Functional Response Parameters Research Articles

Does the superfluous killing exhibited by spiders mask the functional response parameters? A case study from the perspective of biological control

AbstractThe meadow spittlebug Philaenus spumarius L. (Hemiptera: Aphrophoridae) is a xylem‐sap feeder and the most abundant and widespread vector of Xylella fastidiosa (Xanthomonadales: Xanthomonadaceae) throughout Europe. Control strategies for the disease are based on containment and eradication measures regulated by the European Union. Within the context of biological control, the use of natural enemies aims at limiting the insect vector population in agroecosystems. Spiders are generalist predators with potential as biological control agents occupying all the habitats within crops. Crab spiders (Thomisidae) could be potential natural enemies against P. spumarius. The functional response (FR) of a predator represents the intake rate as a function of food availability and allows estimating feeding behaviour parameters such as the prey handling time and attack rate. However, spiders often kill more prey than they consume, unveiling their capacity as natural enemies. We assessed and compared the FR of Xysticus acerbus (Thomisidae) fed on P. spumarius in the laboratory considering (1) the total number of dead individuals and (2) only the consumed ones. We found that although both FRs were of type‐II, they significantly differed. The values of attack rate and handling time for consumed were 0.1 and 3.6, respectively, while for dead, the attack rate was 0.3 and 1.1, being both significantly different. Moreover, the number of overkilled individuals reached a plateau at the highest prey densities. Xysticus acerbus could be a potential natural enemy of P. spumarius. Nevertheless, we suggest that the effect of including the killed but not consumed prey individuals in FR studies using wasteful killing predators should be considered and further studied.

Dynamical study of the theta-logistic predator-prey model incorporating gregarious behavior of prey

Relation between species and their livelihood environment in ecological systems is very complex. For that reason, in order to study predator-prey relations, modeling is essential in biomathematics. The vital components of predator-prey models are prey species' growth function in the absence of apredator and the functional response. In this article, we proposed a predator-prey model with gregarious prey. In the existing literature, square-root functional response incorporates the gregarious behavior of prey. This study considers the generalized square root functional response and theta-logistic growth of prey in the absence of a predator. The effect of functional response parameters on stability, limit cycle, and Hopf bifurcation on the proposed model has been discussed. Numerical analysis is performed on the basis of some hypothetical parameter values to analyze the model numerically.

Evolution of predator–prey interactions during range expansion in an aquatic insect predator

Abstract Many ectotherms are shifting their distributions polewards, which has been associated with the evolution of phenotypic traits and their thermal plasticity. Trophic interactions may determine the dynamics and ecological impact of range expansions. However, it is largely unknown how trait evolution in edge populations shapes trophic interactions. We studied evolutionary changes in the short‐term (functional response) and long‐term predator–prey interactions between an aquatic insect predator (the damselfly Ischnura elegans) and its prey (the water flea Daphnia magna) during the predator's ongoing poleward range expansion in northern Europe. Using a common‐garden warming experiment at 20 and 24°C we tested for differentiation between predator populations from edge and core regions in metabolic rate and functional response parameters, and used these empirical data to estimate the effects of range expansion on the short‐ and long‐term predator–prey interaction strengths. Metabolic rates did not differ between populations from edge and core regions nor between rearing temperatures. Functional response parameters and their thermal plasticity showed signals of evolution during the range expansion. Attack rates did not differ between predators from edge and core regions, but only decreased under warming in predators from the edge region. Handling times decreased under warming in predators from the edge region but increased under warming in predators from the core region. While handling times were shorter in predators from the core region at 20°C, these did not differ between regions at 24°C. As a result, the short‐term interaction strength was higher for predators from the core region at 20°C, but not different between regions at 24°C. The predator–prey system from the edge region showed lower long‐term system stability at 20°C, but this region difference disappeared under warming because the edge region stability then increased. Our results suggest that rapid evolution of functional response parameters during a predator's range expansion reduced the direct feeding impact on its prey and made the predator–prey system from the edge region more unstable, but not under warming. This provides rare evidence that functional responses can rapidly evolve during range expansions, potentially destabilizing food web dynamics. Read the free Plain Language Summary for this article on the Journal blog.

