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Tegenaria atrica is a species common in continental Europe and the Republic of Ireland but on the British mainland it has long been regarded as a relatively rare import that has failed to establish. The recent discovery of this species in some numbers and over several years in Burnopfield, County Durham, represented the first-reported, self-sustaining population. We show here that the species is widespread across a large swathe of country comprising parts of north County Durham, Tyne and Wear, and south-east Northumberland — an area of some 710 km2. Within a core range of approximately 400 km2, the other species in the Tegenaria atrica group, T. saeva and T. gigantea, tend to be uncommon or absent. The distributions of these three closely related species raise questions regarding the origins of the T. atrica population, the effect of chance and priority in initial establishment, and the role of possible competitive interactions between them. Although determining ecological processes from present patterns of distribution is fraught with difficulties, it seems likely that T. atrica established and subsequently spread following a chance introduction, possibly in the Victorian era, to a region then devoid of close competitors. In the 1960s, when T. saeva and T. gigantea expanded their distributions northwards, priority effects may have protected the T. atrica population from invasion by these species, or at least slowed down the process. Future surveys are required to determine just how resistant the T. atrica population is to invasion and whether it, too, is expanding its range.
Harvestmen possess several chemical substances as a defence against predators. Among these, gonyleptidine has been one of the most studied and best characterized. This substance, produced by the harvestman Acanthopachylus aculeatus, is composed mainly of noxious substances such as benzoquinone. However, little is known about the secondary effects caused by the ingestion of this substance. Web-building spiders are an appropriate group to test the effects of several neurotoxic compounds, since the effects of these substances are directly reflected in their behaviour, notably in web construction. The aim of this study was to analyse the influence of the ingestion of gonyleptidine on spider web building, using as a model the orb weaver Araneus lathyrinus. We designed two experimental groups composed of subadult specimens. In one we offered larvae of Tenebrio molitor as prey for the spider; each mealworm was contaminated with 2.0 µl of gonyleptidine. In the control group the spiders were fed with uncontaminated T.molitor larvae. We found adverse effects on the group of spiders contaminated with the gonyleptidine, such as the construction of irregular webs, and loss of predatory capability. These results suggest that, when ingested, the gonyleptidine deteriorates the spider's coordination, similar to the effect of neurotoxic substances, like some pesticides. Our findings indicate that gonyleptidine has not only a repellent—defensive function but also a toxic effect on predators.
Attacks by predators and parasitoids on spider eggs are common. To counteract their negative effect, spiders have evolved a series of behaviours and features related to their egg sacs. In the genus Deinopis (Deinopidae) the tightly woven external layer of the egg sac seems to be an effective barrier. This layer consists of two sub-layers: the outer sub-layer is constructed of thin threads densely woven with an apparently hardened liquid that cements the threads together, and an inner sub-layer that seems to be even more compact and in which threads are not discernible. Threads of the external layer are presumably produced by the cylindrical glands, but other glands may be involved in production of the liquid substance.
A provisional checklist of spiders (Arachnida: Araneae) documented from Sudan (here differentiated into the Republic of Sudan and South Sudan) is compiled, based on published records in the literature. Collectors of historical note include Carl Jickeli, Antonín Stecker, Louis Vossion, Maurice Potter, Stanley Flower, Harold King, Eberhard Fraas, Franz Werner, Leonard Jägerskiöld, Willoughby Lowe, Hubert Lynes, Mary Steele, James Macdonald, Pierre Benoit, John Cloudsley-Thompson, and John Lewis. 113 species from 28 families have been documented from the Republic of Sudan, and 59 species in 18 families from South Sudan. Nineteen species are common to both countries, yielding a total of 153 species in 30 families for Sudan in its traditional sense. The most diverse families (with more than three species recorded) are Salticidae, Araneidae, Thomisidae, Lycosidae, Sparassidae, Philodromidae, Oxyopidae, Theridiidae, and Gnaphosidae. Published records largely derive from Khartoum State, Red Sea State, South Kordofan State, and North Kordofan State (all with 10 or more species records) in the Republic of Sudan, and from Bahr El Jabal (Central Equatoria) and Upper Nile State (with 38 and 26 species respectively) from South Sudan.
Few studies have been made on the peri-copulatory behaviour and the outcome of multiple mating in secondarily derived cul-de-sac spiders. Here, molecular markers (allozymes) are used to confirm multiple-paternity in wild-collected females of the Silver Stretch spider, Tetragnatha montana, showing that sperm competition is a potentially important driver in the evolution of its mating system. Estimates of P2 (the relative paternity accrued to second males) were obtained from laboratory-staged double matings. It is shown that paternity can accrue to either or both of the mating males: the long-standing hypothesis that there is a biased paternity advantage to second males as a result of the cul-de-sac spermathecal configuration is, therefore, not supported by this study. Simple measures of male mating performance also do not seem to correlate with paternity, although the sample size of successful egg sacs is small. A model of sexually antagonistic, co-evolutionary manipulation of access to the fertilization set may provide a mechanism for the evolution of the derived cul-de-sac condition in the tetragnathids.
The genus AmblyocarenumSimon, 1892 is removed from synonymy with CyrtaucheniusThorell, 1969. The separate identity of the genera Cyrtauchenius and Amblyocarenum is reconfirmed in comparative morphological studies of at least six newly collected species that, before the synonymizing of Cyrtauchenius and Amblyocarenum in 1985, would have been attributed to either of the two genera respectively. Comparison of this new collection with cyrtaucheniid species kept in the type collections of Mediterranean cyrtaucheniids in the MNHN, Paris, confirmed the separate identity of both Cyrtauchenius and Amblyocarenum. Further comparative studies of Cyrtauchenius, Amblyocarenum and three representative genera of non-Mediterranean cyrtaucheniids showed substantial morphological similarity between the genera Cyrtauchenius, Acontius, Ancylotrypa and Bolostromus and marked morphological differences between Amblyocarenum and all examined cyrtaucheniid genera. From these observations a close relationship between Cyrtauchenius and the non-Mediterranean Cyrtaucheniidae is inferred, while Amblyocarenum is tentatively thought to have its closest relatives in the African Nemesiidae.