911 resultados para Ant colony optimisation


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Standing at the corner of Tenth and O streets in the city of Lincoln, Nebraska, any week-day morning between 7:30 and 8 o'clock, you may see pass by you from ten to twenty women with little black woolen shawls on their heads. Ask any citizen who they are, and ninety-nine times in one hundred he will tell you they are "Russians" who live down on the bottoms, that they are going out into the offices and homes to wash and scrub and clean house, and that their husbands are street laborers or work for the railroad. He may then grow confidential and tell you that he "has no use for these people", that "they are only half human", and that he "would just as soon see the Chinese come here as those people". As a matter of fact the greater part of his information is incorrect, partly through race prejudice but chiefly through ignorance of their history. These people, of whom there are about 4,000 in the city (Including "beet fielders"), are Germans, not Russians: they are Teutons, not Slavs; they are Lutheran and Reformed, not Greek Catholics. To be sure they and their ancestors lived in Russia for over one hundred years and they came here directly from the realm of the Czar whoso bona fide citizens they were—but they never spoke the Russian language, never embraced the Greek religion, never intermarried with the Russians, and many of their children never saw a Russian until they left their native village for the new home in America. They despise being called "Russians" just as an Italian resents "Dago"; a Jew, "Sheeny"; and a German, "Dutchman". Ask them where they came from and most of the children and not a few of the grown people will say, "Germany". If you pursue your questioning as to what part of Germany, they will tell you "Saratov" or "Samara" - two governments in the eastern part of Russia on the lower course of the Volga river. The misconceptions concerning the desirability of these German-Russians as citizens arise from their unprogressiveness as compared with those Germans who come to us directly from the mother country. During their century's sojourn in Russia they have been out of the main current of civilization, a mere eddy in the stream of progress. They present a concrete example of arrested development, The characteristics which differentiate them from other Germans are not due to an inherent lack of capacity but to different environment. Notwithstanding this, the German- Russians have some admirable qualities. They bring us large stores of physical energy and an almost unlimited capacity for work. The majority of them are literate although the amount of their education is limited. They are thrifty and independent, almost never applying for public aid. They are law abiding, their chief offenses being those which are traceable to their communal life in Russia. They are extremely religious, all their social as well as spiritual life being bound up in the church which they support right royally. To be sure, the saloon gets their vote (the prohibition vote among them is increasing); but "was not the first miracle that Christ performed the turning of water into wine? If they would shut up the shows (theaters), they wouldn't need to shut up the saloons". The object of this paper is to give the historical setting in which the German-Russians have lived as one means to a better understanding and appreciation of them by our own citizens.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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We present a new approach to determine the number and composition of guilds, using the hyperdiverse leaf-litter ant fauna as a model, based on appropriate morphological variables and species co-occurrence null models to describe the complex assemblages of interacting Species Community structure at the 1-m(2) scale. We obtained 18 linear morphometric measures from 949 workers of 171 leaf-litter ant species (18762 measurements) surveyed in four Atlantic Forest localities to test whether the assemblages are morphologically structured; the morphological characters were selected to indicate diet and foraging habits. Principal components analysis was used to characterize the morphospace and to describe the guild structure (number of species and composition). The guild proportionality assembly rule (significant tendency toward constant proportion of species in guilds) was assessed at the 1-m(2) scale. Our analysis indicates that the division of leaf-litter ants into guilds is based mainly on microhabitat distribution in the leaf-litter, body size and shape, eye size, and phylogeny. The same guild scheme applied to four more sites shows that different Atlantic Forest areas have the same leaf-fitter ant guilds. The guild proportionality assembly rule was confirmed for most guilds, Suggesting that there are guild-specific limitations on species coexistence within assemblages; on the other hand, in a few cases the variance in guild proportion was greater than expected under the null assumptions. Other studies on ant functional group classification are partially supported by our quantitative morphological analysis. Our results, however, imply that there are more compartments than indicated in previous models, particularly among cryptic species (confined to soil and litter) and tropical climate specialists. We argue that a general null model for the analysis of species association based oil morphology can reveal objectively defined groups and may thus contribute to a robust theory to explain community structure in general and have important consequences on studies of litter ant community ecology in particular.

