6,445 research outputs found

    Description of the immature stages of the planthopper Lacertinella australis (Hemiptera: Delphacidae)

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    The five immature stages of the planthopper Lacertinella australis(Remes Lenicov and Rossi Batiz) (Hemiptera: Delphacidae: Saccharosydnini) are described and illustrated. The main characters that al-lowed us to distinguish the various stages were body size, number of tarsomeres and metatibial spines, and number of teeth on the spur. New biological data based on laboratory rearing and field observations showed that L. australiscan carry out its biological cycle successfully on the graminaceous pampas grass (Cortaderia spp. Stapf (Poales: Poaceae)). In addition, the efficient rearing in captivity, the high survivor-ship registered, and overwintering only on this host plant suggests that L. australisis a potential biocontrol agent of this invasive graminaceous weed. This study provides information about the immature stages, including a key for their identification, based on laboratory reared specimens and field observations.Se describen e ilustran las cinco etapas inmaduras de la especie de Saccharisydnini Lacertinella australis(Remes Lenicov and Rossi Batiz) (Hemiptera: Delphacidae). Los principales caracteres que permitieron distinguir las diferentes etapas fueron: tamaño corporal, número de espinas en los tarsómeros y metatibia y número de dientes en el espolón tibial. Nuevos datos biológicos, basados en la cría de laboratorio y obser-vaciones de campo, mostraron que L. australispuede realizar su ciclo biológico exitosamente en la graminácea cortadera (Cortaderiaspp. Stapf (Poales: Poaceae)). Además, la eficiente crianza en cautive-rio y la alta supervivencia registrada en esta planta hospedera, sugieren que L. australis podría ser usada como un potencial agente de control biológico de esta maleza invasora. Este estudio proporciona informa-ción sobre las etapas inmaduras, incluyendo una clave para su identificación, basada en individuos provenientes de la cría de laboratorio y de campoFil: Rossi Batiz, Maria Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Marino, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; Argentin

    Semi-Parametric Empirical Best Prediction for small area estimation of unemployment indicators

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    The Italian National Institute for Statistics regularly provides estimates of unemployment indicators using data from the Labor Force Survey. However, direct estimates of unemployment incidence cannot be released for Local Labor Market Areas. These are unplanned domains defined as clusters of municipalities; many are out-of-sample areas and the majority is characterized by a small sample size, which render direct estimates inadequate. The Empirical Best Predictor represents an appropriate, model-based, alternative. However, for non-Gaussian responses, its computation and the computation of the analytic approximation to its Mean Squared Error require the solution of (possibly) multiple integrals that, generally, have not a closed form. To solve the issue, Monte Carlo methods and parametric bootstrap are common choices, even though the computational burden is a non trivial task. In this paper, we propose a Semi-Parametric Empirical Best Predictor for a (possibly) non-linear mixed effect model by leaving the distribution of the area-specific random effects unspecified and estimating it from the observed data. This approach is known to lead to a discrete mixing distribution which helps avoid unverifiable parametric assumptions and heavy integral approximations. We also derive a second-order, bias-corrected, analytic approximation to the corresponding Mean Squared Error. Finite sample properties of the proposed approach are tested via a large scale simulation study. Furthermore, the proposal is applied to unit-level data from the 2012 Italian Labor Force Survey to estimate unemployment incidence for 611 Local Labor Market Areas using auxiliary information from administrative registers and the 2011 Census

    Evaluation of the effect of irrigation on biometric growth, physiological response and essential oil of Mentha spicata (L.)

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    A field experiment was performed on spearmint (Mentha spicata L.) under different irrigation regimes in a hilly area of Southern Italy. Objectives of the study include evaluating the physiological and biometrical response of mint from plant establishment up to its complete maturation, as well as the yield composition in essential oil at two different dates. Increasing levels of water stress affected later developing leaves and plant’s water status and net photosynthesis (from the beginning of stress (DAT 63), while affecting negatively the biometric response very soon and significantly from 35 DAT. Photosynthesis limitation played a critical role from DAT 53 on, namely later, in the harvest period (DAT 35–70). Under severe water stress, crop restricted water losses by modulating stomatal closure and, at harvest, showing lowered mesophyll conductance. Irrigation treatments did not affect the concentration of organic compounds, while the yield of essential oils was negatively affected by water stress due to reduced crop growth, in terms of total and leaf biomass, leaf area index (LAI) and crop heightinfo:eu-repo/semantics/publishedVersio

    Multiple imputation and selection of ordinal level 2 predictors in multilevel models. An analysis of the relationship between student ratings and teacher beliefs and practices

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    The paper is motivated by the analysis of the relationship between ratings and teacher practices and beliefs, which are measured via a set of binary and ordinal items collected by a specific survey with nearly half missing respondents. The analysis, which is based on a two-level random effect model, must face two about the items measuring teacher practices and beliefs: (i) these items level 2 predictors severely affected by missingness; (ii) there is redundancy in the number of items and the number of categories of their measurement scale. tackle the first issue by considering a multiple imputation strategy based on information at both level 1 and level 2. For the second issue, we consider regularization techniques for ordinal predictors, also accounting for the multilevel data structure. The proposed solution combines existing methods in an original way to solve specific problem at hand, but it is generally applicable to settings requiring to select predictors affected by missing values. The results obtained with the final model out that some teacher practices and beliefs are significantly related to ratings about teacher ability to motivate students.Comment: Presented at the 12th International Multilevel Conference is held April 9-10, 2019 , Utrech

    Study of the immature stages of two species of the biting midge genus Culicoides (Diptera: Ceratopogonidae)

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    Pupa of Culicoides insignis Lutz, 1913, and larva and pupa of Culicoides bambusicola Lutz, 1913 are fully described. They are illustrated and photographed using binocular microscope, phase-contrast stereoscope at oil immersion and scanning electronic microscopy, from material collected in Corrientes and Misiones provinces, Argentina. Palatum, maxilla and hypopharynx of the fourth instar larva of C. bambusicola as well as the cephalothoracic sensilla and sensillar pattern of the fi rst and fourth abdominal segment of the pupa are described for both species. The immatures of C. bambusicola are compared with Culicoides debilipalpis Lutz, 1913. Pupa of C. insignis is compared with the following related congeners: C. maruim Lutz, 1913, C. charruus Spinelli & Martinez, 1992, and C. annetae Spinelli & Borkent, 2004.Fil: Marino, Pablo Ignacio. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Cazorla, Carla Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; ArgentinaFil: Ronderos, Maria Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentin
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