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Department of Zoology


George Salt: entomologist and ecologist

It is the convention for Biographical Memoirs of the Royal Society that the signature of the subject appears under their portrait photograph at the start of the account. Underneath Walter Bird’s 1956 photograph of George Salt, George’s signature is clear and without any affectations, very like the work and character of its owner. It is not, perhaps, too surprising that although George Salt’s years of birth and death were 1903 and 2003, he died before his birthday in 2003 thus avoiding the fuss of a hundredth.

Visitors to the Conversazione of the Cambridge Natural History Society, held in the Elementary Laboratory, may well have seen some of George Salt’s calligraphy or his watercolour paintings. After his retirement from the Department, he was able to give more time to his work with scripts, both as a practitioner and a historian. This was a long-standing interest and his work was sufficiently distinguished that there are examples of it in King’s College Library, the Royal Library at Windsor, the Fitzwilliam Museum, and the British Library. The Fitzwilliam Museum also has the tools of his calligraphic trade, drawn from different cultures and characteristically researched in great detail. George’s work in calligraphy, his watercolour painting, and his scientific work involving the manipulation of small insects all shared the need for manipulative precision at which he excelled. That attention to detail extended to his appearance; he was one of the last generation habitually to wear a suit and tie to the Department (Rex Parrington, Director of the Museum was another), and he put on a well-pressed lab coat for work at the bench in his room in the Main Building.

George Salt’s Royal Society Biographical Memoir was written by Sir Patrick Bateson who was doubtless able to call on George’s own account of his life in a large manuscript that George deposited in the Royal Society archives in 1966:  ‘An Account of my Doings 1924-1966’ (archive number MS/816). Pat Bateson’s Biographical Memoir is a major source of information about George Salt’s life, and it is particularly valuable for aspects of his life before he arrived in Cambridge. Another valuable source is the article written by Roderick Fisher (R.C. Fisher (1986). George Salt and the development of experimental insect parasitology. J. Insect Physiol. 32: 249-253). Fisher himself was a research student with George. He went on to King’s College, London, and then to University College, London, where he continued to work in related areas. His article was written for the XVII International Congress of Entomology, Hamburg, 1984, and helpfully lists all of George Salt’s relevant papers between 1926 and 1980, and puts them in context.

Pat Bateson knew George Salt well, both through the Department of Zoology, where they were colleagues, and also through their King’s College Fellowships. Bateson himself came up to King’s in 1957 (he had supervisions with George), went on to become a Fellow in 1964, and eventually Provost from 1988 to 2003. George had been a Fellow since 1933, remarkably soon after joining James Gray in the Department in 1931 as a Royal Society Moseley Research Student. George was appointed to a University Lectureship in 1937, and to a Readership (in Animal Ecology) in 1965. He retired in 1971.

It is clear from accounts of those who knew him well that George’s reputation for austerity was at least partly a matter of a quiet, reserved and unassuming nature. However, he was physically robust with a good deal of experience of demanding field conditions, and he was capable of calling on skills rather unexpected to those who encountered him in Cambridge. Pat Bateson’s Memoir of George recalls that,

‘He had worked for a year in the wild up-country of Colombia. He always went about armed, was often shot at, and once, in broken Spanish, had to persuade a bandit not to kill him. Who would have guessed when, later in life walking through the mountains of Austria, he would take down the guitar, usually to be found on the wall of each mountain hut, and sing folk songs in bad German to pay for his night’s keep?’

The young George Salt spent many of his growing years, and got his education, in Canada, but he was born in Britain, in Loughborough. His family moved to Calgary when he was seven years old, and he grew up very much as an outdoors boy, used to a tough climate and limited family resources. Those who knew George might well have been surprised to learn that his family, friends and colleagues knew him as ‘Jim’. He reverted to his real first name only when he married in 1939, and he remained George from then on.

