Spiders of the Carmanah Valley, Vancouver Island, British Columbia were examined to determine differences in species assemblages in a regenerating clearcut and an ancient forest, and characterize life histories of the different species. Twenty-three families (113 species, 76 genera) were collected using Malaise traps. Diversity was greater in the regenerating clear-cut than in the ancient forest. The latter was dominated by the web-building guild. Assemblages in the two habitats were significantly different and species that preferred the regenerating forest tended toward spring/summer stenochronous life histories compared to fall stenochronous in the ancient forest. Eight species showed non-random distribution patterns relative to the riparian corridor formed by Carmanah Creek. Species that used both habitats did not show a shift in timing of reproduction despite differences in abiotic conditions. More adults were collected in the ancient forest habitat than in the regenerating clear-cut, while more immatures were found in the regenerating clear-cut.

<p> The western corn rootworm, or WCR, (<i>Diabrotica virgifera virgifera </i> LeConte) is the most significant pest of field corn (<i>Zea mays</i>) in the United States, and has recently expanded its range into Europe. Since 2004, hybrid corn containing Bt toxins targeting the corn rootworm complex have been heavily adopted and are now the primary control measure for this pest in North American corn production. </p><p> The evolution of resistance is an ongoing concern, and to ensure Bt products will retain their usefulness, insect resistance management (IRM) tactics using various refuge structures have been adopted. One of the key tenets of the refuge strategy is that males and females emerging from Bt and refuge plantings mate randomly. A violation of this largely untested assumption would lead to acceleration of resistance development. </p><p> To generate empirical field data on mating rates between beetles emerging from Bt and refuge plants, field cage studies using field populations of WCR in Indiana were utilized. Various refuge configurations were tested; all refuge plants were labeled using the stable isotope N15. This mark persists in the adult beetles after eclosion, allowing for collection and analysis of isotopic ratios of beetles in mating pairs. This approach was used to test the random mating assumption in Bt and refuge beetles collected from field cages. Other data collected include emergence rates, timing and sex ratios for each of the treatments. </p><p> Results indicate that mating based on natal host may not be as important of a factor as initially thought. Mixed mating occurs at a high rate when there are higher numbers of susceptible rootworms even though the measured fitness parameters between <i>Cry3Bb1</i> and refuge adults were significantly different (p&lt; 0.05). The main indication from this study is that not enough susceptible individuals are produced from a 5% refuge-in-a-bag strategy which is the dominant form of refuge planting in the United States. </p>

In order to analyze the inducible defense response of hybrid poplar (Populus trichocarpa x P. deltoides), macroarrays were used to profile transcript patterns elicited by wounding and by regurgitant from forest tent caterpillar (FTC; Malacosoma disstria), a poplar defoliator. FTC regurgitant proved to be a potent elicitor of defense gene expression and was shown to contain the insect-derived elicitor volicitin. Comparison of inducible defense responses elicited by FTC regurgitant and wounding with pliers revealed qualitatively similar responses in terms of transcript accumulation. Extensive overlap was also observed in the sets of induced genes from locally- and systemically-induced leaves. Systemic responses were further investigated and shown to also be inducible in roots, which implies shoot-root systemic signaling. Comparative macroarray analysis showed similarities between inducible responses in leaves and roots, including genes that encode previously identified leaf herbivore defense genes. The macroarray analysis also established a suite of marker genes for future studies of herbivore defense in poplar, many of which may play key roles in the defense response and are candidates for further study. Among these genes were several inducible Kunitz trypsin inhibitors (KTIs), which were investigated further with biochemical analyses. The sequenced poplar genome was used to select KTI genes that represent the diversity of this family. Recombinant proteins were generated and showed that the poplar KTI genes encode functional proteinase inhibitors and that they are functionally distinct, i.e. they have specific proteinase substrate preferences. Moreover, wounding increases accumulation of KTI proteins, as well as protease inhibitor activity in leaves, supporting a defensive role for this protein family. These proteins were therefore tested for their ability to inhibit insect digestive proteases from FTC and bertha armyworm. The poplar KTIs tested all inhibited at least some protease activity from FTC midgut extracts. The strongest inhibitor of FTC proteases, TI3. was further tested in bioassays and shown to reduce larval growth of FTC when incorporated into insect diet. confirming that this KTI functions as an anti-herbivore protein. In addition, analysis of FTC midguts from T13 feeding experiments showed that larvae responded to TI3 by producing more gut proteases. This hyperproduction of proteases may exacerbate the antinutritive effects of TI3 by reducing pools of essential amino acids.

