Dissertations / Theses on the topic 'Insect reproductive behaviour'

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Insect hosts that have been already parasitized are considered a low quality resource, which may affect the number of ovipositions made by other parasitoids. Since the amount of eggs laid affects the host immune response, the offspring survivorship may also be affected. For this reason, it is necessary to understand to what point the energy spent in superparasitizing is an advantage that allows supression of host immune response and provides adequate resources for the imatures to develop within their host. This study had the objective of finding the number of ovipositions from Palmistichus elaeisis (Hymenoptera: Eulophidae) allowing optimal offspring fitness and to analyze if immune response the melonworm Diaphania hyalinata L. (Lepidoptera: Crambidae) is correlated with the density of posture by the parasitoid. Pupae of D. hyalinata received from one to five parasitoid ovipositions. The total number of offspring produced, the number of males and females emerging from the host, sex ratio, life cycle, average body mass and biomass produced per parasitized pupae were recorded for the different oviposition densities. Digital x-ray imaging of parasitized hosts were recorded to assessing the immature parasitoid developmental until adult emergence. Incidence of unviable parasitoid larvae was also recorded. The survivorship of P. elaeisis was daily assessed. Hemocyte dynamics and encapsulation capacity of D. hyalinata against P. elaeisis was evaluated for each number of ovipositions, from one to five. The Parasitoid developmental time decreased with increased oviposition density and three ovipositions provided higher offspring and particularly female production, and optimal larval fitness. Progeny body mass and sex ration were not affected by oviposition density. Female and male survived longer with one oviposition of the female parasitoid. Parasitoid emergence increased with the number of parasitoid ovipositions and 100% parasitism and corresponding 100% host pupa mortality were achieved with all oviposition densities. Increased number of ovipositions decreased the number of total hemocytes, and also of granulocytes, plasmatocytes and prohemocytes in the circulating host hemolymph. Oenocytes and espherulocytes were not affect by the number of parasitoid ovipositions in the host. The melanization and encapsulation rates decreased with the number of ovipositions by P. elaeisis. Three ovipositions by the parasitoid female allowed optimal progeny production and parasitoid performance. Superparasitism is a strategy of P. elaeisis for optimal progeny fitness balancing optimal progeny performance with amelioration of host immune response.
Hospedeiros parasitados são considerados de baixa qualidade e podem influenciar no número de oviposições de parasitoides, influenciando na sobrevivência da progênie, pois, a quantidade de ovos depositados afeta a resposta imune do hospedeiro. Por isso, torna-se necessário saber até quando o investimento de superparasitar é vantajoso ao ponto de suprimir a resposta imune do hospedeiro e favorecer uma ótima competição de imaturos dentro do hospedeiro. O objetivo desta pesquisa foi reconhecer a densidade ótima de posturas de Palmistichus elaeisis (Hymenoptera: Eulophidae) para produção de progênie, e saber se a resposta imune do hospedeiro Diaphania hyalinata L. (Lepidoptera: Crambidae) ao parasitismo se relaciona a esta densidade ótima. Pupas de D. hyalinata foram expostas a uma, duas, três, quatro e cinco posturas por uma mesma fêmea do parasitoide. O número total de progênies, de machos e fêmeas emergidos, razão sexual, ciclo de vida, peso médio e biomassa produzida foram analisados. A velocidade de pupação, tempo entre pupa e emergência de P. elaeisis e a porcentagem de pupas com imaturos inviáveis deste parasitoide foram observados em pupa de D. hyalinata em sistema de radiografia digital. A sobrevivência de adultos de P. elaeisis foi avaliada diariamente. A porcentagem de emergência da progênie foi avaliada. A dinâmica hemocitária e a capacidade de encapsulação por pupas de D. hyalinata contra P. elaeisis foi avaliada mediante o número de posturas. Larvas de P. elaeisis empuparam mais rápido e o tempo entre o período de pupa e a emergência foi praticamente constante com três oviposições, variando para os demais tratamentos. Três oviposições proporcionou o maior número de fêmeas, total de emergidos e desempenho e, menor tempo de desenvolvimento dos parasitoides. O peso da progênie e a razão sexual foram semelhantes entre os indivíduos. Fêmeas e machos de pupas com uma oviposição sobreviveram mais que os demais tratamentos. A porcentagem de emergência de parasitoides aumentou com o número de posturas. O parasitismo foi de 100% em todos os tratamentos. Pupas com quatro e cinco oviposições não tiveram larvas inviáveis. O aumento do número de posturas reduziu o número de hemócitos totais e de granulócitos, plasmatócitos e prohemócitos circulantes na hemolinfa de pupas de D. hyalinata. Oenocitóides e esferulócitos circulantes mostraram padrão aleatório entre os tratamentos. A taxa de encapsulamento e de melanização decresceram com o aumento de oviposições de P. elaeisis. A oviposição por três vezes maximizou a progênie, reduziu o tempo de desenvolvimento e aumentou o desempenho de P. elaeisis. O superparasitismo é uma estratatégia em P. elaeisis para o aumento de sobrevivência e desempenho da prole.

