In the nineteenth century, entomology consisted largely ofinsect taxonomy: entomologists were experts at classifyingand preparing their subjects, the delicate bodies of insects.In addition to taxonomy, a field called ‘forest zoology’emerged in Germany during the nineteenth century, whichoccupied itself primarily with animals of interest to thenobility: game animals to be maximized in size and number,and forest insects that were now perceived by some as re-ducing the potential wood crop. As part of the new politicaland economic practices associated with the Enlightenmentmovement, forests became economic resources to be man-aged rationally for maximum wood and antler production.

From Nutzwald to Kulturwald

Untroubled by these irreconcilable tenets, forest zoologistssuch as Julius Ratzeburg (1801–1871) began their entomo-logical work and described the various life stages of for-est insects as well as the traces they left as ‘damage’on theleaves and under the bark of forest trees1. As we shall see,their perspective on forests and forest insects was very dif-ferent from that of their successors, the economic en-tomologists of the early twentieth century. In Ratzeburg’sworld there were two kinds of forest – primeval and utili-tarian (Urwald and Nutzwald) – and these did not differ inthe number and kind of insects they housed unless foresterswere able to decrease the numbers of insects in commercialforests.

Before about 1890, entomologists in this tradition sawinsects as local occurrences of limited numbers, in uniquegeographical and biological locations, in a particular dis-trict at a specific time, in certain parts of the trees, withthe wood of the trees being in a specific condition, at cer-tain temperatures, moisture and amount of light, and so on.During the nineteenth century, the practices used againstinsects were derived from kitchen gardens, handicraftsand entomological collection: picking individual insectsby hand; shaking them off trees and collecting them;wrapping sticky collars around individual tree stems totrap wingless insect stages. These practices all shared onefeature: they targeted individual trees and insect bodies.Thus, the ways forest entomologists saw insects and theways they treated them agreed: the individual occurrencesof insects could be dealt with by handling individual plantand insect bodies.

This view on insects and forests changed around 1900as part of larger social, political and economic transfor-mations taking place at the turn of the century. Thedynamics of modernization in Germany and other nationsbetween 1870 and 1914 brought with it changes both inwhat people perceived as dangerous and in the ways theyperceived dangers. Among these new destabilizing threatswere ‘masses’ of people. The most famous text generatingthese threatening masses was Gustave LeBon’s Psychologyof the Masses, a German translation of which appeared in19082. The ‘masses’ represented many of these dangersand were integral to the self-definition of bourgeois menas threatened individuals, threatened by the deindividual-izing features of industrialization, such as standardiz-ation, that infiltrated even bourgeois life.

In this literature, many symbolic bodies, individual aswell as collective, were reconfigured as threatened orthreatening and strategies against these threats were de-veloped. Prominent among the many fields where these

28 Endeavour Vol. 24(1) 2000 0160-9327/00/$ – see front matter © 2000 Elsevier Science Ltd. All rights reserved. PII: S0160-9327(99)01261-2

Chemical-warfare techniques for insect control: insect ‘pests’ in Germany before and afterWorld War ISarah Jansen

During World War I, chemical-warfare practices were introduced into economic entomology in Germany.Fritz Haber, ‘the father of chemical warfare’, realized that Germany could not win the war and thus lookedfor ‘civilian’ uses for his chemical arsenal. Before the war, there was a rhetoric of dangerous ‘masses’ ofinsects but the large-scale techniques needed to deal with them had not been developed. The gap betweenrhetoric and practices enabled entomology to integrate chemical weapons into its working methods. Thisarticle traces transformations in the ways of seeing insects and their control from the mid-nineteenthcentury to after World War I.

Sarah Jansen

Completed a BSc in biology at McGill University and a PhD in his-tory at the Technical University of Braunschweig. She is currently a research scholar at the Max-Planck Institute for the History ofScience in Berlin. She has published Naturwissenschaftlerinnenund Ingenieurinnen and several articles. This article is based onmaterials and arguments drawn from her forthcoming bookSchädlinge: Geschichte eines wissenschaftlichen und politischenKonstrukts 1840–1920 and from Ref. 26.

changes took place was science, and new sciences emergedas part of this larger movement. Among them were theyoung sciences of forestry, agriculture and economic ento-mology, which replaced the forest zoology of the nineteenthcentury. Forests, fields and vineyards became stages for thepart these sciences played in reconfiguring life and society.

