Santschi

Behav Ecol Sociobiol (1990) 27:295-306 Behavioral Ecology and Sociobiology © Springer-Vcrlag 1990

On the brink of introducing sensory ecology: Felix Santschi (1872-1940)- Tabib-en-Neml 1 Riidiger Wehner

Department of Zoology, University of Ziirich, CH-8057 Zfirich, Switzerland

is especially in the latter work, dealing with what we would now call the proximate and ultimate causes of insect behaviour, that Santschi stands out from his fellow-scientists with respect to both the fresh conceptual approach he took to old problems and the analytical methods by which he tackled them; but due to his geographical and academic isolation his scientific legacy was lost almost completely. In the present account, published on the occasion of the 50th anniversary of his death, I try to bring Santschi's work back to light and to convey some of the sparkling originality and unceasing scientific enthusiasm of his personality.

Fig. 1. Felix Santschi, in about 1925. Drawing based on a photo- graph provided by M. Abderrhaman Mader Ben Abdallah, Kai- rouan

Preface. It is not always the latest craze that marks progress in science, and it is not only the work published in the most recent years that is worth considering. Even a cursory glance at the history of science reveals the obvious: New conceptual approaches arise here and there, but only a few flourish. Many are not pursued because they are pre-paradigmatic and hence not appre- ciated by contemporary scientists, or because the experimental techniques are not yet available to answer the questions raised, or simply because the proponent of a new approach happens to live outside the conventional scientific community and publishes his experiments and conclusions in inaccessible places. A case in point - in all three respects - is the work of Felix Santschi.

Swiss by birth and raised in the French speaking part of the country, Santschi spent most of his life in North Africa, where he practised as a successful physician. His main activities and scientific interests, however, were taxonomical and behavioural studies of ants. It

Introduction

On April 15, 1914, three artists - Paul Klee, August Macke und Louis Moilliet 2 _ travelled from Tunis south to Kalaa Srira, a small village in the North African sahel. There they changed trains and took the now abandoned dead-end line to Kairouan 3, the Mecca of the Maghreb, the "Light of Islam". In the middle of a vast, flat and dusty plain, encircled by its ramparts, the old capital of the Aghlabites, from afar, must have looked to the European artists like a city from the past. Founded in the early days of the Arabs' conquest of North Africa, the first Islamic city in the Maghreb had soon changed from an armed camp into a centre of Arab civilization provided with a magnificent mosque and several other sanctuaries, or zaouias. It was the geometric design and architectonic simplicity of these medieval buildings - the mosaic arrangement of cubes and domes and the delicate shades of colour - by which Klee was so impressed that he became frantically engaged in painting a number of water-colours which should later become milestones in the development of Cubist art. While enjoying a memor- able day of enormous productivity inspired by the pic- turesque Islamic scenery of the old medina 4 Paul Klee did not seem to be aware of the fact that another Euro-

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to have allowed him to be far ahead of his time. Every- one who at present surveys the large body of his published work on insect behaviour, will immediately be impressed by the elegance of Santschi's prose and, even more so, by the originality and uniqueness of his conceptual and experimental approaches. Groundbreaking research is often regarded as being a matter of picking the right problem at the right time. Santschi certainly picked it at the wrong time - and hence did not break ground. Seen in the light of the Kuhnian perspective 6, his work having remained unrecognized by his contem- poraries was certainly pre-paradigmatic. In fact, Sant- schi did not recruit a single follower. When he died fifty years ago, in 1940, the three short obituaries published in small entomological journals (Kutter 1940; Do- nisthorpe 1941 ; Sachtleben 1941) v did not even mention, let alone appreciate, his painstaking experimental work in behavioural biology and sensory physiology. It is the aim of this article to draw attention to this work and to the unsung hero who performed it under the most unusual circumstances.

Fig. 2. Paul Klee, 1914, 45 "Rote und weisse Kuppeln" (Red and White Cupolas, Kairouan). Water-colour painted on Japanese vel- lum and mounted on cardboard, 14.6 x 13.7 cm, signed at the upper left. Kunstsammlung NRW, Diisseldorf. Copyright ©1990 COS- MOPRESS, Geneva, and PRO LITTERIS, Zurich

pean admirer of Kairouan, the Swiss physician Dr. Felix Santschi (Fig. 1), had permanently established himself less than a mile away from where he had just painted the "Red and White Cupolas" (Fig. 2).

In 1901, at the age of twenty-nine, Santschi moved from his home-town Lausanne to North Africa. First he took up residence in Tunis, but as the metropolitan life of the capital accentuated by the modern savoir-vivre of the French administration did not appeal to him, he finally settled down, the very next year, in the remote inland city of Kairouan (Fig. 3). Here he lived and worked for the rest of his life as both a highly esteemed physician and an extremely creative, but now almost forgotten biologist 5. In the world of modern science he is praised merely for having discovered that animals are able to use the sun as a compass, and - less enthusiasti- cally - for having described and named an uncanny quantity of almost 2000 species, subspecies, varieties, and sub-varieties of ants. However, as all his more than 200 papers were published in French in rather inaccessible places like the "Bulletin de la Socikt~ d'Histoire Na- turelle de l'Afrique du Nord" or the "M&noires de la Soei~td Vaudoise des Sciences Naturelles ", most of his scientific legacy remained unread.