Immune cell molecular pharmacodynamics of lanreotide in relation to treatment response.

e16213 Background: Lanreotide is clinically effective in advanced neuroendocrine tumors (NETs). The inhibitory effect of lanreotide on tumor cells proliferation is due to binding to somatostatin receptors (SSTR1-5). It has been demonstrated that immune cells express SSTR1-5 differentially. The exact effect of somatostatin analogs (SSAs) on T cells function is not understood. Methods: In vitro and in vivo effects of lanreotide on immune cells were investigated, with regards to clinical response correlates. In vitro, SSTR1-5 expression was measured on CD4+ T helper cells, CD8+ cytotoxic T cells, and CD4+CD25+ T regulatory cells from healthy donors (HD), and lanreotide effect on key functional immune response parameters (NFkB, NFAT, ERK1/2 signaling, IFN, and IL-2 production) were studied. To assess in vivo effects of lanreotide on immune cells of NET pts, peripheral blood mononuclear cells (n = 16) obtained pre and 3 months post treatment were studied for gene and protein expression profiles in sorted T cell subsets using a NanoString immune cell panel. Results: HD T cells had high expression of SSTR2 and low/no expression of the other SSTRs. In vitro, lanreotide had no effect on the functional immune response parameters investigated. For the in vivo study, the patient cohort consisted of 8 responders (no progression by 19 months) and 8 non-responders. Clinicopathological features, see table. Pretreatment immunological competence of responders was greater than non-responders, as indicated by upregulation of TCR signaling (in CD4+) and interferon signaling (in CD8+ and T reg). Irrespective of clinical response, lanreotide had most significant effect on CD8+ T cells, down regulating WNT, TCR, and NF-kB signaling. Compared to non-responders, responders had down regulation of cytokine and chemokine signaling but upregulation of ubiquitination and proteasome degradation associated genes. Several myeloid specific genes were found to be significantly changed in the CD4 T helper population, possibly due to co isolated myeloid cells interacting with T cells during sorting. Conclusions: The in vivo immune effects of lanreotide seen reflect the relevance of parameters in tumor microenvironment such as interactions with myeloid components of the immune system not accounted for under the experimental in vitro conditions.[Table: see text]

Biology and functional response of the predator, Dortus primarius (Distant) (Hemiptera: Miridae) preying on Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae)

BackgroundDortus primarius (Distant) (Hemiptera: Miridae) is a general predator reported from the oriental region. This bug is naturally found in many crop ecosystems where it feeds on thrips, aphids, insect eggs and other soft-bodied insects. Although, the rearing protocol of this predatory mirid has been developed, the efficiency of this predator as a biocontrol agent is limited and needs to be investigated. The thrips, Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae), is a polyphagous pest that attacks many crops in polyhouse in India. Therefore, in the present study, biology and functional response of this predator to different densities of F. schultzei larvae in the laboratory was investigated.ResultsThe mirid predator was able to develop from egg to adulthood on tomato infested plant with F. schultzei larvae in 23–24 days with 15 and 11.76% mortality of 4th and 5th instar nymphs, respectively. Both 5th instar and female adults exhibited a type III functional response. At highest prey density (40) both 5th instar and female adults consumed 21.6 and 28.6 thrips larvae per day, respectively. Functional response parameters, viz. attack rate, handling time, a/Th and T/Th showed the potency of this predator against F. schultzei.ConclusionBased on the high fecundity, predation rate and density dependent behaviour, it is predicted that D. primarius might be an efficient and potential predator. However, further research is needed to assess its release rate and other ecological studies in the field situation.

Thermal plasticity and evolution shape predator-prey interactions differently in clear and turbid water bodies.