Beginnning in about 1890, pictures and texts appearedthat presented forest insects as insect ‘masses’. The main,but not only, protagonist of this development was KarlEscherich (1871–1951), who, in 1907, was a young pro-fessor of forest entomology and an ardent supporter ofdarwinism and social darwinism. In an influential textpublished in 1907, Escherich drew a dramatic Malthusianpicture of the ‘mass’ propagation or ‘mass’ multiplicationof forest insects3. He also extended the discourse on‘degeneration’ of German culture (Kultur) to include for-ests, which, unlike Ratzeburg, he didn’t see as utilitarianbut as cultured forests (Kulturwald), thus transferringKultur, one of the most loaded terms in German nationalself-definition, to the field of insect control.

According to Escherich, the German Kulturwald wasthreatened by degeneration, much like human society andculture when freed from natural selection. In a naturalforest, natural selection would check the Malthusian ‘mass’multiplication of insects but, with natural selection inacti-vated, ‘abnormal mass propagations’ and ‘multiplicationcatastrophes’ were taking place every day in Germanforests. In 1912, Escherich specified his program.

The forest zoologist should not focus too much on the obser-

vation of individual animals. It’s not the individual caterpil-

lar that produces the calamity, but the society of millions of

caterpillars… To project from the individual observation to

the appearance of devouring masses and the effects of masses,

to change thinking from the individual observation to the big

picture, that is the most difficult step for the forest zoologist.4

Escherich’s texts turned local and limited insects into‘insect masses’ and the afflicted trees into a Kulturwaldendangered by insects. The constant danger of degener-ation emanating from the insect masses defined this Kultur-wald, whereas the Nutzwaldof the nineteenth century hadnot been seen as endangered. As ‘masses’, forest insectsthreatened the collective body of the German forest, asymbol of German culture5. The task of forest entomolo-gists had changed accordingly: instead of economicallyimproving the output of individual woods, they now pro-tected a huge endangered symbolic body.

Forest hygiene

However, in contrast to the new rhetoric, insect control didnot change in practice between 1890 and 1914. Escherichhimself advocated a ‘forest hygiene’ analogous to ‘socialhygiene’ but, like his colleagues, he had little to say aboutits techniques. As before, the treatments were directed to-wards individual tree and insect bodies, and were gener-ally artisanal. Workers still attached sticky collars aroundindividual tree stems (Figure 1) and practices heralded as‘new’, such as using a watering can to apply petroleum tothe spongy nests of the gypsy moth, brought changes in

detail but not in scale. Surely, if one wanted to save wholeKulturwälder (and there are no woods in Germany thatare not cultivated), one needs to be armed with more thana few watering cans.

A few economic entomologists experimented with cyan-ide gases, applied either in closed boxes in the laboratoryor under tent constructions spread laboriously over eachfruit tree in a field (Figure 2), a technique already tried incalifornian orchards. Although some authors hoped forimprovement, the gases proved to be more toxic to theplants than to the insects6. A discrepancy emergedbetween new ways of seeing insects and forests –Escherich’s ‘masses’ and ‘degenerate forests’ – and oldpractices, which targeted individual bodies that could bemanipulated by hand. Those who feared for the Germanforest were stranded between the immensity andsignificance of the perceived threat and their rather modestremedies. It was in this perceived crisis that economicentomology was, in 1913,institutionalized in a GermanAssociation for Economic Entomology, presided over fordecades by Escherich7.