Practising as a physician in North Africa and hence cut off from most of the scientific world of his days, Santschi was a scientific loner. In taxonomy, his geographic and academic isolation prevented him from catching up with the first wave of new systematics then riding high in the Anglo-Saxon world, but in the field of behavioural biology this very same isolation seemed

Life of an eccentric: practising as a doctor in Kairouan

When he had finished the painting reproduced in Fig. 2 Paul Klee could have easily visited Santschi at the doctor's house near the Bab Djeladine or Gate of the Tan- ners 8 now known as the Bab Ech-Chouhada, the Gate of the Martyrs. After having left the zauoia of Sidi Amor Abbada, where the five elegantly ribbed domes had inspired him to paint the "Red and White Cupolas", he might have turned into the Boulevard Idris Premier and then followed the narrow Rue Hornet el Bey (Fig. 4). Even nowadays both streets, like many others (Fig. 5), are lined with houses of sun-dried brick or rough white- wash decorated with woodwork and wrought-iron painted in a soft green or blue, with fine trellises protect- ing wooden loggias, or - in Andalusian fashion - with clay dishes in which climbing plants grow. He would then have reached the Rue Ali Bel Houane, the main street of the old town, where bakers, butchers and grocers sell their products and where the Caf6 Hal- faouine is now, as it was then, a major meeting point of the citizens of Kairouan. Having passed the zaouia of Sidi Abid el Ghariani with its decoration of tiles and ornately worked wood and stucco, his attention would have suddenly been drawn to a white marble slab an- nouncing in black Arabic letters that the house in front of him 9 was the home of "Dr. Felix Santschi, provided with the Diploma of the Medical Sciences, treating all diseases, performing eye surgery, removing tubercles, helping women in labour, curing sick arms, legs and feet". From the entrance located within a narrow doorway (Fig. 6) a steep staircase led to the rooms in which Santschi practised and lived with his family. The consult- ing-room into which the stairway opened was mostly crowded with a mixed group of workmen, merchants and bedouines suffering from all possible kinds of infec- tions and injuries. Behind a curtain that separated a tiny compartment from the remainder of the room,

Santschi treated them all. Combining the skills of a wide range of medical professions he was a general practition- er, a specialist in internal diseases, a pediatrician, a den- fist, and an eye surgeon - all rolled into one ~0. A single example might suffice to demonstrate his manual abili- ties and expertise. He would use a copper-knife to couch the cataract by penetrating the cornea of the eye, cutting loose the lens and pushing it back into the vitreous body

by this applying a method already used in medieval times ~ a. It was his medical skill and versatility, his indus- triousness and kind human disposition by which he se- cured recognition among the citizens of Kairouan. Even nowadays one can meet one or the other old inhabitant of the city who praises the "medecin et chercheur " w h o m he had met or consulted when he was young.

The recognition of a European by the or thodox Islamic community of Kairouan (see Figs. 7 and 8) did not go without saying. In Santschi's days, every evening after the last call of the muezzin the gates of the ramparts were closed, and with the exception of Santschi no non- believer was allowed to stay overnight within the con- fines of the holy city.

Why had Santschi retreated to such a remote place in North Africa? The main answer to this question lies in his educational background. As the son of a paper- hanger, he had never entered the normal Swiss High School system officially leading to University and Medi- cal School, but started as a craftsman. His intelligence and scientific capabilities were discovered only after he had applied for and obtained a position as a preparator in the Acad6mie Lausanne. Here, Edouard Bugnion,

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Professor of Anatomy at the University of Lausanne, immediately recognized the extraordinary performance of the young technician and encouraged him to study medicine. However, after Santschi had finished his studies he was not permitted to practise as a medical doctor in his native country, because due to his unusual career he had never obtained the necessary Swiss High School Diploma. As a consequence, he readily accepted an invi- tation of the French government to start working in Tunisia, a country then under the patronage of the French administration.

Santschi tremendously enjoyed living in Kairouan ~ 2. He was like the prince in the Arabian tale, who had shot his arrow farther than he knew and then went out to find it. Here in Kairouan he was his own free man - able to practise his broad medical skill unrestrained by the regulations of a Medical Council, and able to freely divide his time between his professional duties and his scientific interests in insect taxonomy and behaviour. Usually he would treat his patients only in the morning and evening hours and spend the remainder of the day collecting and observing ants outside the ramparts of the town. Then his assistant, Bou Hadiba, had to take care of the less severe cases, give injections, distribute medicine, and collect honoraria. Santschi never wrote a bill, but let Bou Hadiba decide how much money any particular patient, poor or rich, was able to pay. In order to make this procedure more appealing to his assistant, Santschi allowed Bou Hadiba to keep ten per cent of whatever he had squeezed out of the patients' pockets as his salary.

F i g . 3. Aerial view of the medina of Kairouan as seen from the northeast. The foreground is occupied by the Great Mosque, the Jamafi Sidi Oqba Ben Nail, the oldest and purest example of Islamic architecture in the Maghreb. Santschi's house was located in the part of the medina that is shown near the upper margin of the picture

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Fig. 4. A typical small street in the western quarter of the Kairouan medina, south of the Rue Hornet el Bey, not far from the house in which Santschi practised and lived from 1902 to 1940 (see Fig. 6)

All this added to the eccentricity which the people of Kairouan clearly noted in Santschi's behaviour. Fur- thermore, throughout the fourty years he lived in this remote North African town Santschi did not really adapt

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to the Arab style of hfe. He neither wore Arab clothes, nor ever acquired a fair amount of knowledge of the Arab language. Performing most of his biological work in the immediate outskirts of Kairouan, he did not travel much: sometimes to the oases in the south or to the Djebel Trozza and the other mountainous regions in the west. Unlike some of his contemporary fellow-eccentrics, who joined native bedouins and travelled with them through yet unexplored parts of the Old World deserts, e.g. Hans Helfritz (1934), Freya Stark (1951) and Wilfred Thesiger (1960), Felix Santschi remained very much a French speaking European within an Arabian world.

an expedition to Columbia and Venezuela organized and headed by his academic supervisor Bugnion and the Comte de Dalmas. The expedition was accompanied by Bugnion's brother-in-law, Auguste Forel a 3. Without any doubt, it was the fortunate coincidence of the young student with this eminent figure in brain research and entomology that definitely shaped Santschi's future scientific ambition, thinking and career a4.