Warming and eutrophication negatively affect freshwater ecosystems by modifying trophic interactions and increasing water turbidity. We need to consider their joint effects on predator-prey interactions and how these depend on the thermal evolution of both predator and prey. We quantified how 4°C warming and algae-induced turbidity (that integrates turbidity per se and increased food for zooplankton prey) affect functional response parameters and prey population parameters in a common-garden experiment. We did so for all combinations of high- and low-latitude predator (damselfly larvae) and prey (water fleas) populations to assess the potential impact of thermal evolution of predators and/or prey at a high latitude under warming using a space-for-time substitution. We then modelled effects on the system stability (i.e. tendency to oscillate) under different warming, turbidity and evolutionary scenarios. Warming and turbidity had little effect on the functional response parameters of high-latitude predators. In contrast, warming and turbidity reduced the handling times of low-latitude predators. Moreover, warming increased the search rates of low-latitude predators in clear water but instead decreased these in turbid water. Warming increased stability (i.e. prevented oscillations) in turbid water (except for the 'high-latitude predator and high-latitude prey' system), mainly by decreasing the prey's carrying capacity and partly also by decreasing search rates, while it did not affect stability in clear water. Algae-induced turbidity generally decreased stability, mainly by increasing the prey's carrying capacity and partly also by increasing search rates. This resembles findings that nutrient enrichment can reduce the stability of trophic systems. The expected stability of the high-latitude trophic system under warming was dependent on the turbidity level: our results suggest that thermal plasticity tends to destabilize the high-latitude trophic system under warming in clear water but not in turbid water, and that thermal evolution of the predator will stabilize the high-latitude system under warming in turbid water but less so in clear water. The extent to which thermal plasticity and evolution shape trophic system stability under warming may strongly differ between clear and turbid water bodies, with their contributions having a more stabilizing role in turbid water.

Short-term thermal acclimation modulates predator functional response.

Phenotypic plastic responses to temperature can modulate the kinetic effects of temperature on biological rates and traits and thus play an important role for species adaptation to climate change. However, there is little information on how these plastic responses to temperature can influence trophic interactions. Here, we conducted an experiment using marbled crayfish and their water louse prey to investigate how short‐term thermal acclimation at two temperatures (16 and 24°C) modulates the predator functional response. We found that both functional response parameters (search rate and handling time) differed between the two experimental temperatures. However, the sign and magnitudes of these differences strongly depended on acclimation time. Acclimation to 16°C increased handling time and search rate whereas acclimation to 24°C leads to the opposite effects with shorter handling time and lower search rate for acclimated predators. Moreover, the strength of these effects increased with acclimation time so that the differences in search rate and handing time between the two temperatures were reversed between the treatment without acclimation and after 24 h of acclimation. Overall, we found that the magnitude of the acclimation effects can be as strong as the direct kinetic effects of temperature. Our study highlights the importance of taking into account short‐term thermal plasticity to improve our understanding of the potential consequences of global warming on species interactions.

Revisiting the influence of learning in predator functional response, how it can lead to shapes different from type III.

Predator/parasitoid functional response is one of the main tools used to study predation behavior, and in assessing the potential of biological control candidates. It is generally accepted that predator learning in prey searching and manipulation can produce the appearance of a type III functional response. Holling proposed that in the presence of alternative prey, at some point the predator would shift the preferred prey, leading to the appearance of a sigmoid function that characterized that functional response. This is supported by the analogy between enzyme kinetics and functional response that Holling used as the basis for developing this theory. However, after several decades, sigmoidal functional responses appear in the absence of alternative prey in most of the biological taxa studied. Here, we propose modeling the effect of learning on the functional response by using the explicit incorporation of learning curves in the parameters of the Holling functional response, the attack rate (a), and the manipulation time (h). We then study how the variation in the parameters of the learning curves causes variations in the shape of the functional response curve. We found that the functional response product of learning can be either type I, II, or III, depending on what parameters act on the organism, and how much it can learn throughout the length of the study. Therefore, the presence of other types of curves should not be automatically associated with the absence of learning. These results are important from an ecological point of view because when type III functional response is associated with learning, it is generally accepted that it can operate as a stabilizing factor in population dynamics. Our results, to the contrary, suggest that depending on how it acts, it may even be destabilizing by generating the appearance of functional responses close to type I.

Functional response of Amblyseius eharai (Acari: Phytoseiidae) on Tetranychus urticae (Acari: Tetranychidae).

Amblyseius eharai is a generalist predatory mite that consumes spider mites, rust mites, thrips, and pollen, with a high adaptability to various plants. To better understand ecological and behavioral aspects of this species, we investigated its functional response to different stages of two-spotted spider mite, Tetranychus urticae. Furthermore, we compared its environmental adaptability with that of other referenced phytoseiids using a temperature-dependent model of the intrinsic rate of increase. We were able to calculate the functional response parameters of both sexes of A. eharai when preying on eggs or larvae of T. urticae and, for females only, when preying on the deutonymph of T. urticae. Among the various combinations tested herein, A. eharai females preying on T. urticae larvae had the highest attack rate and shortest handling time. For eggs of T. urticae, A. eharai showed a lower attack rate; however, its handling time for eggs was significantly shorter compared to other phytoseiids. Using T. urticae larva as a prey, the attack rate of female A. eharai was higher and the handling time of both sexes of this species was shorter than those of other phytoseiid mites. Amblyseius eharai populations can show maximum performance quickly due to this species’ lower optimal temperature for population growth (28.1°C) compared to other phytoseiid mites. Thus, we provided evidence that this predatory mite has the potential to be a new, effective biological control agent of greenhouse pests such as T. urticae due to its high predation capacity and low optimal temperature.

