Guerin, Patrick

2012, Gurba, A., Harraca, V., Perret, J. L., Casera, S., Donnet, S., Guerin, Patrick

Tsetse flies Glossina spp. (Diptera; Glossinidae) are blood-feeding vectors of disease that are attracted to vertebrate hosts by odours and visual cues. Studies on how tsetse flies approach visual devices are of fundamental interest because they can help in the development of more efficient control tools. The responses of a forest tsetse fly species Glossina brevipalpis (Newstead) to human breath are tested in a wind tunnel in the presence or absence of a blue sphere as a visual target. The flight responses are video recorded with two motion-sensitive cameras and characterized in three dimensions. Although flies make meandering upwind flights predominantly in the horizontal plane in the plume of breath alone, upwind flights are highly directed at the visual target presented in the plume of breath. Flies responding to the visual target fly from take-off within stricter flight limits at lower ground speeds and with a significantly lower variance in flight trajectories in the horizontal plane. Once at the target, flies fly in loops principally in the horizontal plane within 40 cm of the blue sphere before descending in spirals beneath it. Successful field traps designed for G. brevipalpis take into account the strong horizontal component in local search behaviour by this species at objects. The results suggest that trapping devices should also take into account the propensity of G. brevipalpis to descend to the lower parts of visual targets.

2009, Becher, P. G., Guerin, Patrick

Larvae of the grapevine moth Lobesia botrana (Lepidoptera: Tortricidae) are a major pest of vine, Vitis vinifera. As larvae have limited energy reserves and are in danger of desiccation and predation an efficient response to plant volatiles that would guide them to food and shelter could be expected. The responses of starved 2nd or 3rd instar larvae to volatile emissions from their artificial diet and to single host plant volatiles were recorded on a locomotion compensator. Test products were added to an air stream passing over the 30 cm diameter servosphere. The larvae showed non-directed walks of low rectitude in the air stream alone but changed to goal-oriented upwind displacement characterised by relatively straight tracks when the odour of the artificial diet and vapours of methyl salicylate, 1-hexanol, (Z)-3-hexen-1-ol, terpinen-4-ol, 1-octen-3-ol, (E)-4,8-dimethyl-1,3,7-nonatriene and (Z)-3-hexenyl acetate were added to the air stream. This chemoanemotactic targeted displacement illustrates appetence for certain volatile cues from food by starved Lobesia larvae. Analysis of the larval behaviour indicates dose dependent responses to some of the host plant volatiles tested with a response to methyl salicylate already visible at 1 ng, the lowest source dose tested. These behavioural responses show that Lobesia larvae can efficiently locate mixtures of volatile products released by food sources as well as single volatile constituents of their host plants. Such goal-oriented responses with shorter travel time and reduced energy loss are probably of importance for larval survival as it decreases the time they are exposed to biotic and abiotic hazards. (C) 2009 Elsevier Ltd. All rights reserved.

2001, Guerenstein, Pablo G., Guerin, Patrick

Olfactory receptors in basiconic and grooved-peg sensilla on the antenna of fifth-instar Triatoma infestans nymphs respond to host odours. Gas chromatography analyses of host odour extracts coupled to electrophysiological recordings from basiconic sensillum receptors indicate that nonanal is a constituent of sheep wool and chicken feather odour that stimulates one of the receptors in this type of sensillum. Similar analyses revealed isobutyric acid in rabbit odour to be a chemostimulant for one of the receptors in grooved-peg sensilla. The response of the aldehyde receptor was higher to heptanal, octanal and nonanal than to other aliphatic aldehydes, and the response of the acid receptor was higher to isobutyric acid than to other short-chain branched and unbranched acids. The behavioural responses of fifth-instar T. infestans nymphs to nonanal and isobutyric acid in an air-stream on a servosphere indicate that, whereas nonanal causes activation of the bugs, isobutyric acid induces an increase in upwind displacement, i.e. odour-conditioned anemotaxis. Binary mixtures of these compounds did not improve the attraction obtained with isobutyric acid alone. A comparison of the behavioural and electrophysiological responses of the bugs to different amounts of isobutyric acid in air suggests that attraction is obtained at concentrations that causes low-to-moderate increases in the firing rate of the acid-excited receptor in the grooved-peg sensilla, whereas at a dose that evokes relatively high firing rates (>40 Hz) no attraction is obtained.