Six years after he had arrived in North Africa, Sant- schi (1907) started a long series of papers bearing witness to his never tiring taxonomic effort (Fig. 9). This effort was mainly directed towards the detection, identification and nomenclatorial registration of new infraspecific forms and categories within a number of ant genera. Provided with a sharp eye for even subtle differences in colour, cuticular structure or type of pubescence as, he "enriched" the biological literature, and the museum collections as well, with a plethora of new subspecies, varieties, races and stirpes 16. Unfortunately, however, he was never explicit about the standards he used in the application of these lower categories• This went so far that he would indistinguishably use trinomial and tetranomial nomenclatures with the stirps, for example, defining a taxon which in one case was identical with and in another case subordinate to the rank of a subspecies. Regretfully, this effort yielded a jumble of new names and types accompanied only occasionally by mostly unworkable keys and very few figures 17.

Why did Santschi, gifted with extraordinary powers of observation, and - as shown below - with a clear grasp of the essential, fail to make his own mark in taxonomy? The main reason seems to be that Santschi tacitly adhered to an essentialist - or typological - species concept• There is not the slightest indication in his writings, either in his publications or in his correspondence, that he had accepted or even known of Darwin's fundamental claim that "all true classification is genealogical" as. He might have believed in evolutionary theory in general, and in Darwinism in particular, as

The taxonomist: splitting insect species

Among biologists Santschi is most widely known for his industrious activity in the field of ant taxonomy. He became attracted to ants in 1896 when he joined

Fig. 5. The house of Santschi's best local friend, M. Abderrahman Mohamed Abdallah was located within the labyrinth of narrow streets occupying the northeastern part of the medina, about 200 metres from Santschi's home. Since the beginning of this century, this quarter of the town has changed the least

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had his influential teacher Forel ~9, but this common belief had not affected his taxonomic endeavours.

In hindsight, of course, it is unfair to blame Santschi for not having introduced the modern concept o f " population systematics" by himself. Even the founders of the neo-Darwinian synthetic theory of evolution on which the new systematics was firmly based conceded that the replacement of the typological species concept by the concept of a populationally conceived biological species was an exceedingly slow process (e.g. Mayr 1982; Hull 1988). The books that more than any others initiated and forcefully entertained the Modern Synthesis ap- peared either shortly before (Dobzhansky 1937) or after Santschi's death (Huxley 1942; Mayr 1942; Simpson 1944). Certainly, some aspects of the new theory of classification - the subspecies problem or the concept of the polytypic species - had already been discussed early in this century, e.g. by the entomologist Poulton (1908) and the ornithologist Rensch (1929), but Santschi, con- fined to his North African refuge, had no access to academic institutions, libraries and hence such publications.

In none of his taxonomic papers did Santschi ever articulate the truths and concepts he accepted without question. Hence it is difficult to judge what his silent assumptions were and whether he was at all aware of the framework of ideas underlying his deliberate splitting of species into a fine-grain hierarchy of infraspecific taxa. For a certainty, we can merely say that, out in the field, Santschi did not realise the amount of stocha- stic and geographical variation of the characters he used in defining his species novae, subspecies novae, stirpes novae, variationes novae and the like. He considered this nested hierarchy of forms as a structure rather than a process, and used methods of what we would now call non-numerical phenetics to describe this structure. Had the phenomenon of geographic variation once struck his eyes, e.g. in the North African populations of Cam- ponotus, Cataglyphis or Messor, it would have given his alert mind pause for thought.

Fig. 7. At the foot of the ramparts of the medina the "cemetery of great men" symbolizes that the light of the Holy City has not dimmed throughout the centuries and that Kairouan has kept up the tradition of the past. In Santschi's times there were more graves located within the cemeteries outside the ramparts than inhabitants living inside the ramparts of the town

Fig. 6. Santschi's house as seen from the narrow doorway leading to the entrance. The picture was taken on 8 August 1977

The experimenter: dissecting insect behaviour

There is a certain tragedy that Santschi largely failed in the field of study for which he was most renowned, namely insect taxonomy; but he developed brave new ideas and made completely unexpected discoveries in ar- eas in which his contributions were neglected. As is often the case in science, new ideas are destined to bite the dust - and Santschi's ideas have remained there ever since.

Although I have assigned, in the title of this article, Santschi's most original contributions to the field of "sensory ecology", I must issue an immediate disclaim- er. Santschi himself never used this modern term 2°. However, in his approach towards analysing insect behaviour in general, and ant navigation in particular, he addressed questions about the sensory capacities of an animal so much from the perspective of the animal's behavioural ecology that it is probably not too gross an oversimplification to state that Santschi was on the brink of introducing the concept of sensory ecology. Re- cently, for example, in the neurophysiological investiga- tion of bat echolocation certain types of interneurone tuned to faint broad-band acoustical stimuli were dis- carded altogether as "unwanted noise" until the behav-

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Jander 1970). According to this concept animals were regarded as automatons more or less passively drawn into line by external stimuli. Santschi never took more than a casual interest in such concepts. His intellectual approach was completely different (see e.g. Santschi 1923 b). First, he envisaged the problem of animal orientation in its real-world perspective, i.e. realised that a particular sensory capacity was tailored to fulfill specific ecological needs rather than to satisfy simplistic models. This is the ecological perspective of his approach. Sec- ond, he dissected the particular mode of behaviour into its individual components and further analysed these components by well designed experiments. Here we en- counter the physiologist's perspective. Let us exemplify this dual approach by outlining what in my eyes is Sant- schi's most elegant - and most important - contribution to the behavioural sciences: the analysis of spatial orientation in ants.

