Development of oviposition behavior of Brachymeria intermedia, a parasitoid of the gypsy moth, Lymantria dispar.

Brachymeria intermedia is an introduced endoparasitoid of the gypsy moth, Lymantria dispar. To gain understanding of the basic mechanisms by which B. intermedia influence population densities of the gypsy moth, the oviposition behavior of this parasitoid was studied. Both the physiological state and the informational state of the animal at a certain point in time may influence the development of the behavior. Factors of the physiological state here investigated are egg load and age of the female parasitoid. Factors of the informational state here investigated are the number of hosts previously encountered, the host species encountered and characteristics of the sites where pupae previously were encountered. Chapter 1 contains the introduction and outline of the study. Chapter 2 shows that experience is an important factor influencing the rate of acceptance of hosts by the parasitoid. The sequence of behaviors before ovipositor insertion does not change with experience. Chapter 3 shows that parasitoids, deprived of hosts from emergence, accumulate eggs up to a certain level, but have a low rate of acceptance. Early exposure to pupae increases the rate of acceptance. B. intermedia adjust their egg production to host availability. Chapter 4 shows that the rate of acceptance for an alternate host increased with age in parasitoids, deprived of hosts from emergence. Rearing the parasitoids on an alternate host and/or oviposition experience on an alternate host did not influence the rate of acceptance of the alternate host. After oviposition experience on the alternate host contaminated with kairomone, uncontaminated hosts were accepted at the same rate as gypsy moth. Chapter 4 shows that B. intermedia is able to use learned visual cues, thereby restricting their searching area to a microhabitat previously found to be profitable. Under laboratory conditions and under semi-natural conditions, parasitoids could be trained to search for pupae either on the ground or on a tree model. Subsequent training to the other microhabitat reversed this effect. The studies show that both the physiological state and the informational state of the parasitoid influence oviposition behavior. Questions are raised and discussed as to the extent of polyphagy of B. intermedia in North America

The asymptotic structure of nearly unstable non-negative integer-valued AR(1) models

This paper considers non-negative integer-valued autoregressive processes where the autoregression parameter is close to unity. We consider the asymptotics of this `near unit root' situation. The local asymptotic structure of the likelihood ratios of the model is obtained, showing that the limit experiment is Poissonian. To illustrate the statistical consequences we discuss efficient estimation of the autoregression parameter and efficient testing for a unit root.Comment: Published in at http://dx.doi.org/10.3150/08-BEJ153 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Local Asymptotic Equivalence of the Bai and Ng (2004) and Moon and Perron (2004) Frameworks for Panel Unit Root Testing

This paper considers unit-root tests in large n and large T heterogeneous panels with cross-sectional dependence generated by unobserved factors. We reconsider the two prevalent approaches in the literature, that of Moon and Perron (2004) and the PANIC setup proposed in Bai and Ng (2004). While these have been considered as completely different setups, we show that, in case of Gaussian innovations, the frameworks are asymptotically equivalent in the sense that both experiments are locally asymptotically normal (LAN) with the same central sequence. Using Le Cam's theory of statistical experiments we determine the local asymptotic power envelope and derive an optimal test jointly in both setups. We show that the popular Moon and Perron (2004) and Bai and Ng (2010) tests only attain the power envelope in case there is no heterogeneity in the long-run variance of the idiosyncratic components. The new test is asymptotically uniformly most powerful irrespective of possible heterogeneity. Moreover, it turns out that for any test, satisfying a mild regularity condition, the size and local asymptotic power are the same under both data generating processes. Thus, applied researchers do not need to decide on one of the two frameworks to conduct unit root tests. Monte-Carlo simulations corroborate our asymptotic results and document significant gains in finite-sample power if the variances of the idiosyncratic shocks differ substantially among the cross sectional units

Toy story: homophily, transmission and the use of simple models in assessing variability in the archaeological record

The interpretation of spatial and temporal patterns in the archaeological record remains a long-standing issue in the discipline. Amongst many methods and interpretations, modelling of ‘biased transmission’ has proved a successful strategy to tackle this problem. Here, we investigate a type of biased transmission, homophily, that is the tendency of individuals to associate and bond with similar others. In contrast to other social sciences, homophily remains underused in archaeology. In order to fill this gap, we develop six distinct variants of a well-established modelling framework borrowed from social science, Axelrod’s Cultural Dissemination Model. These so-called toy models are abstract models used for theory-building and aim at exploring the interplay between homophily and various factors (e.g. addition of spatial features such as mountains and coastlines, diffusion of innovations and population spread). The relevance and implications of each ‘toy model’ for archaeological reasoning are then discussed

Kwaliteit van de arbeid in pluimveehouderijsystemen als alternatief voor de legbatterij

Doel van het project is het beoordelen van de kwaliteit van de arbeid in de belangrijkste momenteel bekende huisvestingssystemen voor leghennen (inclusief de batterijhuisvesting). Op basis van deze integrale beoordeling van de arbeidskwaliteit zullen de gezondheidskundige implicaties voor de werkende mensen in elk van die huisvestingssystemen worden aangegeve

Efficient Estimation in Semiparametric Time Series: the ACD Model

In this paper we consider efficient estimation in semiparametric ACD models. We consider a suite of model specifications that impose less and less structure. We calculate the corresponding efficiency bounds, discuss the construction of efficient estimators in each case, and study tvide a simulation study that shows the practical gain from using the proposed semiparametric procedures. We find that, although one does not gain as much as theory suggests, these semiparametric procedures definitely outperform more classical procedures. We apply the procedures to model semiparametrically durations observed on the Paris Bourse for the Alcatel stock in July and August 1996.

Preliminary Results on Chemical Thinning of Apple Blossoms with Ammonium Thiosulphate, NAA, and Ethephon

Preliminary tests were carried out using ammonium thiosulphate as a chemical thinning agent for apple ('Cox's Orange Pippin' and 'Braeburn') blossoms. Ethephon and NAA (1-napthylacetic acid) were included for comparison. Whole tree sprays of 37g/l ammonium thiosulphate over-thinned 'Cox's Orange Pippin' blossoms and severely scorched blossoms, foliage, and apical meristems. Ethephon at 0.35 g/l also over-thinned, and NAA thinned to an intermediate extent when compared with the controls. When the lower concentration of 3.7 g/l ammonium thiosulphate was directly applied to stamens and styles of 'Braeburn' blossoms by brush, initial fruit set was only 30% that of untreated blossoms. When 0.35 g/I ethephon was directly applied by brush to spur leaves or petals of 'Braeburn' blossoms at pink bud, initial fruit set was only 23% that of untreated blossoms. lt is concluded that ammonium thiosulphate has the potential to thin apple blossoms. Further experiments to define optimum concentrations and spray volumes are needed