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Species traits are essential for inferences on ecology and the evolution of organisms. Spiders are the most abundant and diversified terrestrial predators, playing an important role in a range of ecosystem services. Here, I present datasetse on all traits of zodariid spiders, which are known to be free-living ground-dwellers occurring on all continents (except Antarctica) with the highest species diversity in Australia. I collated the data from published resources. The datasets includes nearly 100 000 trait records on all (90) genera and almost all species (1249) of the family. The majority of the 88 traits collected are morphometric, followed by those relating to ecology, reproduction, and physiology. Morphometric traits were available for the majority of species. Other trait classes were only available for some species. I provide a standardized classification of selected categorical traits (habitat, microhabitat, retreat type, circadian activity, prey, primary defensive, and predators). This is the first complete database of traits of a whole spider family, which is available through the World Spider Trait database. [ABSTRACT FROM AUTHOR]

Modern agricultural pest management systems rely on naturally occurring generalist predators to promote pest suppression. Still, little research has been done to assess their overall effectiveness, especially over the winter period when their potential is high. In this study, we focused on three genera of winter-active spiders Clubiona, Philodromus, and Anyphaena, common predators on pear trees in Central Europe during winter and early spring. We investigated their predation activity, natural diet, and prey preference using molecular gut content and abundance data obtained from cardboard bands, which served as natural shelters. We compared these characteristics between two distinct biocontrol-promoting managements—integrated pest management (IPM) and organic management (ORG). We found the proportion of prey-positive spider individuals during the winter period to be lower compared to the spring period with Anyphaena having by far the highest proportion. The prey composition during winter was more diverse in ORG orchards, but in both managements, it was inclined toward pests, mostly pear psyllids. Conversely, in early spring, despite psyllids still being a part of the diet, spiders in IPM orchards preyed more frequently on neutral prey (mostly dipterans), while the spiders from organic orchards preyed mostly on pests (lepidopterans). Although more data are needed to assess trophic interactions and the overall efficiency of these winter-active predators in complex arthropod food webs present in pear orchards, the results obtained from this research provide the first evidence of higher pest predation during a period of agricultural quiescence. [ABSTRACT FROM AUTHOR]

Prey-specialised spiders are adapted to capture specific prey items, including dangerous prey. The venoms of specialists are often prey-specific and less complex than those of generalists, but their venom composition has not been studied in detail. Here, we investigated the venom of the prey-specialised white-tailed spiders (Lamponidae: Lampona), which utilise specialised morphological and behavioural adaptations to capture spider prey. We analysed the venom composition using proteo-transcriptomics and taxon-specific toxicity using venom bioassays. Our analysis identified 208 putative toxin sequences, comprising 103 peptides < 10 kDa and 105 proteins > 10 kDa. Most peptides belonged to one of two families characterised by scaffolds containing eight or ten cysteine residues. Toxin-like proteins showed similarity to galectins, leucine-rich repeat proteins, trypsins and neprilysins. The venom of Lampona was shown to be more potent against the preferred spider prey than against alternative cricket prey. In contrast, the venom of a related generalist was similarly potent against both prey types. These data provide insights into the molecular adaptations of venoms produced by prey-specialised spiders. [ABSTRACT FROM AUTHOR]

Spiders are among the most diversified and abundant predators in terrestrial ecosystems across the world, but information on their prey is limited. Particularly, there is paucity of data for prey-specialised species, such as palpimanid spiders. Here we investigated the trophic strategy of four palpimanid species (Diaphorocellus biplagiatus, Otiothops birabeni, Palpimanus gibbulus, and P. potteri) representing all three subfamilies (Chediminae, Otiothopinae, Palpimaninae) and three geographic areas (Mediterranean, South America, South Africa) in order to infer a trophic strategy for the entire family Palpimanidae. We predicted that all palpimanids are specialised araneophagous predators. We used molecular gut-content analysis, combined with comparative analysis of morphological trophic traits. We found all four species to catch spiders more than insects. All species captured spiders belonging to several families, but predominantly those of the cursorial guild. The diet composition did not differ between sexes and juveniles. The breadth of trophic niche was narrow for all species, suggesting stenophagy. Using comparative analysis of morphological traits (thick cuticle, stout forelegs, scopulae on forelegs, and stridulatory apparatus) and araneophagy, we estimated that preying on spiders combined with the morphological traits is ancestral state for the entire family. We suggest that the whole family Palpimanidae includes araneophagous species. [ABSTRACT FROM AUTHOR]