Synthesizing drivers of fish functional responses across species

AbstractFishes are subject to numerous stressors, including climate change, fishing and impacts by alien species. One of the challenges in understanding species and community responses to these stressors is identifying how they modify predator–prey interactions, a key process shaping aquatic food webs. Here, we aim to synthesize how species traits, such as size, activity level and alien status, and environmental factors, such as water temperature, shape the functional response: the change in predator consumption rate in relation to changes in prey density. We compiled over 300 fish functional responses and examined sources of variation in two key parameters dictating its shape: handling times and space clearance rates. We found that compared to cold waters, warmer waters were characterized by decreased handling times and increased space clearance rates for smaller predators, but had an opposite effect for bigger predators, suggesting that, across species, altered predation rates may underlie the decrease in size at higher temperatures (the temperature‐size rule). We also found that the negative effect of increased temperature on the functional response of larger predators is more pronounced in active species. Finally, we found that known alien species do not exhibit different functional response parameters when examined on their native prey, suggesting that alien species are not primed for invasion via their high functional response. Together, these asymmetric changes imply that, across species, warmer waters may alter predator–prey relationships differentially according to predator size, prey size and activity levels.

Bionomics of transverse ladybird beetle, Coccinella transversalis on cowpea aphid, Aphis craccivora

Cowpea aphid, Aphis craccivora Koch is one of the important pests of legumes. It is a cosmopolitan and polyphagous pest causing 30-35% damage to vegetable crops globally. Chemical control of this pest is not only expensive but also has deleterious effects on human health, environment and non-target organisms. Biological control is one of the most important components of integrated pest management to achieve eco-friendly and sustainable management of crop pests. Coccinellid predator, Coccinella transversalis Fab. is an efficient predator known for its appetite on cowpea aphid under vegetable ecosystem. With this background, we conducted a study on biology, morphometric and functional response of C. transversalis on cowpea aphid under laboratory conditions (27±1°C and 65±5% RH) at Biological Control Lab, ICAR-Indian Agricultural Research Institute, New Delhi, during 2016-17. Type of functional response was determined through polynomial logistic regression of proportion of prey consumption to the density of prey. Functional response parameters were obtained by fitting the data to the Holling's and Roger's equations. Total life span of male and female was ranged from 47-64 and 60-71 days, with a mean of 56±6.2 and 66±3.9 days, respectively. Both male and female of C. transversalis were found to exhibit Type II functional response. Female has showed high attack rate (1.99±0.141) compared to male (1.90±0.088) with maximum prey consumption of 84.41 and 80.51 aphids/day, respectively. Handling time obtained for males (0.0124 day) was higher than females (0.0118 day).

Functional Response and Predation Rate of Dicyphus cerastii Wagner (Hemiptera: Miridae).

