Charles Bonnet and his Danae: the discovery of parthenogenesis
Charles Bonnet was born in
Réaumur is one of the most amazing people in the history of science, with interests ranging over the whole of science and technology, from bees to the building of bridges (Ratcliffe 2005). He greatly influenced the way in which science developed in the 18th century, by advocating and practising experimentation to dissociate the “true marvels” of the natural world from the myths and prejudices with which they had become so closely entangled in medieval times. He was also a great communicator. The young Bonnet found the wide-ranging ideas of Réaumur about insects especially exciting. A major part of the third volume of Réaumur’s Mémoires pour servir a l’Histoire des Insects, published in 1737, was devoted to the natural history of aphids and their natural enemies. In this volume, Réaumur suggested an experiment to rear aphids in isolation in order to prove whether, as had long been suspected, they could give birth without mating. Réaumur had tried to do this experiment himself several times, but without success.
So, in May 1740, Bonnet decided that he
would make his own attempt, using an aphid of the black bean aphid (Aphis fabae) group collected from a
spindle tree. He placed a twig of spindle bearing a few leaves in water in a
glass vial, and buried the vial up to its neck in soil in a flower-pot. On one
of the leaves he then placed a single aphid that he had observed being born,
and inverted a glass vase over the twig so that its rim was in close contact
with the surface of the soil. Then his vigil began, keeping daily watch on his
“little prisoner” from 4 or
in the morning until 9 or
at night, and maintaining a precise account of everything that happened. Using
a hand-lens he observed its moults with some trepidation, fearing at each one
that it would fall from the plant and be lost.
Eventually the day arrived when his charge attained adulthood, and his
patience was soon rewarded. The young aphid born at on
Fig. 1 Bonnet’s table recording the births of the 95 offspring (pucerons = aphids) of the virgin mother aphid in his 1740 experiment. The asterisks signify births that he did not actually observe.
Today, even to a non-scientist, this may
seem a simple, almost naïve experiment. In the context of his time, however,
its design and careful execution were exceptional, and won him the immediate
honour of admission as the youngest corresponding member of the
However, he was still worried that some prior impregnation might have occurred, and its effects passed down in some way through the generations. The trouble was that Bonnet, living more than 150 years before the science of genetics, had no real conception of how the essential characters of a species were passed from one generation to the next, nor of the real significance of sexual reproduction. His interpretation of his experiments was rooted in the idea of preformation; that is, that every female contained the preformed “germs” of all her descendants, and that these would develop if they were stimulated to do so as a result of insemination by a male, and then provided by the female with adequate nutrition. He knew he had demonstrated that aphid “germs” could develop without any stimulation by the semen of a male, or at least that mating did not have to occur in every generation, but he was unaware that the resultant offspring differed in any significant way from those resulting from sexual reproduction.
Bonnet knew that some aphid species had
sex, and in fact he described and studied the behaviour of males and egg-laying
females of the sexual generation of a large aphid* (“l’éléphant des pucerons” - probably Lachnus roboris) on the branches of oak. He then moved on to other lines of
investigation in zoology and botany and made other important discoveries, for
example he was the first to show that insects breathed through the series of
lateral pores that we now call spiracles. Later in life his eyesight
deteriorated and he was forced to cease his studies of living organisms.
Instead he turned his attention to philosophical matters. His ideas on evolution – he was one of the
first biologists to use this word – were very influential at the time, but were
of course very different to those of
Fig. 2 Charles Bonnet in the 1770s.
To explain the fossil findings of extinct species, Bonnet suggested that the earth is periodically struck by global disasters in which most organisms died, but then the survivors climbed to a new level in the scale of nature (“Bonnet’s ladder”). Thus, minerals became plants, plants became insects, and higher up the ladder fish became birds, and birds became quadrupeds. Man was of course at the top of his evolutionary ladder, and would develop into angels after the next global disaster. To our eyes today, Bonnet’s scheme of things (assuming that he was not entirely right!) comprises a remarkable mixture of truth and misconception.
In the next article I shall describe what we now know about the way in which aphids develop from unfertilised eggs. It will become evident that, 250 years later, we still have no complete answer to the mysteries of aphid parthenogenesis.
C. (1745) Traite d’insectologie ou
Observations sur les Pucerones. Durand,
Ratcliff, M.J. (2005) Experimentation, communication and patronage: a perspective on René-Antoine Ferchault de Réaumur (1683-1757). Biology of the Cell 97: 231-233.