Batesian mimics benefit from their phenotypic similarity to their models. An apparent paradox is the presence of many inaccurate mimics in nature. Many hypotheses have been proposed to explain their existence, including the relaxed selection hypothesis, which postulates that the level of mimetic resemblance avoided by predators is context-dependent. More specifically, predators avoid mimics of lower resemblance that imitate highly noxious models due to the high cost of mistakenly attacking such models. We tested this hypothesis using data on 93 pairs of ant-mimicking spider species and their models. We measured the mimetic resemblance in each spider to its putative model. Then, we estimated the noxiousness of ant models on the basis of their defensive arsenal (i.e. mandibles, spines, sting, and chemical defense). In support of the relaxed selection hypothesis, we found a negative correlation between model noxiousness and mimetic accuracy. The proportion of the variability in mimetic accuracy explained by model noxiousness was not high, indicating that other factors influence the evolution of mimetic accuracy. Finally, this comparative analysis provides evidence of the influence of model noxiousness on mimetic accuracy in a Batesian mimicry system. [ABSTRACT FROM AUTHOR]

In Batesian mimicry, the mimic gains protection from predators by imitating a noxious model. Some myrmecomorphic species use ants as models as ants have strong defensive capabilities. Ants are highly mobile models, and besides colour, shape, and size, mimics also imitate their movement. Yet, former studies focused mainly on static traits. Here, I tested the hypothesis that artificially increased speed of movement reduces the probability of the mimic being identified. First, images of 14 myrmecomorphic spider species and their models were used for humans to rank their mimetic accuracy. Humans were used as surrogate predators to obtain scores for each mimetic pair. In the second experiment, the effect of movement playback speed on the probability of identification was investigated, again using humans. Videos of mimics were played at different speeds, and the identification probability was recorded. While ants were correctly identified at any playback speed, the identification of myrmecomorphic spiders declined with increasing playback speed. In other words, the latency to correct identification increased with playback speed. Overall, mimics with higher accuracy scores were more difficult to identify while moving. The natural speed of movement of accurate mimics was similar to that of inaccurate ones. Movement is thus an important trait for myrmecomorphic species. [ABSTRACT FROM AUTHOR]

Telomeres are protective structures at the ends of eukaryotic chromosomes, and disruption of their nucleoprotein composition usually results in genome instability and cell death. Telomeric DNA sequences have generally been found to be exceptionally conserved in evolution, and the most common pattern of telomeric sequences across eukaryotes is (TxAyGz)n maintained by telomerase. However, telomerase-added DNA repeats in some insect taxa frequently vary, show unusual features, and can even be absent. It has been speculated about factors that might allow frequent changes in telomere composition in Insecta. Coleoptera (beetles) is the largest of all insect orders and based on previously available data, it seemed that the telomeric sequence of beetles varies to a great extent. We performed an extensive mapping of the (TTAGG)n sequence, the ancestral telomeric sequence in Insects, across the main branches of Coleoptera. Our study indicates that the (TTAGG)n sequence has been repeatedly or completely lost in more than half of the tested beetle superfamilies. Although the exact telomeric motif in most of the (TTAGG)n-negative beetles is unknown, we found that the (TTAGG)n sequence has been replaced by two alternative telomeric motifs, the (TCAGG)n and (TTAGGG)n, in at least three superfamilies of Coleoptera. The diversity of the telomeric motifs was positively related to the species richness of taxa, regardless of the age of the taxa. The presence/absence of the (TTAGG)n sequence highly varied within the Curculionoidea, Chrysomeloidea, and Staphylinoidea, which are the three most diverse superfamilies within Metazoa. Our data supports the hypothesis that telomere dysfunctions can initiate rapid genomic changes that lead to reproductive isolation and speciation. [ABSTRACT FROM AUTHOR]

The spiders of the genus Dysdera are renowned for including woodlouse specialists. In the Canary Islands, Dysdera underwent remarkable local diversification, and 48 endemic species have been reported to date. We aim to disentangle the evolutionary history underpinning this diversity, with particular emphasis on the evolution of the trophic ecology. We collected specimens belonging to 17 Dysdera species along with the co-occurring potential prey. We performed prey capture experiments with these specimens to assess which species accepted woodlice as prey and how they captured them and used statistical extrapolation and published phylogenetic information to infer the evolution of these dietary and behavioral traits. We identified four capture tactics and trait reconstruction analyses that inferred oniscophagy as the ancestral state. We found several instances of polyphagy that evolved from trophic specialist ancestors. When including the trophic strategy, predatory behavior, body size, and habitat type, it was revealed that at all sites, the co-occurring Dysdera species differed by at least one trait, suggesting the role of adaptive radiation via character displacement. We hypothesize that the colonization of the newly emerged islands by the Dysdera species was probably followed by the recurrent evolution of both woodlice specialists and non-oniscophagous species. The radiation of Dysdera in the Canary Islands indicates that diet specialization can evolve to polyphagy. [ABSTRACT FROM AUTHOR]

