Biological characteristics and parasitism capacity of Trichogramma pretiosum Riley (Hymenoptera, Trichogrammatidae) on eggs of Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae).

ABSTRACT. Biological characteristics and parasitism capacity of Trichogramma pretiosum Riley (Hymenoptera, Trichogrammatidae) on eggs of Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae). This study aimed at evaluating the biological characteristics and the capacity of parasitism of a Trichogramma pretiosum Riley, 1869 (Hymenoptera, trichogrammatidae) strain (T. pretiosum RV) collected in Rio Verde County, State of Goiás, Brazil. The study was carried out on eggs of Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera, Noctuidae) and conducted under controlled environmental conditions at different constant temperatures. The biological parameters determined were: developmental time (egg-adult; days); emergence (%); sex ratio; number of progeny/egg; number of generation/year; thermal constant (K); temperature threshold (Tb); daily number of parasitized eggs; cumulative parasitism (%); total number of eggs parasitized by T. pretiosum; and female longevity. To study the T. pretiosum parasitism capacity, 20 S. frugiperda eggs (? 24 h old) were placed into 8.0 cm x 2.0 cm glass vials containing one female (? 24 h old) each. Trials were carried out in a completely randomized experimental design, with 20 replications at each temperature. The environmental chambers (BOD type) were set at 18ºC, 20o C, 22o C, 25o C, 28o C and 32o C ± 1o C, 70 ±10% relative humidity, and 14/10 h (L:D) photoperiod. The eggs of S. frugiperda were replaced daily until parasitoid death. Results have shown an inverse correlation between developmental time and temperature, with statistically significant differences among means, except at 25ºC and 28ºC (10 days). Parasitoid emergence (%) was also influenced by temperature. The lowest percent emergence was observed at 32ºC, and the highest ones at 18ºC and 20ºC temperatures. The temperature did not affect T. pretiosum sex ratio and number of parasitoids per egg, thus allowing changes in the temperature to control insect mass production in the laboratory to meet the needs for field releases. RESUMO: Características biológicas e capacidade de parasitismo de Trichogramma pretiosum Riley (Hymenoptera, Trichogrammatidae) em ovos de Spodoptera frugiperda (J. E. Smith) (Lepidóptera, Noctuidae). O objetivo deste estudo foi avaliar as características biológicas e a capacidade de parasitismo de uma linhagem de Trichogramma pretiosum Riley, 1869 (Hymenoptera, Trichogrammatidae), coletada em Rio Verde, Goiás, Brasil (T. pretiosum RV). O estudo foi feito com ovos de Spodoptera frugiperda (J. E. Smith) (Lepidóptera, Noctuidae) e conduzido sob condições ambientais controladas e em diferentes temperaturas constantes. Os parâmetros biológicos determinados foram: período de desenvolvimento (ovo-adulto; dias); emergência (%); razão sexual; número de progênie/ovo; número de gerações/ano; constante térmica (K); temperatura base (Tb); número de ovos parasitados diariamente; parasitismo acumulado (%); número total de ovos parasitados por fêmea de T. pretiosum; e longevidade das fêmeas. Para estudar a capacidade de parasitismo de T. pretiosum, 20 ovos de S. frugiperda (? 24 h de idade) foram colocados em tubos de vidro (8,0 x 2,0 cm) contendo uma fêmea (? 24 h de idade) cada. Os experimentos foram conduzidos em delineamento experimental inteiramente casualizado, com 20 repetições por temperatura. As BODs foram reguladas para temperaturas constantes de 18ºC, 20oC, 22oC, 25oC, 28oC e 32oC, umidade relativa de 70 ±10% e fotoperíodo de 14/10 h (L:E). Os ovos de S. frugiperda foram substituídos diariamente até a morte do parasitóide. Os resultados mostraram uma relação inversa entre o tempo de desenvolvimento e a temperatura, com médias apresentado diferenças estatisticamente significativas entre si, com exceção das temperaturas de 25ºC e 28oC (10 dias). A emergência do parasitóide (%) também foi influenciada pela temperatura. A menor porcentagem de emergência foi observada a 32oC e a maior nas temperaturas de 18ºC e 20oC. A temperatura não alterou a razão sexual nem o número de parasitóides por ovo, permitindo mudanças na temperatura para controlar a produção de insetos em laboratório, com o fim de atender às necessidades das liberações no campo