1999, McMahon, Conor, Guerin, Patrick, Kazimirova, M, Labuda, M, Nuttall, Patricia

The responses of Amblyomma variegatum adults to constituents of their aggregation-attraction pheromone presented in an air stream were studied using a locomotion compensator. Behaviours to vapours from two mixtures were compared, the first a 1:1 mixture of o-nitrophenol and methyl salicylate, the second a four component mixture (R) containing o-nitrophenol, methyl salicylate, 2,6 dichlorophenol and phenyl acetaldehyde in the ratio 10:10:2:1, respectively No difference was found between the kineses responses ofA. variegatum adults for either mixture: both elicited an increase in angular velocity and a reduction in speed, Moreover; attraction to vapours of either mixture was reduced significantly as the source dose was increased: both mixtures were good attractants at a source dose of 10 mug of the main components, but were not attractive at source doses 100 times higher. As with many other arthropods, A. variegatum adults are responsive to the ratio, as well as to the dose, of constituents in an attractant mix. We suggest that the quantity and ratios of compounds in attractive mixtures released from commercial dispensers should be measured before use in any control programme.

2012, Schmera, D., Guerin, Patrick

BACKGROUND: The codling moth is the most serious pest of deciduous tree fruit (apples, pears, crabapples, walnuts, quince) worldwide. The high frequency of insecticide treatments per season has resulted in breakdown of codling moth control owing to insecticide resistance. As an alternative, integrated pest management includes mating disruption to achieve population suppression in orchards. Under this scheme, the sex pheromone of the codling moth, (E, E)-8,10-dodecadien-1-ol (codlemone), is released from dispensers in crops to hinder mating by luring males. Increasing the attractiveness of codlemone formulations to codling moth males can be regarded as a key to increasing the efficacy of mating disruption. With this aim, the effects of adding plant volatiles on the behavioural responses of codling moth males to codlemone were tested. RESULTS: Adding R(+)-limonene, linalool, (E)-beta-farnesene or ethyl (E, Z)-2,4-decadienoate to codlemone significantly increases the proportion of males flying to the pheromone source in a wind tunnel. The response level is equivalent to that of males responding to females releasing codlemone. Using real-time recordings, it is shown how these four plant products also shorten the response time of males to codlemone under the behavioural criteria time to activation, time till upwind flight is induced and time to pheromone source contact. CONCLUSION: Shortening the response time and increasing source location by males of dispensers releasing codlemone with R(+)-limonene, linalool, (E)-beta-farnesene or ethyl (E, Z)-2,4-decadienoate added would enhance mating disruption through better engagement ofmales with dispensers, to the detriment of females. (C) 2011 Society of Chemical Industry

2004, Otalora-Luna, F., Perret, J. L., Guerin, Patrick

A combination of 1,000 ppm CO2 plus 30-40 ppb NH3 in an air stream induced Rhodnius prolixus nymphs walking on a servosphere to perform a series of appetence behaviours. Shortly after the onset of stimulation the nymphs turned sharply upwind towards the source of the chemostimuli (within 13 +/- 9 s) from mostly downwind and crosswind walks in the air stream alone. The mean vector angles of these upwind tracks were concentrated in a cone 60degrees either side of due upwind. The upwind walking bugs stopped more frequently but for a shorter duration and walked at a higher speed than before stimulation. During stops in the presence of the chemostimuli the bugs frequently corrected their course angles and extended their forelegs to reach higher with their antennae in the air. In the air stream alone R. prolixus nymphs frequently sampled the sphere surface with the antennae and cleaned their antennae with the foreleg tarsi. However, the nymphs only briefly tapped the left or right antennal flagellum on the corresponding first leg tarsus and never touched the servosphere surface in the presence of the chemostimuli. After chemostimulus removal from the air stream the bugs continued to respond with the same appetence responses as during stimulation, but walked more tortuously in a crosswind direction in an effort to regain contact with the chemostimuli.

