1_Chestnut (Castanea sativa Mill.) is one of the economically more important trees in the north of Portugal. Spiders, as generalist predators, are potential controlling agents of pests, yet the composition of the community of spiders associated with this crop is only poorly known. The objective of this study was to determine the spider communities in the canopies of chestnut trees subject to three different soil management practices in northeastern Portugal. Three chestnut groves each subject to a different agricultural practice (grazed, tilled or untilled) were studied in 2008 and 2009. The Araneae communities were sampled by beating the branches and the individuals collected were identified to family and species when possible. To investigate the structure of the spider community in each grove the abundance and family richness of spiders were calculated and compared between managements. In total, 4172 spiders were collected and, in both years, the three most abundant families were Araneidae, Philodromidae and Linyphiidae. In 2008, there was a greater abundance of spiders in the grazed, followed by the tilled and untilled groves, but no significant differences among groves. However, in 2009 there was a greater abundance of spiders in the tilled grove, followed by grazed and untilled groves and the differences between the untilled and the other two groves were significant. Araniella, Oxyopes and Anyphaena were the most abundant genera in the three groves. This study showed that soil management may influence the diversity of spiders, but the effects were weak and not consistent between years., 2_The reduction or absence of a suitable habitat for spiders under the trees in the tilled treatment might have resulted in the spiders migrating up into the canopy. However, based on the weak effects on spider abundance recorded and its potentially adverse effects on soils, tillage is not recommended for managing the incidence of pests in chestnut groves., Jacinto Benhadi-Marin ... [et al.]., and Obsahuje seznam literatury
Pro rok 2016 se evropským pavoukem roku stal křižák Cyclosa conica. Po morfologické stránce je tento druh nezaměnitelný díky přítomnosti hrbolku na zadním konci hřbetu zadečku. Jeho kolová síť je vybavena vertikálním stabilimentem se zapředenými zbytky kořisti či detritu. Pavouk na kořist číhá uprostřed stabilimenta. Při ohrožení je schopen na síti vibrovat tak, že se pro predátora stane takřka nedetekovatelným., The araneid Cyclosa conica was chosen as European Spider of the Year for 2016. Morphologically the spider is characterised by a single tubercle on the hind part of the dorsal abdomen. Its web carries a vertical stabilimentum with remnants of prey and other detritus. The spider waits for its prey in the middle of the stabilimentum. When disturbed, it vibrates on the web, so it becomes almost undetectable., and Milan Řezáč.
Time of oviposition and investment in reproduction output are a crucial decision for animals which could affect their fitness. In this study, the factors determining the time of oviposition and the consequences it has for clutch size and juvenile survival were investigated in the orb-web spider Argiope bruennichi. Egg-sacs laid at different times in the field were collected and inspected for eggs, hatching success and presence of parasites. Relationships between spider body condition, clutch size and time of oviposition were established. The influence of supplementary food on the number of eggs in a clutch and on the time of oviposition was determined both in the field and laboratory. Early clutches were larger and the eggs in late clutches were not heavier than those in early clutches indicating that spiders invested more in eggs at the beginning of the reproductive period. Furthermore, eggs in late egg-sacs were less likely to hatch and more likely to be parasitized. Clutch size was linked to spider body condition but not the time of oviposition. In the field, additional food to females resulted in larger clutches but did not influence the time of oviposition. Laboratory experiments showed that the daily rate of prey consumption affected egg oviposition.