Notes on the Brown Widow Spider, Latrodectus Geometricus (Araneae: Theridiidae) in Brazil

Three species of the cosmopolitan genus Latrodectus were reported by Bucherl (1964) as occurring in Brazil: L. mactans mactans (Fabricius) from Recife, Pernambuco and from P6rto Alegre, Rio Grande do Sul; L. curacaviensis (Muller) from the beaches of Guanabara and Bahia; and L. geometricus C. L. Koch from the city of P6rto Alegre, Rio Grande do Sul and from the states of Minas Gerais, Bahia and Rio de Janeiro. Levi (1959) cited records of L. geometricus from the states of Paraiba, Pernarnbuco, Minas Gerais and Rio de Janeiro. In the United States L. geometricus has been reported as an introduced species from both Hawaii (Levi, 1967) and Florida (Levi and Levi, 1968). The present paper contains observations on L. geometricus in the state of Espirito Santo and in the city of Manaus, Amazonas, Brazil in 1969 and 1970

A Study in the Summer Phenology of Dionychious Spiders from Northern Minnesota Forests

Dionychious ground layer spiders from Larix and Populus stands were collected by pitfall traps. The typical pattern of dominant, influent and accessory species was well marked. Populus stands had greater diversity of species than Larix stands. Those species characterized by large male:female sex ratios had sharp peaks in the first month of collecting, and others had smaller early season peaks or early season and late season peaks. Traps with an apron leading to the trap caught twice as many specimens compared to traps without an apron

Spiders (Araneae) from the Panský diel (Starohorské vrchy Mts, Slovakia)

Spiders were collected at the massif 'Panský diel' near the city of Banská Bystrica (Central Slovakia). We recorded 252 spider species for the territory and one new species for Slovakia. Although the summit reaches an altitude of 1.100 m a.s.l., more or less thermophilous species apparently prevail here, especially at lower moderate sites. On the other hand, only several typical oreophilous species were documented. Many recorded species are scarce or even very rare. This indicates the very high value of this territory from both a genetic and an environmental perspective

Unlearning Fear Out-Group Others

Maroney describes a neuroscientific fear-extinction study as preliminary evidence supporting the notion that out-group hostilities might be influenced by biological predispositions. In the fear-extinction study, subjects were conditioned to fear the presentation of black or white faces with the introduction of an electric shock when such faces appeared on a screen. Then the experimenters stopped using the shock when that race\u27s faces appeared on the screen. Subjects\u27 fear was extinguished much more effectively when the subject was conditioned to fear faces of individuals of her own race than when the subject was conditioned to fear faces of individuals of another race

The Victorian Naturalist

v.114 (1997

Current reversal and exclusion processes with history-dependent random walks

A class of exclusion processes in which particles perform history-dependent random walks is introduced, stimulated by dynamic phenomena in some biological and artificial systems. The particles locally interact with the underlying substrate by breaking and reforming lattice bonds. We determine the steady-state current on a ring, and find current-reversal as a function of particle density. This phenomenon is attributed to the non-local interaction between the walkers through their trails, which originates from strong correlations between the dynamics of the particles and the lattice. We rationalize our findings within an effective description in terms of quasi-particles which we call front barriers. Our analytical results are complemented by stochastic simulations.Comment: 5 pages, 6 figure

New Integrality Gap Results for the Firefighters Problem on Trees

The firefighter problem is NP-hard and admits a $(1-1/e)$ approximation based on rounding the canonical LP. In this paper, we first show a matching integrality gap of $(1-1/e+\epsilon)$ on the canonical LP. This result relies on a powerful combinatorial gadget that can be used to prove integrality gap results for many problem settings. We also consider the canonical LP augmented with simple additional constraints (as suggested by Hartke). We provide several evidences that these constraints improve the integrality gap of the canonical LP: (i) Extreme points of the new LP are integral for some known tractable instances and (ii) A natural family of instances that are bad for the canonical LP admits an improved approximation algorithm via the new LP. We conclude by presenting a $5/6$ integrality gap instance for the new LP.Comment: 22 page

Trophic Transfer of Arsenic from an Aquatic Insect to Terrestrial Insect Predators.

The movement of energy and nutrients from aquatic to terrestrial ecosystems can be substantial, and emergent aquatic insects can serve as biovectors not only for nutrients, but also for contaminants present in the aquatic environment. The terrestrial predators Tenodera aridifolia sinensis (Mantodea: Mantidae) and Tidarren haemorrhoidale (Araneae: Theridiidae) and the aquatic predator Buenoa scimitra (Hemiptera: Notonectidae) were chosen to evaluate the efficacy of arsenic transfer between aquatic and terrestrial environments. Culex tarsalis larvae were reared in either control water or water containing 1000 µg l(-1) arsenic. Adults that emerged from the control and arsenic treatments were fed to the terrestrial predators, and fourth instar larvae were fed to the aquatic predator reared in control or arsenic contaminated water. Tenodera a. sinensis fed arsenic-treated Cx. tarsalis accumulated 658±130 ng g(-1) of arsenic. There was no significant difference between control and arsenic-fed T. haemorrhoidale (range 142-290 ng g(-1)). Buenoa scimitra accumulated 5120±406 ng g(-1) of arsenic when exposed to arsenic-fed Cx. tarsalis and reared in water containing 1000 µg l(-1) arsenic. There was no significant difference between controls or arsenic-fed B. scimitra that were not exposed to water-borne arsenic, indicating that for this species environmental exposure was more important in accumulation than strictly dietary arsenic. These results indicate that transfer to terrestrial predators may play an important role in arsenic cycling, which would be particularly true during periods of mass emergence of potential insect biovectors. Trophic transfer within the aquatic environment may still occur with secondary predation, or in predators with different feeding strategies