Parmi les modes de communication les plus exploités chez les insectes, la communication chimique figure en bonne place. D’ailleurs, la recherche moderne consacrée aux signaux chimiques émis et perçus par les individus d’une même espèce n’a de cesse de se développer depuis plus de 50 ans. A travers ce travail de thèse, nous nous sommes intéressés à ces phéromones associées au comportement sexuel de Gastrophysa viridula (Coleoptera :Chrysomelidae). Nous avons menés, dans ce cadre, plusieurs bioessais comportementaux liés pour la plupart à des analyses chimiques par chromatographie gazeuse couplée à une spectrométrie de masse (GC-MS).

La fonction la plus évidente de la phéromone sexuelle de G. viridula est l’induction du comportement sexuel mâle. Cet « aphrodisiaque », probablement constitué de plusieurs composés cuticulaires (des alcanes méthylés lourds), est émis par la femelle et déclenche par contact la sortie de l’édéage des mâles. Etonnamment, ces composés se retrouvent aussi chez les mâles de G. viridula dont le comportement sexuel est alors induit au contact de composés cuticulaires mâles. Ceci constituerait la cause proximale des comportements homosexuels observés chez les mâles de G. viridula. Nous avons ensuite étudié le rôle des composés cuticulaires dans l’isolement sexuel entre G. viridula et G. cyanea. Le comportement sexuel des mâles des deux espèces est en effet induit préférentiellement par les femelles conspécifiques. Pour G. viridula, cette préférence est visiblement attribuable aux composés cuticulaires. Enfin, les signaux chimiques sont parfois indicateurs du degré de compétition spermatique rencontré par un mâle et permettent à celui-ci d’ajuster la quantité de spermatozoïdes transmis à une femelle. Avant d’étudier l’implication de tels signaux chez G. viridula, nous avons souhaité mettre en évidence un ajustement de la quantité de spermatozoïdes transmis par des mâles soumis à divers degrés de compétition spermatique. Nos résultats ne nous permettent malheureusement pas de signaler un tel effet.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Thesis (Ph. D.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 31, 2008) Vita. Includes bibliographical references.