Trophic interactions of cave arthropods have been understudied. We used molecular methods (NGS) to decipher the food web in the subterranean ecosystem of the Ardovská Cave (Western Carpathians, Slovakia). We collected five arthropod predators of the species Parasitus loricatus (gamasid mites), Eukoenenia spelaea (palpigrades), Quedius mesomelinus (beetles), and Porrhomma profundum and Centromerus cavernarum (both spiders) and prey belonging to several orders. Various arthropod orders were exploited as prey, and trophic interactions differed among the predators. Linear models were used to compare absolute and relative prey body sizes among the predators. Quedius exploited relatively small prey, while Eukoenenia and Parasitus fed on relatively large prey. Exploitation of eggs or cadavers is discussed. In contrast to previous studies, Eukoenenia was found to be carnivorous. A high proportion of intraguild predation was found in all predators. Intraspecific consumption (most likely cannibalism) was detected only in mites and beetles. Using Pianka's index, the highest trophic niche overlaps were found between Porrhomma and Parasitus and between Centromerus and Eukoenenia, while the lowest niche overlap was found between Parasitus and Quedius. Contrary to what we expected, the high availability of Diptera and Isopoda as a potential prey in the studied system was not corroborated. Our work demonstrates that intraguild diet plays an important role in predators occupying subterranean ecosystems. [ABSTRACT FROM AUTHOR]

The evolutionary history of prey specialisation differs among spider species, particularly among active wandering species which have evolved a variety of prey-capture tactics. Here, we conducted a comparative analysis of prey specialisation and prey capture behaviour in Gnaphosidae. We used nine species each representing a different genus and investigated their acceptance of spiders and ants as prey, on which they may specialise, and their attack behaviour. Then we collected such data for another about 20 species from literature. The studied species used only either biting or silk (followed by biting) to constrain prey during attack. For each species, we measured selected morphological characteristics—specifically, the relative sizes of cheliceral fangs and spinnerets as well as the number of spigots on spinnerets—and related them to the ability to catch spiders (araneophagy) and ants (myrmecophagy) and mode of attack behaviour. We found the relative fang size to be significantly shorter for myrmecophagous species. Other traits were not related to prey specialisation or attack behaviour. They used silk particularly for larger prey. Use of silk was a conditional strategy in some species. We reconstructed the phylogenetic relationships among the studied genera using molecular and morphological data. We found that araneophagy was frequent but myrmecophagy was rare among recent taxa. Comparative analysis revealed that araneophagy is an ancestral state, while myrmecophagy was less likely and repeatedly lost. The use of silk for prey immobilisation was also as likely as unlikely for ancestors and has been repeatedly lost. [ABSTRACT FROM AUTHOR]

Among spiders, taxonomically the most diversified group of terrestrial predators, only a few species are stenophagous and feed on ants. The levels of stenophagy and ant-specialisation vary among such species. To investigate whether stenophagy is only a result of a local specialisation both fundamental and realised trophic niches need to be estimated. Here we investigated trophic niches in three closely-related spider species from the family Gnaphosidae (Callilepis nocturna, C. schuszteri, Nomisia exornata) with different levels of myrmecophagy. Acceptance experiments were used to estimate fundamental trophic niches and molecular methods to estimate realised trophic niches. For the latter two PCR primer sets were used as these can affect the niche breadth estimates. The general invertebrate ZBJ primers were not appropriate for detecting ant DNA as they revealed very few prey types, therefore ant-specific primers were used. The cut-off threshold for erroneous MOTUs was identified as 0.005% of the total number of valid sequences, at individual predator level it was 0.05%. The fundamental trophic niche of Callilepis species included mainly ants, while that of N. exornata included many different prey types. The realised trophic niche in Callilepis species was similar to its fundamental niche but in N. exornata the fundamental niche was wider than realised niche. The results show that Callilepis species are ant-eating (specialised) stenophagous predators, catching mainly Formicinae ants, while N. exornata is an ant-eating euryphagous predator catching mainly Myrmicinae ants. [ABSTRACT FROM AUTHOR]

