bluuebunny/crossref_metadata_2025 huggingface dataset:
Mexican diabroticite beetles: I. Laboratory test on host breadth of Acalymma and Diabrotica spp.
Authors: Eben Astrid , Barbercheck Mary E. , Martín Aluja S.
Published: October 2003

Choice tests were conducted to determine relative degree of specialization of feeding behavior of 11 Mexican diabroticite species in the genera Acalymma and Diabrotica (Chrysomelidae: Luperini). Adult beetles were offered a choice between cotyledons of a non‐bitter (not containing cucurbitacin) cucurbit (C. pepo L. var. Crookneck), corn (Zea mays L.), and beans (Phaseolus vulgaris L.). In a second assay a bitter (containing cucurbitacin) cucurbit (C. pepo L. var. Ambassador) was added to the array of plants offered. Neonates of two species of Acalymma and one species of Diabrotica were offered a choice between roots of a non‐bitter and a bitter cucurbit, and between a bitter cucurbit and corn.

Adult insects showed distinct preferences in the first assay. All Acalymma spp. tested accepted only the non‐bitter cucurbit as host, whereas Diabrotica spp. preferred either the cucurbit or the noncucurbit hosts. When the bitter cucurbit was offered together with the other three hosts, all species changed their host choice and significantly preferred the bitter cucurbit. Neonates of all three species tested significantly preferred the bitter cucurbit roots over the non‐bitter roots, and the corn roots over the bitter cucurbit.

The observation that all Mexican diabroticite species tested left suitable hosts when bitter cucurbits were offered in a choice situation supported the hypothesis that the association between diabroticites and Cucurbitaceae is mediated by plant chemical compounds. For both, the Acalymma spp., which were found to be cucurbit specialists, as well as for the polyphagous Diabrotica spp., cucurbitacin B acted as a strong feeding arrestant which implies that the chemical mediation of this interaction might be an evolutionary conservative trait within the tribe.
Increased parasitization of California red scale in the field after exposing its parasitoid, Aphytis melinus, to a synthetic kairomone
Authors: Hare J. Daniel , Morgan David J.W. , Nguyun Tuyun
Published: October 2003

The introduced parasitoid, Aphytis melinus DeBach (Hymenoptera: Aphelinidae), utilizes a kairomone, O‐caffeoyltyrosine, to recognize California red scale, Aonidiella aurantii (Maskell) (Homoptera: Diaspididae). Wasps used in augmentative release programs for California red scale on California citrus are reared on oleander scale, Aspidiotus nerii Bouché (Homoptera: Diaspididae), themselves reared on squash. Previous laboratory studies demonstrated that wasps reared on oleander scale but exposed to O‐caffeoyltyrosine before bioassay more readily accepted California red scale covers for probing than wasps reared similarly but not exposed to O‐caffeoyltyrosine. The goal of this study was to determine if wasps reared on oleander scale but exposed to O‐caffeoyltyrosine actually parasitized a greater number of field‐reared California red scale than unconditioned wasps. In order to distinguish between progeny of conditioned and unconditioned wasps in the field, we utilized two A. melinus strains that carried different electrophoretically distinguishable alleles. In half of the releases, Strain ‘A’ was conditioned to O‐caffeoyltyrosine and Strain ‘B’ served as the control, while this pattern of conditioning was reversed for the remaining releases. Although there were differences in the rates of population growth of the two strains, whichever strain was the conditioned strain left a greater than expected number of progeny compared to the control strain in all comparisons. Exposure of A. melinus reared in commercial insectaries to O‐caffeoyltyrosine prior to release may be a means to improve the effectiveness of such wasps in augmentative release programs to control California red scale.
Quiescence in the Colorado potato beetle, Leptinotarsa decemlineata
Authors: Acheampong S. , Mitchell B.K.
Published: October 2003

Quiescence (death feigning) was induced in the Colorado potato beetle, Leptinotarsa decemlineata by mechanical disturbance of live and artificial plants on which beetles were walking, feeding or grooming. The response consisted of a sudden cessation of activity lasting 12 to 500 s. Recovery from this immobile state was usually preceded by either antennal or leg movement. The time taken for beetles to come out of the immobile state (i.e. recovery time) was not dependent on age or sex of beetles or on stimulus duration, but was dependent on degree of displacement and on satiation level. Repeated stimulations led to longer recovery times and to a smaller proportion of responding beetles. Stimulation within the immobile state also prolonged recovery time. The most effective frequency of mechanical disturbance for startling beetles was 30 Hz. This response is presumed to be part of the extensive defense repertoire of this beetle, but we have so far been unable to discover a natural enemy that will elicit it.
Potential impact of Coleomegilla maculata predation on adaptation of Leptinotarsa decemlineata to Bt‐transgenic potatoes
Authors: Arpaia Salvatore , Gould Fred , Kennedy George
Published: October 2003