He certainly could, however, be rather intimidating on first meeting, especially in his later years. It is also clear that his reputation in King’s was as someone reactionary and occasionally explicitly disapproving. The less charitable might suggest that such a reputation was perhaps not too difficult to acquire at King’s in certain periods. However, George clearly came to terms with Bloomsbury, for example, because he could sometimes be seen helping the aged novelist E.M. Forster (a resident Fellow) into his taxi outside King’s. In fact, like many who have a reputation for social conservatism, George Salt was conspicuously kind and considerate to individuals. Many attested to his careful support of undergraduates in his role as a Tutor, and he seems to have been completely without prejudice in any direction. Pat Bateson does record that George voted against the admission of women to King’s, but it seems extraordinarily unlikely that he was ever other than helpful and kind to individual women, either in science or outside it. His apparent air of austerity was perhaps fostered partly by his rare ability to listen patiently to you until you had finished making your point (even if you didn’t have a point to make, in which case he would eventually tell you) and by the fact that, later in life, he suffered from deafness in one ear, and was reluctant to let you know if you were speaking on the wrong side of him.

George Salt’s forty years in Cambridge produced a great deal of his most distinguished work, but his research career began in 1924 at Harvard with the American entomologist William Morton Wheeler (a scientific influence, incidentally, on that later Harvard resident E.O. Wilson). It seems to have been Wheeler who introduced the young George, recently graduated from the University of Alberta, to insect parasites, notably the parasitism of Andrena bees by stylopids. Crucially, for George’s later studies, the parasites affect not only the morphology of the hosts, but also their behaviour and physiology.

In 1925 George made a research trip to Cuba, on a Harvard studentship, where he studied sugar-cane borers. This work was the subject of his first published scientific paper in 1926. His second paper (on ant mimicry), that same year, contained a plate painted by George himself. His skill as an artist was a help in his work throughout his scientific career, and became an important part of his personality, particularly in later life. Two years after this experience he was appointed by the United Fruit Company to study pests of bananas in Columbia.

In 1927, W.R. Thompson, by then appointed as Director of the Farnham House Laboratory under the auspices of the Imperial Institute of Entomology, had recruited George Salt to its staff (he arrived in 1928). Roderick Fisher quotes from a 1934 paper, in which George Salt writes that, ‘Consideration, no matter how inspired, of such data can only result in conjecture. The solution of a problem so essentially dynamic must be supported by experimental evidence.’ The problem in question was the regulation of hosts by their parasites, and it had, of course, both pure and applied importance. In 1927 host-parasite relations had been the subject of attention from mathematical ecologists, including Vito Volterra and W.R. Thompson, himself. Although the research that George undertook at Farnham House was largely successful, his eventual reservations about the limitations of the approach taken there appear to have precipitated his move to Cambridge.

George’s early work in the Department of Zoology was dominated by studies on the tiny hymenopteran Trichogramma evanescens. He was able to demonstrate that female T. evanescens can tell which of the host eggs in which they attempt to lay their own eggs have already been visited by other evanescens individuals.

At the outbreak of the Second World War, however, George and others in the Department, including Frank (F.S.J.) Hollick, were diverted to a project to examine the possibilities of controlling the wire worms that reduced the all-important cereal crops. The studies led to the development of the legendary Salt-Hollick soil washing machine (described by Salt and Hollick in a 1944 paper in Annals of Applied Biology). The emphasis was on a thorough ecological study of the enemy, and the sampling techniques developed have subsequently been used by others in a variety of contexts, including the survey of mosquito larvae.

Several years after the War, George engineered a sabbatical year (1948-49) in East Africa. He deployed the Salt-Hollick machine to advantage to study soil ecology and collected extensively at high altitude. His high altitude work was possible because he was already proficient in Alpine mountaineering and, indeed, had given a lecture to the Alpine Club in 1946. The online archive of King’s College has a display of George’s watercolours used to illustrate his talk (although he did not finally finish these until 1974). The web site also has an image of the letter of thanks written to George after his talk, and a very fine portrait photograph of George, taken by A.C. Barrington-Brown (perhaps best known for his photographs of Crick and Watson in the old Cavendish Austin Building with their model of the DNA molecule).  The most useful route to the complete holdings for George Salt in the King’s College Archive Centre is through the entry page in The National Archives