This discrepancy between ways of seeing and ways ofacting was resolved during World War I. However, ento-mologists, who were trained as taxonomists and/or medi-cal doctors, did not have the knowledge to solve theproblem they saw. The introduction of physical–chemicaltechnologies of chemical warfare into entomology underwar conditions eventually provided a solution to the ento-mologists’ dilemma. By 1916, Fritz Haber (1868–1934),known as ‘the father of chemical warfare’, had begun tothink about possible civilian uses for his chemical weapons.The war was not going in Germany’s favour and Haberwanted to preserve his power, his expertise and possibly

Endeavour Vol. 24(1) 2000 29

Figure 1 Workers attaching sticky glue to textured collars wrapped around treestems. Reproduced from Ref. 19.

also his neck in peace time.The field he suggested as a ‘civilian’ application of

chemical weapons was pest control. From 1916 on, Haberand several entomologists whom he enlisted as fellowcombatants experimented with gaseous poisons for thispurpose. Economic entomologists who, like Escherich,had seen themselves as medical hygienists concernedwith ‘parasites’ in diseased social organisms now turnedinto scientific soldiers ready to combat ‘enemies’ in theshape of either French soldiers or caterpillars.

Two target fields were identified for chemical warfareas pest control: the enclosed spaces of buildings such asbarracks and flour mills, and the open spaces of forests.Owing to their size, both were targets technically beyondthe reaches of pre-World-War-I forest entomology. Thetransfer of chemical-warfare techniques into entomologybegan with the battle against body lice and the gassing ofbuildings. The institutional and technological links forgedin this martial enterprise were then extended to battling

forest insects and treating whole forests with poison.

Lice and people

Under war conditions, ‘lice infestation’ of German soldiersand of the civilian people in the ‘East’ became a new objectof economic entomology. New human ‘masses’ were pro-duced under war conditions and threatened the collectivebody of the German army. They had a geopolitical location,the ‘East’, and were made up of two groups: firstly, Russianand Polish prisoners of war, who were crowded andpenned up in huge prisoner camps; and secondly, localcivilian populations, classified as ‘Polish/Russian/Jewish’and cordoned off in their villages. Racist rhetoric and theliving conditions forced on them established these peopleas ‘dirty’, ‘lousy’ and ‘typhoid carriers’.

The prolific Jeremiah of these new threatening masseswas the zoologist Albrecht Hase (1882–1962), who hadvolunteered for the German army and was an officer. Hebegan his work by publishing counts and descriptions oflice and people; for example, he showed a shirt cut inRussian fashion on which he had counted 3800 lice. Theshirt had been worn by a Russian soldier who had beenunable to change his clothes for weeks. Hase was pleasedabout the large PoW camps that provided him with suchample material for his studies but he regretted that onecould not feasibly confine the civilian population inconcentration camps.

He began his treatments of buildings and equipmentwith steam but soon switched to various poisons madeavailable to him by the army’s weapons headquarters fortreating clothes, equipment and buildings8. However,Hase was a zoologist and he had no training in physicalchemistry to enable him to use these substances effec-tively. Providing a zoologist with the powerful poisonoussubstances of chemical warfare but not with combatantsfrom this enterprise proved to be of limited use in pestcontrol with chemical weapons.

At this time, Fritz Haber was thinking about poison-ing ‘pests’ in agriculture and forestry, about which heknew close to nothing. In 1917, he planned to build a newinstitute to undertake research on poisonous gases inpeace time, with pest control as a major goal. In aprogrammatic text circulated in 1917, he derived the useof chemical weapons on insects from the toxicologicalresearch undertaken on soldiers in the battlefield and on mammals in the laboratory. In a rather labouredargument, he suggested that extending toxicologicalknowledge not only from humans down to larger ani-mals but also from larger animals down to the smallest,would produce insights that could be very useful toagriculture and forestry. A military unit to combat insectpests had already been formed. For this strategy to besuccessful, the knowledge of entomologists and botanistsneeded to be combined with that of chemists. The re-sulting knowledge, Haber concluded, could turn into themost important development of chemical warfare9. Thefirst successful battle led by these new disciplines wasstaged against a flour moth, when mills were gassed withcyano compounds provided by the chemical companyDegussa, whose American branch had already produced

30 Endeavour Vol. 24(1) 2000

Figure 2 A tent is put on a tree ‘like a large butterfly-net’ to create a closed space for fumigation. Reproduced from Ref. 20.

the cyanides for the small-scale experiments in californianorchards10.

Haber and Hase met in 1918. Their cooperation, begunonly at the end of the war, continued for years to comewhen Hase, now officially employed at a Reich ResearchInstitute on Agriculture and Forestry, illegally testedchemical weapons as insecticides. Work with chemicalweapons had been prohibited by the Treaty of Versaillesin 1919 but Haber laundered funds from the Germanarmy outside Germany and declared them as donations toagricultural research from wealthy individuals. However,they could publish their research on cyanide gases, whichhad not been effective as chemical weapons against human‘enemies’ in the field.