The role of generalist predators in biological control remains controversial as they may not only reduce pest populations but also disrupt biocontrol exerted by other natural enemies. Here, we focus on spiders as a model group of generalist predators. They are among the most abundant and most diverse natural enemies in agroecosystems. We review their functional traits that influence food-web dynamics and pest suppression at organisational levels ranging from individuals to communities. At the individual and population levels, we focus on hunting strategy, body size, life stage, nutritional target, and personality (i.e., consistent inter-individual differences in behaviour). These functional traits determine the spider trophic niches. We also focus on the functional and numerical response to pest densities and on non-consumptive effects of spiders on pests. At the community level, we review multiple-predator effects and effect of alternative prey on pest suppression. Evidence for a key role of spiders in pest suppression is accumulating. Importantly, recent research has highlighted widespread non-consumptive effects and complex intraguild interactions of spiders. A better understanding of these effects is needed to optimize biocontrol services by spiders in agroecosystems. [ABSTRACT FROM AUTHOR]

The morphological, physiological, and behavioural traits of organisms are often used as surrogates for actual ecological functions. However, differences in these traits do not necessarily lead to functional differences and/or can be context-dependent. Therefore, it is necessary to explicitly test whether the surrogates have general ecological relevance. To investigate the relationship between the hunting strategies of predators (i.e., how, where, and when they hunt) and their function, we used euryphagous spiders as a model group. We used published data on the diet composition of 76 spider species based on natural prey and laboratory prey acceptance experiments. We computed differences in the position and width of trophic niches among pairs of sympatrically occurring species. Pairs were made at different classification levels, ranked according to the dissimilarity in their hunting strategies: congeners, confamiliars (as phylogenetic proxies for similarity in hunting strategy), species from the same main class of hunting strategy, from the same supra-class, and from different supra-classes. As for niche position computed from the natural prey analyses, species from the same class differed less than species from different classes. A similar pattern was obtained from the laboratory studies, but the congeners differed less than the species from the same classes. Niche widths were most similar among congeners and dissimilar among species from different supra-classes. Functional differences among euryphagous spiders increased continuously with increasing difference in their hunting strategy. The relative frequency of hunting strategies within spider assemblages can, therefore, influence the food webs through hunting strategy-specific predator-prey interactions. [ABSTRACT FROM AUTHOR]

It is rare to find a true predator that repeatedly and routinely kills prey larger than itself. A solitary specialised ant-eating spider of the genus Zodarion can capture a relatively giant prey. We studied the trophic niche of this spider species and investigated its adaptations (behavioural and venomic) that are used to capture ants. We found that the spider captures mainly polymorphic Messor arenarius ants. Adult female spiders captured large morphs while tiny juveniles captured smaller morphs, yet in both cases ants were giant in comparison with spider size. All specimens used an effective prey capture strategy that protected them from ant retaliation. Juvenile and adult spiders were able to paralyse their prey using a single bite. The venom glands of adults were more than 50 times larger than those of juvenile spiders, but the paralysis latency of juveniles was 1.5 times longer. This suggests that this spider species possesses very potent venom already at the juvenile stage. Comparison of the venom composition between juvenile and adult spiders did not reveal significant differences. We discovered here that specialised capture combined with very effective venom enables the capture of giant prey. [ABSTRACT FROM AUTHOR]

Female mate choice is regarded as a strong selective force that significantly affects male mating success. In extreme cases, mate rejection can result in sexual cannibalism. However, males may choose between their partners as well. The killing of potential female mates, i.e. reversed form of sexual cannibalism, may be related to male mate choice. We examined male mate choice in the spider Micaria sociabilis, focusing on the roles of female mating status (virgin/mated), size and age. Reversed cannibalism reached its highest frequency in the period of generation overlap, i.e. when young males from the summer generation met old(er) females from the spring generation. These results suggest discrimination against old(er) females. The frequency of cannibalism was not affected by female mating status or female size. However, larger males from the summer generation were more cannibalistic than smaller males from the spring generation. We conclude that reversed sexual cannibalism might be an adaptive mate choice mechanism and can be explained in the context of the aggressive spillover hypothesis. [ABSTRACT FROM AUTHOR]