L’abondance des insectes phytophages est déterminée par l’influence de facteurs biotiques et abiotiques qui affectent leurs traits d’histoire de vie. Chez les espèces phytophages à reproduction sur capital, la qualité de la plante hôte sur laquelle les individus effectuent leur développement larvaire est un facteur critique affectant le succès reproducteur des adultes. Curieusement, si l’effet de la plante hôte sur le potentiel reproductif des femelles a été largement décrit, il n’a été que peu étudié sur celui des mâles. Par ailleurs, chez les lépidoptères, lors de l’accouplement, la femelle reçoit du mâle un cadeau nuptial sous la forme d’un spermatophore contenant des spermatozoïdes ainsi que des sécrétions produites par les glandes accessoires. Ces sécrétions constituent des bénéfices directs pour la femelle qui pourra les remobiliser pour augmenter sa fécondité. Mon projet de thèse vise à déterminer l’influence de la plante hôte sur les performances reproductives des mâles et d’en évaluer les conséquences sur le potentiel reproductif des femelles et sur l’évolution des stratégies de choix de partenaire chez un papillon ravageur de la vigne, l’Eudémis (Lobesia botrana). Les expériences menées au cours de ces trois années de thèse révèlent que la nutrition larvaire sur différents cépages de vigne module fortement les réserves énergétiques des mâles, affectant leur potentiel reproductif à travers la taille et le contenu des spermatophores qu’ils transfèrent aux femelles pendant l’accouplement. De plus, l’investissement du mâle dans la production de spermatophores décline au cours d’accouplements successifs, les mâles n’étant capables de produire qu’un seul spermatophore riche en nutriments au cours de leur vie. Ces deux facteurs (nutrition larvaire et expérience sexuelle), qui affectent fortement la qualité reproductive des mâles, ont d’importantes conséquences sur le potentiel reproductif de leur partenaire. En effet, les femelles recevant des spermatophores riches en nutriments et en spermatozoïdes ont plus de descendants que celles recevant des spermatophores de moins bonne qualité. Enfin, les femelles semblent capables de discriminer parmi les mâles en se basant sur des critères reflétant leur qualité reproductive, s’accouplant préférentiellement avec ceux leur procurant le plus de bénéfices directs. Ainsi, les résultats de cette thèse confirment l’importance d’intégrer l’effet mâle quand on s’intéresse à l’évolution des populations de phytophages. De plus, identifier les facteurs écologiques modulant les interactions entre les partenaires sexuels chez les espèces menaçant les cultures est crucial pour pouvoir optimiser les programmes de gestion de ces ravageurs
The abundance of phytophagous insects is determined by numerous interacting biotic and abiotic factors. In capital-breeding phytophagous insects, larval host plant quality is a key determinant of the adult phenotype and the performance of both males and females. Curiously, if the effect of host plant quality on female reproductive success is well-established, little effort has been conducted to determine this effect on male reproductive success. Moreover, in Lepidoptera, males transfer to females a spermatophore containing sperm and accessory gland products rich in nutrients that could be reinvested into female reproduction. The aim of this thesis was to evaluate how male larval nutrition on different host cultivars affects male reproductive traits which could, in turn, influence female reproductive output and mate choice strategies in an important grapevine pest, the European grapevine moth (Lobesia botrana). During these three years, we found that the host cultivar for the larvae strongly influences the energy reserves of male adult moths, affecting ultimately their reproductive potential through the size and content of spermatophores they transfer to females at mating. Moreover, male investment in the spermatophore declines over consecutives matings, suggesting that spermatophores are energetically expensive to produce in this monandrous capital breeding species. Thus ‘male quality’ depends on both the male larval origin and mating history, and females receiving protein-rich spermatophores at mating have an overall greater reproductive output than females mated with poor quality males producing less nutritionally rich spermatophores. Finally, females are able to discriminate among males and mate more with males having high sperm quality (virgin males or males from certain cultivars or geographical origins) to obtain substantial direct benefits.The results of this thesis confirm the importance of considering the “male effect” when trying to understand the evolution of phytophagous populations. Moreover, identifying the ecological conditions that influence the mating success of male and female in crop-pest species may lead to a better management of these crop pests

Cette thèse CIFRE porte sur la biologie, le comportement et le biocontrôle du frelonasiatique Vespa velutina, un prédateur invasif d’abeilles. Depuis son introduction en France, ce frelonétend maintenant son aire de répartition en Europe, impactant à la fois l’environnement etl’apiculture. L’objectif de ces travaux sera d’enrichir le savoir sur cette espèce pour perturber ledéveloppement des colonies de V. velutina à différents niveaux afin d’en limiter la prolifération. Lepremier axe porte sur la biologie des reproducteurs de V. velutina, afin d’empêcher la fondation decolonies en amont. Ce travail précise les données concernant la maturation sexuelle des mâles de V.velutina, compare certains traits liés à la fertilité des fondatrices avec celles du frelon européen, etmet en évidence une plus grande précocité et fertilité de V. velutina. Le deuxième axe porte sur labiologie des colonies, de la collecte à la distribution des ressources dans le nid. A l’aide de pucesélectroniques marquant des ouvrières (technique RFID), nous avons mesuré le rayon d’action et seslimites chez les ouvrières V. velutina. En marquant de la nourriture avec des métaux lourds, nousavons pu suivre l’évolution de sa distribution dans les colonies suivant leur structure. Le troisièmeaxe porte sur le biocontrôle de V. velutina avec des champignons entomopathogènes. Nous avonsévalué l’efficacité de différents isolats et de leur mode d’application contre V. velutina, puis décrit unchampignon naturellement parasitant V. velutina. Ces travaux ont permis de faire avancer lesconnaissances sur la biologie et la physiologie des frelons, mais également de proposer des pistes decontrôle durable de l’invasion européenne de V. velutina
This CIFRE thesis deals with the biology, the behavior and the biological control of aninvasive predator of bees, the hornet Vespa velutina. Since its introduction in France, this hornet isnow invading most countries in occidental Europe, dealing damages both to the environment and thebeekeeping activity. In order to limit its proliferation, a good strategy could consist in disrupting itscolony development at different levels, explored in this work. The first axis deals with V. velutinareproductive biology, exploring the different paths to prevent colonies creation. First we describedthe sexual maturation of males in V. velutina, and second we compared different traits linked tofertility between foundresses of V. velutina and the European hornet, thus highlighting V. velutinahigher precocity and fertility potential. The second axis explored the biology of colonies, fromresource collection to resource distribution in the nest. Using RFID technic, we assessed the actionrange and its boundaries in V. velutina workers. We also labelled food and observed its distribution inV. velutina colonies in function of the colony size and structure. The third axis deals with V. velutinabiocontrol, using entomopathogenic fungi. We evaluated the efficiency of different isolates anddifferent application methods on V. velutina, and described a wild fungus found naturally parasitizingV. velutina. This work brought knowledge on biology behavior and physiology of this invasive hornet,and also proposed options that could be assayed for a durable control of V. velutina

Regulation of reproduction is one central feature of social life. In particular, only a few individuals are in charge of producing offspring in eusocial species. This division of the reproductive labour is mainly mediated by pheromones emitted by the queens in social insects. These queen pheromones may signal the presence of a fertile queen so that workers react accordingly by taking care of her and not reproducing.