One product of the cooperation between the zoologistHase and Haber’s team was the development of the proto-type of the cyano-pesticide ‘Zyklon’11, later used by theNazis to murder people classified as human ‘pests’. Haber’sgroup provided the technical apparatus and procedures tospread the gas evenly in a room, the toxicological knowl-edge about the concentrations of gas needed to kill certainorganisms and the personnel trained in handling chemicalweapons both in the lab and in the battlefield (Figure 3).The entomologists identified and counted the insects to becombatted. However, the enclosed spaces of barracks andmills were not the only battlegrounds of chemical warfareagainst insects.

Laboratories and battlegrounds

The battlegrounds of chemical warfare against human‘enemies’ had been open spaces, fields and forests, andgassing these presented different technical challengesfrom gassing buildings. World War I has been called alarge-scale laboratory and chemical warfare is certainlyone horrible support for this observation12. The experi-mental subjects were soldiers, who died excruciatinglypainful deaths or were physically and emotionally muti-lated for the rest of their lives (Figure 4). Countless num-bers of monkeys, dogs, cats and mice were exposed tothese substances, not only in the lab but also in the field(Figure 5) and also died under torment.

The greatest technical difficulty in this deadly endeavourlay in directing clouds of poisonous gas selectively to-wards spaces occupied by the enemy. In chemical war-fare, open space was a laboratory exposed to suddenchanges in weather. ‘Accidents’ occurred when the windsturned and drove the poisonous clouds into one’s owntrenches. Forests were among these open spaces servingboth as laboratories and battlegrounds, and many experi-ments investigated the behaviour of gaseous poisons inforests (Figure 6). By the end of the war, Haber’s groupand their allied enemies both had considerable knowledgeabout the properties of various poisonous gases in openspaces and about their toxicological effects on humans,animals and plants13.

When Haber first suggested using warfare techniques tocombat forest insects, shortly before the end of the war,he had in mind the techniques of aerial rather than chemi-cal warfare: he planned to bombard a pine forest plaguedby moths. Evidently, either Haber was not aware of the

fact that a pine forest would burn down immediately whenbombarded with fire bombs or he didn’t care whether theforest to be protected was destroyed along with the‘enemy’ moths; possibly, protecting the forest from themoths was only a pretense to allow the testing of bomberaeroplanes and the effects of fire bombs on forests.Whether out of concern for the pine forest or the lack of

Endeavour Vol. 24(1) 2000 31

Figure 3 Cyano carbureter in 1917. Tools from garden and kitchen are integratedin the apparatus. Reproduced from Ref. 21.

Figure 4 Dead Russian soldiers in their trenches after a gas attack. Reproducedfrom Ref. 22.

suitable aeroplanes, this plan was not carried out in191914.

Six years later, in 1925, Haber’s plan was realized, witharsenic shells replacing the fire bombs. A forest was bom-barded with arsenic from an aeroplane specially constructedfor this purpose by the aircraft manufacturer Junkers15

(Figure 7). The primary goal of these large-scale open-airexperiments was military. Knowledge about distributionpatterns of powdered poisons discharged from aeroplaneswas of interest to the military, as were the short- and long-term toxicological effects on insects, game and domesticanimals. Confidential memoranda reveal that the damagedone by large numbers of caterpillars in the bombardedforests provided nothing more than a publicly acceptablereason – so it was hoped – for what was actually a secretmilitary action to test techniques of aerial chemical war-fare16. Nevertheless, the warfare techniques used for chemi-

cal weapons and for aerial bombardment led to the standardprocedures for economic entomology that are in use today.

