491 resultados para WEAVING SPIDERS
Resumo:
Munduruku gen. nov. is proposed for the type species Munduruku bicoloratum sp. nov., from Juruti and Santarém, Pará, Brazil. The main diagnostic character of Munduruku gen. nov. is the presence of a subapical, lanceolate keel on the male palpal bulb, which is unique among the basal taxa of Theraphosinae with type III-IV urticating setae. The female spermathecae consist of two spheroid receptacles with funnel-shaped necks, each of which bears a sclerotized area. In both sexes, the abdomen is remarkably patterned, an uncommon feature in adults of New World theraphosids. Both the bulbus lanceolate keel and the abdominal color pattern are hypothesized as synapomorphies of the genus.
Description of two new species of Plesiopelma (Araneae, Theraphosidae, Theraphosinae) from Argentina
Resumo:
Two new species of Plesiopelma Pocock, 1901 from northern Argentina are described and diagnosed based on males and habitat descriptions are presented. Males of Plesiopelma paganoi sp. nov. differ from most of species by the absence of spiniform setae on the retrolateral face of cymbium, aspect of the palpal bulb. Plesiopelma aspidosperma sp. nov. differs from most species of the genus by the presence of spiniform setae on the retrolateral face of cymbium and it can be distinguished from P. myodes Pocock, 1901, P. longisternale (Schiapelli & Gerschman, 1942) and P. rectimanum (Mello-Leitão, 1923) by the separated palpal bulb keels and basal nodule of metatarsus I very developed. It differs from P. minense (Mello-Leitão, 1943) by the shape of the palpal bulb and basal nodule on metatarsus I well developed. Specimens were captured in Salta province, Argentina, inhabiting high cloud forests of Yungas eco-region.
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Three new species of Neodrassex Ott, 2012 are described from Brazil: N. cachimbo sp. nov. from state of Pará, N. nordeste sp. nov. from state of Piauí and N. ibirapuita sp. nov. from state of Rio Grande do Sul.
Resumo:
The spider Latrodectus mirabilis (Holmberg, 1876) is commonly found in cereals crops of central Argentina. We studied its diet composition at the field and capture rate on leaf-cutting ants based on laboratory experiments. This study comprises the first approach that documents the diet of L. mirabilis in wheat and oat fields of central Argentina. We identified 1,004 prey items collected from its webs during the last phenological stages of both cereal crops. The prey composition was variable but the spiders prey mainly on ants (Formicidae, Hymenoptera), who represented more than 86% of the total. Meanwhile, in the capture rate experiences we registered a high proportion of ants captured by spiders at the beginning of experiences, capturing the half of the ants from total in the first four hours. Summarizing, we reported a polyphagous diet of this spider species in wheat and oat fields. Ants were the most important prey item of this spider, as found in other Latrodectus spiders around the world.
Resumo:
A new species of Fernandezina Birabén, 1951, F. nica sp. nov. is described from Rio Grande do Sul state, in southern Brazil. Fernandezina pulchra Birabén, 1951, is registered for Brazil and a new geographic record in Brazil is presented for F. pelta Platnick, 1975.
Resumo:
The Araneidae is a speciose family including web-spinning spiders that are very abundant in various terrestrial ecosystems. Several studies demonstrate that changes in vegetation surrounding rivers, streams and brooks affect the associated araneofauna. The aim of this research was to compare differences found in diversity (abundance and richness), composition and phenology of Araneidae spiders sampled in different habitats in four riparian forest catchments in southern Brazil. Samples were taken from riparian forests in four rivers of Rio Grande do Sul State: Piratini, Camaquã, Sinos and Maquiné rivers, each in a different hydrographic basin. Samples were taken twice seasonally on each basin during two years, sampling the araneofauna of the tree-shrub strata with beating tray. Six transects were employed on each basin, two per habitat: edge with grassland, forest interior and river edge. Araneids totalled 20 genera and 65 species. Comparing riparian forests significant differences are found. Spider abundance differed among riparian forests as well as species richness. Overall, Piratini river riparian forest had the higher abundance and richness for Araneidae; the lower values were in Sinos river forest. The stronger degradation and fragmentation of the riparian forests of Sinos river probably influenced the results, with human disturbance gradients associated negatively to web building. We present data on the diversity of these spiders, which were very abundant in the riparian forest interior and very rich in species in the grassland/riparian forest edge. Species composition also differs among the studied habitats (the above plus river/riparian forest edge). For the most abundant species the phenological pattern across the seasons was also analysed.