The relationship between Leptinotarsa decemlineata Say egg density and Coleomegilla maculata DeGeer predatory behavior was investigated at different spatial scales (plant‐to‐plant and plot‐to‐plot). Both adult C. maculata location and daily egg consumption rates were monitored over time in greenhouse and field tests. Despite aggregation in areas of highest prey density by C. maculata, egg consumption was inversely related to egg mass density at the smallest and the largest spatial scales tested. The experimental data on predation rates in high and low density field treatments were included in a mathematical model to simulate impact of natural enemies on the rate of L. decemlineata adaptation to Bt‐toxin‐expressing transgenic potato plants when Bt‐expressing plants are mixed at the plot‐to‐plot level with normal potato plants. Results showed that C. maculata predatory behavior could decrease the rate at which L. decemlineata adapted to Bt‐toxins if plot‐to‐plot mixed‐plantings were used.
Spectral efficiency of the glasshouse whitefly Trialeurodes vaporariorum and Encarsia formosa its hymenopteran parasitoid
Authors: Mellor H. E. , Bellingham J. , Anderson M.
Published: October 2003

Using the electroretinogram (ERG) technique the spectral efficiency of the compound eye of the glasshouse whitefly Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae) and its main parasitoid Encarsia formosa (Gahan) (Hymenoptera: Aphelinidae) was measured at selected wavelengths between 340 nm and 670 nm. The form of the ERG for both T. vaporariorum and E. formosa was found to be monophasic in nature. For both male and female T. vaporariorum and female E. formosa a primary peak of efficiency occurred in the blue‐green‐yellow region, peak 520 nm and a secondary peak in the ultraviolet (UV) region. The compound eye of female E. formosa gave a significantly greater response in the UV region than either the dorsal or ventral regions of the compound eye of T. vaporariorum relative to the responses in the blue‐green‐yellow region. T. vaporariorum has divided compound eyes with distinct dorsal and ventral regions. In this study it was found that the percentage response in the UV, of the dorsal region of the eye, is significantly greater than that of the ventral region of the eye relative to the percentage response in the blue‐green‐yellow region and there is a significant shift in the blue‐green yellow peak towards the right of the spectrum.
Effects of diet and mating status upon corpus allatum activity, oocyte growth, and salivary gland size in the ring‐legged earwig
Authors: Rankin Susan M. , Dossat Heather B. , Garcia Kathryn M.
Published: October 2003

The effect of diet on mating behavior and the subsequent effects of diet and mating status on the biosynthesis of juvenile hormone III, basal follicle length, salivary gland size and total body weight were assessed in the ring‐legged earwig, Euborellia annulipes (Lucas) (Family Carcinophoridae; subfamily Carcinophorinae) during the first 15 days of adult life (the first gonadotrophic cycle of those fed presumably near‐optimal diets of catfood) and again on day 25 (late vitellogenesis of the second gonadotrophic cycle of those fed catfood). Diets of catfood, honey, fructose and total starvation, respectively, imposed on 0‐day adult females did not affect sexual receptivity, mating success or duration of mating as assessed on day 7. With the addition of a group of virgin, catfood fed females, we noted that only those females maintained on catfood oviposited within 25 days; enforced virginity virtually abolished oviposition. Total food deprivation of females as well as diets of honey or fructose abolished the cycles in total body weight, basal follicle length, salivary gland size and juvenile hormone production. Thus, starvation decreased the reproductive success of these insects, and carbohydrates only (fructose) or in combination with trace amounts of nutrients and protein (honey) were not sufficient to promote reproduction and associated cycles in this insect. Furthermore, virgins failed to undergo the decreases in salivary gland size that were characteristic of mated females. Among mated, catfood‐fed females, the second cycle in juvenile hormone production appeared to be smaller than the first.
Infestation of maize by Prostephanus truncatus initiated by male‐produced pheromone
Authors: Scholz D. , Borgemeister C. , Meikle W.G. , Markham R.H. , Poehling H.‐M.
Published: October 2003

Delta traps baited with maize cobs, which were infested each with one male Prostephanus truncatus (Horn) (Col.: Bostrichidae), were distributed in southern Benin and collected after one, two, three and four weeks. The numbers of P. truncatus caught during the different trapping periods were not significantly different. Sixty‐four percent of the trapped P. truncatus were females. Females attracted during the one‐week trapping period produced a mean of 6.9 progeny during the seven days. The sex ratio of the progeny was 1:1. Trap catches with the infested cobs were on average 13 times lower than catches with 2 mg of the artificial pheromone. Estimation of P. truncatus densities in a maize store at the beginning of the storage period (based on laboratory data) revealed that small initial numbers of P. truncatus, possibly attracted by a single male, sufficed to initiate high infestation rates later in the storage season.
Variation in performance of western flower thrips populations on susceptible and partially resistant cucumber
Authors: Jan de Kogel Willem , van der Hoek Marieke , Mollema Chris
Published: October 2003

Biotypic variation is of major concern in breeding for host plant resistance to insects. The existence or development of aggressive biotypes can lead to a rapid break‐down of host plant resistance. Therefore the study of biotypic variation should be included in breeding programs for resistance to insects. In the present study we measured the reproduction of randomly collected females of ten different populations of the insect herbivore Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) on one susceptible and two resistant cucumber (Cucumis sativus L.) accessions. Significant differences between thrips populations were observed on all three cucumber accessions. None of the populations had a significantly higher reproduction than the Dutch reference population NL1. For three populations, the Dutch population NL1, a population from New Zealand (NZ), and an Italian population (IT), partial life history parameters, such as reproduction rate, developmental time and survival were determined and the relative rate of increase rr was calculated. On all three cucumber accessions the rr‐value of population NZ was lower than of populations NL1 and IT. It is concluded that there is biotypic variation in F. occidentalis with regard to performance on cucumber plants with different levels of resistance. Reproduction is a good criterion for differentiating biotypes of F. occidentalis on cucumber.
Discrimination of oilseed rape volatiles by the honeybee: combined chemical and biological approaches
Authors: Pham‐Delègue M. H. , Blight M. M. , Kerguelen V. , Le Métayer M. , Marion‐Poll F. , Sandoz J. C. , Wadhams L. J.
Published: October 2003