Simple SummaryBiological control (BC) is an effective way to regulate pest populations in horticultural crops, allowing the decrease of pesticide usage. On tomato, predatory insects like plant bugs or mirids provide BC services against several insect pests. Native predators are adapted to local conditions of climate and ecology and therefore may be well suited to provide BC services. Dicyphus cerastii is a predatory mirid that is present in the Mediterranean region and occurs in tomato greenhouses in Portugal. However, little is known about its contribution to BC in this crop. In this study, we evaluated how prey consumption is affected by increasing prey abundance on four different prey, in laboratory conditions. We found that the predator can increase its predation rate until a maximum is reached and that prey characteristics like size and mobility can affect predation. Dicyphus cerastii showed high predation rates for all prey species tested, allowing us to conclude that this species is an interesting predator for BC in tomato crops.Dicyphine mirids are important biological control agents (BCAs) in horticultural crops. Dicyphus cerastii Wagner can be found in protected tomato crops in Portugal, and has been observed feeding on several tomato pests. However, the predation capacity of this species is poorly studied. In order to investigate the predation capacity of D. cerastii, and how it is affected by prey size and mobility, we evaluated the functional response (FR) and predation rate of female predators on different densities of four prey species: Myzus persicae 1st instar nymphs (large mobile prey), Bemisia tabaci 4th instar nymphs, Ephestia kuehniella eggs (large immobile prey) and Tuta absoluta eggs (small immobile prey). Experiments were performed on tomato leaflets in Petri dish arenas for 24 h. Dicyphus cerastii exhibited type II FR for all prey tested. The predator effectively preyed upon all prey, consuming an average of 88.8 B. tabaci nymphs, 134.4 E. kuehniella eggs, 37.3 M. persicae nymphs and 172.3 T. absoluta eggs. Differences in the FR parameters, attack rate and handling time, suggested that prey size and mobility affected predation capacity. Considering the very high predation rates found for all prey species, D. cerastii proved to be an interesting candidate BCA for tomato crops.

Thermal evolution ameliorates the long‐term plastic effects of warming, temperature fluctuations and heat waves on predator–prey interaction strength

Abstract How thermal evolution may affect trophic interactions and its implications for trophic system stability remains unstudied. To advance insights in how global warming shapes trophic interactions, we need to consider besides increases in mean temperatures, also daily thermal fluctuations (DTF) and heat waves (HW), and how their effects are modulated by thermal evolution. Using a common‐garden approach, we tested how each thermal factor affected predator metabolic rate and functional response parameters, and used these responses to predict long‐term predator–prey interaction strength between larvae of the damselfly Ischnura elegans and the water flea Daphnia magna. Using high‐ and low‐latitude predator populations with the latter being exposed to higher mean temperatures, higher DTF and more frequent HW, we assessed the potential impact of thermal evolution at the high latitude using a space‐for‐time substitution. In line with thermal adaptation, growth rates were faster and handling times shorter in low‐latitude compared to high‐latitude larvae at 24°C while the opposite was true at 20°C. Warming weakened the long‐term interaction strength, except for the high‐latitude trophic system at DTF and HW where plastic responses therefore may not stabilize the high‐latitude system. This extends the emerging insight that temperature variation may make ectotherms more vulnerable to warming. The contributions of metabolic rate, search rate and handling time in shaping thermal effects on interaction strength differed between latitudes. A key finding was that thermal evolution may further weaken the long‐term interaction strength of the high‐latitude trophic system under increases in mean temperatures, even at DTF and potentially also at HW. Our results underscore the importance of daily thermal fluctuations and heat waves in shaping predator–prey interactions, and may suggest an overall stabilizing contribution of predator thermal evolution ameliorating thermal plastic effects on food web stability. A free Plain Language Summary can be found within the Supporting Information of this article.

The Stochastic Nature of Functional Responses

Functional responses are non-linear functions commonly used to describe the variation in the rate of consumption of resources by a consumer. They have been widely used in both theoretical and empirical studies, but a comprehensive understanding of their parameters at different levels of description remains elusive. Here, by depicting consumers and resources as stochastic systems of interacting particles, we present a minimal set of reactions for consumer resource dynamics. We rigorously derived the corresponding system of ODEs, from which we obtained via asymptotic expansions classical 2D consumer-resource dynamics, characterized by different functional responses. We also derived functional responses by focusing on the subset of reactions describing only the feeding process. This involves fixing the total number of consumers and resources, which we call chemostatic conditions. By comparing these two ways of deriving functional responses, we showed that classical functional response parameters in effective 2D consumer-resource dynamics differ from the same parameters obtained by measuring (or deriving) functional responses for typical feeding experiments under chemostatic conditions, which points to potential errors in interpreting empirical data. We finally discuss possible generalizations of our models to systems with multiple consumers and more complex population structures, including spatial dynamics. Our stochastic approach builds on fundamental ecological processes and has natural connections to basic ecological theory.

Disentangling the nonlinear effects of habitat complexity on functional responses.