2000, McMahon, Conor, Guerin, Patrick

Male Amblyomma variegatum ticks feeding on a host release a mixture of o-nitrophenol and methyl salicylate which serves to attract conspecifics. The behavioural responses of A. variegatum on a servosphere to these volatiles presented in an air stream are detailed hers. In still air, ticks walked on all eight legs, but with long halts. In contrast, the air stream caused continuous walking and induced a reaching response where the forelegs actively sampled the air. Such reaching increased the angular velocity and reduced walking speed, effects that were amplified in the presence of vapours from o-nitrophenol and methyl salicylate in the air flowing over the ticks. Vapour from a 1:1 mixture of o-nitrophenol and methyl salicylate was attractive over a 10(4)-fold concentration range providing an increase in upwind displacement of 20-40%, significantly higher than the natural ratio where o-nitrophenol vapour predominates. Although the responses to o-nitrophenol vapour were variable when presented alone, this chemical was consistently attractive when delivered with steer hair odour - unattractive on its own. Moreover, the upwind walk to this combination did not cause a change in speed or angular velocity. This supports the hypothesis that the response to the pheromone is enhanced by host odour.

2012, Joris, Caroline, Guerin, Patrick

Les glossines (Diptera, Glossinidae) constituent 31 espèces et sous-espèces réparties en trois sous-genres. Elles sont actuellement limitées à l’Afrique sub-saharienne et préfèrent trois habitats: la savane, les zones riveraines et la forêt. Les deux sexes sont strictement hématophages et peuvent transmettre la trypanosomiase au cours de leur repas de sang qui provoque la maladie du sommeil chez les humains et le nagana chez des animaux. Environ 60 millions de personnes et 50 millions de bovins dans 20 pays africains risquent continuellement l’infection, ce qui provoque des pertes économiques énormes.
Les mouches tsé-tsé détectent les hôtes à proximité à l’aide de repères visuels, dont le contraste, la forme et la couleur, et de signaux olfactifs à distance. Comme elles sont ovovivipares, la dynamique de population des mouches tsé-tsé est caractérisée par un taux de croissance faible. Des pièges et cibles appâtés peuvent ainsi épuiser une population en quelques années seulement. Les stimulants olfactifs principalement utilisés dans les pièges sur le terrain contre les mouches tsé-tsé sont l’1-octène-3-ol, le 3-n-propylephénol, le p-crésol et de l’acétone.
Les plantes fournissent aux mouches tsé-tsé non seulement habitat et refuge, mais en plus elles offrent des endroits protégés du soleil pour la larviposition aux femelles. La faculté naturelle des mouches pour trouver une couverture adaptée sous la végétation n’a attiré que peu d’attention. Tenant compte du rôle des sites de repos péridomestiques, il est important de considérer les produits chimiques volatils dérivés de plantes pour le développement de nouveaux pièges appâtés pour attirer toutes les tsé-tsé des 3 sous-genres. Il est possible que les mouches tsé-tsé font un usage parcimonieux de chimiostimuli (par exemple 1-octène-3-ol qui est présent dans les odeurs d’hôte autant que les substances volatiles de plantes) pour trouver hôte ou abris sous les plantes.
En utilisant l’electroantennographie, les réponses sensorielles aux produits volatils couramment trouvés dans les plantes ainsi qu’aux odeurs d’hôtes ont été enregistrées chez des mouches tsé-tsé des trois habitats africains. Les produits comprennent des monoterpènes, des sesquiterpènes et des C6-alcohols et aldehydes (GLVs). Nous avons démontré que les espèces de glossines des trois habitats africains perçoivent les composants végétaux volatils d’une manière similaire, dont plusieurs à des seuils de détection similaires à l’1-octène-3-ol. Pour les études comportementales, la L-térébenthine est particulièrement interéssante, car il s’agit d’un mélange de terpènes simples avec un seuil de détection bas, avec le limonène et l’α-pinène comme composants principaux, accompagnés de monoterpène ocimène et d’aromatiques p-cymène. La L-térébenthine est relativement facile à obtenir, peu coûteuse et peut être produite directement en Afrique.