Honeybees (Apis mellifera L.) were individually subjected to a classical conditioning procedure in order to obtain an olfactory conditioned proboscis extension response. To relate the behavioural response directly to antennal detection abilities, a technique was developped for coupling proboscis extension responses and electroantennogram recordings, with the stimulation being provided by the effluent of a gas chromatograph (GC). Bees were conditioned with a six‐component mixture being part of oilseed rape (Brassica napus L.) floral volatiles, and tested with the individual components separated by GC. Responses of the conditioned bees were compared to those of unconditioned bees. No behavioural response was obtained in the control group, neither to the individual components nor to the mixture. Conditioning induced behavioural responses for three components, and an increase of electroantennogram responses for all components. A second experiment was conducted with an air entrainment extract of oilseed rape flower volatiles. Behavioural responses of conditioned and unconditioned bees were recorded. Responses obtained from conditioned bees tested with the air entrainment extract showed six groups of behaviourally active GC peaks. Unconditioned bees showed the same pattern of responses but at a lower level. The coupled technique described here appears to be a reliable tool for locating active components in a synthetic as well as in a natural mixture of floral volatiles. The effects of conditioning on odour discrimination and on its sensory correlates are discussed.
Effect of entomopoxvirus infection of Pseudaletia separata larvae on the oviposition behavior of Cotesia kariyai
Authors: Kyei‐Poku George K. , Kunimi Yasuhisa
Published: October 2003

Parasitoid behavior and oviposition were monitored to investigate the ability of Cotesia kariyai (Watanabe) (Hymenoptera: Braconidae) to distinguish between entomopoxvirus‐infected and noninfected larvae of Pseudaletia separata Walker (Lepidoptera: Noctuidae). Comparison of individual means revealed that searching time was not significantly different between treatments. Ovipositional time, however, differed significantly after day 8 post virus inoculation. The parasitoid adopted ovipositional posture on infected and noninfected host irrespective of the stage of infection and did not distinguish infected from noninfected larvae up to 4 days post infection. Mean number of larvae stung by the parasitoid was not influenced by the length of time interval between exposure to the virus. However, duration of ovipositor insertion was influenced by the time interval between exposure to the virus and subsequent exposure to parasitoid females. Female parasitoids did not completely reject infected larvae as unsuitable for egg deposition. However, 5 days after virus inoculation they rejected significantly more infected than noninfected larvae. Furthermore, significantly more eggs were laid in noninfected than infected larvae from day 5 following virus administration. These observations suggest that probing by Cotesia kariyai may provide information concerning host suitability.
Foliar form, colour and surface characteristics influence oviposition behaviour of the carrot fly
Authors: Degen Thomas , Städler Erich
Published: October 2003

Various leaf models made of paper were presented to carrot flies, Psila rosae (F.) (Diptera: Psilidae) in choice assays to investigate the effect of non‐chemical plant traits on oviposition behaviour. The surrogate leaves differed in colour, shape, surface coating, size and stem length. In the presence of host‐plant extracts, physical factors strongly influenced oviposition. Green, yellow and orange three‐dimensional models similar in shape to host‐plant leaves (pinnately or ternately compound or dissected) and with a thin cover of paraffin wax were most acceptable to the females. Egg‐laying was not affected by leaf size, but was negatively correlated with stem length. The results obtained by testing models with simple leaf silhouettes were confirmed in an experiment using more lifelike imitations of real host and non‐host leaves. The findings are discussed by an extensive review of similar studies in three other phytophagous fly species (cabbage root fly, onion fly, Hessian fly).
Influence of temperature on bionomics of cotton aphid, Aphis gossypii, on cotton
Authors: Xia J.Y. , van, der Werf W. , Rabbinge R.
Published: October 2003

Life table parameters of Aphis gossypii Glover (Homoptera: Aphididae) on Gossypium hirsutum L. were determined at six temperatures (10, 15, 20, 25, 30, and 35 ± 0.5 °C) in the laboratory. Relationships of life table parameters with temperature were described with mathematical equations. Development was fastest at 30 °C, with a pre‐larviposition period of 4.6 d. Survival to adult was greatest at 25 °C (81%). Fecundity was highest at 25 °C, with a total fecundity of 28.3 nymphs per female and a mean reproductive rate of 3.1 nymphs per female per day. Threshold temperatures for development in the first through fourth instar and the adult were 8.2, 8.0, 7.2, 6.2 and 7.9 °C, respectively. The durations of these stages, expressed as temperature sums above these thresholds, were 24.2, 23.7, 23.0, 25.5 and 168.8 degree‐days (D°), respectively. A. gossypii achieved its maximum net reproductive number (24.4 nymphs per female) and greatest intrinsic rate of increase (0.386 d−1) at 25 °C. The high relative rate of population increase at 25 °C results in a daily population increase of 47% and a doubling time of only 1.8 d, illustrating the tremendous growth capacity of A. gossypii populations under favourable conditions. Compared to literature sources, our source of A. gossypii, fed on cotton, showed a comparatively great heat tolerance.
The scaling of body size and mass in a host‐parasitoid association: influence of host species and stage
Authors: Nicol C.M.Y. , Mackauer M.
Published: October 2003