Here I investigated two aspects of the reproduction of two polygynous ant species. The first one, Linepithema humile, is a unicolonial, highly polygynous and invasive species. It has been the focus of numerous studies about queen pheromones; in particular, it has been reported that queen cuticular hydrocarbons (CHC) profile is related to queen fertility. The other one, Tapinoma erraticum, is a multi-colonial, weakly polygynous and native species. Workers can lay haploid eggs in the absence of the queens which is impossible for Linepithema workers.

The major part of my thesis dealt with the queen fertility signalling issue. In the first two chapters I demonstrate the link between queen fertility and queen pheromone output. I first study a queen releaser pheromone, the queen retrieval behaviour. This behaviour is performed by the workers who lay a chemical trail toward a queen located outside the nest. I successfully show this behaviour to be related to queen fertility, and not mating status, in L. humile and T. erraticum since only fertile queens (mated or not) induce such recruitment. I then highlight the role of queen fertility in the prevention of worker reproduction in T. erraticum. Again, mated fertile queens and unmated fertile queens are both able to induce such primer effect. In a third chapter I report that CHC profiles may discriminate female castes (workers, queens, virgin queens, and virgin egg-laying queens) in T. erraticum. Finally, chapter 4 summarizes my attempts to prove that CHC may be involved in queen retrieval or queen attraction. None of the various bioassays tested allows me to demonstrate the putative role of CHC as queen pheromone.

In a second part, I was interested in the consequences of sex determination in T. erraticum. Chapter 5 presents the flow cytometry methodology (FC) which allowed me to score the number of sperm cells from spermathecae of several ant species, and to demonstrate that polygynous species (such as L. humile and T. erraticum) store less sperm than monogynous ones. FCM also allows determining the ploidy of sperm and adult somatic cells and chapter 6 which presents a large survey on the ploidy level within the species T. erraticum. This species displays diploid males that may produce diploid sperm which in turn can father a viable triploid female progeny. I report differences in the frequency of triploidy among female castes, the proportion of triploid workers being more important than triploid virgin queens whereas I never observed triploid mated fertile queens. Such results greatly suggest a putative regulatory mechanism involved in the rearing of triploid females. In the last chapter I investigated two populations that differ in the occurrence of triploid workers. I report these populations to vary in the number of queens and workers per nest.

/La régulation de la reproduction est un aspect essentiel de la vie sociale. En particulier, chez les espèces eusociales, seuls quelques individus sont impliqués dans la production de la descendance. Dans les sociétés d’insectes, une telle division du travail reproducteur est principalement assurée par l’émission de phéromones par les reines. Ces phéromones royales renseignent les membres de la colonie sur la présence d’une reine fertile, de telle sorte que les ouvrières réagissent en s’occupant d’elle et en s’abstenant de se reproduire.

Au cours de ce travail, je me suis intéressé à deux aspects de la reproduction au sein de deux espèces de fourmis polygynes. La première espèce, Linepithema humile, est invasive, unicoloniale et hautement polygyne dans les régions à climat méditerranéen. Elle a fait l’objet de nombreuses études portant notamment sur les phéromones royales. En particulier, il a été montré que le profil d’hydrocarbures cuticulaires (HCC) des reines est corrélé à leur fertilité. La seconde espèce, Tapinoma erraticum, est une espèce indigène, multi-coloniale et faiblement polygyne. Ses ouvrières sont capables de pondre des œufs mâles en absence de reines, ce dont sont incapables les ouvrières de Linepithema.

