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This study explores the eff ect of nutritional composition on the fi tness of consumers in a quadri-trophic food web. Specifi cally, we studied how enrichment of the food of fruit fl ies Drosophila melanogaster (Meigen, 1830) transfers to the spider Phylloneta impressa (L. Koch) (Theridiidae) and its parasitoid wasp, Zatypota percontatoria Mueller (Ichneumonidae). We reared fruit fl ies on balanced, protein-enriched, and lipid-enriched diets, and observed several fi tness-related traits in both the predator and the parasitoid. In spiders, we did not fi nd signifi cant diff erences among treatments in their body size and the probability of building a cocoon web. In parasitoids, we failed to fi nd signifi cant diff erences among treatments in the time to wasp pupation, the duration of pupation, the length of the wasp tibia and pronotum, and the body mass. However, the sex ratio of hatched wasps diff ered signifi cantly among treatments from the expected 1 : 1. In the balanced diet group, the majority of wasps were males. There was a signifi cant positive relationship between the spider prosoma size and the length of the wasp fore wing. Our results suggest that the quality of the food of the primary consumer had little eff ect on the fi tness of the organism at the fourth trophic level. [ABSTRACT FROM AUTHOR]

To determine the causes of the variation in the seasonal dynamics of Harmonia axyridis (Pallas) in Central Europe, numbers of adults and larvae of this invasive species were recorded on trees (Acer, Betula, Tilia) throughout the growing seasons from 2011 to 2016. Each year beetles were collected every two weeks, using a standardized sweeping method. The seasonal dynamics was expressed as plots of abundance (number of individuals per 100 sweeps) against time (Julian day) and these plots (seasonal profiles) were compared in terms of their size (area under the seasonal profile curve), range, timing and height of the mode (maximum abundance). Timing and size of seasonal profiles varied among hostplants, years and sites. Abundance of larvae paralleled aphid occurrence and peak abundance of adults followed that of larvae 10 to 20 days later. Population dynamics before and after the peak were determined by dispersal. Adults arrived at sites before the start of aphid population growth and persisted there long after aphid populations collapsed. The abundance of H. axyridis decreased from 2011 to 2013 and then increased, achieving the previous levels recorded in 2015 and 2016. The variation in seasonal profiles revealed that H. axyridis, in terms of its response to environmental conditions, is a plastic species and this fl exibility is an important factor in its invasive success. [ABSTRACT FROM AUTHOR]

Flowers of dicotyledonous plants host communities of arthropod species. We studied the community associated with dandelion (Taraxacum section Ruderalia), a complex of apomictic micro-species abundant in central Europe. Identification of microspecies in the field was impracticable. These plants produce an abundance of flowers that host arthropod communities that are not yet fully documented. We investigated species occurrence, its diurnal and seasonal variation and some of the factors that determine the abundance of the dominant species. Insect and spiders were collected from 2010 to 2012 at a locality in Prague. Whole capitula were harvested at weekly intervals and resident arthropods were identified. Diurnal variation in insect presence and the effect of pollen and microclimate on some of the species were also examined. The insect community (> 200 species) consisted mainly of species of Hymenoptera (86 spp.), Coleoptera (56 spp.), Diptera (46 spp.) and Heteroptera (23 spp.). The most abundant were Thysanoptera (2 spp.). Pollen eaters/collectors and nectar feeders dominated over predators and occasional visitors. From April to mid-August, the insect community was dominated by Coleoptera, and later by Diptera and Hymenoptera. Except for Meligethes spp. and species breeding in the capitula, the insects occupied flowers during the daytime when the flowers were open (10-12 h in spring and only 2-4 h in late summer). The presence of Meligethes spp. in particular flowers was associated with the presence of pollen; the occurrence of Byturus ochraceus with pollen and flower temperature. Although pollination is not necessary, dandelion plants produce both nectar and pollen. The community of arthropods that visit dandelion flowers is rich despite their being ephemeral. The composition of local faunas of flower visitors, presence of floral rewards and flower microclimate are important factors determining the composition of the flower community. [ABSTRACT FROM AUTHOR]