We describe the allometry of body mass and body size as measured by hind‐tibia length in males of Monoctonus paulensis (Ashmead) (Hymenoptera: Braconidae, Aphidiinae), a solitary parasitoid of aphids. To assess the influence of host quality on allometric relationships, we reared parasitoids on second and fourth nymphal instars of four different aphid species, Acyrthosiphon pisum (Harris), Macrosiphum creelii Davis, Myzus persicae (Sulzer) and Sitobion avenae (F.), under controlled conditions in the laboratory. Dry mass was positively correlated with hind‐tibia length, and could be predicted from it, in unparasitized aphids, in aphid mummies containing parasitoid pupae, and in the parasitoid. The reduced‐major‐axis scaling exponents for the regression of dry mass on hind‐tibia length were species‐specific in aphids, reflecting differences in volume and shape between species. In mummified aphids, the stage at death influenced the size/mass relationship. In males of M. paulensis, the allometric exponent varied between parasitoids developing in different kinds of host. Individuals developing in pea aphid were absolutely larger in dry mass as well as proportionately larger relative to their hind‐tibia length. We discuss the allometry of body size and body mass in relation to parasitoid fitness.
Evaluation of felt traps to estimate egg numbers of cabbage root fly, Delia radicum, and turnip root fly, Delia floralis in commercial crops
Authors: Bligaard J. , Meadow R. , Nielsen O. , Percy‐Smith A.
Published: October 2003

The use of felt traps to estimate oviposition by the cabbage root fly, Delia radicum (L.), and turnip root fly, Delia floralis (Fall.), was compared with soil sampling at seven localities between 1992 and 1994 in Denmark and Norway. In all, 281 comparisons were made, based on 6800 samples. In 4.6% of these comparisons no eggs were found by either method. In 16% of the comparisons, 2.0±0.41 (±S.E.) eggs were found per soil sample and no eggs were found in felt traps, whereas in 0.7% of the comparisons 0.10±0.03 eggs were found per felt trap and no eggs in soil samples. When eggs were found using both methods, the ratio between soil sampling and felt traps varied from 13.1±3.2 when the egg laying rate was very low to 1.8±0.2 at high egg laying rates. Regression analysis showed significant correlation between felt trap catches and soil sampling (P<0.001), whereas locality did not influence felt trap efficiency (P=0.096). The influence of the physical conditions of felt traps, i.e., whether they were clean and dry, were analysed in a single year. Tentative action thresholds for control measures against cabbage root flies and turnip root flies were developed for cauliflower, Brassica oleracea, convar. botrytis (L.) Alef., var. botrytis, based on data from the literature and the present results.
Capacity of Bembidion lampros and Tachyporus hypnorum to survive periods of starvation in early spring
Authors: Petersen Mette K.
Published: October 2003

The capacity of the polyphagous predators Bembidion lampros Herbst (Coleoptera; Carabidae) and Tachyporus hypnorum F. (Coleoptera; Staphylinidae) to survive starvation in early spring was investigated. The two species are of similar size and live in the same habitat. They have similar life cycles; where adults emerge in autumn, hibernate during winter and disperse during spring into arable fields where they reproduce and then die. Both species showed an ability to survive long periods of starvation after hibernation. However, B. lampros could live without food several weeks longer than T. hypnorum.

Fat content was measured to estimate the energy reserves of beetles in the field. The fat content of B. lampros was at a constant level of 23% both when fed ad libitum in the laboratory and when collected in the field during spring. The fat content of B. lampros was reduced to a level of 7% when they died by starvation. Fat content of T. hypnorum was more variable both when fed ad libitum in the laboratory (17–33%), when collected in the field during the spring (20—26%) and when they died by starvation (10–20%).

Neither the mean longevity of starved beetles nor the fat content of specimens collected in the field indicated that the beetles suffered high mortality due to a food shortage in early spring before movement into arable fields.
Predation, behavior, and attachment by Chrysoperla plorabunda larvae on Brassica oleracea with different surface waxblooms
Authors: Eigenbrode Sanford D. , Kabalo Nelson N. , Stoner Kimberly A.
Published: October 2003

Predation by Chrysoperla plorabunda (Fitch) (Chrysopidae) first instars on Plutella xylostella (L.) (Plutellidae) neonates was measured on nine Brassica oleracea L. types with different surface wax crystal morphology. Forty‐eight‐hour survival of P. xylostella caged on leaves was significantly reduced by C. plorabunda on plants expressing ‘glossy’ mutations that reduce surface waxbloom, but not on plants with normal waxbloom. During 5‐min observations, C. plorabunda spent more time walking and less time ‘scrambling’ (moving the legs with no locomotion) on glossy types than on the normal‐wax types. Adhesive force produced by C. plorabunda on plant surfaces was 20 to 200‐fold greater on glossy types than on normal‐wax types. All the glossy types provided an advantage to C. plorabunda over normal‐wax types by increasing the force of attachment to the leaf suface by the larvae, which in turn increased time allocated to walking, leading to greater predation of P. xylostella larvae. Among glossy and normal wax types together, attachment force and time allocated to walking were significantly correlated with predation by C. plorabunda. Within glossy or normal‐wax types, however, these correlations were not significant. Neither time allocated to walking, nor attachment to the leaf surface was a predictor of predation by C. plorabunda within glossy or normal‐wax types. Although diverse mechanisms therefore contribute to differences in predation, the results show that reduction in waxbloom can substantially affect the mobility and effectiveness of this generalist predator.
Quantitative genetic analysis of biotypes of the brown planthopper Nilaparvata lugens: heritability of virulence to resistant rice varieties
Authors: Tanaka Koichi
Published: October 2003