Les mouches tsé-tsé ayant un vol rapide, nous avons filmé les réactions des G. pallidipes, G. brevipalpis et G. swynnertoni dans une soufflerie en utilisant un système d’enregistrement 3D. En combinant l’effet de sensibilisation du CO₂ avec les composés d’essai, nous avons pu augmenter le nombre de mouches activées par dix et donc détecter des différences dans les réponses comportementales des mouches tsé-tsé aux traitements. Nos résultats montrent que les mouches tsé-tsé répondent à une série de composants végétaux simples et à leurs mélanges. Les composants de plantes individuels avec le meilleur potentiel d’activation parmi les composants testés étaient le S-(-)-limonène et le p-cymène. Les meilleurs résultats ont été obtenus avec un mélange monoterpène comprenant la L-térébenthine montrant un très bon effet activateur sur G. pallidipes, G. swynnertoni et G. brevipalpis induisant également beaucoup de mouches à effectuer une recherche locale à l’extrémité de la chambre de vol. À la dose optimale testée (10 μg /min), la L-térébenthine était comparable à l’haleine humaine en termes d’activation et d’induction de comportement de recherche locale par G. pallidipes et G. swynnertoni. Dans notre étude, nous n’avons constaté aucune différence entre les réactions comportementales des mâles et des femelles G. pallidipes à l’haleine humaine, le CO₂ présenté seul et au l’1-octène-3-ol, des produits généralement associés à des hôtes, mais nous pouvions détecter des différences entre les réactions comportementales des mâles et des femelles à des composants volatils de plantes (limonène, le p-cymène et L-térébenthine). Comme les G. brevipalpis sur le part de pondre répondaient seulement à la L-térébenthine mais pas à l’haleine humaine on pourrait spéculer que les composants volatils de plantes non seulement transportent des informations sur les hôtes, mais indiquent aussi des sites de larviposition ou de repos, qui sont d’une importance plus grande pour les femelles en raison de leur plus grands besoins énergétiques en vol comparé aux mâles.
Pour évaluer si les composants volatils de plantes pouvaient être utiles sur le terrain, à savoir accroître l’attractivité des pièges ou des cibles, nous avons testé si les composants de plantes attiraient les mouches tsé-tsé vers une cible visuelle et nous avons donc introduit une sphère bleue phthalogène dans la soufflerie pour tester à la fois des stimuli visuels et olfactifs. Nous avons montré que la L-térébenthine en présence de CO₂ augmente le temps et la distance passés en vol autour d’une cible et affecte également la hauteur relative de vol vers la cible et lors de la recherche locale autour d’elle. En présence de L-térébenthine, le vol vers la cible a été plus orienté qu’ avec le CO₂ seul et la recherche locale a eu lieu à une plus faible altitude.
Les résultats présentés dans cette thèse montrent que les mouches tsé-tsé non seulement perçoivent des composants volatils de plantes, mais que ces vecteurs de maladie, en particulier les femelles, sont attirés par les terpènes et les mélanges de terpènes simples présentés avec et sans cible visuelle à des concentrations de 1000 à 10’000 fois inférieures au niveau de CO₂ naturel. De manière générale, ce travail suggère que les composants volatils de plantes sont prometteurs quant é leur intégration dans les techniques de contrôles sémiochimiques pour les mouches tsé-tsé., Tsetse flies (Diptera, Glossinidae) constitute 31 species and subspecies divided into three subgenera. They are currently confined in sub-Saharan Africa and occupy three preferred habitats: savannah, riverine zones and forest. Both sexes are strictly haematophagous and can transmit during their blood meal trypanosomiasis which causes sleeping sickness in humans and Nagana in animals. It is estimated that about 60 million people and 50 million cattle are continuously at risk in 20 African countries resulting in enormous economic losses.
Tsetse flies locate hosts using visual cues including contrast, shape and colour at short range, and olfactory cues at a distance. Tsetse fly population dynamic is characterised by a slow intrinsic growth rate as they are ovoviviparous, so visual baited traps and targets can deplete a population in only a few years. The major olfactory stimulants used in field traps to control tsetse flies are 1-octen-3-ol, 3-n-propylphenol, p-cresol and acetone.
Plants not only provide the habitat and shelter for tsetse flies but also provide females with sunlight-protected places for larviposition. Little attention has been paid to the flies’ propensity for finding suitable cover under vegetation. Keeping in mind the role of peridomestic resting sites, it is important to consider volatile chemicals derived from plants for the development of new odour-baited traps to attract tsetse from all 3 subgenera. It is possible that the tsetse flies make parsimonious use of chemostimuli (e.g. 1-octen-3-ol present in both host odours and plant volatiles) for host finding and shelter under plants.
