spiders are the powerful and efficient predators in almost all ecosystems which have effective role in different pest control. the fauna of these arthropods was surveyed during 2005-2009, and their population fluctuations and activities were studied in mazandaran paddy fields in 2005-2006. a total of 53 spider species of 44 genera were collected and identified from paddy fields of mazandaran pr...

Resource competition is thought to play a major role in driving evolutionary diversification. For instance, in ecological character displacement, coexisting species evolve to use different resources, reducing the effects of interspecific competition. It is thought that a similar diversifying effect might occur in response to competition among members of a single species. Individuals may mitigat...

In order to control a wild insect population with SIT (Sterile Insect Technique), it is necessary to estimate this population. This can be done with experimental data (using traps), combined with appropriate dispersal models, like those studied in [1, 2]. However the observed trap data depend on some (unknown) population parameters, like the diffusivity, and some (unknown) trap parameters, like...

the following United Nations websites: household size – www.unstats.un.org/unsd/demographic/ sconcerns/housing/housing2.htm (median year for these data from different countries was 1991); density per room – www.unstats.un.org/unsd/ demographic/products/socind/housing.htm;and general population density – www.unstats.un.org/ unsd/demographic/products/dyb/dyb2006/Table03. pdf. Spearman’s correlati...

Population density varies widely among U.S. metro areas. A simple, static general equilibrium model demonstrates that moderate differences in metro areas’ consumption amenities can cause extremely large differences in their population density. Such amenities are more strongly capitalized into housing prices than into wages. Empirical results suggest that amenities do indeed help to support high...

Population density affects individual performance, though its effects are often mixed. For sessile species, increases in population density typically reduce performance. Still, cases of positive density-dependence do occur in sessile systems and demand explanation. The stress gradient hypothesis (SGH) predicts that under stressful conditions, positive effects of facilitation may outweigh the ne...

BACKGROUND Previous work suggests that the association between urbanicity and schizophrenia may be greatest in those with pre-existing vulnerability. AIMS To test for synergism in risk of schizophrenia between population density and a combined exposure of poor premorbid social and cognitive functioning. METHOD For 371 603 adolescent males examined by the Israeli Draft Board on social and co...

The recent development of capture-recapture methods for estimating animal population density has focused on passive detection using devices such as traps or automatic cameras. Some species lend themselves more to active searching: a polygonal plot may be searched repeatedly and the locations of detected individuals recorded, or a plot may be searched just once and multiple cues (feces or other ...

Streptococcus suis types 1 and 2 were detected in nasal swabs taken from five litters of piglets sampled twice weekly from birth. The two types had been detected in all pigs by the time they were 38 and 25 days old respectively with mean ages of first detectable infection being 13.5 and 8.5 days. The prevalence of infection was not affected by housing conditions or the population density of pig...