The virulence of Nilaparvata lugens Stål (Homoptera: Delphacidae) to a resistant variety of rice, Oryza sativa L., is suggested to be under polygenic control. To determine whether the virulence of N. lugens is a quantitative character that has continuous distribution or a threshold character that has a few discontinuous phenotypic forms and is determined by some underlying continuous variable, I examined the frequency distribution of honeydew excretion that has been used as a measure of ability of attacking the rice plants, and the relationship between honeydew excretion and the oviposition rate of N. lugens females using a japonica rice line Saikai 190 which has a resistance gene Bph 1. The frequency distribution in honeydew excretion significantly differed from the normal distribution, but two distributions below and above 10 mg honeydew excretion for two days did not significantly deviate from normality, suggesting a bimodal distribution. There were significant differences in the proportion of females ovipositing and the number of eggs deposited between the female groups that excreted 0–10 mg honeydew and more than 20 mg honeydew. Within these female groups, however, the reproductive performances were not different. Thus, virulence of N. lugens can be analyzed as a threshold character that has two distinct phenotypes, virulent and avirulent. I estimated the heritabilities of the virulence of N. lugens by parent‐offspring regression using the percentage of virulent females in a full‐sib family. The estimates of heritability were 0.41 on Saikai 190 and 0.55 on ASD7, carrying the bph 2 gene. These results show that the N. lugens population has substantial genetic variation in virulence. The regression coefficients on female and male parents were similar, suggesting similar genetic contributions by both parents. When the parental families were examined on Saikai 190 and the progeny on ASD7, the regression coefficient approached zero. There may be a low genetic correlation between virulences to the two varieties.
Effects of Brassica oleracea waxblooms on predation and attachment by Hippodamia convergens
Authors: Eigenbrode Sanford D. , Kabalo Nelson N.
Published: October 2003

Four mutations that reduce waxbloom in Brassica oleracea L. were examined for their effects on predation, mobility, and adhesion to the plant surface by the general predator Hippodamia convergens (Guérin‐Menéville) (Coleoptera: Coccinellidae). The mutations reduce waxbloom to different degrees, but all produce a ‘glossy’ phenotype. Plants tested were inbred lines, near isogenic lines, or segregating F2 populations, depending on the mutation. In an experiment on caged leaves, predation of Plutella xylostella L. larvae by H. convergens adult females was significantly greater on glossy types as compared with ‘normal‐wax’ or wild‐type counterparts. Although the trend was the same for each mutation, individual comparisons between glossy and normal‐wax lines or segregants were only significant for two of them, those producing mutant alleles gla and gld. Individual H. convergens were observed to spend more time walking on leaf edges and less time walking on leaf surfaces of normal‐wax plants than glossy plants. Hippodamia convergens also obtained better adhesion to the surfaces of glossy plants than to normal‐wax plants when tested using a centrifugal device. Two of the mutations produced similarly strong effects on predation, behaviour, and adhesion by H. convergens. These two are the same previously determined by us to provide the strongest similar effects on another generalist predator, Chrysoperla plorabunda (Fitch). The results indicate that waxbloom variation in nature could affect herbivore populations through its effects on generalist predators.
The population ecology of Amorbus Dallas (Hemiptera: Coreidae) species in Australia
Authors: Steinbauer Martin J.
Published: October 2003

Species of Amorbus Dallas (Hemiptera: Coreidae) appear to exhibit a tight link between oviposition preference and nymphal performance: females apparently select vigorous plant modules to facilitate the development of their offspring. Such behaviour suggests that these insects should exhibit population dynamics consistent with the latent classification proposed by Price et al. (1990). While this empirical hypothesis is intuitively appealing it does not appear to incorporate current population dynamics theory. Berryman's ecodynamics (1992) offers the potential to describe a species' population dynamics which is grounded in a quantitative theoretical framework. The population ecology of Amorbus species from Australia is considered in relation to these hypotheses.
Behavioural correlates of genetic divergence due to host specialization in the pea aphid, Acyrthosiphon pisum
Authors: Caillaud Marina C.
Published: October 2003

Host specialization plays a central role in the diversification of herbivorous insects and yet we know very little about the evolution of this trait. Populations of the pea aphid, Acyrthosiphon pisum (Harris), are specialized and locally adapted to either alfalfa or clover. Preference for either plant produces assortative mating, and gene flow between alfalfa and clover populations is consistently restricted (Via, 1991a,b, 1994). Behavioural studies of freely‐moving aphids on the plant surface for 30 min suggest that host preference is chemically mediated, involves chemoreception, and is most likely due to secondary compounds located in the epidermal or mesophyll cells. Pea aphids do not distinguish between hosts and non‐hosts at a distance but determine whether the plant is suitable or not after only a short probe. Thirty‐minute recordings of the activities of aphid stylets using an electrical monitoring system (EPG), where aphids are attached to a gold wire with silver paint, provide a different picture, suggesting that EPG experiments do not accurately reflect natural behaviour during the first 30 min of the aphid‐plant interaction.
The ground and excited state potential energy surfaces of nitromethane related to its dissociation dynamics after excitation at 193 nm
Authors: Arenas Juan F. , Otero Juan C. , Peláez Daniel , Soto Juan
Published: October 2003