Melting curve of 4^4He: no sign of the supersolid transition down to 10 mK

We have measured the melting curve of $^4$He in the temperature range from 10 to 400 mK with the accuracy of about 0.5 $\mu$bar. Crystals of different quality show the expected $T^4$-dependence in the range from 80 to 400 mK without any sign of the supersolid transition, and the coefficient is in excellent agreement with available data on the sound velocity in liquid $^4$He and on the Debye temperature of solid $^4$He. Below 80 mK we have observed a small deviation from $T^4$-dependence which however cannot be attributed to the supersolid transition because instead of decrease the entropy of the solid rather remains constant, about $2.5\times10^{-6}$ $R$Comment: 4 pages, 2 figures, published in Physical Review Letter

Zero-Field Dichroism in the Solar Chromosphere

We explain the linear polarization of the Ca II infrared triplet observed close to the edge of the solar disk. In particular, we demonstrate that the physical origin of the enigmatic polarizations of the 866.2 nm and 854.2 nm lines lies in the existence of atomic polarization in their metastable lower levels, which produces differential absorption of polarization components (dichroism). To this end, we have solved the problem of the generation and transfer of polarized radiation by taking fully into account all the relevant optical pumping mechanisms in multilevel atomic models. We argue that `zero-field' dichroism may be of great diagnostic value in astrophysics.Comment: 10 pages, 3 figure

Parasitism capacity of Trichogramma pretiosum on eggs of Trichoplusia ni at different temperatures.

ABSTRACT: Trichogramma spp. are egg parasitoids of various pest species of Lepidoptera including Trichoplusia ni, an important pest of plants in the genus Brassica. Of the climatic conditions that can impair Trichogramma spp. parasitism capacity, the temperature is critical. Thus, the objective of this research was to evaluate the parasitism capacity of Trichogramma pretiosum on eggs of T. ni at 18, 21, 24, 27, 30, and 33ºC; 70±10% RH; and 12/12 hours photophase (L/D). Fresh eggs of the host moth were offered to T. pretiosum daily. The parasitism rate varied between 8 and 11.4 eggs/female at the temperatures evaluated for the first 24 hours. The highest number of parasitized eggs per female occurred at 24ºC (53.0 parasitized eggs/female). The period of parasitism and the mean longevity of females were inversely related to the temperature. Temperature heavily influences the parasitism rate of T. pretiosum on eggs of T. ni, and the best overall performance of the parasitoid occurs from 24 to 27ºC. RESUMO. Trichogramma spp. são parasitoide de ovos de várias espécies pragas de Lepidoptera incluindo Trichoplusia ni, uma importante praga de plantas do gênero Brassica. Das condições climáticas que podem influenciar a capacidade de parasitismo de Trichogramma spp., a temperatura é uma das principais. Portanto, o objetivo deste trabalho foi avaliar a capacidade de parasitismo de Trichogramma pretiosum em ovos de T. ni nas temperaturas de 18, 21, 24, 27, 30 e 33ºC; 70±10% UR; e 14/12h fotofase. Ovos frescos de T. ni foram oferecidos diariamente para T. pretiosum. A taxa de parasitismo nas primeiras 24h variou de 8 a 11,4 ovos/fêmea do parasitoide entre as temperaturas avaliadas. O maior número de ovos parasitados por fêmea ocorreu a 24ºC (53,0 ovos parasitados/fêmea). O tempo de parasitismo e a longevidade média dos parasitoides adultos foram inversamente relacionados à temperatura. Temperatura influência enormemente no parasitismo de T. pretiosum em ovos de T. ni, e os melhores resultados do parasitoide foram obtidos de 24 a 27ºC

Origin of spatial variations of scattering polarization in the wings of the Ca {\sc i} 4227 \AA line

Polarization that is produced by coherent scattering can be modified by magnetic fields via the Hanle effect. According to standard theory the Hanle effect should only be operating in the Doppler core of spectral lines but not in the wings. In contrast, our observations of the scattering polarization in the Ca {\sc i} 4227 \AA line reveals the existence of spatial variations of the scattering polarization throughout the far line wings. This raises the question whether the observed spatial variations in wing polarization have a magnetic or non-magnetic origin. A magnetic origin may be possible if elastic collisions are able to cause sufficient frequency redistribution to make the Hanle effect effective in the wings without causing excessive collisional depolarization, as suggested by recent theories for partial frequency redistribution with coherent scattering in magnetic fields. To model the wing polarization we apply an extended version of the technique based on the "last scattering approximation". This model is highly successful in reproducing the observed Stokes $Q/I$ polarization (linear polarization parallel to the nearest solar limb), including the location of the wing polarization maxima and the minima around the Doppler core, but it fails to reproduce the observed spatial variations of the wing polarization in terms of magnetic field effects with frequency redistribution. This null result points in the direction of a non-magnetic origin in terms of local inhomogeneities (varying collisional depolarization, radiation-field anisotropies, and deviations from a plane-parallel atmospheric stratification).Comment: Accepted in May 2009 for publication in The Astrophysical Journa