendant
An intendant (; ; ) was, and sometimes still is, a public official, especially in France, Spain, Portugal, and Latin America. The intendancy system was a centralizing administrative system developed in France. In the War of the Spanish Success ...
of the royal and military
Order of Saint Louis
The Royal and Military Order of Saint Louis () is a dynastic order of chivalry founded 5 April 1693 by King Louis XIV, named after Saint Louis (King Louis IX of France). It was intended as a reward for exceptional officers, notable as the fi ...
. He discharged his duties with scrupulous attention, but refused the pay. He took great delight in the systematic study of natural history. His friends often called him "the
Pliny of the 18th century".
He loved retirement and lived at his country residences, including his chateau La Bermondière,
Saint-Julien-du-Terroux, Maine, where he had a serious fall from a horse, which led to his death. He bequeathed his manuscripts, which filled 138 portfolios, and his natural history collections to the Académie des Sciences.

Réaumur's scientific papers deal with many branches of science. His first, in 1708, was on a general problem in geometry. His last, in 1756, on the forms of birds' nests. He proved experimentally the fact that the strength of a
rope
A rope is a group of yarns, Plying, plies, fibres, or strands that are plying, twisted or braided together into a larger and stronger form. Ropes have high tensile strength and can be used for dragging and lifting. Rope is thicker and stronger ...
is more than the sum of the strengths of its separate strands. He examined and reported on the auriferous (gold-bearing) rivers, the
turquoise
Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula . It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its hue.
The robi ...
mines, the forests and the
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
beds of France. He devised the method of
tinning
Tinning is the process of thinly coating sheets of wrought iron or steel with tin, and the resulting product is known as tinplate. The term is also widely used for the different process of coating a metal with solder before soldering.
It is ...
iron that is still employed, and investigated the differences between iron and steel, correctly showing that the amount of
carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
is greatest in
cast iron
Cast iron is a class of iron–carbon alloys with a carbon content of more than 2% and silicon content around 1–3%. Its usefulness derives from its relatively low melting temperature. The alloying elements determine the form in which its car ...
, less in steel, and least in
wrought iron
Wrought iron is an iron alloy with a very low carbon content (less than 0.05%) in contrast to that of cast iron (2.1% to 4.5%), or 0.25 for low carbon "mild" steel. Wrought iron is manufactured by heating and melting high carbon cast iron in an ...
. His book on this subject (1722) was translated into English and German.
He was noted for a
thermometer
A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...
he constructed on the principle of taking the
freezing point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...
of water as 0°, and graduating the tube into degrees each of which was one-thousandth of the volume contained by the bulb and tube up to the zero mark. It was an accident dependent on the particular alcohol employed which made the boiling-point of water 108°; mercurial thermometers graduated into 80 equal parts between the freezing- and boiling-points of water are named
Réaumur thermometers but diverge from his design and intention.
Réaumur wrote much on natural history. Early in life he described the locomotor system of the
Echinodermata
An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, ...
, and showed that the supposed ability of replacing their lost limbs was actually true. He has been considered as a founder of
ethology
Ethology is a branch of zoology that studies the behavior, behaviour of non-human animals. It has its scientific roots in the work of Charles Darwin and of American and German ornithology, ornithologists of the late 19th and early 20th cen ...
.
In 1710 he wrote a paper on the possibility of spiders being used to produce silk, which was so celebrated at the time that the
Kangxi Emperor
The Kangxi Emperor (4 May 165420 December 1722), also known by his temple name Emperor Shengzu of Qing, personal name Xuanye, was the third emperor of the Qing dynasty, and the second Qing emperor to rule over China proper. His reign of 61 ...
of China had it translated into Chinese. His observations of wasps making paper from wood fibres have led some to credit him with this change in paper-making techniques. It was over a century before wood pulp was used on any industrial scale in paper making.
He studied the relationship between the growth of insects and temperature. He also computed the rate of growth of insect populations and noted that there must be
natural checks since the theoretical population numbers achievable by
geometric progression
A geometric progression, also known as a geometric sequence, is a mathematical sequence of non-zero numbers where each term after the first is found by multiplying the previous one by a fixed number called the ''common ratio''. For example, the s ...
were not matched by observations of actual populations.