The relevant low-lying singlet and triplet potential energy surfaces in the photolysis of nitromethane have been studied by using the multistate extension of the multiconfigurational second-order perturbation theory in conjunction with large atomic natural orbital-type basis sets. The proposed mechanism for the photolytic decomposition of CH3NO2 provides a consistent and reinterpreted picture of the available experimental results. Two reaction paths are found in the photolysis of nitromethane after excitation at 193 nm: (1) Major Channel, CH3NO2(1A′)+hν(193 nm)→CH3NO2(2A″)→ lim  ICCH3NO2(2A′)→CH3(1A1′)+NO2(1 2B1)→ lim −hν′ICCH3(1A1′)+NO2(1 2A1)→ lim 193 nmhνCH3(1A1′)+NO(A 2Σ+)+αO(3P)+βO(1D). (2) Minor Channel, CH3NO2(1A′)+hν(193 nm)→CH3NO2(2A″)→CH3(1A1′)+NO2(1 2A2)→CH3(1A1′)+NO(X 2Π)+αO(3P)+βO(1D), being α and β fractional numbers. No ionic species are found in any dissociation path. Additionally, the respective low-lying Rydberg states of nitromethane and nitrogen dioxide have been studied too.
Global minima for rare gas clusters containing one alkali metal ion
Authors: Hernández-Rojas Javier , Wales David J.
Published: October 2003

We present candidate structures for the global minima of N-atom rare gas clusters containing one additional alkali metal ion, LJNM. Lennard-Jones and Mason–Schamp potentials are used to represent the rare gas–rare gas and rare gas–alkali metal ion interactions, respectively. Results are presented for parameters appropriate to both Ar–K+ and Xe–Cs+ systems. When the ion is closer in size to the rare gas atoms (for XeNCs+) the global minima tend to be based on icosahedral packing. However, when the ion is relatively small (for ArNK+) the global minima below a certain size threshold are based on structures where the ion has lower coordination numbers. For larger clusters the global minima are again based on icosahedral packing. The latter structures can be found with minimal computational effort using the known global minima for clusters bound by Lennard-Jones or Morse potentials, substituting one atom at a time by the ion and minimizing.
The dissociation adiabaticity parameter and the strong field dissociation of H2+
Authors: Paci Jeffrey T. , Wardlaw David M.
Published: October 2003

Walsh et al. have proposed a dissociation adiabaticity parameter, γDv≡(Dv/2Upm)1/2, where Dv is the dissociation energy from vibrational state v and Upm is the molecular ion system’s ponderomotive energy [T. D. G. Walsh, L. Strach, and S. L. Chin, J. Phys. B 31, 4853 (1998)]. We modify this parameter and assess its utility in the interpretation of kinetic energy distributions of the atoms and protons that are produced by quantum wave-packet simulations of the H2+ dissociation process. This modified parameter, γmol, is found to be a useful indicator of when a dissociation process can be best described using multiphoton processes involving field dressed electronic states (γmol>1) or when it can be better described in the quasistatic approximation as barrier suppressed dissociation (γmol<1). Field dressed electronic states and oscillating potential energy curve tails govern the behavior at the extreme values of γmol, i.e., γmol≫1 or ≪1, respectively.
A constrained maximum entropy method in polymer statistics
Authors: La Penna Giovanni
Published: October 2003

A modified version of the maximum entropy principle, called “constrained maximum entropy” method (MEC), is revisited to combine the information obtained in computer simulations of polymers with external information in the form of configurational averages. A random-temperature molecular dynamics trajectory is being proposed as a biased random walk in configurational space to be reweighted by using the given average information. This random walk, generating a “meta” configurational probability, has been found to contain relevant information on the system. The method is compared with other computational techniques, like the generalized-ensemble and configurational-biased Monte Carlo, for simple models in the field of polymers and biopolymers. The main features of polymer configurational distribution functions of interest in polymer physics are consistent among the different methods in a wide range of temperatures and especially at room conditions. The advantage of the MEC approach is in taking into account all the degrees of freedom in the model, thus allowing applications in complicated biopolymers in the explicit solvent.
Effect of solvent on molecular conformation: Microwave spectra and structures of 2-aminoethanol van der Waals complexes
Authors: Tubergen Michael J. , Torok Charles R. , Lavrich Richard J.
Published: October 2003

Rotational spectra of the C13 isotopomers of the 2-aminoethanol monomer have been recorded in natural abundance using a Fourier-transform microwave spectrometer. The two sets of C13 isotopomer rotational constants were used to complete the 2-aminoethanol substitution structure. Rotational spectra of the van der Waals complexes 2-aminoethanol–water and 2-aminoethanol–argon were also recorded. Sixteen a-, b-, and c-type transitions were fit to the Watson A-reduction Hamiltonian for 2-aminoethanol–argon yielding A=4986.762(2) MHz, B=1330.693(3) MHz, and C=1143.933(3) MHz. Fifteen a- and b-type transitions for 2-aminoethanol–water were fit to A=4886.451(5) MHz, B=3356.038(2) MHz, and C=2311.715(2) MHz. The spectra are assigned to the lowest-energy ab initio [MP2/6-311++G(d,p)] structures of the two complexes. The conformation of 2-aminoethanol is unchanged in the argon complex, and the argon is 3.775 Å from the monomer center of mass. A network of intermolecular hydrogen bonds in the 2-aminoethanol–water complex replaces the intramolecular hydrogen bond of the monomer, and formation of the network requires the OCCN torsional angle to increase from 57° to 75° and the O–N distance to increase from 2.796 to 3.100 Å.
Higher-order continuum approximation for rarefied gases
Authors: Spiegel Edward A. , Thiffeault Jean-Luc
Published: October 2003

