Potential of Blaptostethus pallescens Poppius (Hemiptera: Anthocoridae) on Tetranychus truncatus Ehara (Prostigmata: Tetranychidae)

Efficiency, functional and numerical responses of anthocorid bug Blaptostethus pallescens Poppius on the spider mite, Tetranychus truncatus Ehara were examined under laboratory conditions. Nymphs of B. pallescens exhibited a Hollings type II functional response when females of spider mite were offered at densities of 10, 20, 30, 40, 50, 60 and 70 mites/bug. Individual fifth instar bugs consumed up to 45.3 adult females of T. truncatus in 24 h at prey mite densities of 60 mites/ bug. Studies on numerical response revealed that the nymphs of the anthocorid bug failed to complete development when the food was restricted to mite alone. Numerical response studies on adult bugs, when offered T. truncatus at densities of 10, 20, 30, 40 and 50 females showed no significant differences in the average fecundity of the female bug. Results indicate that the anthocorid predator, B. pallescens has a very high predatory potential though with a weak numerical response.

Combined Anchoring: Prosecution and defense sentencing recommendations as sequential anchors in the courtroom

Purpose: When making judgments under uncertainty not only lay people but also professional judges often rely on heuristics like a numerical anchor (e.g., a numerical sentencing demand) to generate a numerical response. As the prosecution has the privilege to present its demand first, some scholars have speculated about an anchoring-based unfair disadvantage for the defence (who has the last albeit less effective word in court). Despite the plausibility of this reasoning, it is based on a hitherto untested assumption that the first of two sequential anchors exerts a greater influence on a later judgment (a primacy effect). We argue that it is also conceivable that the last word in court has a recency advantage (a recency effect) or that order does not matter as both demands even each other out (a combined anchor). Methods: We report a pre-registered experiment with German law students (N=475) who were randomly assigned to six experimental conditions in a study on legal decision-making order to test these three possibilities. Results: Results indicate an influence of both the prosecution and the defence recommendation, but no effect of order. Conclusion: This provides strong support for combined anchoring even for knowledgeable participants and rich case material. Specifically, the data are best compatible with the notion that both anchors exert an influence but each on different individuals. The implications of this finding for theory and legal decision-making are discussed.

On the difficulty to think in ratios: a methodological bias in Stevens’ magnitude estimation procedure

In the field of new psychophysics, the magnitude estimation procedure is one of the most frequently used methods. It requires participants to assess the intensity of a stimulus in relation to a reference. In three studies, we examined whether difficulties of thinking in ratios influence participants’ intensity perceptions. In Study 1, a standard magnitude estimation procedure was compared to an adapted procedure in which the numerical response dimension was reversed so that smaller (larger) numbers indicated brighter (darker) stimuli. In Study 2, participants first had to indicate whether a stimulus was brighter or darker compared to the reference, and only afterwards they estimated the magnitude of this difference, always using ratings above the reference to indicate their perception. In Study 3, we applied the same procedure as in Study 2 to a different physical dimension (red saturation). Results from Study 1 (N = 20) showed that participants in the reversal condition used more (less) extreme ratings for brighter (darker) stimuli compared to the standard condition. Data from the unidirectional method applied in Study 2 (N = 34) suggested a linear psychophysical function for brightness perception. Similar results were found for red saturation in Study 3 (N = 36) with a less curved power function describing the association between objective red saturation and perceived redness perception. We conclude that the typical power functions that emerge when using a standard magnitude estimation procedure might be biased due to difficulties experienced by participants to think in ratios.

Dynamics of a plant-herbivore model with a chemically-mediated numerical response

A system of two ordinary differential equations is proposed to model chemically-mediated interactions between plants and herbivores by incorporating a toxin-modifiednumerical response. This numerical response accounts for the reduction in the her-bivore's growth and reproduction due to chemical defenses from plants. It is shownthat the system exhibits very rich dynamics including saddle-node bifurcations, Hopfbifurcations, homoclinic bifurcations and co-dimension 2 bifurcations. Numerical sim-ulations are presented to illustrate the occurrence of multitype bistability, limit cycles,homoclinic orbits and heteroclinic orbits. We also discuss the ecological implicationsof the resulting dynamics.

Functional and numerical responses of Neoseiulus barkeri (Acari: Phytoseiidae) on two-spotted spider mite: the effect of patch condition and additional food source

Parameters that describe foraging behavior play a key role in selection of natural enemies used in biological control programs. These parameters are greatly affected by patch condition and food source type. This study was carried out to evaluate foraging behavior in Neoseiulus barkeri (Hughes) (Acari: Phytoseiidae), a predatory mite of Tetranychus urticae Koch under different patch and diet conditions. The predation rate of N. barkeri at different egg and nymph densities of T. urticae (2, 4, 8, 16, 32, 64, 128) was investigated in both limited and unlimited patches either in the presence or absence of pollen as an additional food source under laboratory conditions. A Type II functional response was determined for N. barkeri on eggs or nymphs of T. urticae in both unlimited and limited patches. The type of functional response was not affected by presence or absence of pollen. The numerical response, in terms of eggs laid, increased curvilinear with increasing prey density. The numerical response was similar in shape to a Type II functional response. The efficiency of conversion of ingested food (ECI) of female N. barkeri decreased in all treatments when prey density increased. The type of patch (limited or unlimited) and prey stage (egg or nymph in the presence or absence of pollen) can affect searching efficiency (a) and handling time (Th) (functional response) as well as daily fecundity and ECI (numerical response) of the phytoseiid predator mite, N. barkeri with implications for its use in biological control.