The rate of population increase of three mite species, Acarus siro (L.), Lepidoglyphus destructor (Schrank) and Tyrophagus putrescentiae (Schrank), was studied on various types of barley and at various combinations of temperature and humidity. The mites were added into the chambers and incubated for 21 days on seven different kinds of barley coming from four sites, including six cultivars and a mixture. The population increase of all species was higher on the mixture than on any other cultivar, except for Sebastian and Calgary. The increase of mites was studied at constant temperatures ranging from 5 to 35 °C and relative humidity (RH) ranging from 50 to 90 %. Positive rate of increase was found above 70 % RH for all species. The optimal humidity was at 85 % RH for A. siro and L. destructor and at 90 % RH for T. putrescentiae. As concerns the temperature, positive rate of increase was found at temperatures higher than 10, 15 and 20 °C for A. siro, L. destructor and T. putrescentiae, respectively. The temperature optima were at 23, 25, and 30 °C for A. siro, L. destructor and T. putrescentiae, respectively. Model estimated on laboratory data was then fitted to temperature and humidity records from August to November in the Czech grain store. Estimated population rate of increase was rarely positive: for A. siro it was for 24 %, for L. destructor for only 1 % and for T. putrescentiae for only 7 % days of the study period. It is concluded that in the climatic conditions of the Czech Republic the population increase of three mite pests is negligible during autumn and winter. [ABSTRACT FROM AUTHOR]

Invasive species often displace native species and can affect ecological processes in invaded habitats. If invasive species become abundant, changes in prey availability may be particularly harmful to specialist predators. The Argentine ant, Linepithema humile Mayr, is an important invasive species on nearly all continents. Spiders of the genus Zodarion are specialised ant-eating predators native to the Mediterranean yet it is unknown if they can exploit invasive ant species. Here we studied spatial and temporal abundance of this invasive ant and the native spider, Zodarion cesari Pekár, during 4 years in four citrus groves. Circadian activity of both spiders and ants, and capture efficiency and prey specificity of the predator were also evaluated. The abundance of Z. cesari was strongly correlated to L. humile abundance. The predatory activity of spiders varied seasonally with differences on the relative frequency of spiders capturing ants depending on the time of the year. In laboratory, Z. cesari displayed most efficient capture upon the native ant Tapinoma nigerrimum (Nylander) and the invasive ant L. humile in comparison with five other native ant species. These results demonstrate that the native spider Z. cesari is successfully exploiting the invasive ant species L. humile and is likely a locally monophagous predator. We suggest that Z. cesari shifted away from native T. nigerrimum post invasion as both ant species are phylogenetically related and of similar size. [ABSTRACT FROM AUTHOR]

Prey-specialised predators have evolved specific cognitive adaptations that increase their prey searching efficiency. In particular, when the prey is social, selection probably favours the use of prey intraspecific chemical signals by predatory arthropods. Using a specialised ant-eating zodariid spider, Zodarion rubidum, which is known to prey on several ant species and possesses capture and venom adaptations more effective on Formicinae ants, we tested its ability to recognise chemical cues produced by several ant species. Using an olfactometer, we tested the response of Z. rubidum towards air with chemical cues from six different ant species: Camponotus ligniperda, Lasius platythorax and Formica rufibarbis (all Formicinae); and Messor structor, Myrmica scabrinodis and Tetramorium caespitum (all Myrmicinae). Z. rubidum was attracted to air carrying chemical cues only from F. rufibarbis and L. platythorax. Then, we identified that the spiders were attracted to airborne cues coming from the F. rufibarbis gaster and Dufour's gland, in particular. Finally, we found that among several synthetic blends, the decyl acetate and undecane mixture produced significant attraction of spiders. These chemicals are produced only by three Formicine genera. Furthermore, we investigated the role of these chemical cues in the communication of F. rufibarbis and found that this blend reduces their movement. This study demonstrates the chemical cognitive capacity of Z. rubidum to locate its ant prey using chemical signals produced by the ants. The innate capacity of Z. rubidum to olfactory detect different ant species is narrow, as it includes only two ant genera, confirming trophic specialisation at lower than subfamily level. The olfactory cue detected by Zodarion spiders is probably a component of the recruitment or trail pheromone. [ABSTRACT FROM AUTHOR]