Je me suis principalement intéressé à la question de la signalisation de la fertilité des reines. Dans les deux premiers chapitres, je démontre le lien existant entre la fertilité des reines et la production de phéromone royale. J’ai d’abord étudié une phéromone incitatrice (releaser) qui provoque un recrutement royal. Ce comportement collectif très caractéristique correspond à la mise en place d’une piste chimique en direction d’une reine découverte par les ouvrières en dehors du nid. Je montre que ce comportement est lié à la fertilité de la reine chez les espèces L. humile et T. erraticum car seules les reines fertiles (fécondées ou non) sont capables de d’induire le recrutement royal. Je mets ensuite en évidence le rôle de la fertilité des reines dans la régulation de la reproduction des ouvrières de T. erraticum. A nouveau, les reines fécondées fertiles et les reines vierges fertiles sont toutes deux capables d’induire un même effet déclencheur (primer), en l’occurrence, l’inhibition de la reproduction des ouvrières. Dans un troisième chapitre, je montre que les profils d’hydrocarbures (HCC) permettent de distinguer sans ambiguïté les différentes castes femelles (ouvrières, reines fertiles, reines vierges et reines vierges pondeuses) chez T. erraticum. Enfin, le chapitre 4 résume mes tentatives pour démontrer le rôle des HCC dans les phénomènes de recrutement royal ou d’attractivité des reines. Aucun des bio-essais réalisés ne me permet de démontrer l’implication des HCC dans la phéromone royale.

Dans une seconde partie, je me suis intéressé aux conséquences du déterminisme du sexe chez T. erraticum. Le chapitre 5 présente cytométrie de flux (CF), une méthode qui me permet de compter les spermatozoïdes stockés dans les spermathèques de quelques espèces de fourmis et de montrer que les reines des espèces polygynes (telles que L. humile et T. erraticum) stockent moins de sperme que les espèces monogynes. La CF permet aussi de déterminer le niveau de ploïdie des cellules spermatiques ou somatiques chez l’adulte. Je me sers de cette application dans le chapitre 6 afin d’étudier le niveau de ploïdie au sein de l’espèce T. erraticum. Je montre que, dans les populations étudiées, il existe des mâles diploïdes et que ces mâles peuvent produire du sperme diploïde fertile, capable d’engendrer une descendance femelle triploïde. Je note des différences dans la fréquence des femelles triploïdes :la proportion d’ouvrières triploïdes est significativement plus importante que celle des reines vierges triploïdes. De plus, je n’ai jamais observé la présence de reines fécondées fertiles triploïdes. De tels résultats suggèrent fortement la présence d’un phénomène de régulation au cours de l’élevage du couvain triploïde. Dans le dernier chapitre, j’ai étudié deux populations de T. erraticum qui diffèrent au niveau de la proportion d’ouvrières triploïdes. Ces populations présentent des différences significatives dans le nombre de reines et d’ouvrières par nid.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