Master of Science / Department of Entomology / Frank Arthur / The control of Indianmeal moth [Plodia interpunctella (Hübner)], a commonly found serious stored product pest around the world, relies mainly upon chemical control methods. Because of recent changes in the laws and regulations governing pesticide usage in the United States, there is an increasing need for finding safer chemicals to control insect pests. Hydroprene, an insect growth regulator, is considered to be a safe alternative. In this study, I quantified the effects of hydroprene on two critical life stages of Indianmeal moth, the eggs and 5th instar wandering phase larvae. Maximum development time in the untreated controls was 13.6 ± 0.6 d at 16°C and minimum development time was 2.3 ± 0.4 d at 32°C. At 20°C and 24°C, the effect of hydroprene on egg development became more evident; development time generally increased with exposure interval, with some variability in the data. The mean egg mortality among all temperatures was 7.3 ± 4.6%. Among the treatments, mortality of eggs increased as the exposure periods increased within any given temperature, with a dramatic increase in mortality with increase in temperature. Egg mortality was lowest at 16°C when exposed for 1 h (0 ± 3%), but mortality gradually increased up to 32 ± 3% when exposed for 18 h. Within each exposure interval, there was a direct increase in mortality as the temperatures increased. For the 5th instar wandering phase larvae, the longest development time among the treatments of 47.2 ± 1.3 d occurred at 16ºC when the larvae were exposed for 30 h, whereas the shortest development time of 7.0 ± 0.5 d occurred when the larvae were exposed for 1 h at 32ºC. Among treatments, the greatest larval mortality (82.0 ± 0.1%) occurred when larvae were exposed for 30 h at 28ºC, while the minimum mortality of 0.0 ± 0.5% occurred at 16ºC when larvae were exposed for 1 h. Response-surface models derived from this study can be used in simulation models to estimate the potential consequences of hydroprene on Indianmeal moth population dynamics.

Doctor of Philosophy / Department of Entomology / Gerald R. Reeck / John C. Reese / Salivary secretions are a key component of aphid-plant interactions. Aphids’ salivary proteins interact with plant tissues, gaining access to phloem sap and eliciting responses which may benefit the insect. In an effort to isolate and identify key components in salivary secretions, we created a salivary gland cDNA library. Several thousand randomly selected cDNA clones were sequenced. We grouped these sequences into 1769 sets of essentially identical sequences, or clusters. About 22% of the clusters matched clearly to (non-aphid) proteins of known function. Among our cDNAs, we have identified putative oxido-reductases and hydrolases that may be involved in the insect's attack on plant tissue. C002 represents an abundant transcript among the genes expressed in the salivary glands. This cDNA encodes a novel protein that fails to match to proteins outside of aphids and is of unknown function. In situ hybridization and immunohistochemistry localized C002 in the same sub-set of cells within the principal salivary gland. C002 protein was detected in fava beans that were exposed to aphids, verifying that C002 protein is a secreted protein. Injection of siC002-RNA caused depletion of C002 transcript levels dramatically over a 3 day period after injection. With a lag of 1 – 2 days, the siC002-RNA injected insects died, on average 8 days before the death of control insects injected with siRNA for green fluorescent protein. It appears, therefore, that siRNA injections of adults will be a useful tool in studying the roles of individual transcripts in aphid salivary glands.