Sensory responses of tsetse flies from all three African habitats to volatile products commonly found in plants as well as host odours were recorded using the electroantennogram techniques. Products included monoterpenes, sesquiterpenes and green-leaf volatiles. We have shown, that tsetse species from all three African habitats perceive volatile plant compounds in a similar manner, several at detection thresholds similar to 1-octen-3-ol. Of main interest for behavioural studies is L-turpentine, as it is a simple terpene mixture with a low detection threshold, with limonene and α-pinene as main components , along with the monoterpene ocimene and aromatic p-cymene, and it is relatively easily obtained, inexpensive and can be produced directly in Africa.
Tsetse flies are fast flyers, so we filmed the responses of G. pallidipes, G. brevipalpis and G. swynnertoni in the wind tunnel using a 3D recording system. By combining the sensitising effect of CO₂ with the test compounds we were able to increase the number of activated flies by tenfold and were therefore able to detect differences in the behavioural responses of tsetse flies to treatments. Our results show that tsetse flies respond to a series of single plant compounds and their mixtures. The single plant compounds tested with the best activation potential were S-(-)-limonene and p-cymene. The best results were achieved with the monoterpene mixture comprising L-turpentine showing a very good activating effect on G. pallidipes, G. swynnertoni and G. brevipalpis and also inducing many flies to perform a local search at the upwind end of the wind tunnel. At the optimal dose tested (10μg/min) L-turpentine was comparable to human breath in terms of activating and inducing local search behaviour by G. pallidipes and G. swynnertoni. In our study we found no differences in behavioural responses of male and female G. pallidipes to human breath, CO₂ alone and 1-octen-3-ol, products usually associated with hosts, but we could detect differences in behavioural responses of males and females to volatile plant compounds (limonene, p-cymene and L-turpentine). As pregnant G. brevipalpis responded only to L-turpentine but not human breath one could speculate that volatile plant compounds not only carry information about hosts, but also indicate larviposition or resting sites, both of which are of greater importance for females due to the higher energy demands of flying than for males.
To assess whether volatile plant compounds could be of use in the flied, i.e. increasing trap and target encounters, we tested if plant compounds attract tsetse flies to a target and therefore introduced a phthalogen blue sphere into the wind tunnel to test combined visual and olfactory stimuli. We showed that L-turpentine in the presence of CO₂ increases the time and distance spent flying around a target and also affects the relative hight of flight to the target and of the local search at the target. With L-turpentine presented, flight to the target was more directed than with CO₂ alone and the local search around the sphere was lower in elevation.
The results presented in this thesis show that tsetse flies not only perceive volatile plant compounds, but that these vectors of disease, especially females, are attracted by terpenes and simple terpene mixtures presented with and without a visual target at amounts 1000 to 10’000 times lower than background CO₂ levels. Overall this work suggests that volatile plant compounds hold promise for integration into semiochemicalbased control techniques for tsetse flies., Tsetse-Fliegen (Diptera, Glossinidae) unterteilen sich in 31 Arten und Unterarten, welche in drei Untergattungen eingeteilt werden. Ihre Verbreitung ist zur Zeit auf ein Gebiet südlich der Sahara begrenzt, wo sie drei bevorzugte Habitate besiedeln: Savanne, Uferzonen von Flüssen und Seen sowie Waldregionen. Beide Geschlechter sind rein haematophag und können während ihrer Blutmahlzeit Trypanosomen übertragen, welche bei Menschen die Schlafkrankheit und bei Tieren Nagana auslösen. Geschätzte 60 Millionen Menschen und 50 Millionen Tiere sind in den 20 betroffenen afrikanischen Ländern ständig in Infektionsgefahr, was zu enormen ökonomischen Verlusten führt.
Auf kurze Distanz finden Tsetse-Fliegen ihre Wirte durch visuelle Signale wie Kontrast, Form und Farbe und auf längere Distanz durch olfaktorische Stimuli. Bedingt durch ihren Ovoviviparismus ist die Populationsdynamik der Tsetse-Fliegen durch ein langsames intrinsisches Wachstum charakterisiert, wodurch Kontrollmassnahmen eine Population in wenigen Jahren auslöschen können. Die wichtigsten in Fallen verwendeten Köder sind 1-Octen-3-ol, 3-n-Propylphenol, p-Cresol und Aceton.