This thesis investigated the autecology of the dacine species, Bactrocera cacuminata (Hering) (Diptera: Tephritidae: Dacinae). I specifically focused on the adult phase of the life cycle and resources believed to be significant to this life stage. The prevailing paradigm in dacine ecology predicts that the larval host plant serves as the centre of dacine activity, a state mediated by mutualistic associations with fruit fly-type bacteria. Contrary to predictions, an explicit test of this hypothesis found that the host plant of B. cacuminata, Solanum mauritianum Scopoli, acted almost exclusively as a site for oviposition and larval development. Other key adult behaviours, most notably feeding and mating, were rare at the host plant. Even in disturbed habitats, the paucity of key adult behaviours such as mating was striking. Adult flies of this species were therefore hypothesized to be utilizing other components of their habitat, i.e. resources vital to their life history requirements. Some of the resources that B. cacuminata are known to respond to include sugar, protein, methyl eugenol and the host plant. The latter three resources are believed to be critical in the reproductive success of dacine flies in general. I assessed the physiological status of flies arriving at these resources to determine if flies of different status foraged for resources differently. In dacines, the internal reproductive structures of the male and female flies have been used as predictors of physiological status. I quantified expansion of the male ejaculatory apodeme in B. cacuminata with age of fly and found that there is a threshold apodeme size that is strongly correlated Abstract with sexual maturity. Maturity of female flies could be accurately predicted by ovarian development. Using these methods to assess the physiological and nutritional status of flies arriving at resources (larval host plant, protein and methyl eugenol) in the field, I discovered that only sexually mature and mated females were responding to the host plant, while the males at the host plant were sexually immature. This confirmed the hypothesis that the host plant primarily served as an oviposition site. Additionally, this study revealed that sexually mature males with high nutritional reserves were most commonly collected at methyl eugenol (a plant-derived chemical that elicits a strong response in males of many dacine species) at dusk, the time of peak sexual activity in this species. This indicated that methyl eugenol was perhaps a significant resource in the context of the reproductive behaviour of this species. Methyl eugenol (ME) is one of group of phenyl propanoids to which males of certain species of Dacinae respond. The current hypothesis of the role of these phenyl propanoids is that they function as pheromone precursor chemicals. Response to these chemicals is hypothesized to be a trait under sexual selection. In Bactrocera dorsalis (Hendel), this effect is so strong that a single feeding on ME results in a strong mating advantage up to a month after males feed on the chemical. Bactrocera cacuminata fed on multiple occasions on ME in a laboratory bioassay. After a single 24-hour exposure to ME, investigations of mating competitiveness did not reveal any obvious advantage for ME-fed males over unfed males. However, ME-fed males did enjoy a higher mating success 16 and 32 days after exposure to the chemical, suggesting that some physiological benefits unrelated to the pheromone synthesis was driving this delayed advantage. Investigation of the physiological consequences of feeding on ME revealed no enhancement of nutritional or energetic reserves, suggesting that the delayed mating advantage observed was more likely a chance event. An alternate hypothesis about the proximate function of ME, proposed by Robert Metcalf, is that it serves as a mate rendezvous site. As mating behaviour was notably absent at the host plant, I tested Metcalf’s hypothesis. A field-cage experiment, spatially separating adult resources (host plant, methyl eugenol, sugar and protein) clearly demonstrated that methyl eugenol was functioning as a mate rendezvous stimulus for B. cacuminata. This is the first direct support for Metcalf’s hypothesis. A synthesis of the literature revealed that significantly greater ecological and evolutionary information was required to understand the basis of dacine response to phenyl propanoids. Different dacine species may be utilizing these chemicals differently, even if their evolutionary origin may have been as a plant based kairomone. My studies show that generalizations on the ecology and behaviour of Dacinae, often extrapolated from research on a few pest species, do not hold up in the case of B. cacuminata. This suggests that a more autecological, species-specific approach is required in dacine research, before any predictive generalizations can be made.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Predators capture, kíll and consume theír prey. Thís ís the only ap- proach consídered ín rnost studíes Of predator-prey ínteractíons. However, sorne recent studíes have been concerned Wíth the índírect effects Of pre- datíorL When threatened, prey can change theír behavíor, thus reducing theír chances Of death. Frorn thís perspectíve, experíments performed wíth rnosquítoes specíes ín aquatíc envíronments shows that, ín several ínstances, preys are able to ídentífy the presence Of predators. Thís perceptíon leads to behavíoral alteratíons such as fernale ovíposítíon repellency and reduced foragíng 1arvae. However, the type Of sígnal perceíved by the prey, the írn- portance Of índuced responses to the survíval Of índívíduals, and the reasons for these evolve ín sorne species and not others, remain under díscussíon. The objectíve Was to deterrníne Whether chemícal cues of predator larva Toxorhyn- chites theobaldi (Díptera: Culícídae) are capable Of ínñuencíng the behavíor Of fernales and ímmatures ín three prey species Of the sarne farníly, although wíth Very dístínct behavíor (Culea: molli8, Limatus durhamii and Aedes al- bopictu5). We found that, the ínfusíon Where T. theobaldi larvae Was shel- tered, probably releasíng chernícal sígnals, had a lower proportíon of larvae (5.4 %) of C. molli5, cornpared Wíth control (95.6 %), índícatíng ovíposítíon repellency. Meanwhíle, the other two specíes ovíposíted índíscrímínately on ínfusíon treated and controL We also observed that the presence of traces of the sarne predator, C. mollis larvae spend rnost of theír tíme ín rest (82.7 compared Wíth no sígns of T. theobaldi (49.3 %). However. L. durhamii and A. albopictus larvae do not show behavíoral changes ín the presence of the sarne sígnals. Yet, C. mollis larvae ís preyed upon ín a smaller proportíon than the others, suggestíng that these changes ínñuence ín species Vulnera- bílíty. Frorn these results, ít ís argued that the líkelíhood of the development of defensive responses índuced by predatíon rísk ís related to several factors such as hístoríc of contact Wíth the predator, the ovíposítíon strategy of the females and the ñxed and ñexíble behavíor standard and posítíoníng of 1ar- Vae. Also ís díscussed the ímportance of natíve predators to curb the ínvasíon of exotíc species and díseases spread by these Vectors.
Predadores capturam, abatem e consomem suas presas. Esta é a única abordagem considerada na maior parte dos estudos da ínteração predador- presa. Entretanto, alguns trabalhos recentes têrn se preocupado com os efeitos indiretos da predação. Quando ameaçadas, presas podem alterar seu comportamento, reduzindo suas chances de morte. Sob essa perspectiva, experimentos realizados com espécies de mosquitos em ambientes aquáticos demonstram que, em diversas situações, presas são capazes de identificar a presença de predadores. Tal percepção induz alterações comportamentais como a repelência de ovíposição das fêmeas e redução no forrageamento das 1arvas. Entretanto, o tipo de sinal percebído pelas presas, a importância das respostas induzidas para a sobrevivência dos indivíduos, e as razões destas evoluírem ern algumas espécies, e não em outras, permanecem em discussão. O objectivo do trabalho foi verificar se pistas químicas da presença larva predadora Toxorhynchites theobaldi (Díptera: Culícídae) influenciam o comportamento tanto de fêmeas ovípositantes quanto de imaturos de três espécies de presas da mesma famílía, entretanto com comportamentos bastante distintos, sendo elas Culex molli5, Limatus durhamii e Aedes albopictus (Díptera: Culícídae). Verificamos que, na infusão onde larvas de T. theobaldi permaneceram abrigadas previamente, liberando possíveis sinais químicos, foi encontrada uma menor proporção de larvas (5,4%) de C. molli5, quando comparado com o controle (95,6%) , indicando repelência na ovíposição Enquanto isso, as outras duas espécies ovíposítaram indiscriminadamente na infusão tratada e na controle. Observamos tarnbérn que, na presença de indícios desse mesmo predador, imaturos de C. mollis passaram maior parte do tempo ern repouso (82,7%), quando compadrado com a ausência de sinais de T. theobaldi (49,3%). Entretanto, ímaturos de L. durhamii e A. albopic- tus não apresentam alterações comportamentais na presença dos mesmos sinais. Ainda, C. mollis é predado em uma menor proporção que as demais, sugerindo que essas alterações influenciam na Vulnerabilidade das espécies. A partir desses resultados, é discutido que a probabilidade da evolução de respostas defensivas induzidas pelo risco de predação está relacionada a diversos fatores como o histórico de contato com o predador, a estratégia de ovíposição das fêmeas e o padrão fixo e flexicível de comportamento e posícionarnento das 1arvas. É abordada também a importância dos predadores nativos em conter a invasão de espécies exóticas e a disseminação de doenças por elas Veiculadas.