Fig. 8. Kufic inscription carved into one of the antique columns surrounding the courtyard of the Great Mosque of Kairouan. Long before Santschi moved to the old capital of the Aghlabite Empire, Kairouan had lost its political prominence but retained its religious distinction and spiritual influence. Many of Santschi's experiments on insect navigation were performed in the near-desert steppe just outside the old burial grounds

ioural ecology of the particular species of bat revealed their paramount significance in the detection of ground- dwelling prey (Neuweiler 1989). To Santschi such noise would have been music. By combining his high powers of observation with the same experimental skill he practised as a physician Santschi not only noticed the pecu- larities and idiosyncrasies of a particular behavioural trait but immediately grasped and worked out its biological significance - and often it was the biological significance that, in the first place, shaped his thinking towards designing the right experiment.

Before substantiating this claim we should take a quick look at the scientific background against which we must view Santschi's achievements. In the beginning of the century experimental biology concentrated on the combined effort of cell biology, embryology and genetics in order to explain how an organism developed ontogen- etically. The study of the organism's sensory and neural machinery and how this machinery finally mediated behaviour was in its infancy and - whenever done - completely disconnected from observations on how the animal behaved in its real world. Part of the reason why the experimenter remained in the sterile surround- ings of his laboratory certainly was that natural history studies had not been restored yet to a position of respect- ability in biology.

The most striking example of the somewhat artificial and formalistic look taken in those days at sensory guid- ance in animals was the taxis concept. Developed early in this century (Loeb 1913; Kiihn 1919) it was flourish- ing until late in the 1960s (Fraenkel and Gunn 1940;

Ecological perspective

When Santschi started his experimental work, ant orientation was considered to be mainly a question of orientation by scent-trails. For example, in the beginning of this century the controversy was raging high whether or not ants could "smell" the inbound-outbound polar- ity of a trail (Bethe 1898; Wasmann 1901; Forel 1902a, 1903; Escherich 1906). Santschi immediately realised that this quibble bypassed the main problem: The most common foraging pattern of ants did not consist in trail following but in searching along circuitous routes and returning along straight courses (trajets individuels) zl. In accomplishing the necessary feats of computation the ant could rely on some kind o f " mnemic" representation (Brun 1914) of the landmarks within its entire foraging range, or on what we now would call idiothetic integration (sens rnusculaire; Pieron 1904, 1912). In those days, some researchers even resorted to mysticism and invoked an inscrutable internal mechanism, the "sens de percep- tion des directions absolues dans l'espace" (Cornetz 1914), which Santschi (1930) facetiously dubbed "'sens zero ". The first two explanations could be ruled out experimentally by lifting the ants off the ground and displacing them to novel territory, but the third, of course, was difficult to refute. Here a long and heated controversy started between Santschi and Cornetz, a French engineer then working in Algeria. As this dispute shows, Santschi had a nose for controversy and did not back off when embroiled in it. Even though nowadays Cornetz' opinion seems barely worth considering, I mention this historical point at issue because it is here that Santschi's "way of seeing" is most clearly expressed. Santschi offered operational hypotheses which, as we shall see below, were testable and derived from the ant's rather than the human perspective. Behavioural ecology rather than some preconceived idea of how the system should work was his guide. Unlike Loeb he saw the complexity of the task, but unlike Cornetz he considered it treatable. In the behavioural biology of his days, this was a rare combination of intellectual skills.

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Fig. 9. Plate 1 of Santschi's 1929 monograph on the genus Cataglyphis. Line drawings of petiole, thorax, maxillary palps, head and tibia of workers, reproductive females and males of various Cataglyphis species

F. S A N T S C H I , - - C A T A G L Y P H I S .

First and foremost, in tackling the problem of ant navigation (Fig. 10) Santschi realised that the animal needed a compass alongside a ruler, to integrate its course, and that this compass had to be based on external cues, but had to be independent of local landmarks. It is the analysis of the compass problem to which we turn now.

Physiological perspective

The search for the compass cues used in insect navigation is a remarkable sequence of false but profitable leads, fortunate choices and clarifying new ideas (Lub- bock 1891; Viehmeyer 1900; Wasmann 1901; Turner 1907). To Santschi the pessimistic argument favoured by his opponent Cornetz that the animal's performance was much too complex to be amenable to analytical research was not as impeccable as it seemed in those days. Santschi could draw an important conclusion already from one of his first experiments (Santschi 1911): When he screened off the sun and reflected it with a mirror from the other side, an ant returning to its nest would change its course by 180 ° . This famous mirror experiment showed for the first time that animals could use skymarks for navigation. At present, this is nearly the only known and widely cited result of Santschi's behavioural experiments, but even here the citations pro- vide little more than the mere fact that Santschi discovered the sun compass - and tacitly generalize that ants would use this compass whenever the sun is visible. Santschi himself was much more careful to eschew such unsupported generalizations than his later referees were.