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The Neotropical ant genus Lachnomyrmex Wheeler, 1910 is revised for the first time. A revised generic description is provided for workers and gynes; males remain unknown. Morphological patterns combined with geographical data led to the recognition of 16 species, of which 10 are here described as new: L. amazonicus sp. n., L. fernandezi sp. n., L. grandis Fernandez & Baena, L. haskinsi Smith, L. lattkei sp. n., L. longinodus Fernandez & Baena, L. longinoi sp. n., L. mackayi sp. n., L. nordestinus sp. n., L. pilosus Weber, L. laticeps sp. n., L. platynodus sp. n., L. plaumanni Borgmeier, L. regularis sp. n., L. scrobiculatus Wheeler, and L. victori sp. n. The gynes of L. grandis, L. haskinsi, and L. pilosus are described for the first time. Illustrated identification keys for workers, distribution maps, and high resolution illustrations are supplied for all species. Some Lachnomyrmex species are relatively common in the leaf-litter of submontane wet forests in Central and South America; others remain known by very few individuals. The relatively small and apparently monogynic Lachnomyrmex colonies inhabit small nests in the ground, among rotten leaves and inside fallen logs. Workers generally forage alone on the ground or within the leaf litter, but have been recorded also on tree trunks, and apparently do not recruit nestmates.

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The recent increase in leaf litter ants sampling effort in Neotropical wet forests has revealed new and interesting records of the highly specialized myrmicine ant genus Stegomyrmex Emery, previously considered as extremely rare. We present a modified diagnosis for the genus and describe Stegomyrmex bensoni n. sp. and S. olindae n. sp., based on, respectively, workers, males, and gyne (central-north Brazil) and on a single worker (northern Brazil). Stegomyrmex vizottoi Diniz (southeastern Brazil) is redescribed and compared with S. olindae n. sp.; these species present significant differences in size, sculpturation, and sting apparatus morphology. The males of S. vizottoi are described for the first time. A key for workers and queens and a distribution map for the five know Stegomyrmex species are provided.

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The composition of the ant fauna was examined in public squares of three municipalities that compose the hydrographic basin of the Upper Tiete River: Biritiba Mirim, Salesopolis, and Mogi das Cruzes. Richness, frequency of occurrence, similarity, and influence of seasons on the species composition were examined. The method was standardized as sampling units consisted of a set of three baits arranged in a triangle with vertices two meters apart. Sardines in oil were used as attractant. A total of 86 species was collected. Myrmicinae and Pheidole were the richest subfamily and genus, respectively. Eighty species were collected in Mogi das Cruzes, 49 in Salesopolis, and 45 in Biritiba Mirim, with 34 species common to the three areas. The ordination analysis (NMDS) revealed the presence of two distinct communities: one in Mogi das Cruzes and another in Biritiba Mirim-Salesopolis. These data were supported by the dendogram based on the Bray-Curtis dissimilarity index. This result might be associated with the distinct geographic and demographic characteristics of the areas. Regarding seasonality, the composition of the fauna of Mogi das Cruzes is independent of the season of the year, unlike the observed in Biritiba Mirim and Salesopolis.

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Despite recognition of key biotic processes in shaping the structure of biological communities, few empirical studies have explored the influences of abiotic factors on the structural properties of mutualistic networks. We tested whether temperature and precipitation contribute to temporal variation in the nestedness of mutualistic ant-plant networks. While maintaining their nested structure, nestedness increased with mean monthly precipitation and, particularly, with monthly temperature. Moreover, some species changed their role in network structure, shifting from peripheral to core species within the nested network. We could summarize that abiotic factors affect plant species in the vegetation (e.g., phenology), meaning presence/absence of food sources, consequently an increase/decrease of associations with ants, and finally, these variations to fluctuations in nestedness. While biotic factors are certainly important, greater attention needs to be given to abiotic factors as underlying determinants of the structures of ecological networks.

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The nests of Myrmelachista are found in tree trunk cavities and branches. The biology of these arboreal ants is still relatively unknown. We investigated the nesting behaviour of this genus in fallen dry twigs in the Atlantic rainforest of southeastern Brazil. Physical characteristics of the nests, colony demographics, presence of breeders and ant worker sizes were recorded. Samples were collected weekly for 12 months, along open, sunny and undisturbed trails within forest remnants. In all, 202 nests were collected and six species were recorded. Myrmelachista ruszkii had the highest population of immatures and the greatest number of nests found. Myrmelachista nodigera had the smallest workers, was the least populous and the colony was housed in the finest branches. These results expand the current knowledge about the diversity and biology of Myrmelachista in the Brazilian Atlantic forest, and describe polydomic nests and competitive behaviour of M. ruszkii.

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The immatures of males of two species of Camponotus ants (Hymenoptera: Formicidae) are described and compared by light and electron microscopy. The numbers of larval instars were determined: Camponotus rufipes Fabricius (Hymenoptera: Formicidae) have four instars; and Camponotus vittatus Forel have three. Male larvae of the two species are similar to previously described Camponotus larvae, sharing the following traits: basic shape of body and mandible, presence of 'chiloscleres', 'praesaepium' (some specimens), labial pseudopalps, and ten pairs of spiracles. However, larvae of the two species can be separated by bodily dimensions and based on their hair number and types. Worker larvae of C. vittatus previously described are extensively similar to male larvae, with only a few inconspicuous differences that may result from intraspecific variation or sexual differences.