Resumo:
ABSTRACT A new species of Phrixotrichus Simon, 1889, P. pucara sp. nov., is described and illustrated based on a male from Pucará river, Neuquén province, Argentina. Male can be distinguished from all other species of the genus by the presence of a long strong spine on inner face of prolateral branch of tibial apophysis; also, it differs from P. scrofa (Molina, 1788) and P. vulpinus (Karsch, 1880) by a serrated prolateral keel of the male palpal bulb. Male resembles P. jara Perafán & Pérez-Miles, 2014 but can be distinguished by the uniform color on dorsal cephalothorax and by the palpal organ morphology being wider on the bulb base and embolus shorter and thicker, with the tip of embolus not so directed retrolaterally and prolateral keel bearing a serrated edge with three teeth. Additionally, P. vulpinus is reported for the first time for Argentina along with new distributional data.
Resumo:
ABSTRACT Alpaida venger sp. nov. is described based on males and females from Pedra Branca State Park, Rio de Janeiro, Brazil. This species seems to be related to Alpaida scriba (Mello-Leitão, 1940) and Alpaida alticeps (Keyserling, 1879) due to similar body shape and color, but is easily distinguished by the very elongated median apophysis, the massive lobe of tegulum and the hooked paracymbium of male palp. Females have elongated epigyne as A. scriba, but can be distinguished by the wider lips and shorter scape.
Resumo:
ABSTRACT We described a new species of spider, Alpaida clarindoi sp. nov. (Araneidae), from the southwestern Amazon forest. The new species is distinguished from most Alpaida by the presence of a pair of shoulders spines. Females can be separated from similar species by the subquadrangular shape of the epigynum, and males by the shape of the terminal apophysis and the tegulum, which possess an apical pointed tip. Alpaida clarindoi sp. nov. is described based on both sexes.
Resumo:
An ephydrid, Hyadina porteri Brèthes, 1919, is found to be a senior synonym of Hippelates australis Sabrosky, 1955. New combination: Liohippelates porteri (Brèthes). Two new species, Pseudogaurax souzalopesi from Peru and P. silbergliedi from Panama are described and placed in the synopsis by Sabrosky (1966).
Resumo:
Postembryonic development of Misumenops pallida (Keyserling) (Araneae, Thomisidae), one of the most abundant predator species in soybean fields in Buenos Aires Province (Argentina) was studied. The life cycle was observed in the laboratory from egg sacs collected in the field, and from egg sacs spined in the laboratory by gravid females collected in the field. Results indicated that instar length and feeding rate increased throughout the life cycle being higher in females than in males. Greater mortality was observed to third and fourth instars decreasing thereafter. These results may contribute to deternmine the efficiency of this species as a natural enemy of insect pests of soybean.
Resumo:
The role of ecology in the evolution and maintenance of arthropod sociality has received increasing research attention in recent years. In some organisms, such as halictine bees, polistine wasps, and social spiders, researchers are investigating the environmental factors that may contribute to high levels of variation in the degree of sociality exhibited both among and within species. Within lineages that include only eusocial members, such as ants and termites, studies focus more on identifying extrinsic factors that may contribute to the dramatic variation in colony size, number of queens, and division of labour that is evident across these species. In this review, I propose a comparative approach that seeks to identify environmental factors that may have a common influence across such divergent social arthropod groups. I suggest that seeking common biogeographic patterns in the distribution of social systems or key social traits may help us to identify ecological factors that play a common role in shaping the evolution of sociality across different organisms. I first review previous studies of social gradients that form along latitudinal and altitudinal axes. Within families and within species, many organisms show an increasing degree of sociality at lower latitudes and altitudes. In a smaller number of cases, organisms form larger groups or found nests cooperatively at higher latitudes and altitudes. I then describe several environmental factors that vary consistently along such gradients, including climate variables and abundance of predators, and outline their proposed role in the social systems of terrestrial arthropods. Finally, I map distributions of a social trait against several climatic factors in five case studies to demonstrate how future comparative studies could inform empirical research.