In societies where all individuals are reproductively totipotent and yet, at a given time only one of them reproduces, it is interesting to examine the factor(s) that may influence and predict who will be the reproductive. I am investigating various behavioural, morphological and physiological parameters in the primitively eusocial wasp Ropalidia marginata, and their role in determining the current reproductive and her future successors. In several group-living species, especially in primitively eusocial ones, a strong link between behavioural dominance and reproductive dominance is observed. Hence, I am also investigating the possible determinants of behavioural dominance in R. marginata. I have carried out my study on artificially constituted pairs of wasps as well as in natural colonies in laboratory cages, which represent the founding phase and the established phase in the colony cycle, respectively. Chapter 1: Behavioural and Reproductive Dominance in Pairs of R. marginata Age and body size had no effect on behavioural dominance in pairs of R. marginata, whereas prior experience of behavioural dominance affected future dominance status, indicating presence of winner- and loser-effects. Dominance ranks are relatively stable. This is different from what has been found in colonies, where dominance ranks sometimes change on a daily basis. Body size had no effect, whereas age and behavioural dominance had a significant effect on reproductive dominance in pairs, with older individuals and more dominant individuals having a higher probability of becoming the reproductive. Since no relationship was found between age and behavioural dominance, we predict that the underlying mechanisms by which age and behavioural dominance affect reproductive dominance and independent of each other. This study gives a clear indication that age and behavioural dominance are important variables that determine the reproductive individual during the founding phase of the colony. Chapter 2: Comparison of Dominance Indices and Recommendations for their Use When several individuals interact with each other as in colonies, in a differential and sometimes in a preferential manner, it is difficult to attribute dominance ranks to individuals. Dominance indices are employed to simplify these interactions and rank individuals in dominance hierarchies. Since the rationale behind using a particular dominance index is seldom given in behavioural literature, a comparison of three dominance indices was carried out in second part of the thesis. Each index was gauged on how similar are its ranks as compared to other two indices. Indices were also compared based on the number of untied or unique ranks they attributed. The index that gave least number of ties in ranks was assumed to be better than others. In addition to data from R. marginata colonies, I used data from R. cyathiformis colonies (a congeneric species which behaves more like a typical primitively eusocial species), and artificial data sets, to increase variability in the interaction patterns. We found that each of the indices had their own advantages and disadvantages. In species like R. marginata and R. cyathiformis, where only a few pairs show interactions, and among those who do, very few show reversals, Frequency-based Dominance Index (FDI) is the recommended index of choice. Studies like these will help in understanding how dominance indices operate under certain situations before applying them to construct hierarchies. Chapter 3: Behavioural and Reproductive Dominance in Colonies of R. marginata Age does not affect behavioural dominance, whereas winner and loser effects exist in colonies of R. marginata, just as in pairs. When analysed in detail, I found that colonies of R. marginata showed fewer proportion of pairs interacting, and lower frequency/hour/pair of dominance-subordinate interactions as compared to experimentally paired individuals (from 1st chapter). However, the dominance displays and behaviours were much more intense and severe in colonies. After dominance hierarchies are already established in colonies, frequent need to show dominance behaviour may not arise, due to familiarity between interacting individuals. However, since individuals are possibly aware of each others’ strengths due to past interactions, dominance behaviours are much more severe when contests do happen. My results show that there might be some similarities in terms of determinants of behavioural dominance between pairs and colonies, but the expression of behavioural dominance is quite different. From earlier work it was already known that if the queen/reproductive of the colony disappears or is experimentally removed, one of the individuals shows extreme levels of aggression. This individual, referred to as the potential queen (PQ), will go on to become the next queen of the colony. Her behavioural profile, from the emergence till she establishes herself as the next queen have been well studied earlier. What was not known were the factor(s) that determine the identity of the PQ. It was also unclear what happens when the queen as well as the PQ are both removed, simultaneously or in quick succession. To test whether there is a longer reproductive hierarchy in R. marginata, the queen and the first potential queen of a nest were removed. I found that successive potential queens emerged as readily as the first potential queen, and with dominance profiles comparable to the first PQ, indicating that a reproductive hierarchy indeed exists, at least up to five PQ’s. It was also found that these potential queens were acceptable to all other individuals, as there was not a single act of behavioural dominance directed toward any potential queen. It was also observed that all PQs went on to become queens if the previous queen or PQ was not returned. When tested for various morphological, physiological, behavioural and life history traits (factors possibly influencing the position of an individual in the reproductive hierarchy), we found that age is the only variable that emerges as an important predictor of reproductive succession, with older animals having a higher chance to succeed as next queens of the colony, although even age is not an absolute predictor. Unlike in the pairs, in colonies of R. marginata behavioural dominance is not a good predictor of an individual’s ability to be the queen or the potential queens. The four most important findings of my study are: (i) the first demonstration of winner and loser effects in social insects; (ii) the demonstration that behavioural dominance influences reproductive dominance in pairs but not in colonies; (iii) demonstration of a long reproductive queue among individuals of a colony; and (iv) discovering that age is an important predictor of the identity of the queen and the future queens of the colony. I believe these findings will add significantly to our growing knowledge of the social biology of R. marginata. Finally, my work shows that pairs of R. marginata, representing the founding phase of the colony, behave more like a typical primitively eusocial species, whereas colonies which represent the established phase of the colony cycle behave more like highly eusocial species. Finding the characters of two different forms of sociality in the same species in different phases of the colony cycle makes R. marginata an excellent model system to study evolution of eusociality.

