How many victims will a pitfall make?

A model for the trapping of animals with a circular pitfall is formulated. The model's assumptions are: (1) The animals move independently according to the same Brownian motions. (2) The boundary of the pitfall acts as an absorbing or elastic barrier. (3) Initially a fixed number of animals is independently homogeneously distributed over a finite study area (a), or the initial positions follow a homogeneous planar Poisson process (b). The model depends on three free parameters: (i) the motility of the animals, (ii) their reaction to the pitfall, (iii) the initial density.It appears that the catches in disjoint time intervals are multinomially (a) or independently Poisson (b) distributed. The parameters of these distributions are obtained by solving certain partial differential equations.Estimation and testing problems are considered, and the data of some laboratory and field experiments are analyzed. It appears that it is possible to estimate both the animals' motility and density from a pitfall experiment. However, the accuracy is very low. To solve this problem at least partially, experiments for the separate estimation of parameters other than the density are discussed.     

A pitfall in the computer-aided quantitation of autoradiograms

Computer-aided quantitation of autoradiograms is now available as a result of recent developments in optical scanners and microcomputers. Data expressed as optical density values, however, are based on the unverified assumption that optical density and radioactivity density are linearly correlated. This article demonstrates the need to construct a calibration curve which should be used to calculate radioactivity density values more precisely.     

A simple design for a rain-resistant pitfall trap

Summary. Heavy rain causes major problems with using pitfall traps to collect ants and other surface-active arthropods. A simple design for a rain-resistant pitfall trap is described. The trap is constructed by grinding a hole in the side of a plastic vial and then covering it with fine-gage wire screen. This hole allows excess water to drain out the side of the trap. A method for quickly setting small-diameter pitfalls into the ground with an auger and a battery-powered drill is also described.Received 23 December 2003; revised 23 July 2004; accepted 7 October 2004.     

Sampling epigeal arthropods: an evaluation of fenced pitfall traps using mark-release-recapture and comparisons to unfenced pitfall traps in arable crops

The efficiency of fenced pitfall traps for estimating the density of commonly occurring epigeal predatory beetles was examined using mark-release-recapture. Most beetles of those recovered were recaptured within one week of their release. For seven of the ten species tested recapture rates were over 70%, with higher rates for the larger species. The predatory arthropod species composition captured using fenced pitfall traps was compared to unfenced pitfall traps in winter wheat, spring barley and winter oilseed rape. Compositional analysis revealed that the dominance structure of seven carabid beetle (Coleoptera: Carabidae) taxa differed between the trap types and month of sampling in winter wheat and spring barley, but differences were small with the exception of a few taxa. Linear relationships between the two techniques were found for some carabid and rove beetles (Coleoptera: Staphylinidae). The dominance structure of seven linyphiid spider (Araneae: Linyphiidae) taxa differed between the two trap types in wheat but not barley, although large differences were restricted to two taxa. No linear relationships between the two techniques were found for any of the Linyphiidae examined. Rove beetles were more effectively sampled using the fenced compared to unfenced pitfall traps.     

Using demographic data to better interpret pitfall trap catches

The results of pitfall trapping are often interpreted as abundance in a particular habitat. At the same time, there are numerous cases of almost unrealistically high catches of ground beetles in seemingly unsuitable sites. The correlation of catches by pitfall trapping with the true distribution and abundance of Carabidae needs corroboration. During a full year survey in 2006/07 in the Lake Elton region (Volgograd Area, Russia), 175 species of ground beetles were trapped. Considering the differences in demographic structure of the local populations, and not their abundances, three groups of species were recognized: residents, migrants and sporadic. In residents, the demographic structure of local populations is complete, and their habitats can be considered "residential". In migrants and sporadic species, the demographic structure of the local populations is incomplete, and their habitats can be considered "transit". Residents interact both with their prey and with each other in a particular habitat. Sporadic species are hardly important to a carabid community because of their low abundances. The contribution of migrants to the structure of carabid communities is not apparent and requires additional research. Migrants and sporadic species represent a "labile" component in ground beetles communities, as opposed to a "stable" component, represented by residents. The variability of the labile component substantially limits our interpretation of species diversity in carabid communities. Thus, the criteria for determining the most abundant, or dominant species inevitably vary because the abundance of migrants in some cases can be one order of magnitude higher than that of residents. The results of pitfall trapping adequately reflect the state of carabid communities only in zonal habitats, while azonal and disturbed habitats are merely transit ones for many species of ground beetles. A study of the demographic structure of local populations and assessment of the migratory/residential status of particular carabid species are potential ways of increasing the reliability of pitfall trap information.     

The efficiency of pitfall trapping for polyphagous predatory Carabidae

ABSTRACT.

• 1 The efficiency of pitfall trapping was investigated for seven carabid species, using time-lapse video recording equipment, in the laboratory.
• 2 The effects of differing substrates, trap designs and seasons of collection on the capture rates of the carabids was also investigated.
• 3 Capture rate differed significantly between the species studied. The differences in capture rates between the species were unrelated to beetle size, speed of movement and diurnal behaviour.
• 4 Few differences arose in the capture rates when type of substrate or trap or season of capture were changed.

     

A mathematical model on sampling diplopods using pitfall traps

Summary Trapping of three species of diplopods, viz. Cylindroiulus punctatus (Leach), Tachypodoiulus niger (Leach) and Polydesmus angustus Latzel with pitfall traps in areas with known densities follows a definite mathematical relationship. The number of each species trapped is density dependent upto a lavel: beyond that the increased density levels are not proportionately reflected in the catches. Ecological and mathematical implications of the observations are discussed.     

Classical cadherins.

Cadherins represent a gene family of Ca(2+)-dependent cell adhesion molecules (CAMs) identified during development and in adult organs. They generally mediate cell-cell adhesion by homotypic interaction, although heterotypic binding between different cadherin molecules is possible. Molecular cloning and sequence comparison has led to the characterization of a highly homologous group of 'classical' cadherins and more distantly related members, together composing a gene superfamily. The classical cadherins are transmembrane glycoproteins which exhibit, in addition to the structural homologies, a very similar overall protein topology. Protein sequence comparison has led to the identification of domains of common functional importance. The cytoplasmic domains of cadherins associate with peripheral cytoplasmic proteins termed catenin alpha, beta and gamma with molecular weights of 102, 88 and 80 kDa respectively. This complex formation seems to regulate the adhesive function of cadherins, most likely by connecting cadherins with actin microfilaments. Possible implications of catenins for cadherin function are discussed.     

Behavioural responses of three linyphiid spiders to pitfall traps

The behaviour of three linyphiid spider species (Araneae: Linyhiidae) towards pitfall traps was investigated in an experimental arena. Capture efficiencies were low with a mean of between 16 and 57 traps being encountered before spiders were caught. Survival time, trap encounter rate, trap entry rate and reactions towards vegetation were all found to be species-specific. These behaviours are considered to affect differentially pitfall trap efficiency and may partially explain the lack of clear relationship between pitfall trap catch and density found in published studies.