Resumo:
Four-lane undivided roadways in urban areas can experience a degradation of service and/or safety as traffic volumes increase. In fact, the existence of turning vehicles on this type of roadway has a dramatic effect on both of these factors. The solution identified for these problems is typically the addition of a raised median or two-way left-turn lane (TWLTL). The mobility and safety benefits of these actions have been proven and are discussed in the “Past Research” chapter of this report along with some general cross section selection guidelines. The cost and right-of-way impacts of these actions are widely accepted. These guidelines focus on the evaluation and analysis of an alternative to the typical four-lane undivided cross section improvement approach described above. It has been found that the conversion of a four-lane undivided cross section to three lanes (i.e., one lane in each direction and a TWLTL) can improve safety and maintain an acceptable level of service. These guidelines summarize the results of past research in this area (which is almost nonexistent) and qualitative/quantitative before-and-after safety and operational impacts of case study conversions located throughout the United States and Iowa. Past research confirms that this type of conversion is acceptable or feasible in some situations but for the most part fails to specifically identify those situations. In general, the reviewed case study conversions resulted in a reduction of average or 85th percentile speeds (typically less than five miles per hour) and a relatively dramatic reduction in excessive speeding (a 60 to 70 percent reduction in the number of vehicles traveling five miles per hour faster than the posted speed limit was measured in two cases) and total crashes (reductions between 17 to 62 percent were measured). The 13 roadway conversions considered had average daily traffic volumes of 8,400 to 14,000 vehicles per day (vpd) in Iowa and 9,200 to 24,000 vehicles per day elsewhere. In addition to past research and case study results, a simulation sensitivity analysis was completed to investigate and/or confirm the operational impacts of a four-lane undivided to three-lane conversion. First, the advantages and disadvantages of different corridor simulation packages were identified for this type of analysis. Then, the CORridor SIMulation (CORSIM) software was used x to investigate and evaluate several characteristics related to the operational feasibility of a four-lane undivided to three-lane conversion. Simulated speed and level of service results for both cross sections were documented for different total peak-hour traffic, access densities, and access-point left-turn volumes (for a case study corridor defined by the researchers). These analyses assisted with the identification of the considerations for the operational feasibility determination of a four -lane to three-lane conversion. The results of the simulation analyses primarily confirmed the case study impacts. The CORSIM results indicated only a slight decrease in average arterial speed for through vehicles can be expected for a large range of peak-hour volumes, access densities, and access-point left-turn volumes (given the assumptions and design of the corridor case study evaluated). Typically, the reduction in the simulated average arterial speed (which includes both segment and signal delay) was between zero and four miles per hour when a roadway was converted from a four-lane undivided to a three-lane cross section. The simulated arterial level of service for a converted roadway, however, showed a decrease when the bi-directional peak-hour volume was about 1,750 vehicles per hour (or 17,500 vehicles per day if 10 percent of the daily volume is assumed to occur in the peak hour). Past research by others, however, indicates that 12,000 vehicles per day may be the operational capacity (i.e., level of service E) of a three-lane roadway due to vehicle platooning. The simulation results, along with past research and case study results, appear to support following volume-related feasibility suggestions for four-lane undivided to three-lane cross section conversions. It is recommended that a four-lane undivided to three-lane conversion be considered as a feasible (with respect to volume only) option when bi-directional peak-hour volumes are less than 1,500 vehicles per hour, but that some caution begin to be exercised when the roadway has a bi-directional peak-hour volume between 1,500 and 1,750 vehicles per hour. At and above 1,750 vehicles per hour, the simulation indicated a reduction in arterial level of service. Therefore, at least in Iowa, the feasibility of a four-lane undivided to three-lane conversion should be questioned and/or considered much more closely when a roadway has (or is expected to have) a peak-hour volume of more than 1,750 vehicles. Assuming that 10 percent of the daily traffic occurs during the peak-hour, these volume recommendations would correspond to 15,000 and 17,500 vehicles per day, respectively. These suggestions, however, are