Structural complexity of habitats modifies trophic interactions by providing refuges and altering predator and prey behaviour. Nonlinear effects on trophic interaction strengths driven by these mechanisms may alter food web dynamics and community structure in response to habitat modifications. However, changes in functional response, the relationship between prey density and feeding rate, along habitat complexity (HC) gradients are little understood. We quantified functional responses along a HC gradient from an entirely unstructured to highly structured habitat in a freshwater system, using dragonfly larvae (Aeshna cyanea) preying on Chaoborus obscuripes larvae. To disentangle mechanisms by which changes in HC affect functional responses, we used two different approaches-a population-level and a behavioural experiment-applied an information theoretic approach to identify plausible links between HC and functional response parameters, and compared our results to previous studies. Functional response shape did not change, but we found strong evidence for nonlinear dependence of attack rate and handling time on HC in our study. Combined results from both experiments imply that attack rate increased stepwise between the unstructured and structured habitats in line with the threshold hypothesis, because the predators gained better access to the prey. Handling time was lowest at an intermediate HC level in the population-level experiment while the direct estimate of handling time did not vary with HC in the behavioural experiment. These differences point towards HC-driven changes in foraging activity and other predator and prey behaviour. Most previous studies reported stepwise decrease in attack rate in line with the threshold hypothesis or no change with increasing HC. Moreover, changes in the handling time parameter with HC appear to be relatively common but not conforming to the threshold hypothesis. Overall, increased HC appears to, respectively, weaken and strengthen trophic links in 2D and 3D predator-prey interactions. We conclude that detailed understanding of HC effects on food webs requires complementary experimental approaches across HC gradients that consider predator foraging strategies and predator and prey behaviour. Such studies can also help guide conservation efforts as addition of structural elements is frequently used for restoration of degraded aquatic habitats.

Estimating predator functional responses using the times between prey captures.

Predator functional responses describe predator feeding rates and are central to predator-prey theory. Ecologists have measured thousands of predator functional responses using the same basic experimental method. However, this design is ill-suited to address many current questions regarding functional responses. We derive a new experimental design and statistical analysis that quantifies functional responses using the times between a predators' feeding events requiring only one or a few trials. We examine the feasibility of the experimental method and analysis using simulations to assess the ability of the statistical model to estimate functional response parameters and perform a proof-of-concept experiment estimating the functional responses of two individual jumping spiders. Our simulations show that the statistical method reliably estimates functional response parameters. Our proof-of-concept experiment illustrates that the method provides reasonable estimates of functional response parameters. By virtue of the fewer number of trials required to measure a functional response, the method derived here promises to expand the questions that can be addressed using functional response experiments and the systems in which they can be measured. Thus, we hope that our method will refine our understanding of functional responses and predator-prey interactions more generally.

Generation-Dependent Functional and Numerical Responses of a Naturally Fungus-Infected Colony of Habrobracon hebetor (Hymenoptera: Braconidae) Reared on Ephestia kuehniella (Lepidoptera: Pyralidae) in Iran.

The functional and numerical responses of Habrobracon hebetor (Say) were assessed over 30 sequential generations (G) on different densities (2, 4, 8, 16, 32, 64, and 128 fifth-instar larvae) of the Mediterranean flour moth, Ephestia kuehniella (Zeller). Seven tested generations (G2inf, G4inf, G6inf, G8inf, G10inf, G15inf, and G30inf) had already been naturally infected by a fungus species, whereas only the second generation (G2) had the colonies of both infected (G2inf) and uninfected (G2uninf) individuals. All infected generations, as well as the uninfected generation, showed a Type III functional response. A high variation was found in the handling times (Th) of the parasitoid through 30 sequential generations, and G10inf had the longest handling time. The shortest handling time and the maximum estimated attack rate (T/Th) were observed in G2inf. No significant difference in terms of the number of parasitized hosts was found among all infected generations, as well as between G2inf and G2uninf. Although the handling times in G2inf and G2uninf were close to each other, the attack coefficient of G2uninf was more than that of G2inf. The attack coefficient and handling time of infected generations increased from G2inf to G10inf and then decreased in the higher generations. The most plausible parameters of functional response of infected generations were observed in Ginf. A negative relationship between eggs laid and host densities was observed in the infected generations (G2inf, G4inf, G6inf, G8inf, and G10inf). G2uninf and, among infected generations, Ginf were the best generations for practical utilization in inundative release programs.