[
He also studied botanical and agricultural matters, and devised processes for preserving birds and eggs. He elaborated a system of artificial incubation, and made important observations on the digestion of carnivorous and graminivorous (grass-eating) birds. One of his greatest works is the , 6 vols., with 267 plates (Amsterdam, 1734–1742). It describes the appearance, habits and locality of all the known insects except the beetles, and is a marvel of patient and accurate observation. Among other important facts stated in this work are the experiments which enabled Réaumur to prove the correctness of Peyssonel's hypothesis, that ]coral
Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...
s are animals and not plants.
He was elected a Fellow of the Royal Society
Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the Fellows of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural science, natural knowledge, incl ...
in November 1738 by virtue of the fact that:His Name hath been known for many years among the Learned by Several Curious disertations published in the Memoirs of the Royal Academy of Sciences at Paris & in particular by a very Learned and usefull book wrote in French entitled 'The Art of Converting Forged Iron into Steel' and 'the Art of Soft'ning Cast Iron' printed at Paris 1722 4to and lately by his 'Curious Memoires relating to the History of Insects' at Paris in 4to three Volumes of which work have been Laid before the Royal Society.
He was elected a foreign member of the Royal Swedish Academy of Sciences
The Royal Swedish Academy of Sciences () is one of the Swedish Royal Academies, royal academies of Sweden. Founded on 2 June 1739, it is an independent, non-governmental scientific organization that takes special responsibility for promoting nat ...
in 1748.
He is commemorated in numerous place names including the rue Réaumur and the Réaumur - Sébastopol metro station in Paris and the Place Réaumur, Le Havre.
Selected works
* Réaumur, R.-A. F. de. 1722. L'art de convertir le fer forgé en acier, et l'art d'adoucir le fer fondu, ou de faire des ouvrages de fer fondu aussi finis que le fer forgé. Paris, France.
* Réaumur, R.-A. F. de. 1734–1742. Mémoires pour servir à l'histoire des insectes. Six volumes. Académie Royale des Sciences, Paris, France.
* Réaumur, R.-A. F. de. 1749. Art de faire éclorre et d'élever en tout saison des oiseaux Domestiques de toutes espèces. Two volumes. Imprimerie royale, Paris, France.
* Réaumur, R.-A. F. de. 1750. The art of hatching and bringing up domestic fowls. London, UK.
* Réaumur, R.-A. F. de. 1800. Short history of bees I. The natural history of bees . . . Printed for Vernor and Hood in the Poultry, by J. Cundee, London, UK.
* Réaumur, R.-A. F. de. 1926. The natural history of ants, from an unpublished manuscript. W. M. Wheeler, editor and translator. ncludes French text.Knopf, New York City, USA. Reprinted 1977. Arno Press, New York City, USA.
* Réaumur, R.-A. F. de. 1939. Morceaux choisis. Jean Torlais, editor. Gallimard, Paris, France.
* Réaumur, R.-A. F. de. 1955. Histoire des scarabées. M. Caullery, introduction. Volume 11 of Encyclopédie Entomologique. Paul Lechevalier, Paris, France.
* Réaumur, R.-A. F. de. 1956. Memoirs on steel and iron. A. G. Sisco, translator. C. S. Smith, introduction and notes. University of Chicago Press, Chicago, Illinois, USA.
Publications
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Notes
References
*
External links
*
Digitalies text of ''Mémoires pour servir a l'histoire des insectes''
Website of the Manoir Des Sciences at Reaumur
Gaedike, R.; Groll, E. K. & Taeger, A. 2012: Bibliography of the entomological literature from the beginning until 1863 : online database – version 1.0 – Senckenberg Deutsches Entomologisches Institut.
{{DEFAULTSORT:Reaumur, Rene Antoine Ferchault De
1683 births
1757 deaths
18th-century French writers
18th-century French male writers
Fellows of the Royal Society
French entomologists
Creators of temperature scales
French Roman Catholics
Members of the French Academy of Sciences
Members of the Royal Swedish Academy of Sciences
Order of Saint Louis recipients
People from La Rochelle