Pflanzen stellen nicht nur die Lebensräume und Verstecke für die Tsetse-Fliegen, sondern dienen den Weibchen auch als sonnengeschützte Ablageplätze für ihre Larven. Bisher wurde der Fähigkeit der Fliegen Unterschlüpfe unter der Vegatation zu finden, wenig Beachtung entgegengebracht. Berücksichtigt man die Rolle der hausnahen Ruheplätze, müssen flüchtige Pflanzenstoffe für die Entwicklung neuer Köder zum Anlocken der Tsetse-Arten aus allen drei Untergattungen betrachtet werden. Möglicherweise erlaubt die sparsame Benutzung von Chemostimuli (wie z. B. 1-Octen-3-ol, welches Bestandteil von Wirt- und Pflanzendüften ist) den Tsetse-Fliegen Wirte wie auch Verstecke unter Pflanzen zu finden.
Anhand von Elektroantennogrammen wurden die sensoriellen Antworten auf flüchtige Produkte, welche üblicherweise in Pflanzen und Wirten vorhanden sind, bei Tsetse- Fliegen aus allen drei Habitatstypen gemessen. Zu den Produkten gehörten Monoterpene, Sesquiterpene und Grün-Blattduftstoffe (GLVs). Wir konnten zeigen, dass Tsetse- Arten aus allen afrikanischen Habitaten flüchtige Pflanzenstoffe in ähnlicherWeise wahrnehmen. Einige dieser Produkte weisen eine ähnlich tiefe Detektionsschwelle auf wie 1-Octen-3-ol. Von speziellem Interesse für die Verhaltensstudien ist L-Terpentin, eine einfache Mischung aus Terpenen mit einer niedrigen Detektionsschwelle. Seine Hauptbestandteile sind Limonen und α-Pinen mit dem Monoterpen Ocimen und dem Aromaten p-Cymen. Zu seinen Vorteilen gehört, dass es relativ einfach und günstig direkt in Afrika produziert werden kann.
Da Tsetse-Fliegen sehr schnelle Flieger sind, filmten wir das Verhalten von G. pallidipes, G. brevipalpis und G. swynnertoni mit einem 3D-Aufnahmeverfahren in einem Windkanal. Indem wir den Sensibilisierungseffekt von CO₂ mit den Testprodukten kombinierten, konnten wir die Anzahl der aktivierten Fliegen um ein zehnfaches erhöhen, und so Unterschiede in ihrem Verhalten auf Behandlungen feststellen. Unsere Resultate zeigen, dass Tsetse-Fliegen auf eine Reihe von flüchtigen Pflanzenstoffen sowie ihren Mischungen reagieren. Die einfachen Pflanzenprokdukte mit dem grössten Aktivierungspotential waren S-(-)-Limonen und p-Cymen. Die besten Resultate in Bezug auf Aktivierung, Flug- und Suchverhalten am Ende desWindkanals von G. pallidipes, G. brevipalpis und G. swynnertoni wurden mit der Monoterpenmischung L-Terpentin erhalten. Die Wirkung von L-Terpentin in seiner optimalen getesteten Dosis (10μg /min) war in Bezug auf sein Aktivierungspotential und als Auslöser des Suchverhaltens am Ende des Windkanals von G. pallidipes und G. swynnertoni vergleichbar mit der Wirkung menschlichen Atems.
In unserer Untersuchung wurden keine Unterschiede im Verhalten von männlichen und weiblichen Fliegen bei menschlichem Atem, CO₂ und 1-Octen-3-ol, also Produkten, die normalerweise mit denWirten in Verbindung gebracht werden, festgestellt. Jedoch konnten Unterschiede in ihrem Verhalten zu flüchtigen Pflanzenstoffen (Limonen, p-Cymen und L-Terpentin) festgestellt werden. Da tragende G. brevipalpis auf L-Terpentin, nicht jedoch auf menschlichen Atem reagierten, könnte spekuliert werden, dass flüchtige Pflanzenstoffe nicht nur Informationen zu Wirten, sondern auch zu Larvablege- und Ruheplätzen tragen. Diese beiden Informationen sind für tragende Weibchen aufgrund ihres grösseren Energieverbrauchs beim Fliegen von grösserer Bedeutung als für Männchen.
Zum evaluieren, ob flüchtige Pflanzenstoffe im Feld von Nutze sein könnten, z. B. zum Erhöhen der Attraktivität der Fallen, testeten wir, ob diese Pflanzenprodukte die Fliegen zusätzlich zu einem visuellen Signal anziehen könnten. Dazu führten wir eine enzianblaue Kugel in den Windkanal ein und konnten so die Kombination von visuellen und olfaktorischen Stimuli testen. Wir konnten zeigen, dass L-Terpentin in Kombination mit CO₂ nicht nur die Zeit und die Flugdistanz vergrösserten, die die Fliegen um die Kugel herum verbrachten, sondern auch die relative Flughöhe und die Höhe des Suchverhaltens um die Kugel herum beeinflussten. Im Beisein vom L-Terpentin waren die Flüge und die Höhe des Suchverhaltens, verglichen mit CO₂ alleine, tiefer.
Die Resultate dieser Doktorarbeit zeigen, dass Tsetse-Fliegen nicht nur flüchtige Pflanzenstoffe wahrnehmen, sondern dass insbesondere die Weibchen, von Terpenen und einfachen Terpenmischungen angezogen werden, und dies sowohl im Beisein von visuellen Stimuli wie auch ohne. Sie reagieren auf diese Stoffe schon in Mengen, die 1000 bis 10’000 mal kleiner sind als die natürlichen CO₂ -Mengen. Schliesslich zeigt diese Arbeit eine Möglichkeit zur Integration der flüchtigen Pflanzenstoffe in die bestehenden Tsetse-Kontrolltechniken auf.