Sexual cannibalism particularly before mating is costly for the male victim but also for the female aggressor if she risks remaining unmated. The aggressive spillover hypothesis explains the persistence of this behavior as a maladaptive side effect of positive selection on aggressiveness in a foraging context. The hypothesis predicts that the occurrence of sexual cannibalism is explained by female aggressiveness but is not related to male phenotype or behavioral type. An alternative hypothesis invokes sexual selection and makes the opposite prediction namely that sexual cannibalism is an expression of female choice and should hence mainly target males of low quality. We tested the above hypotheses on a sexually dimorphic nephilid spider Nephilengys livida, known for male monopolization of females via genital damage, female genital plugging, and mate guarding, by staging mating trials during which we recorded mating behaviors and occurrences of pre- and postcopulatory cannibalism. We did not restrict assessment of aggressiveness to the mating and foraging context but also included aggression against same sex conspecifics. To assess female personalities, i.e., consistent individual differences in behavior including aggressiveness, we repeatedly tested them for intra-sex aggression, voracity towards prey, locomotory activity, and boldness. Females exhibited consistent differences in intra-sex aggressiveness, latency to attack prey, and boldness. Aggressive females had shorter latencies to attack prey and were more active than non-aggressive ones. In contrast to the predictions of the aggressive spillover hypothesis, females that were aggressive towards prey and towards other females were not more likely to attack a male than non-aggressive females. In support of the mate choice hypothesis, less aggressive males were more likely attacked and cannibalized than more aggressive ones. This hints at sexual selection for aggressiveness in males and raises the question of mechanisms that maintain variation in male aggressiveness. [ABSTRACT FROM AUTHOR]

The ecology of selected species of spiders (Araneae), harvestmen (Opiliones), and the neglected tropical order Schizomida, alien to Europe, is discussed. Their geographic origins and pathways of introduction, by transportation with goods, are similar to other predatory terrestrial arthropods. Occurrence in buildings (synanthropy) is a prerequisite for range expansion in many arachnid species. Thelytokous parthenogenesis facilitated spread of a few spider, harvestman and schizomid species outside their native range. Both prey generalists and specialists (woodlice-eating Dysdera crocata and ant-eating Zodarion rubidum) are among species successfully expanding their range. Alien arachnids include individual species belonging to many different families. We stress the absence of true invasiveness of alien arachnids in Europe. Some unusual adverse effects of alien arachnids were recorded, such as pollution of buildings and clogged car fuel system ventilation tubes. Frequency of painful biting and threat to native biota are low. [ABSTRACT FROM AUTHOR]

In a predator-prey system where both intervenients come from the same taxon, one can expect a strong selection on behavioural and morphological traits involved in prey capture. For example, in specialised snake-eating snakes, the predator is unaffetced by the venom of the prey. We predicted that similar adaptations should have evolved in spider-eating (araneophagous) spiders. We investigated potential and actual prey of two Palpimanus spiders ( P. gibbulus, P. orientalis) to support the prediction that these are araneophagous predators. Specific behavioural adaptations were investigated using a high-speed camera during staged encounters with prey, while morphological adaptations were investigated using electron microscopy. Both Palpimanus species captured a wide assortment of spider species from various guilds but also a few insect species. Analysis of the potential prey suggested that Palpimanus is a retreat-invading predator that actively searches for spiders that hide in a retreat. Behavioural capture adaptations include a slow, stealthy approach to the prey followed by a very fast attack. Morphological capture adaptations include scopulae on forelegs used in grabbing prey body parts, stout forelegs to hold the prey firmly, and an extremely thick cuticle all over the body preventing injury from a counter bite of the prey. Palpimanus overwhelmed prey that was more than 200% larger than itself. In trials with another araneophagous spider, Cyrba algerina (Salticidae), Palpimanus captured C. algerina in more than 90% of cases independent of the size ratio between the spiders. Evidence indicates that both Palpimanus species possesses remarkable adaptations that increase its efficiency in capturing spider prey. [ABSTRACT FROM AUTHOR]

Female St Andrew's Cross spiders control copulation duration by timing sexual cannibalism and may thereby control paternity if cannibalism affects sperm transfer. We have investigated the effect of copulation duration on sperm transfer and documented sperm storage patterns when we experimentally reduced the ability of females to attack and cannibalise the male. Virgin males and females were paired and randomly allocated either to a control treatment, where females were allowed to attack and cannibalise the male during copulation, or to an experimental treatment, where females were unable to cannibalise the male. The latter was achieved by placing a paintbrush against her chelicerae during copulation. Our experimental manipulation did not affect copulation duration or sperm storage. However, the number of sperm stored by the female increased with copulation duration only if the male was cannibalised, suggesting that cannibalism increases relative paternity not only through prolonged copulation duration following a fair raffle model but also through the cannibalism act itself. Future studies should explore whether cannibalised males ejaculate more sperm or whether females selectively store the sperm of cannibalised males. [ABSTRACT FROM AUTHOR]