The biology and behavior of the codling moth, Cydia pomonella (L.), was studied to determine factors responsible for differences in susceptibility to moth damage among apple and pear cultivars. In release experiments, codling moth adults were intercepted in significantly greater numbers in host (apple, pear) than in non-host (maple) trees, suggesting a directed response rather than random movement to host trees. There was no correlation between adult preference for certain hosts and the susceptibility of the hosts to codling moth attack. Adults were guided by cues from the tree canopy, foliage and fruit. Cues from host fruit were less important at the beginning of the season. Similar adult behavior patterns were observed in different coding moth strains. However, moths reared on apples were guided more by olfactory cues from fruit than sterilized moths reared on artificial diet. The percentage of moths mating under caged conditions was higher in apple and pear than in maple trees. In host plants, stimuli from fruit were not essential for mating. The egg distribution in the field varied through the season depending on the host cultivar. However, mean distance of eggs to fruit, as well as larval travel speed, was not different among host cultivars. Selection of an oviposition site by the adult female was affected by several factors, including visual, chemical, and tactile stimuli of host fruit, as well as anatomical (pubescence) and chemical (oviposition stimulants) properties of leaves. There were no differences in natural mortality and developmental rates of the egg stage on host cultivars. However, there were significant differences in first instar larval mortality among hosts over most of the season. Mortality was much higher on 'Anjou' than on 'Bartlett' and 'Red Delicious', except at the end of the season. Differential first instar mortality was due to the different rate of success in entering the fruit. The ability to penetrate fruit was correlated with infestation levels observed in the field and related both to neonate behavior and anatomical characteristics of host fruits. Larval food source did not affect larval and pupal development rates, adult fecundity, or egg viability.
Graduation date: 2001