Doctor of Philosophy / Department of Entomology / C. M. Smith / Brenda Oppert / Coleopteran insects compensate for dietary protease inhibitors by a number of mechanisms. To study this compensation response at the molecular level, the digestive proteases of Tenebrio molitor were studied. Biochemical studies of the pH optima and inhibitor sensitivity of proteases indicated the cysteine proteases were mostly in the anterior and serine proteases were in the posterior midgut of T. molitor larvae. Expressed Sequence Tags (ESTs) from T. molitor larval midgut cDNA libraries contained sequences encoding putative digestive proteases. Of a total of 1,528 cDNA sequences, 92 cDNAs encoded proteases, and 50 full-length cDNAs were grouped into serine, cysteine and metallo protease classes. Sequences tmt1a, tmt1b and tmt1c were identified as genes encoding isoforms of T. molitor trypsin, and tmc1a encoded T. molitor chymotrypsin. The general distribution cysteine protease transcripts in the anterior and serine protease transcripts in the posterior midgut, of T. molitor larvae, was in agreement with the biochemically-characterized compartmentalization of proteases. Expression analyses of selected transcripts demonstrated varied expression patterns across five developmental stages of T. molitor, with maximal expression of most protease transcripts in first instar larvae. Dietary serine and cysteine protease inhibitors fed in combination to early-instar T. molitor larvae caused a significant delay in larval growth in 21-day-old larvae. Real-time quantitative PCR analysis of RNA isolated from larvae fed different protease inhibitor treatments indicated that dietary inhibitors affected the expression of serine and cysteine proteases. Larvae fed soybean trypsin inhibitor, a serine protease inhibitor, compensated by the hyperproduction of proteases from the same class, as well as the upregulation of cysteine proteases. A cysteine protease inhibitor, E-64, caused a reduction in the hyperproduction of all proteases, and, in combination with the soybean trypsin inhibitor, lowered the compensation response of T. molitor larvae to negligible levels. These data suggest that T. molitor larvae are more sensitive to the effects of cysteine protease inhibitors, perhaps because these proteases are the first line of defense for larvae against plant protease inhibitor. The bioassay and molecular studies suggested that combinations of inhibitors that target both serine and cysteine proteases are needed to effectively control larval infestations of T. molitor.

Doctor of Philosophy / Department of Entomology / James R. Nechols / Tetranychus kanzawai Kishida and Panonychus citri (McGregor) are the two major arachnid pests of screenhouse-cultivated papayas in Taiwan. Control of these mites has become more difficult because both pests have become resistant to most registered miticides. This laboratory study investigated the feeding behaviors, predatory potential, and prey preference of a domesticated line of Mallada basalis Walker, a commonly-occurring chrysopid in Taiwan, to both of these pest mites. A laboratory assessment on control efficacies of different predator:prey release ratios to single and mixed-pest species was also conducted. Behavioral study showed that all larval stages of M. basalis exhibited a high rate of acceptance of all life stages of both T. kanzawai and P. citri. Second and third instar predators foraged actively during most of the 2-h tests. Numbers and rates of prey consumption were measured for each instar of predator and prey. Results showed that consumption increased and prey handling time decreased as predator life stage advanced, and prey stage decreased. Mallada basalis exhibited both a shorter handling time and corresponding higher consumption rate on P. citri compared with T. kanzawai. Handling time and consumption rate also were positively affected by increasing prey density. Mallada basalis did not exhibit notable species or life stage preferences, and prior feeding experience on one mite species did not affect subsequent prey choice between the two mites. Lacewings significantly reduced T. kanzawai and P. citri populations at a predator:prey ratio of 1:30 and this improved at ratios of 1:15 and 1:10. Control of T. kanzawai was slightly better than P. citri when the mites occurred singly and together. Consumption by M. basalis increased with temperature up to 30C. I conclude that M. basalis has high potential for augmentative biological control of papaya mites. Further field investigations are needed for making final recommendations.