He noted that his mirror experiment worked much more easily in some genera of ants (e.g. Messor, Fig. 11; Aphaenogaster; Monomorium) than in others (e.g. Cata- glyphis); when the elevation of the sun was low rather than when it was high; or when the wind had stopped blowing rather than when it had not. These observations already indicated to Santschi that the sun compass was only one part within an integrated navigational system, and that this part could play different roles depending on the stimulus situation available and the foraging ecology of the species in question. Even at the present writing, the intricacies of these interdependencies have not been worked out in any animal species. One lesson we can already learn at this point of Santschi's argumenta- tion certainly is that a particular navigational subsystem serves only a limited function within the animal's overall system of navigation and that appreciating and elucidat- ing this limited function will be a decisive first step in unravelling the way the particular subsystem works.

A second type of argument made by S antschi (1913 b) in reply to a counter-argument of Cornetz (1913a, b) is worth noting in this context. When Cornetz argued that due to its daily movement across the sky the sun could not be used as an orientational cue, Santschi re- marked that the animal might well possess an internal representation of time 22 and associate different spatial positions of the sun with different times of day: " A moving skymark is not less reliable than a stationary landmark if its movement is completely regular and pre- dictable" (Santschi 1913b: 234). In his days, this state- ment will have raised many a brow (see e.g. Brun 1914: 183), but Santschi seemed to have been convinced that evolution was surely capable of such a design, given

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Memoires de la Societd Vaudoise des Sciences Naturelles N ° ~ 1923

L ' o r i e n t a t i o n s i d 6 r a l e d e s f o u r m i s ,

et quelques cousid~rations sur leurs dil[~renles possibilit~s d'orienlation,

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( K a i r o u a n . Tunisie).

A 31. le pro[e~seur D r Edouard Bugnion , Hort~age de son ancien ~l~ve el assistant.

I. CLASSIFICATIOX DES DIVERSES POSSIBILITIES D'ORIEXTATIO.~ CHEZ LES FOUR~IIS ~

Toute orientation biologique 6rant une relation de lieu. cons- eiente ou subconsciente, d'un organisme a\-ec une ou plusieurs parties du monde ambiant, c'est-fi-dire comprenant d'une part un organe r6cepteur et de l'autre une source d'irritation, on peut baser unc classification des diverses formes d'orientation ehez les fourmis, soit d'aprfs les diff~rents appareils sensoriels, soit, au contraire, selon la diversit6 des irritants. C'est cette derni6re alter- native que nous avons adopt6e peusant que, moins explorfe, elle peut conduire fi de nouveaux horizons, non, toutefois, sans recourir, occasionnellement, fi la premi6re.

La mati~re se r6vfle par des propri6t6s qui lui sour inh6rentes (consistance, forme), et d'autrcs qui s'eu d6gagent et agissent A distance (6manations, attraction), d'o~t une premi6re grande divi- sion qui nous donne, d'une part :

1 o L'orientalion lopoeslhdsique dans laquelle r6tre est oblig6 tie progresser dans un contact direct de la source d'irritation, dans une d6pendance eonstante du terrain, ce qui r6duit cousid6rable- ment sa libert6 d'aetion et, d'autre part :

t Ce premier chapitre n ' c s t q u ' u n b re f r~sum~ d e la p remiere pa r t i e de ce m~moire. tel qu ' i l a 6t6 p r ~ e n t 6 /l la sP.ance g6n6rale de d~cembre 1922 de la S. V. S. N. ¢ t que des raisons d'~conomie m'ont ob~ig6 de scantier. Elle pa raJ t ra in extenso duns la Ret,ue Zool. Alr icain e 192~.

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Fig. 10. F ron t page of Santschi 's fundamenta l account on celestial navigation in ants (Santschi 1923 a)

even when tested after sunset (Santschi 1911, 1913a; Fig. 12) or when presented only with a limited patch of daytime sky excluding the sun (Santschi 1923 a). The latter experimental paradigm was achieved by moving a cardboard cylinder along with the ant as it walked. Santschi concluded from a detailed sequence of experiments that the ants might be able to detect intensity gradients in the sky 24, most probably in the ultraviolet range of the spectrum 2s, or perceive some other celestial cue invisible to the human eye 26. He even proposed experiments including the use of ultraviolet emitting Mer- cury lamps, but as such optical equipment was not available to him in Kairouan, he was finally left alone with the question: "What is it in this small patch of blue sky that guides the ant back home?" (Santschi 1923a: 159). Santschi did not know. Even though he took a keen interest in certain phenomena of atmospheric optics (ultraviolet radiation, green flash 27), he apparent- ly was not aware of skylight polarization - and hence not able to make one of the most striking discoveries in insect sensory physiology 2s.

There are several other fields of insect orientation - e.g. the ways insects exploit the direction of the wind or establish and use pheromone trails 29 - to which Santschi has made important contributions. However, as was the case with his work on visual orientation, nearly all of these findings remained unnoticed and had to await their later rediscoveries.

Apart from his experimental results and his elucida- tion of hitherto unknown sensory and behavioural capacities it was his new "way of seeing" by which Santschi stands out from his fellow insect behaviourists. He neither regarded his experimental animals as Loebian sim- pletons, which moved only in order to achieve some kind of sensory equilibrium, nor did he look at their extraordinary navigational capabilities with a mere mix- ture of intuition and awe. By combining ecological rea- soning with observational skills he took a middle way. Gifted with the extraordinary power of dwelling on the finest of fine details of the animal's behavioural perfor-

need. Unfortunately, Santschi (1923a) performed only very few experiments to substantiate the point in question, and these experiments were not conclusive 23. Nev- ertheless, he continued to refute the argument that the ants had to be superb astronomers to acquire the information necessary for using skymarks as a compass: " I t is as superfluous for a navigating ant to possess pro- found astronomical knowledge as it is for a grazing cow to possess any kind of botanical knowledge" (Santschi 1923 a: 160). This humorous comparison nicely conveys the message that the animal has to solve the tasks with which it rather than the human investigator must con- tend - or to put it in modern neurological terms: Sant- schi did not consider the ant's brain to be essentially a "stripped-down" version of the human brain.

