Semi-natural habitats are key components of rural landscapes because they shelter a significant number of overwintering arthropods that are beneficial to agriculture. However, woodlots are semi-natural habitats with high patch-level heterogeneity and this aspect has been poorly studied. The purpose of this study was to determine the influence of woodlot heterogeneity on overwintering ground beetles. Woodlot heterogeneity was characterized in terms of distance from the woodlot boundary and date of the most recent logging operation. We used emergence traps to quantify the population density of ground beetles that overwintered in the different parts of the woodlot. In woodlot edges the densities and species richness of ground beetles were significantly higher than in the rest of the woodlot. Ground beetles that are active in crop fields overwintered in the edges but not in the inner zone of the woodlot. Species assemblages of ground beetles overwintering in the edges were highly diverse. The date of the most recent logging operation did not explain the distribution of ground beetles that overwintered in the woodlot. Our results show that woodlots, and in particular their edges, are used as a winter shelter by ground beetles that spend part of their life in crops, which potentially favours biological control in adjacent crop fields. and Anthony Roume, Annie Ouin, Laurent Raison, Marc Deconchat.
\noindent We introduce new estimates and tests of independence in copula models with unknown margins using ϕ-divergences and the duality technique. The asymptotic laws of the estimates and the test statistics are established both when the parameter is an interior or a boundary value of the parameter space. Simulation results show that the choice of χ2-divergence has good properties in terms of efficiency-robustness.
The univoltine leaf miner Chromatomyia fuscula Zetterstedt is a Scandinavian cereal pest. We wanted to compare the phenology of C. fuscula in southern Norway with that of its most important natural enemies: 15 parasitoids of the families Eulophidae and Pteromalidae (Hymenoptera: Chalcidoidea). The use of two Malaise traps in an organically-grown spring barley field and its boundary through 6 seasons (1992-1997) also allowed us to compare these two habitats and to observe the effect of harvesting on the parasitoid activity without interference from pesticides. C. fuscula overwinters as an adult and oviposits in May/June. Few specimens of the next generation, emerging in the crop, were caught in the boundary traps, suggesting the fly hibernates elsewhere. In contrast, the F1 generation of the parasitoids was caught in considerable amounts both in the crop and boundary. The abundance of parasitoids was highest in July/August; in the crop it usually started decreasing well before harvesting; in the boundary it peaked two weeks or more after harvesting. The results suggest that many parasitoids (especially females) move from the crop to the boundary (or beyond) before harvesting. In both habitats parasitoid species richness usually increased until harvesting, and thereafter decreased. The pooled parasitoid female proportion was 0.36; in crop and boundary it was 0.30 and 0.66, respectively, and the majority of species had a higher proportion of females in the boundary than in the crop. The phenology of two of the most common parasitoids is presented: The pupal parasitoid Cyrtogaster vulgaris Walker (Pteromalidae) had a high activity in the boundary, also very early (females only) and late (both sexes) in the season. The larval parasitoid Diglyphus begini (Ashmead) (Eulophidae) was less active early and late in the season, and had a much smaller boundary activity than C. vulgaris. Both sexes were present throughout the season. The annual sex ratio of D. begini was density dependent, being highly male biased in the two years with highest catches. In C. vulgaris neither density nor habitat explained the sex ratio. D. begini probably overwinters inside the mine as a preadult, having one generation on C. fuscula in the crop and another one in an alternate host away from the habitats sampled here. C. vulgaris overwinters as fertilized females in the border habitat.
The univoltine leaf miner Chromatomyia fuscula (Zetterstedt) (Diptera: Agromyzidae) is a regular cereal pest in Scandinavia. The fly and its most important parasitoids were studied in a 15.5 ha organically-grown field in southern Norway. Each year (1992-1997), one Malaise trap was placed in the spring barley part (2.5 ha) of the field, and (except for 1994) another along the nearest wooded boundary for the whole season. Because of crop rotation, the traps changed position every year. C. fuscula and 15 parasitoid species previously reared from C. fuscula were sorted from the catches.