2003, Perret, Jean-Luc, Guerin, Patrick, Diehl, Peter-Allan, Vlimant, Michèle, Gern, Lise

The behaviour of Ixodes ricinus nymphs was recorded in 10-day experiments using computer-assisted video-tracking, in the absence of any host stimuli. These ticks switch spontaneously from questing in a desiccating atmosphere to quiescence in a water-saturated atmosphere after dark. Quantification of both questing and quiescence duration demonstrates that questing duration is inversely related to saturation deficit whereas quiescence duration is not. Distance walked after quiescence increased with desiccating conditions, while the distance walked after questing remained unchanged. Almost all locomotor activities of I. ricinus occurred during darkness under either a 14 h:10 h L:D or a 8 h:4 h L:D cycle. We established that all life stages of I. ricinus are equipped to sense shifts in light intensity with bilaterally placed strings of photoreceptors. This permits I. ricinus to use onset of darkness to trigger mobility when desiccation risk is reduced in nature.

2000, McMahon, Conor, Guerin, Patrick

The responses of A. variegatum adults to constituents ot 'their aggregation-attraction pheromone presented in an air stream were studied using a locomotion compensator. The responses to vapours from two mixtures were compared, the first a 1:1 mixture of o-nitrophenol and methyl salicylale, the second a four component mixture ® containing o-nitrophenol, methyl salicylale, 2,6 dichlorophenol and phenyl acetaldehyde in the ratio 10:10:2:1, respectively. No difference was found between the kineses responses of A. variegatum adults for either mixture: both elicited an increase in angular velocity and a reduction in speed. Moreover, attraction to vapours of either mixture was reduced significantly as the source dose was increased: both mixtures were good attractants at a source dose of 10 μg of the main components, but were not attractive at source doses 100 times higher. As with many other arthropods, A. variegatum adults arc responsive to the ratio, as well as to the dose, of constituents in an attractant mix. We suggest that the quantity and ratios of compounds in attractive mixtures released from commercial dispensers should be measured before use in any control programme.