A contingent solution

Haber’s plan to save his chemical weapons by transferringthem to pest control intersected with economic entomolo-gists’ gloomy pictures of insect ‘masses’ devouring theGerman forest. However, the targets of these treatments –or attacks – were not the masses of insects but the forestitself. As in chemical warfare, in which enemy soldiers werekilled or injured as elements of a target space, the forestbecame ‘enemy territory’, the enemy being a moth ratherthan French, English or Russian soldiers. This larger ob-ject (enemy territory) contained the insect masses and thus,although the rhetorical object ‘insect masses’ and the prac-tical object ‘enemy territory’ were not identical, the firstcould be made practical; that is, the insect masses could bekilled by dusting the whole forest with arsenic from an air-craft. In this way, the discrepancy between rhetoric and prac-tice, the crisis of pre-War economic entomology, could beresolved, although not without tensions that occupied botheconomic entomology and ecology for decades to come.

In contrast to many studies of science and the military, thestory told here goes beyond revealing the traffic in practicesand institutions between chemical warfare and economicentomology17. Had we been concerned solely with thesealliances, it would have been enough to begin the story withthe onset of the war. However, the adoption of chemical-warfare techniques by economic entomology offers an op-portunity to investigate how the integration of techniquesfrom one field into another takes place and how knowledgeis reconfigured in this process. For this purpose, we tracedthe trajectory from nineteenth-century forest zoology to earlytwentieth century forest hygiene modelling social hygiene,and finally to the militarized field of economic entomologyduring and after World War I. We observed the gap thatemerged in about 1900 between ways of seeing insects andways of controlling them. What I have tried to argue is thatthe introduction of chemical warfare into economic entomol-ogy can be seen as a contingent solution to this gap – but asolution that produced problems of another scale entirely.

Tracing the transformation of ‘pests’ into ‘enemy’ shedslight on how the discipline of economic entomology bothshaped and established itself. The emerging field gainedpower by connecting with the larger fields, using such termsas ‘purity’, ‘degeneration’and ‘war’, and by integrating war-fare techniques. These links provided a stronger position thaneither the older forest zoology or insect collectors had held.Furthermore, by linking trees afflicted by forest insects to thefate of the German Kulturwald and of German culture atlarge, economic entomology positioned itself as a service tothe nation and contributed to the redefinition of Germansociety as endangered by agents of degeneration, such as‘pests’.

However, this strategy had unforeseeable implications.It linked insects to groups of people constituted as ‘others’,whether as deviant subjects in social hygiene or as en-emies in warfare, and it developed techniques to extermi-nate human and animal life alike. Although this was not a necessary outcome18, the perspective of this devel-

32 Endeavour Vol. 24(1) 2000

Figure 5 Testing chemical weapons on cats in the field.Reproduced from Ref. 23.

Figure 6 Testing the behaviour of poisonous gases in a forest. Reproduced fromRef. 24.

opment in Germany until 1945 includes the genocide ofJews and other human ‘pests’, killed with the insecticideZyklon B.

Acknowledgement

I thank Abigail Lustig for her comments.

Notes and references1 Ratzeburg, J.T.C. (1837, 1840 and 1844) Die Forst-Insecten

(3 vols), Nicolai2 Le Bon, G. (1895, this edition 1908) Psychologie der

Massen, Klinkhardt3 Escherich, K. (1907) Die elementare Macht der

Fortpflanzung.Beilage Allgemeinen Zeitung München223,401–403; Escherich, K. (1907) Die elementare Macht derFortpflanzung. Beilage Allgemeinen Zeitung München224,411–412

4 Escherich, K. (1913) Ein Vorschlag zur Hebung derForstentomologie.Naturwissenschaftliche Z. Land-Forstwirtschaft 10, 591–594, quote from p. 593

5 On symbols for masses see Canetti, E. (1960, this edition1996) Masse und Macht, Fischer, pp. 87–105, esp. pp. 97–98

6 Moritz, J. (1893) Beobachtungen und Versuche, betreffenddie Reblaus,Phylloxera vastatrixPl., und derenBekaempfung.Arbeiten aus dem KaiserlichenGesundheitsamte8, 507–577; Lüstner, G. (1914)Raeucherungen mit Blausaure gegen die Blutlaus(Schizoneura lanigera Hausmann) und die rote austern-formige Schildlaus (Epidiaspis betulae[Bar] Ldgr.).Deutsche Obstbauzeitung60 (8), 174–176. On Americanexperiences see Escherich, K. (1913) Die AngewandteEntomologie in den Vereinigten Staaten, Parey