Doctor of Philosophy / Department of Entomology / James F. Campbell / James R. Nechols / Theoretical and empirical ecological research has emphasized the need for understanding how animals perceive and respond to landscape structure and the importance of integrating both behavioral and landscape approaches when studying movement behavior. Knowledge of insect movement behavior is essential for understanding and modeling dispersal and population structure and developing biologically-based integrated pest management programs. My dissertation research addresses questions concerning how insects respond to landscape structure by examining movement behavior of an important stored-product pest, red flour beetle (Tribolium castaneum), in experimental landscapes. Results show that beetles modify movement behavior depending on landscape structure. Edge effects and interpatch distances may influence landscape viscosity, or the degree to which landscape structure facilitates or impedes movement, resulting in significant differences in velocity and tortuosity (amount of turning) of movement pathways, as well as retention time in landscapes with different levels of habitat abundance and aggregation. Perceptual range, or the distance from which habitat is detected, appears to be limited while beetles are moving in a landscape as they did not respond to a flour resource before physical encounter. Beetles showed differential responses to patches with various characteristics, entering covered patches more quickly than uncovered patches with more resource or the same amount of resource. Permeability of patches changed with subsequent encounters suggesting that full evaluation of patch quality may only occur after entering a patch. Beetles responded to landscape structure differently depending on the activity in which they were engaged. Distribution of movement pathways was similar to that of the habitat, but distribution of oviposition sites were significantly more aggregated than pathways and habitat. Oviposition site choice may be influenced by a complex set of factors which include previous visitation, amount of resource, travel costs, and edge effects. Insights were gained concerning how red flour beetle perceives resources, modifies search strategies, responds to boundaries, and chooses reproductive sites in patchy landscapes. This research provides new information regarding how red flour beetle interacts with landscape structure that has implications in the areas of behavioral and landscape ecology and applications in stored-product insect ecology.

A novel methodology allowed simultaneous investigation of three elements of bumblebee foraging behaviour: spatial encoding of flower position, landmark use, and scent marking. Bumblebees were presented with a row of artificial flowers in a flight cage, one flower offering reward (S+). Testing involved empty (i.e., unrewarding) flowers. In Experiment 1, flower covers presumed to be scent marked (old covers) were switched with one of the unmarked covers, or replaced with new, scent-mark-free covers. Results confirmed previous research: presence of old covers influenced response type rather than floral choice. Choice appeared to have been made using memory. In Experiment 2, the S- were moved during testing to change the relative position of the S+. New covers were used for half of the bees. The flower in the same absolute position (wrong relative position) as the S+ was consistently chosen, suggesting that the S- did not function as landmarks. Contrary to Experiment 1, old covers influenced flower choice. Experiment 3 replicated Experiments 1 and 2. Again, bees preferred absolute position, but results suggest relative position was encoded and influenced choice under certain circumstances. The effect of old vs. new covers continued to be inconsistent: choice means were higher with new covers, and probing often occurred on new covers. Finally, when flower array independent (FAI) information and memory for a flight vector were placed in conflict in Experiment 4, bees showed a bias for using FAI cues. Taken together, these experiments show that the definition of a landmark remains to be clarified, the role of scent marking remains elusive, and bumblebees showed a consistent bias for using FAI information to locate a goal. Contributions of this thesis are placed within the context of research with vertebrate species and natural bumblebee foraging behaviour.