Out of this strictly task- and species-oriented way of thinking came a number of fascinating and truly original experiments. The most remarkable are the ones in which ants were shown to be able to navigate correctly

Fig. 11. Most of Santschi 's experiments on ant navigation, e.g. his first mir ror experiments, were performed with various species of harvester ants belonging to the genus Messor, e .g .M, barbarus and M. arenarius. This picture shows a specimen of the latter species descended by several generations f rom Santschi 's experimental animals

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FZG. 2.

E.rplicalion de Itt ]iyurc 2. 1"Sxprrience c o m b i n ( e de l ' ( ' c ran h o r i z o n t a l e t de l ' r c r a n c y l i n d l i q u e . - - T r a i t s pleins , t r a j e t s l ib res sans ~cran. . . . . T r a i t s f i nemen t point i lh ;s . T r a j e t s c o u v e r t s de l ' & r a n h o r i z o n t a h

oooo P e t i t s cercles. T r a j e t s e n t o u r r s tie l ' r c r a n c y l i n d r i q u e seul . a a a a Gros po in t i l l r . T r a j e t s e n t o u r r s e t e o u v e r t s ties d e u x 6 t r a n s .

Fig. 12. Trajectories of ants returning to the nest, N. During the ants' homeward runs Santschi screened off different parts of the sky. For example, in figures e-f two workers of Monomorium salo- monis were tested after sunset. While returning home, they were surrounded by a cylindrical screen shielding the lower parts of the celestial hemisphere (traces marked by open circles) or, in addition, by a horizontal screen shielding the remainder of the celestial hemisphere (traces marked by filled circles). From Santschi (1923 a)

mances he " s a w " the pa t te rns - the indiv idual modes of behav iour - tha t had emerged f rom adapt ive evolu- t ionary processes. In this sense, his work presaged much of the more detailed studies later per formed by Kar l v. Frisch and his s tudents , bu t also of the fresh look which the newly formed guild of behav ioura l ecologists is current ly tak ing at p roblems of an imal or ien ta t ion and nav iga t ion - and it is in this sense that he can hon- estly be regarded as having been on the b r ink of in t ro- ducing sensory ecology.

Acknowledgements

Having finished writing this essay it is my strong desire - as well as my wife's (see Note 5) - to express our sincere gratitude to all the citizens of Kairouan who freely gave their time to talk to us and to show us around. Without their help and kindness we experienced during our frequent visits to their home town we would not have been able to assemble the many bits and pieces of information out of which the reconstruction of Santschi's life

303

in Kairouan finally emerged. We are especially grateful to Dr. M. Kharat, mayor of Kairouan, for inviting us to see him in his town- hall office, and to the late M. Abderrahman Mader Ben Abdallah.

Remerciements

Aprrs avoir termin6 la rrdaction de cet essai, ma femme (voir la note 5) et moi-m~me tenons ~ remercier, de tout coeur et le plus chaleureusement possible, les personnalitrs de Kairouan qui nous ont regus, ont discut6 avec nous, et nous ont fait visiter leur pays. Sans leur aide et leur hospitalit6 si intimement ressenties lors de nos nombreuses visites chez eux, nous n'aurions jamais pu avoir accrs aux informations qui nous ont pennis de formuler ce que pfit &re la vie de Santschi/t Kairouan.

Nous tenons tout particulibrement ~ trmoigner notre gratitude ~i Monsieur le Docteur Kharat, maire de Kairouan, qui nous a si aimablement re~u dans son bureau officiel, et /t Monsieur Abderrahman Mader Ben Abdallah, drcrd6 depuis lors.

Notes

Tabib-en-Neml, which literally means "ant doctor", was a nick- name given to Santschi by the citizens of Kairouan. It referred to Santschi's medical profession and scientific interests (myrme- cology). The two-weeks journey of Klee, Macke and Moilliet to Tunisia (8-20 April 1914) is considered to be a decisive historical event in the development of expressionistic art (Hausenstein 1921, Du- vignand 1980, Gtise 1982). It was during this short trip to North Africa that August Macke (who a few months later was killed during the First World War) reached the culmination of his artistic endeavours, and that Paul Klee discovered colour as a stylistic means (see Note 4). Most of the time the three friends stayed at the house of the Swiss physician Dr. Ernst J/iggi in Tunis and visited the near-by places of St. Germain, Sidi Bou Said and Carthage, but left the north of Tunisia for a two-days trip to Kairouan (15-17 April 1914). During the time Santschi lived in Kairouan his visitors like Auguste Forel (in 1909) and Heinrich Kutter (in 1927) could reach the town by train. In recent times the track of the old railway line has been removed, but the railway station, a small tidy building constructed in the French colonial style with red tiles and blue window shutters, still exists at the junction of the Rue Etienne and the Rue Ouled Haffouz south of the medina. At present, it houses an office of the Garde National. By the vivid description he gave of his feelings when walking through the Arabic medina (see below) Klee strongly empha- sized the influence the urban scenery of Kairouan had on the development of his way of painting: "I leave my work for now... I am becoming firm, without any effort. The colour has taken possession of me. No need to grab at it. I will possess it for ever, I know this. This is the essence of this happy hour: Myself and the colour have become rolled into one. I am a painter." (Translated from Klee's note-book "Tunis-Reise", p. 151, reprinted in Klee, 1957). It is well known that Klee repeatedly changed the phrasing of the original entries in his note-books (Werckmeister 1989), but the emphatic sentences cited above have remained in this form ever since Klee wrote them down on 16 April 1914. Santschi's life in Kairouan has been reconstructed by interview- ing citizens of the medina who had known Santschi personally or had heard of him through family members or friends. The interviews which the author could not have made without the expertise, enthusiasm and linguistic skills of his wife, Sibylle Wehner-Segesser v. Brunegg, cover the period 1976-1990. In these interviews the most comprehensive information was provided by Dr. M. Kharat0 mayor of Kairouan, and by M. Abder- rahman Mader Ben Abdallah, whose father had been a close