The Hilbert–Chapman–Enskog expansion of the kinetic equations in mean flight times is believed to be asymptotic rather than convergent. It is therefore inadvisable to use lower order results to simplify the current approximation as is done in the traditional Chapman–Enskog procedure, since that is an iterative method. By avoiding such recycling of lower order results, one obtains macroscopic equations that are asymptotically equivalent to the ones found in the Chapman–Enskog approach. The new equations contain higher order terms that are discarded in the Chapman–Enskog method. These make a significant impact on the results for such problems as ultrasound propagation. In this paper, it is shown that these results turn out well with relatively little complication when the expansions are carried to second order in the mean free time, for the example of the relaxation or Bhatnagar–Gross–Krook model of kinetic theory.
Fourth-order statistical moments of the velocity gradient tensor in homogeneous, isotropic turbulence
Authors: Hierro Juan , Dopazo César
Published: October 2003

A compact expression of fourth-order statistical moments of the velocity gradient tensor in homogeneous, isotropic, incompressible turbulence is obtained as a function of its invariants and of generic components of the velocity gradient. This single, compact expression is in full agreement with the four different expressions previously obtained by Siggia as functions of the same invariants and of generic components of the vorticity vector and the strain tensor; however, some discrepancies arise with respect to a similar, single expression obtained by Phan-Thien and Antonia. The used algorithm may be easily extended to handle higher order statistical moments of the velocity gradient.
Vortex breakdown in a slowly varying tube impulsively rotated about its axis with constant angular velocity
Authors: MacDonald D. A.
Published: October 2003

For time t̄<0 viscous fluid is in slow flow through a long straight axially symmetric tube whose radius, ā(x̄), varies slowly with axial distance, x̄. When t̄=0 the tube is impulsively rotated about its axis with angular velocity, Ω̄, at which angular speed it is thereafter maintained. When Re=Wa/ν=O(1) and ε=W̄ā02/νL̄→0, λ=Ωa/W→∞ with Γ=ελ2 finite, MacDonald [Phys. Fluids 12, 3168 (2000)] has shown that during the transition from zero angular velocity to solid body rotation the flow in the tube is strikingly different for a diverging and a converging tube, when Γ is sufficiently large. Here, ε is the Blasius parameter for slowly varying tubes and ā0 and W denote a reference radius and velocity, respectively. When the tube is diverging, a bubble of recirculating fluid, centered on the axis can occur. This bubble satisfies the definitions of vortex breakdown. When the tube is converging, a toroid of recirculating fluid can occur adjacent to the wall of the tube. Streamlines for each of these cases have been presented [D. A. MacDonald, Phys. Fluids 12, 3168 (2000)]. In this article we shall determine Γ0, the lowest value of Γ for which the toroid will occur, and t̄0, the corresponding instant of time at which it first appears in converging tubes. The wall shear stress is shown to become of large magnitude and graphs of its behavior with x̄/L, where L is a representative length in the axial direction, are presented, when νt̄/ā02=0.1, for representative wall profiles. It is found that incipient flow reversal at the walls of the converging tube ā=(ā0/2)[3−tanh(x̄/L)] occurs at x̄/L=−0.5750, and the critical swirl and the time of occurrence are determined. A figure showing the wall stress against axial distance is also presented for a typical diverging tube when t≡t̄ν/ā02=0.1.
Two- and three-dimensional photonic crystals made of macroporous silicon and liquid crystals
Authors: Mertens Guido , Röder Thorsten , Matthias Heinrich , Marsmann Heinrich , Kitzerow Heinz-Siegfried R. , Schweizer Stefan L. , Jamois Cecile , Wehrspohn Ralf B. , Neubert Mary
Published: October 2003

Variations of the refractive index can be utilized in order to shift the stop band in periodic structures, such as photonic crystals. We report on investigations about three-dimensional macroporous silicon structures that are filled with a liquid crystal. Fourier transform infrared measurements indicate that a shift of the photonic band edge can be induced by changing the temperature. The director field in macropores within the silicon structure is investigated by H-NMR2 spectroscopy and compared to director field simulations. The latter method indicates a preferred parallel orientation of the director in the nematic state. Based on this finding, we analyze the optical properties.
Effects of vibration method and wall boundaries on size segregation in granular beds
Authors: Fernando D. N. , Wassgren C. R.
Published: October 2003