The impact of five selective insecticides on the functional response of a potential biological control agent, the spider Philodromus cespitum (Walckenaer) (Araneae: Philodromidae), was studied in the laboratory. This spider is the most abundant beneficial arthropod on trees in commercial orchards in central Europe. We expected that selective insecticides applied at the recommended doses would have no effect or a negligible effect on the spiders’ performance. Our results showed that the mortality of spiders resulting from residual uptake of the chemicals differed among insecticides. Dimilin, NeemAzal, Mospilan, and Integro caused mortality of less than 10%, while SpinTor caused mortality of 17%. All five preparations can be considered harmless in terms of mortality in comparison with Decis, which caused 80% mortality. Exposure to residues of NeemAzal, SpinTor, and Dimilin resulted in a significantly lower predation rate than the control. The lowest predation rate was observed in spiders treated with SpinTor. These results imply that the natural pest control provided by P. cespitum spiders can be weakened by the application of SpinTor, NeemAzal, and Dimilin. On the other hand, the functional response was not significantly affected by the application of Integro and Mospilan. Therefore, these two insecticides are recommended for use in the integrated pest management (IPM) of orchards. [ABSTRACT FROM AUTHOR]

The pest potential of stored product mites depends on the reproduction rate that is affected by the environmental conditions. In this study we investigated the effect of temperature, ranging from 5 to 35°C, on the population growth of three important mite species, Acarus siro, Tyrophagus putrescentiae and Auleroglyphus ovatus at 85% r.h. Starting with 10 individuals the population increase of mites was observed after 3 weeks of cultivation, or after 6 weeks for those kept at low temperatures (5, 10, 12.5, and 15°C). The rate of increase was calculated for each temperature and species. The obtained data were fitted with polynomial models. The mite population growth rates increased with increasing moderate temperatures until 258C, when rm-values were 0.179, 0.177 and 0.190 for A. siro, A. ovatus and T. putrescentiae, respectively. The lower development threshold was 10.2°C in all three species. Estimated upper temperature threshold was higher in T. putrescentiae (49°C) than in A. siro and A. ovatus (38°C). Simulation of the rate of population increase under ideal conditions, using real temperature records obtained from Czech grain stores, showed that the pest mite populations increase only during 3.5 months within a typical 9-month storage season in Central Europe. These results indicate that control of mites, be it chemical, physical or biological, is recommended during the months when allergens and pests are produced, i.e. from September to mid November and in May. [ABSTRACT FROM AUTHOR]

The aim of the study was to develop a stage-structured within-patch model describing predator-prey interactions of Cheyletus eruditus (Schrank) and Acarus siro L. on stored grain. Parameterisation of the model was done using data from the literature. Due to considerable variance in these data, statistical methods were used to extrapolate the parameters. The results of the simulations were compared with the experimental control of A. siro by C. eruditus on wheat. The results indicated that all life-history studies of A. siro yielded overestimated parameters leading to an unnaturally rapid population growth of A. siro on grain. The main reason seems to be the use of high quality food (wheat germs), which considerably increased fecundity. A new model with reduced fecundity was found to correspond well with the observed dynamics in a granary. The model of C. eruditus, including parameters from different sources, produced dynamics quite similar to the observed one. A simulation of biological control under laboratory conditions, on 45 g of wheat, showed that C. eruditus is able to control A. siro within the observed period. In contrast, simulation of the control in a granary showed a marked difference in comparison with the observed dynamics. The discrepancy is attributed to the effects of spatial factors, such as immigration. The predator-prey model developed here appears to be valid for the prediction of the local (within-patch) population dynamics of A. siro and C. eruditus on wheat grain at 20 °C and 80% RH. [ABSTRACT FROM AUTHOR]

Hunting other predators is dangerous, as the tables can turn and the hunter may become the hunted. Specialized araneophagic (spider eating) predators have evolved intriguing hunting strategies that allow them to invade spiders' webs by adopting a stealthy approach or using aggressive mimicry. Here, we present a newly discovered, specialized hunting strategy of the araneophagic spider Poecilochroa senilis (Araneae: Gnaphosidae), which forces its way into the silk retreat of the potential spider prey and immobilizes it by swathing gluey silk onto its forelegs and mouthparts. Poecilochroa senilis has been reported from the nests of a several, often large, spider species in the Negev desert (Israel), suggesting specialization on spiders as prey. Nevertheless, in laboratory experiments, we found that P. senilis has a wider trophic niche, and fed readily on several small insect species. The specialized nest-invading attack was used more frequently with large spiders, and even small juvenile P. senilis were able to attack and subdue larger spiders. Our observations show that specific hunting tactics, like nest usurpation, allow specialized predators to overcome defences of dangerous prey. [ABSTRACT FROM AUTHOR]