304

friend of Santschi. In addition, important details of Santschi's personality, his professional and personal way of life were readily reported to us by many other citizens of Kairouan. Further information came from the Swiss myrmecologist Dr. H. Kutter and his wife who had visited Santschi in May 1927. Mrs. Kutter has later described this journey in a series of reports published in a local newspaper (Kutter 1930). Several aspects of Santschi's way of life and thinking were deduced from the correspondence between Drs. Santschi and Kutter (partly left to the author by the latter). Only a few photographs portraying Felix Santschi in Kairouan are available. The most expressive one was kindly given to the author by M. Abderrahman Mader Ben Abdallah. It is this portrayal (unfortunately partly destroyed by termites) that has been used in designing Fig. 1.

6 Kuhn (1962), Hoyningen-Huene (1989). 7 In addition, two anonymous notes about Santschi's death ap-

peared in Entomologist's Rec J Var 53: 56, 1941 and Rev Soc Ent Argent 13: 344, 1947. The latter note published in Spanish reports that Santschi was a Corresponding Member of the Ento- mological Society of Argentine.

8 Santschi's presence in Kairouan was even mentioned in the most common contemporary travel guide of North Africa (Baedeker 1909: 389). More circumstantial descriptions of his life and professional achievements are provided by two Tunisian encyclo- paedias (Lambert 1912 : 359, Chatelain 1937: 249).

9 Santschi's house located at the Rue Ali Bel Haouane, close to the Bab Ech-Chouhada, was originally owned by the Habous, a religious organization. Santschi bought the first floor where he practised and lived with his family (his wife and his two children: his son Vir and his daughter Rose Id61e). In the mid 1950s the owner of the bookstore "Librairie Ridha Ajra" now occupying the basement of the house bought Santschi's apart- ment from Santschi's heirs. At present, it is rented to a woman hairdresser, Coiffeur Imen.

lO Among the citizens of Kairouan, Santschi had soon gained a reputation as a capable and skillful doctor. He treated his patients not only at the doctor's house, but visited them - by bicycle - in their own homes to which he was freely admitted even without the need of knocking at the door. He would also go to treat the bedouins living in their tents in the arid plains around Kairouan, especially in the area of the Bassins des Aghla- bites.

x 1 In North Africa, the method of couching the cataract was practised until far into this century (personal communication by Dr. med. habil. C. Huber). For historical comments see Duke-Elder (1969).

12 Santschi never showed the slightest desire to leave Kairouan and to return to Europe. It was only at the end of his life, in 1939, when he was seriously ill that he spent a six-months convalescent holiday in Marseille. Still ill - and later diagnosed suffering from stomach cancer - he returned to Kairouan. Next year, when his physical condition deteriorated even more, his family finally forced him to leave his beloved North African second home and to return to Lausanne. There he underwent an operation from which he did not recover. He died in the hospital on 20 November 1940. - Unlike Santschi his wife did not adapt well to the climatic conditions of central Tunisia. She often left Kairouan for Switzerland where she stayed for periods of weeks or months. Then another lady, Mme. Gou- moans, moved into the doctor's house. She worked as a nurse and, in addition, helped Santschi by preparing his ant specimens and taking care of his ant collections.

a3 This expedition to South America is described at length in Fo- rel's autobiography (Forel 1935:170-187).

14 In a two-page certificate dated 18 February 1901 (at Chigny near Morges, Vaud) Forel characterizes Santschi as a capable researcher and helpful, well-disposed colleague whom he had got to know well during their trip to South America. Forel's influence on Santschi was so strong, and extended far beyond the entomological endeavours of the two men, that Santschi adopted most of Forel's philosophical ideas, became a member

of the Order of Good Templars and joined the anti-alcohol movement founded by Forel in Switzerland.

15 Santschi's method of taxonomic splitting may be documented best by referring to his revision of the Cataglyphis albicans group. On the one hand, Santschi defned the species C. albicans (Roger 1859) so loosely that it included a number of forms which are now recognized as separate species, e .g .C , fortis (Wehner 1983), C. rubra (Collingwood 1985, Wehner 1986), C. livida (Kugler 1988). On the other hand, he described and named a plethora of infraspecific taxa based exclusively on tiny differences in colour and pubescence of a few worker-caste specimens. He did so even when these differences lay completely within the intra-population range of variation, and when the subspecies (= stirpes, see Note 16) delineated by these differences occurred sympatrically within the same geographical area, as is the case in ssp. kairouana (Santschi 1912), ssp. opaca (Santschi 1912) and ssp. semitonsa (Santschi 1926), which indiscriminately in- habit the central Tunisian lowland steppes surrounding Kai- rouan.