Beginning in 1953 George began work with the ichneumonid parasitoid Nemeritis. The caterpillars of the pyralid flour moth Ephestia can be parasitized by Nemeritis, but the eggs of the parasitoid are only encapsulated by the host in rather specific conditions. George’s work on insect defences against their parasites gained recognition through a large paper in the journal Parasitology in 1960. This was one of his most important publications in terms of its influence on the developing field; indeed, it could justifiably be said that it created the field. George’s student, Roderick Fisher, continued to work with what was by then the well-known Nemeritis/Ephestia system that George had pioneered after his return from a sabbatical year in 1958-59, a year that included six months in Pakistan investigating crop pests. Fisher’s plaintive comments in a 1970 paper in Nature (in which the first reference is to a 1937 paper by his old supervisor) will doubtless resonate with anyone who has struggled to keep up with the changing name of their chosen experimental animal,

‘This communication reports for the first time that qualitative changes in the amino-acid composition and protein components occur in the haemolymph of the Phycitine moth Anagasta (Ephestia) kuehniella Hb. after parasitization by the Ichneumonid parasitoid Devorgilla (Nemeritis) canescens Grav. The generic name of this Insect, well known to experimental zoologists over many years as Nemeritis, has been changed successively in the last decade to Idechthis, Exidechthis, Devorgilla and Venturia. The name Devorgilla is adopted here.’

Another landmark in George Salt’s publications was his book The Cellular Defence Reactions of Insects (Cambridge University Press, 1970). Because the book was in a series intended for biologists more generally, it introduced George’s work to many who otherwise knew nothing of the field. George retired in 1971, but there were more research publications after that date up until 1980. For nearly four decades George had published a series of papers under the running title ‘Experimental studies in insect parasitism’. The emphasis is, of course, squarely on the ‘experimental’. His final paper in the series, number XVI, on Nemeritis, was published in 1973. In the following year he co-authored a paper on ichneumonid egg development with Brad (W.B.) Amos, who was then in the Department of Zoology. Nearly all of George’s papers were single-author works, but this was not his only collaborative publication (apart from the wartime wire worm work) with other members of the Department. In 1967, for example, he had published a paper with Bill (A.V.) Grimstone and Susan (S.J.) Rotheram (his research student at the time) on the encapsulation of parasite eggs by host insects, using electron microscopy. In 1935 George had published with his first research student, Joyce Laing: he married Joyce in 1939.

The young Joyce Laing (born in 1910) won a prize that enabled her to travel, after her schooling, to Canada, when, coincidentally, she visited Alberta. George had, of course, by that time moved on from Canada, but at least the young Joyce will have had some impression of her future husband’s place of upbringing. Joyce retained her interest in zoology, and they were a formidable partnership. Two sons were born (1943 and 1947).

George’s election to the Royal Society came in 1956. (Pat Bateson’s Biographical Memoir has a typographical error, and gives the date as 1965). George’s certificate of election shows that he was proposed by James Gray, seconded by Vincent (V.B.) Wigglesworth, and supported by Carl (C.F.A.) Pantin and Bill (W.H.) Thorpe in Zoology, David Keilin in Parasitology, and, notably, the Canadian entomologist and mathematical ecologist W.R. Thompson (George’s first employer in Britain), among others. None of their signatures is anywhere nearly as readable as that of George. The citation (archive number EC/1956/19) reads,

Distinguished for his studies on parasitic insects. He has provided the most detailed analysis of parasitic sex reversal in insects and of the morphological changes induced in parasites by the nature of their hosts. He has studied with great accuracy factors which determine host selection by parasitic insects and made original and important contributions to the ecology of insects living in the soil. In all these fields the author has developed new lines of approach and made outstanding contributions to academic and applied biology.

A list of publications is attached.

The citation stands as a tribute to George Salt’s work; but, of course, it was written in 1956 and George had another twenty-four years of meticulous, focused publications to go.

Adrian Friday

Photo of George Salt by Antony Barrington Brown, courtesy of Archive Centre, King’s College, Cambridge. Reference: KCAC/1/2/6/1/Salt3