Biology, predatory potential and functional response of Mallada desjardinsi (Navas) on melon aphid, Aphis gossypii glover

This study evaluated the developmental biology, predatory potential, and functional response of Mallada desjardinsi (Neuroptera:Chrysopidae) larval instars fed on melon aphid, Aphis gossypii Glover. The experiment was carried out under laboratory conditions at 25 ± 1 °C, with 70 ± 5% R.H and 12:12 L:D photoperiod. The freshly emerged larvae were reared individually in the Petri plates containing moist blotting paper and cucumber leaves (6 × 6 cm) infested with assorted population of second and third instars of A. gossypii. The results showed that incubation, total larval, pre pupal and pupal periods of M. desjardinsi were 2.90, 12.50, 1.40 and 9.10 days, respectively. Pre oviposition, oviposition and post oviposition period of M. desjardinsi was 11.80, 32.40 and 2.76 days, respectively and each female laid an average of 128.58 eggs. The 1st, 2nd and 3rd instars of M. desjardinsi on an average consumed 30.98, 107.80 and 265.40 aphids, whereas total consumption during life cycle was 298.50 aphids/predator. All the three larval stages of the predator exhibited Type II functional response to the aphid. Based on Rogers’s random predator equation, the predator’s attack rate was the lowest (0.092) in the first instar, while the 3rd instar recorded the highest rate (0.118). Functional response parameters indicate that attack rate increased and handling time decreased with the advancement of the predator stage. From biological control point of view, our data suggest the successful use of M. desjardinsi third instar larvae as voracious feeders in IPM programmes against melon aphid.

Biological Aspects and Life Table Parameters of Phytoseiulus macropilis and Neoseiulus Californicus (Acari: Phytoseiidae), Feeding on Eggs And Immature Stages of Tetranychus urticae (Acari: Tetranychidae) at Different Temperatures

The purpose of this study was to evaluate prey consumption, functional response and life table parameters of the two predatory mites on immature stages and eggs of T. urticae at two constant temperatures 25° and 30°C, in the laboratory of cotton and crops mite research department, Plant Protection Research Institute Sharkeia branch. Developmental periods (Life cycle) of both females and males individuals were longer for N. californicus when fed on immature stages of T. urticae at 25°C (7.14 , 5.79 days) for females and males, respectively. Predatory mite fecundity was affected significantly by types of food and high for P. macropilis when feeding on T. urticae eggs (63.67 eggs/ female) at 25°C; while the less fertility was 33.95 eggs/female for N. californicus when fed on T. urticae eggs at 30°C. The ability of N. californicus preying on immature stages of T. urticae was significantly greater than P. macropilis (146.24 , 92.29 prey) for female and male, respeclively. On the other hand, P. macropilis consumed more eggs than N. californicus (193.89, 132.06 prey) for female and male, respectively at 25°C. Life table parameters showed that generation time (tG) was lower (8.81 days) for P. macropilis when fed on immature stages of T. urticae at 30°C, net reproductive rate (Ro) was higher (28.65) for P. macropils when fed on eggs at 25°C, and both intrinsic rate of natural increase (rm) (0.34) and finite rate of increase (λ) (1.41) were higher when fed on immature stages of T. urticae at 30°C for P. macropilis.

Functional responses are maximized at intermediate temperatures.

Functional responses describe how consumer foraging rates change with resource density. Despite extensive research looking at the factors underlying foraging interactions, there remains ongoing controversy about how temperature and body size control the functional response parameters space clearance (or attack) rate and handling time. Here, we investigate the effects of temperature, consumer mass, and resource mass using the largest compilation of functional responses yet assembled. This compilation contains 2,083 functional response curves covering a wide range of foragers and prey types, environmental conditions, and habitats. After accounting for experimental arena size, dimensionality of the foraging interaction, and consumer taxon, we find that both space clearance rate and handling time are optimized at intermediate temperatures (a unimodal rather than monotonic response), suggesting that the response to global climate change depends on the location of the consumer's current temperature relative to the optimum. We further confirm that functional responses are higher and steeper for large consumers and small resources, and models using consumer and resource masses separately outperformed models using consumer:resource mass ratios, suggesting that consumer and resource body mass act independently to set interaction strengths. Lastly, we show that the extent to which foraging is affected by temperature or mass depends on the taxonomic identity of the consumer and the dimensionality of the consumer-resource interaction. We thus argue that although overall body size and temperature effects can be identified, they are not universal, and therefore food web and community modeling approaches could be improved by considering taxonomic identity along with body size and unimodal temperature effects.