based on the results from one idealized case xi study corridor analysis. Individual operational analysis and/or simulations should be completed in detail once a four-lane undivided to three-lane cross section conversion is considered feasible (based on the general suggestions above) for a particular corridor. All of the simulations completed as part of this project also incorporated the optimization of signal timing to minimize vehicle delay along the corridor. A number of determination feasibility factors were identified from a review of the past research, before-and-after case study results, and the simulation sensitivity analysis. The existing and expected (i.e., design period) statuses of these factors are described and should be considered. The characteristics of these factors should be compared to each other, the impacts of other potentially feasible cross section improvements, and the goals/objectives of the community. The factors discussed in these guidelines include • roadway function and environment • overall traffic volume and level of service • turning volumes and patterns • frequent-stop and slow-moving vehicles • weaving, speed, and queues • crash type and patterns • pedestrian and bike activity • right-of-way availability, cost, and acquisition impacts • general characteristics, including - parallel roadways - offset minor street intersections - parallel parking - corner radii - at-grade railroad crossings xii The characteristics of these factors are documented in these guidelines, and their relationship to four-lane undivided to three-lane cross section conversion feasibility identified. This information is summarized along with some evaluative questions in this executive summary and Appendix C. In summary, the results of past research, numerous case studies, and the simulation analyses done as part of this project support the conclusion that in certain circumstances a four-lane undivided to three-lane conversion can be a feasible alternative for the mitigation of operational and/or safety concerns. This feasibility, however, must be determined by an evaluation of the factors identified in these guidelines (along with any others that may be relevant for a individual corridor). The expected benefits, costs, and overall impacts of a four-lane undivided to three-lane conversion should then be compared to the impacts of other feasible alternatives (e.g., adding a raised median) at a particular location.
Resumo:
Two populations of the wasp Trypoxylon rogenhoferi Kohl, 1884 from São Carlos and Luís Antônio, State of São Paulo, Brazil, were observed and sampled from May 1999 to February 2001 using trap-nests. This mass-provisioning wasp was used to test some aspects of optimal sex allocation theory. Both populations fit all the predictions of the models of Green and Brockmann and Grafen. Maternal provisions determined the size of each offspring, and females allocated well-stocked brood cells to daughters, the sex that benefits most being large. This strategy resulted in a difference in size between the sexes. In São Carlos, female weight at emergence was 1.18 times that of males, in Luís Antônio this value was 1.13. The brood cell volume was correlated with both wing length and weight at emergence in both sexes, and the chance that a given brood cell contained a male offspring decreased with increased brood cell volume. In T. rogenhoferi female body size was related to fitness. Larger females were able to collect more mass of spiders per day, the spiders they captured were heavier, and they provisioned more brood cells per day. They also produced larger daughters. For males, no relationship between body size and fitness was found, but the data were scarce. Since the patterns of provisioning were variable among different females in both study sites, it is possible that the females not follow a unique strategy for sex allocation. The sex ratio and/or investment ratio in the São Carlos population was female-biased and in Luís Antônio, male-biased. In spite of the influence of trap-nests diameters on male production in Luís Antônio, there is some evidence that in São Carlos population the local availability of prey and/or lower rate of parasitism may be major forces in determining the observed sex ratio, but further studies are necessary to verify such hypothesis.
Resumo:
This paper examines changes in the organization of the Spanish cotton industry from 1720 to 1860 in its core region of Catalonia. As the Spanish cotton industry adopted the most modern technology and experienced the transition to the factory system, cotton spinning and weaving mills became increasingly vertically integrated. Asset specificity more than other factors explained this tendency towards vertical integration. The probability for a firm of being vertically integrated was higher among firms located in districts with high concentration ratios and rose with size and the use of modern machinery. Simultaneously, subcontracting predominated in other phases of production and distribution where transaction costs appears to be less important.