7 Anon. (1914) Verhandlungen der Deutschen Gesellschaft fürangewandte Entomologie, 1. Jahresversammlung 1913. Z.Angewandte Entomol.1, 8

8 Hase, A. (1915) Beitraege zu einer Biologie der KleiderlausZ. Angewandte Entomol.2, 265–359; Hase, A. (1915)Praktische Ratschläge für die Entlausung derZivilbevölkerung in Russisch–Polen, Berlin; Hase, A. (1916) Experimentelle Untersuchungen zur Frage derLaeusebekampfung. Z. Hyg. Infektionskrankheiten81,319–378. On different strategies of German and Britisharmies see Weindling, P. (1996) The First World War andthe campaign against lice: comparing British and Germanmeasures. In Die Medizin und der Erste Weltkrieg(Eckart,W. and Gradmann, C., eds), pp. 227–239, Centaurus

9 Confidential memorandum by Fritz Haber, Sept. 18, 1917.Archives of the Max-Planck Society, V. Abt., Rep. 13(Haber), Nr. 1678, 12 pp. Albrecht Hase’s account ofHaber’s efforts is documented in his manuscript Leben von

Prof. Haber,also kept at this archive [V. Abt., Rep. 13(Haber), Nr. 2304]

10 Degussa/Mayer-Wagelin, H. (1973) Aller Anfang ist Schwer.Bilder zur hundertjährigen Geschichte der Degussa1873–1973, pp. 46–48, Degussa

11 Flury, F. and Hase, A. (1920) Blausaeurederivate zurSchadlingsbekampfung. Muenchener Med. Wochenschrift27, 779–780

12 Eckart, W. (1996) ‘Der grösste Versuch, den dieEinbildungskraft ersinnen kann’ – Der Krieg als hygienisch–bakteriologisches Laboratorium undErfahrungsfeld. In Die Medizin und der Erste Weltkrieg(Eckart, W. and Gradmann, C., eds), pp. 299–319,Centaurus

13 Haber, L. (1986) The Poisonous Cloud, Clarendon14 The moths disappeared a year later without any measures

being taken against them15 Escherich, K. (1929) Die Flugzeugbestäubung gegen

Forstschädlinge, Parey16 See also Groehler, O. (1989) Der Lautlose Tod, p. 83,

Rowohlt17 Parts of these wartime connections were described by

O. Groehler [(1989) Der Lautlose Tod, Rowohlt] and by two recent biographers of Fritz Haber:Stoltzenberg, D. (1994) Fritz Haber, pp. 454–467, VCH;Szöllösi-Janze, M. (1998) Fritz Haber, pp. 373–393, Beck.For the USA, similar alliances during WW I aredocumented in Russell, E.P. (1996) ‘Speaking ofannihilation’: mobilizing for war against human and insect enemies, 1914–1945. J. Am. Hist.33,1505–1529

18 Russel (in note 17) shows that during and after WWI,chemical-warfare technology was also integrated intoeconomic entomology in the USA and, during World War II,Japanese soldiers were portrayed as insects. This techniqueof dehumanizing enemy soldiers and thus lowering thethreshold of killing in warfare was not extended tomurdering Japanese civilians in concentration camps

19 Escherich, K. (1913) Fortschritte der Leimtechnik. InTharandter forstliches Jahrbuch(Vol. 64), p. 81

20 Escherich, K. (1913) Die Angewandte Entomologie in denUSA, p.135, Parey

21 Frickhinger, H.W. (1918) Die Mehlmotte, Verlag Natur undKultur, p. 39, Verlag Natur und Kultur

22 Archive of the History of the Max-Planck Society,Berlin–Dahlem, WWI No. 35

23 Archive of the History of the Max-Planck Society,Berlin–Dahlem, WWI No. 2

24 Archive of the History of the Max-Planck Society,Berlin–Dahlem, KWI f. physik. Chemie/Elektrochemie 9/VI

25 Bundesarchiv Berlin R 3602/16226 Jansen, S. (1999) Der ‘kranke deutsche Wald’: Krankheit

Endeavour Vol. 24(1) 2000 33

Figure 7 Aerial and chemical warfare in 1925. Reproduced from Ref. 25.