Few C. fuscula were trapped in the boundary, suggesting that at least the lower vegetation strata were unimportant for the overwintering fly (C. fuscula overwinters as an adult). The parasitoid complex was remarkably stable over years, and 13-15 of the species were: found each year (habitats combined); 0-6 of the species were not found in both habitats each year. Only 4 species attained fractions higher than 10% of the total annual catches in both habitats during the 6 years: the larval parasitoids Diglyphus begini (Ashmead) and Hemiptarsenus unguicellus (Zetterstedt), and the pupal parasitoids Cyrtogaster vulgaris Walker and Chrysocharis pubicornis (Zetterstedt). In the boundary, C. vulgaris dominated every year (43-83%). In the crop, this species alternated with D. begini (1992, 1994) or H. unguicellus (1997) as the dominant species.
In most years, the catches of both the leaf miner and its parasitoids were larger in the crop than in the boundary, but the species number and composition were fairly similar in the two habitats. The parasitoid diversity (Shannon-Wiener H') tended to be higher in the crop (0.8-2.0) than in the boundary (0.8-1.8). Correspondingly, the evenness (both Shannon-Wiener J' and species rank on In abundance) was higher, and the dominance (Berger-Parker) lower, in the crop than in the boundary. Every year, overwintered C. fuscula invaded the crop, but only in 1993 and 1997 did the trapping reveal a distinct next generation, suggesting a very high pre-adult mortality the other years. In 1993 and 1997, C. vulgaris and D. begini had rather similar abundances in the crop, and the lowest combined fractions (less than 60%) of the years, leading to the highest diversity and the lowest dominance through the 6 years (in both habitats).
Our results indicate that the boundary was part of the parasitoids' foraging/overwintering area, and that the boundary was more important to the parasitoids than to their leaf miner host. Boundaries therefore seem to be important for the control of C. fuscula.
This study analyses the chromotope of the suburb of Stínadla (“The Shades”), which plays a key role in the narrative organization of the cult “Stínadla” trilogy by Jaroslav Foglar, comprising his novels Záhada hlavolamu (Mystery of the Conundrum, 1941), Stínadla se bouří (The Shades in Revolt, 1947) and Tajemství velkého Vonta (Secret of the High Vont, 1986). The spacial structure of the trilogy’s text is divided into two spheres — the suburbs separated by a boundary, with their distinctive structure. By crossing this boundary the boys in the Rychlé šípy (“Rapid Arrows”) gang enter Stínadla, a labyrinthine chronotope with radically different rules, a dangerous unknown space where they lose their bearings and continually find themselves in danger. The labyrinthine topology of Stínadla impedes the gang and causes them to get lost. As they are escaping, Rychlé šípy come across transverse passageways between individual locations. The atmosphere is another stylistic and motif-based emanation of the Stínadla chronotope. and The chronotope textually constructed in this manner helps to generate the mysterious adventure story: as by crossing the boundary and infiltrating the Vont community the protagonists find themselves encountering a space where they generate the events of an adventure story. Another emanation of this chronotope is the special caste of boys who inhabit this space — the Vonts, whose character is determined by the topography and architecture of this labyrinthine suburb. The Vonts’ organization is structured on the model of a secret society with sacralized rituals. The “hedgehog in a cage” conundrum as a talisman is a sacral object symbolizing power and safeguarding unity within Stínadla. It is a mysterious object, a quest object, which sets the story in motion, as well as an object with a market value (an invention). In the trilogy the Stínadla chronotope generates three analogous plots, each of which is a mystery story built on the structure of an investigation, a quest for a mysterious object and the revelation of a dark tale from the past, in each of which the motif of the tragic demise of a boy plays a role, together with the mystery of his death and the notes he wrote before his death. The demonic Stínadla even has a destructive effect upon the Rychlé šípy boys themselves, sowing discord amongst them and an atmosphere of suspicion. For example, this chronotope even generates a dark doppelgänger of the exemplary Mirek Dušín.