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Non-myrmecophilous lepidopteran larvae using plants bearing ant attractants such as extrafloral nectaries are good models for studying morphological and behavioural mechanisms against ant predation. Udranomia spitzi (Hesperiidae) is a butterfly whose larvae feed on leaves of Ouratea spectabilis (Ochnaceae), a plant with extrafloral nectaries. We described the early stages of U. spitzi, and used field observations and experiments to investigate the defensive strategies of caterpillars against predatory ants. Larvae pass through five instars and pupation occurs inside larval leaf shelters. Ant-exclusion experiments revealed that the presence of ants did not affect significantly caterpillar survival. Predation experiments showed that vulnerability to ant predation decreased with increase in larval size. The present study showed that predatory ants are not as relevant as demonstrated for other systems, and also illustrates how observational data and field experiments can contribute to a better understanding of the biology and ecology of a species of interest.

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This is the first study which evaluated the influence of cave size and presence of bat guano in ant visitation in Brazilian caves. We provide a list of the ants associated with 27 caves in northeastern Brazil, an area situated in the transition between Cerrado (Brazilian savanna) and Amazon Domain. The study was conducted between January and August 2010. We recorded 24 ant species inserted into 12 genera, 10 tribes, and six subfamilies. The size of the cave and the presence of guano did not influence the richness of ants, and most of the caves had single species. Camponotus atriceps was the species with the larger distribution, being collected in five caves. In addition, we discuss geographic distribution of records and possible ecological roles of ants in cave environments.

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The human granulocyte colony stimulating factor (hG-CSF) plays an important role in hematopoietic cell proliferation/differentiation and has been widely used as a therapeutic agent for treating neutropenias. Nartograstim is a commercial G-CSF that presents amino acid changes in specific positions when compared to the wildtype form, which potentially increase its activity and stability. The aim of this work was to develop an expression system in Escherichia coli that leads to the production of large amounts of a recombinant hG-CSF (rhG-CSF) biosimilar to Nartograstim. The nucleotide sequence of hg-csf was codon-optimized for expression in E. coli. As a result, high yields of the recombinant protein were obtained with adequate purity, structural integrity and biological activity. This protein has also been successfully used for the production of specific polyclonal antibodies in mice, which could be used in the control of the expression and purification in an industrial production process of this recombinant protein. These results will allow the planning of large-scale production of this mutant version of hG-CSF (Nartograstim), as a potential new biosimilar in the market.

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Division of labor among workers is common in insect societies and is thought to be important in their ecological success. In most species, division of labor is based on age (temporal castes), but workers in some ants and termites show morphological specialization for particular tasks (physical castes). Large-headed soldier ants and termites are well-known examples of this specialization. However, until now there has been no equivalent example of physical worker subcastes in social bees or wasps. Here we provide evidence for a physical soldier subcaste in a bee. In the neotropical stingless bee Tetragonisca angustula, nest defense is performed by two groups of guards, one hovering near the nest entrance and the other standing on the wax entrance tube. We show that both types of guards are 30% heavier than foragers and of different shape; foragers have relatively larger heads, whereas guards have larger legs. Low variation within each subcaste results in negligible size overlap between guards and foragers, further indicating that they are distinct physical castes. In addition, workers that remove garbage from the nest are of intermediate size, suggesting that they might represent another unrecognized caste. Guards or soldiers are reared in low but sufficient numbers (1-2% of emerging workers), considering that <1% usually perform this task. When challenged by the obligate robber bee Lestrimelitta limao, an important natural enemy, larger workers were able to fight for longer before being defeated by the much larger robber. This discovery opens up opportunities for the comparative study of physical castes in social insects, including the question of why soldiers appear to be so much rarer in bees than in ants or termites.

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Insect cuticular hydrocarbons including relatively non-volatile chemicals play important roles in cuticle protection and chemical communication. The conventional procedures for extracting cuticular compounds from insects require toxic solvents, or non-destructive techniques that do not allow storage of subsequent samples, such as the use of SPME fibers. In this study, we describe and tested a non-lethal process for extracting cuticular hydrocarbons with styrene-divinylbenzene copolymers, and illustrate the method with two species of bees and one species of beetle. The results demonstrate that these compounds can be efficiently trapped by ChromosorbA (R) (SUPELCO) and that this method can be used as an alternative to existing methods.

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We describe a new species of Oxyepoecus Santschi, 1926, Oxyepoecus regularis sp. nov., based on workers and a gyne collected in "Caatinga Arbórea" (Arboreal Shrubland) in Milagres and "Mata Seca" (Dry Forest) in Boa Vista do Tupim, both in the state of Bahia, Brazil. The gyne of Oxyepoecus browni Albuquerque & Brandão, 2004, collected in the same leaf litter ant survey, is also described. In addition, we present new records for Oxyepoecus species in Northeastern Brazil.