Abstract: Acoustic signalling is widespread in arthropods and appears to be common in spiders, but the function is still unknown in many species. Acoustic signals have several functions and can be used both in interspecific (e.g., to threaten potential predators) and intraspecific (during courtship) communication. In our study, we investigated the intraspecific role of stridulation in the araneophagous Palpimanus spider (Araneae: Palpimanidae). These spiders are specialised in hunting other spiders at all ontogenetic stages. We hypothesised that stridulation is used to avoid cannibalism. We investigated the morphology of the stridulatory apparatus, analysed the acoustic signals that various stages produce, and found two types of stridulation, low- and high-intensity stridulation. Then, we investigated the presence of cannibalism between individuals of variable body size and the use of stridulation during interactions. We found that cannibalism occurred only when the prosoma size difference between the two opponents was more than 200%. Then, we paired conspecific large control Palpimanus with smaller control individual or with individual whose stridulatory organs were impaired and found that impaired spiders suffered significantly higher cannibalism than the control spiders. Our study reveals a novel role of acoustic communication in the conspecific recognition of araneophagous spiders.Significance statement: Cannibalism is widespread among predatory animals. However, cannibalism might not be an optimal strategy for several reasons and should be a less preferred option for predators. Palpimanus spiders are prey specialised predators preying primarily on other spiders thus the risk of cannibalism is even higher than in generalist predators. These spiders possess stridulatory apparatus and they often stridulate following a contact with conspecifics. We found that cannibalism occasionally occurred during contact with conspecifics and that the probability of cannibalism increased with the size difference between the interacting individuals. When the spiders were not able to stridulate during contact, the probability of cannibalism increased significantly. Our results thus show that Palpimanus spiders use stridulation to reduce cannibalism among unequally sized individuals. [ABSTRACT FROM AUTHOR]

In order to avoid sperm competition, males of many taxa apply physical barriers, so-called mating plugs, into female genitalia. Females may control which males deposit a plug through pre-copulatory mate choice or by influencing plug efficacy to avoid costs imposed by plugging. However, subsequent suitors might remove the plugs. We investigated behavioural and morphological aspects of plug deposition and removal in a promiscuous spider, Philodromus cespitum (Philodromidae). We performed mating trials to investigate factors affecting plugging. To identify the plug origin, we conducted a morphological analysis using 3D X-ray microtomography and histology of the male copulatory organ and the female genital tract. In P. cespitum, the plug material is produced in the male genital bulb and transferred to the female together with sperm. The copulation is brief and terminated by the female. After mating, plugging material was found in the genital atrium of all females, covering it to a varying degree (10-100%). The extent of coverage was associated with the duration of movements of male copulatory organ connected with sperm transfer (i.e. full haematodochal expansions) and with the number of taps a male delivered with his legs to the female during courtship. Males larger than the female performed more tapping movements. Mating trials with plugged females revealed that males could remove plugs partly or entirely. Removal success increased with increasing foreleg length ratio between the male who removed the plug and the one who deposited it. We discuss our results in the light of the potential female control of plug deposition and removal. [ABSTRACT FROM AUTHOR]

True predators are characterised by capturing a number of prey items during their lifetime and by being generalists. Some true predators are facultative specialists, but very few species are stenophagous specialists that catch only a few closely related prey types. A monophagous true predator that would exploit a single prey species has not been discovered yet. Representatives of the spider family Ammoxenidae have been reported to have evolved to only catch termites. Here we tested the hypothesis that Ammoxenus amphalodes is a monophagous termite-eater capturing only Hodotermes mossambicus. We studied the trophic niche of A. amphalodes by means of molecular analysis of the gut contents using Next Generation Sequencing. We investigated their willingness to accept alternative prey and observed their specific predatory behaviour and prey capture efficiency. We found all of the 1.4 million sequences were H. mossambicus. In the laboratory A. amphalodes did not accept any other prey, including other termite species. The spiders attacked the lateral side of the thorax of termites and immobilised them within 1 min. The paralysis efficiency was independent of predator:prey size ratio. The results strongly indicate that A. amphalodes is a monophagous prey specialist, specifically adapted to feed on H. mossambicus. [ABSTRACT FROM AUTHOR]