Les réponses comportementales des insectes restent peu connues dès lors qu'on s'éloigne de leur optimum thermique. Les conditions plus extrêmes et variables de température projetées pour les prochaines décennies devraient pousser les organismes à la limite de leur capacité de fonctionnement, dans la mesure où ils ne s'adaptent pas rapidement aux changements. Les réponses comportementales à la température peuvent être kinétiques (résultant de l'accélération/ralentissement des réactions chimiques de l'organisme en fonction de la température) ou intégrées (résultant de l'intégration des informations thermo-sensorielles par le système nerveux central de l'insecte), adaptatives ou contraintes. Distinguer entre ces différents types de réponse permettra de mieux comprendre et prédire la réponse des individus aux nouvelles conditions provoquées par les changements climatiques. Les réponses individuelles pourront alors permettent d’anticiper les conséquences sur les populations. Dans cette thèse, plusieurs comportements d'Anaphes listronoti, un parasitoïde des oeufs du charançon de la carotte (Listronotus oregonensis) ont été observés, à l’intérieur de la fenêtre thermique permettant ses activités. Dans un premier temps, il a été montré que le comportement de marche des femelles A. listronoti ne découlait pas simplement d'une réponse kinétique à la température, mais correspondait à une réponse intégrée telle que l'évitement des conditions thermiques froides et la conservation de l'énergie aux températures élevées. Dans un second temps, l'exploitation d'agrégats d’hôtes a été comparée à différentes températures. La stratégie d'exploitation ne variait pas avec la température, mais des contraintes liées à la manipulation de l'hôte et à la détection des messages chimiques à haute température ont été révélées. Ensuite, le comportement de cour et d'accouplement a été observé en fonction de la température. Les températures suboptimales diminuaient le succès d'accouplement, mais pas le transfert de spermatozoïdes lors d’un accouplement. Des contraintes de reconnaissance entre les partenaires sexuels ont également été observées à températures infra- et supra-optimales. Enfin, un modèle de simulation dynamique intégrant le développement des différents stades de l’insecte et les comportements précédemment étudiés a été conceptualisé. Ce modèle permet de combiner les effets de la température sur les comportements d’un individu et les conséquences sur la population de parasitoïdes, ainsi que sur la population de l’hôte. L’ajout des comportements dans les modèles populationnels n’apporte pas forcément de valeur ajoutée, mais il reste essentiel de les considérer, en particulier dans le cadre des changements climatiques. En effet, si les réponses physiologiques telles que celles associées au développement augmentent jusqu'à un maximum d’environ 35°C, la plupart des comportements deviennent sub-optimaux à partir de 30°C, et cessent presque complètement à 35°C. Dans un contexte de changements climatiques, ces résultats permettent de mieux comprendre et potentiellement prédire les réponses individuelles et populationnelles des insectes aux différentes conditions thermiques. / The behavioural responses of insects remain poorly understood once they move away from their thermal optimum. The more extreme and variable temperature conditions projected for the coming decades should, to the extent that insects do not adapt quickly to changes, push organisms to the limit of their ability to function. Behavioural responses to temperature may be kinetic (resulting from the acceleration/slowing down of the organism's chemical reactions as a function of temperature) or integrated (resulting from the integration of thermo-sensory information by the insect's central nervous system), adaptive or constrained. Distinguishing between these different types of response will help to better understand and predict the response of individuals to new conditions caused by climate change. Individual responses can then be used to infer the consequences on populations. In this thesis, several behaviours of Anaphes listronoti, a parasitoid of the carrot weevil (Listronotus oregonensis) eggs, were observed, depending on the thermal window allowing its activities. Firstly, it was shown that the walking behaviour of A. listronoti females was not simply a kinetic response to temperature, but also corresponded to an integrated response such as avoidance of cold thermal conditions and conservation of energy at high temperatures. In a second step, the exploitation of host patches was compared at different temperatures. The exploitation strategy did not vary with temperature, but constraints related to host handling and detection of chemical cues at high temperatures were revealed. Next, courtship and mating behaviour was observed as a function of temperature. Sub-optimal temperatures decreased mating success, but not sperm transfer during mating. Recognition constraints between sexual partners were also observed at infra- and supra-optimal temperatures. Finally, a model integrating the development of the different stages of the insect and the previously studied behaviours was conceptualized. This model makes it possible to combine the effects of temperature on the behaviour of an individual and the consequences on the parasitoid population, as well as the host population. Adding behaviors to population models does not necessarily add value, but it remains essential to consider them, particularly in the context of climate change. Indeed, while physiological responses such as development increase to a maximum of about 35°C, most behaviours become suboptimal from 30°C onwards, and cease almost completely at 35°C. In a context of climate change, these results allow to better understand and potentially predict the individual and population responses of insects to different thermal conditions.