This paper investigates the rise rate of a large impurity in an otherwise homogeneous granular bed subject to discrete and continuous vertical oscillations. Experiments and two-dimensional discrete element computer simulations reveal that the impurity rise rate depends upon the oscillation method when side-wall convection effects are negligible. For discrete oscillations the rise rate increases monotonically with the oscillation velocity amplitude while for continuous oscillations the rise rate reaches a maximum value at a critical velocity amplitude. The rise rate trends correlate with changes in the bed void fraction. When side-wall convection effects are present, the rise rate of the impurity increases linearly with the oscillation velocity amplitude regardless of the vibration method. The results from the studies presented here reconcile the seemingly inconsistent results reported previously in the literature.
Effect of turbulence on the drag and lift of a particle
Authors: Bagchi P. , Balachandar S.
Published: October 2003

A direct numerical simulation (DNS) is used to study the effect of a freestream isotropic turbulent flow on the drag and lift forces on a spherical particle. The particle diameter is about 1.5–10 times the Kolmogorov scale, the particle Reynolds number is about 60–600, and the freestream turbulence intensity is about 10%–25%. The isotropic turbulent field considered here is stationary, i.e., frozen in time. It is shown that the freestream turbulence does not have a substantial and systematic effect on the time-averaged mean drag. The standard drag correlation based on the instantaneous or mean relative velocity results in a reasonably accurate prediction of the mean drag obtained from the DNS. However, the accuracy of prediction of the instantaneous drag decreases with increasing particle size. For the smaller particles, the low frequency oscillations in the DNS drag are well captured by the standard drag, but for the larger particles significant differences exist even for the low frequency components. Inclusion of the added-mass and history forces, computed based on the fluid velocity at the center of the particle, does not improve the prediction. Different estimates of the fluid velocity seen by the particle are examined. It is shown that the mean drag is insensitive to the fluid velocity measured at the particle center, or obtained by averaging over a fluid volume of the order of the particle size. The fluctuations diminish as the size of the averaging volume increases. The effect of increasing freestream turbulence intensity for the same particle size is studied. Fluctuations in the drag and lift forces are shown to scale with the mean drag and freestream intensity. The standard drag without the added-mass and history forces provides the best approximation to the DNS result.
Chaotic advection in a braided pipe mixer
Authors: Finn Matthew D. , Cox Stephen M. , Byrne Helen M.
Published: October 2003

Chaotic advection is investigated in a “braided pipe mixer” (BPM). This static mixing device consists of an outer pipe containing several intertwining internal pipes, with fluid pumped down the gap. It has recently been proposed, by analogy with the two-dimensional theory of topological chaos, that the BPM should be an effective mixing device, specifically that (i) good mixing might be achieved with only very thin internal pipes, and (ii) the quality of the mixing should be improved if the internal pipes form a mathematical braid. Our results suggest that neither (i) nor (ii) is the case for the BPM studied.
Viscosity of argon at temperatures >2000 K from measured shock thickness
Authors: Macrossan Michael N. , Lilley Charles R.
Published: October 2003

Mott-Smith’s kinetic theory of shock structure [Phys. Rev. 82, 885 (1951); C. Muckenfuss, Phys. Fluids 5, 1325 (1962)] suggests that, for any intermolecular potential, the average number of collisions undergone by a molecule as it crosses the shock approaches a limit as the Mach number increases. We check this with direct simulation Monte Carlo calculations and use it to estimate the gas viscosity at high temperatures from measurements of shock thickness. We consider a monatomic gas (γ=5/3) for five different collision models and hence five different viscosity laws μ=μ(T). The collision models are: the variable hard sphere, σ∝1/g2v, with three values of v; the generalized hard sphere; and the Maitland–Smith potential. For shock Mach numbers M1≳4.48, all these collision models predict a shock thickness Δ=11.0λs±2.5%, where λs is a suitably defined “shock length scale” which depends on a collision cross section derived from the viscosity of the gas at a temperature Tg, characteristic of the collisions between upstream and downstream molecules. Using Δ=11λs and the experimental measurements of shock thickness in argon given by Alsmeyer [J. Fluid Mech. 74, 498 (1976)], we estimate the viscosity of argon at high values of Tg. These estimates agree with the values recommended by the CRC Handbook of Chemistry and Physics, 82nd ed. (CRC Press, Boca Raton, FL, 2001) at T≈1500 K. For T≳2000 K, for which there appear to be no reliable direct measurements of viscosity, our estimated values lie between those recommended by the CRC Handbook and those predicted by the simple power law μ=μref(T/Tref)0.72, with Tref=300 K and μref=2.283×10−5 Pa s. Taking the error in the experimental measurements of Δ as the scatter in the results of Alsmeyer (±2%), we estimate the uncertainty in the viscosity predictions as less than ±5%. To this accuracy, our results agree with the power law predictions and disagree with the CRC Handbook values, for T≳3000 K.
Quantitative measurement of the influence of growth interruptions on the Sb distribution of GaSb/GaAs quantum wells by transmission electron microscopy
Authors: Schowalter M. , Rosenauer A. , Gerthsen D. , Grau M. , Amann M.-C.
Published: October 2003

We investigated the influence of growth interruptions on the morphology of molecular-beam epitaxy grown GaSb/GaAs multiquantum-well structures by transmission electron microscopy (TEM). Profiles of the chemical composition of the GaSb layers were deduced from high-resolution TEM images with the lattice fringe analysis method. We found clear indications of segregation of Sb in GaAs-on-GaSb for a sample grown with growth interruption before and after the growth of the quantum wells. Its efficiency R=0.78±0.03 was derived by fitting the measured composition profiles with the model of Muraki. Determination of the total amounts of deposited GaSb yields a higher amount of GaSb in a sample grown without interruption.