16 Sing. stirps (lat. lineage, stock). The term stirps [st.] describing an infraspecific taxonomic category was introduced by Santschi who in general applied it synonymously with subspecies [ssp.] or race [r.]. The term subspecies was favoured by Wheeler and Emery, while Forel preferred the term race. The additional term variatio [var.] was used by both Forel and Santschi in order to describe individual variations within subspecies, e.g. Lepto- thorax rottenbergi annibalis n.st. colorata n.var. (Santschi 1909). It was Forel (1874, see also 1921: 130-133) who introduced this deliberate splitting of species into subspecies and variations and thus established the use of trinomial and tetranomial nomenclatures. All eminent myrmecologists before Forel, e.g. Fab- ricius, Latreille, Mayr, Nylander and Roger, had strictly used binomials, as was later done by Creighton (1950) whose treatise on the ants of North America marks the end of the "infraspecific intermezzo" in ant taxonomy. In a seminal paper Wilson and Brown (1953) finally claimed that " the subspecies concept is the most critical and disorderly area of modern systematic theory" (p. 100) and convincingly argued that the subspecies trinomial is "bo th illusory and superfluous" (p. 108).

iv In his review on one hundred years of ant taxonomy Brown (1955) harshly criticized these "thousands of dubious names" introduced by Santschi and some of his fellow-splitters, e.g. Viehmeyer, Stitz, Karawajew and Donisthorpe.

18 Darwin (1859: 420). See also Darwin's correspondence (Darwin 1887). Even if we concede that classification and the reconstruction of genealogical relationships are different undertakings (Sober 1989; Martin 1990), Santschi's classifications were not consistently based even on the degree of similarity alone.

19 That Forel - and hence most probably Santschi as well (see Note 14) - did firmly believe in the Darwinian way of evolution can be deduced from a number of sources, e.g. Forel (1874: 17-18, 1902b, 1910a, 1921).

2o The term "sensory ecology" was first used as the title of a book edited by Ali (1978).

21 The problem of path integration in ants has been treated experimentally only very recently (Wehner & Wehner 1986, Mtiller & Wehner 1988).

22 Santschi (1913b) knew of Forel's (1910b: 324-327) experiments in which bees were successfully trained to arrive at a food source at specific times of day.

z3 Similar experiments were performed by Brun (1914: 176-184) with Lasius niger and Formica sanguinea. When ants while returning from a food source were kept in the dark for periods of one to three hours and then released, they did not compensate for the apparent movement of the sun during the time they had spent in the dark. Jander (1957) tried to explain this behaviour by arguing that young foragers might not have learned yet their local sun-azimuth/time function. For a recent investiga- tion see Wehner & Lanfranconi (1981).

14 Santschi (1913a: 385) spoke of "zones trOs brillantes", "'zones demi-obseure'" and "zones obscures ", which the ants seemed

305

to be able to discriminate in the sky. He concluded that such skylight cues (rather than sunlight cues) provided the ants with the most important navigational information. This conclusion was drawn from a number of experiments, in which he had screened off the sun, but had not displayed it by a mirror at another point in the sky. Under these conditions he was never able to deflect the ants from their normal homeward courses.

25 Santschi was informed about Lubbock's (1891 : 201-220) as well as Forel's and Dufour's (1903) experiments, which showed that ants were able to perceive ultraviolet light.

26 Santschi (1913c, 1914, 1915, 1923a) discussed the possibility that ants could see the stars - and could do so even in the daytime sky. He argued that the dark pigment shields surrounding the individual ommatidia of an insect's compound eye (see Fig. 2 in Santschi 1911; Santschi 1913c) might screen off the stray light of the celestial hemisphere to such an extent that the stars became visible within the bright sky. Qualitatively cor- rect, this argument goes back to a remark made by Aristotle (De Generatione Animalium 5, 1. 780b, 21 f) that a person sit- ting at the bottom of a deep well is able to see the stars in the blue diurnal sky. In quantitative photometric terms, however, one can easily show that the sensitivity of insect ommatidia to point-light sources is not sufficient to detect the brightest stars even in the nocturnal sky. Such calculations were first published more than half a century after Santschi had proposed his provoking hypothesis (Rodieck 1973: 272; Kirschfeld 1974). Finally Santschi (1913a) even referred to the claims by the French physicists Le Bon (Klotz 1980) and Blondlot (Nye 1980) to have discovered new kinds of radiation. These so-called N- rays later turned out to be totally imaginary.

27 At sunset Santschi would often hurry up to the roof of his house to observe through his telescope a faint and short-lived optical phenomenon in the western sky, the rayon vert, or green flash (O'Connell 1961). "Comme de l'6m6raude", he would ex- claim to his visitors.

28 The decisive discovery was later made by v. Friseh (1949). Even he, however, was not aware of the phenomenon of skylight polarization. Two physicists, O. Kiepenheuer (Freiburg i.Br.) and H. Benndorf (Graz), informed him about polarized skylight. This information later allowed him to perform his crucial experiments. Even if Santschi had known that skylight was partially linearly polarized (Strutt 1871), for technical reasons it would have been extremely difficult for him to obtain unequivocal proof that ants used this optical phenomenon for navigation. In his days sheets of linear polarizers were not yet available. They were not designed and produced (by Polaroid Corp.) until 1947. Nicol prisms then used in polarized-light microscopy would not have been of any help in open-field experiments em- ploying freely walking animals.

29 Santschi (1913a, 1923b) showed for the first time that chemical trails did not consist of passively applied chemical foot marks, but that the walking ants actively deposited secretions of their anal glands. When Carthy (1950) rediscovered this phenomenon almost 40 years later, he was not aware of Santschi's original observations.

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