Instantaneous Attack Rate Research Articles

Short-term temperature changes affected the predation ability of Orius similis on Bemisia tabaci nymphs

Abstract Bemisia tabaci (Gennadius), a major pest that can adversely affect economies and agriculture globally, is particularly sensitive to climate change-induced temperature fluctuations, which can intensify its outbreaks. Orius similis Zheng, a primary natural predator of B. tabaci, also experiences temperature-related effects that influence its biocontrol efficacy. Thus, understanding the response of O. similis to temperature changes is pivotal for optimizing its biocontrol potential. Herein, our investigations showed that the functional response of O. similis to both high- and low-instar nymphs of B. tabaci adheres to the type II model at temperatures of 19, 22, 25, 28, and 31 °C. At 28 °C, O. similis exhibits the highest instantaneous attack rate (high-instar: 1.1580, low-instar: 1.2112), and the shortest handling time per prey (high-instar: 0.0218, low-instar: 0.0191). The efficacy of O. similis in controlling B. tabaci nymphs follows the sequence: 28 °C > 25 °C > 31 °C > 22 °C > 19 °C. Additionally, search efficiency inversely correlates with prey density. Simulations using the Hessell–Varley interference model indicate that increased density of O. similis under any temperature condition leads to reduced predation rates. Moreover, O. similis shows a predation preference for low-instar nymphs of B. tabaci, with higher predation level observed at the same temperature. In conclusion, for effective control of B. tabaci in field releases, O. similis should be optimally released at temperatures between 25 and 28 °C to preferably target the egg or early nymph stages of B. tabaci and determining the appropriate number of O. similis is important to minimize interference among individuals and enhance biocontrol efficacy.

Dispersal of optimal foragers in a patchy environment: Simulations with a mathematical model and tests of predictions in field experiments

To predict the effect of density on the dispersal of foraging parasitoids, we developed a spatially explicit individual-based model in which parasitoids move among host patches at random but use an optimal decision-rule about when to leave these patches. We used a simple decision rule where an individual forager exploits a patch as long as the instantaneous attack rate is higher than the average attack rate it has experienced in the environment. Such a rule implies that foragers compute and remember attack rates as they forage. Simulations with different combinations of patch distribution, host density, mutual interference, and parasitoid density predicted that dispersal distance should increase with parasitoid density. To test this prediction, we used data from two field experiments in which we released either few or many adults of the aphid parasitoid Aphelinus asychis in replicated sites, and subsequently assessed dispersal from the spatial distribution of parasitoid offspring. In the first experiment, we did not to detect a relation between the number released and dispersal distance, but in the second experiment, dispersal distance increased with initial density, as predicted by our model. We propose two hypotheses to explain the discrepancy between the experiments. Different levels of environmental variability among experiments, resulting from differences in experimental designs, could cause differences in statistical conclusions. However, there could be a threshold density below which dispersal is not density-dependent, and this threshold may have been exceeded in the second experiment where large releases involved many more individuals than in the first experiment. In any case, our approach linked individual behavior and spatial distribution, and our results show that the insect distributions in the field can be predicted, qualitatively, from theory about individual behavior.

Toxicological assessment of cadmium exposure through Hyphantria cunea larvae on the predation fitness of Arma chinensis

Heavy metals are defined as an abiotic factor that affects the efficiency of biological pest control. This study constructed a cadmium (Cd)-polluted artificial diets–Hyphantria cunea–Arma chinensis food chain to analyze the effects of Cd exposure on the ability of A. chinensis to control H. cunea. The results revealed that Cd was transferred through the artificial diet to H. cunea larvae and A. chinensis nymphs via a biological amplification effect. After feeding on Cd-accumulated H. cunea larvae, the body weight of A. chinensis nymphs reduced, mortality increased, developmental duration prolonged, and the expression of growth regulatory genes (EX, cycE, and MER) decreased. Cd activated the antioxidant defense system of the nymphs, accompanied by a significant enhancement in the contents of H2O2 and MDA, marked damage to the midgut sub-microstructure, and a remarkable induction in the expression of genes crucial for the mitochondrial pathway/ER stress–apoptosis pathway. Cd significantly diminished the contents of total amino acids, glucose, free fatty acids, and expression of the genes (HK2, PFK, IDH1, and IDH2) essential for the TCA cycle and glycolysis in the nymphs. The preference of the A. chinensis nymphs to Cd-treated H. cunea larvae was evidently reduced. Cd diminished the search-ability, food intake, instantaneous attack rate, and maximum theoretical daily food intake but prolonged the feeding time of the nymphs. Taken together, Cd exposure reduces the ability of A. chinensis nymphs to control H. cunea and provides a new challenge for the efficiency of insect pest control using natural enemies. These findings have important reference value for optimizing pest control strategies in heavy metal polluted areas.

Resilience mechanisms of Trichopria drosophilae (Hymenoptera: Diapriinae) under global extreme cooling: insights into parasitic response and physiological adaptation.

Global climate warming and frequent extreme low-temperature events have made it essential to investigate the impact of low temperatures on parasitic wasps to protect and strengthen farmland biodiversity, which in turn enhances the biological control potential of natural enemies such as parasitic wasps. We systematically examined how low-temperature stress affects the parasitic functional response of Trichopria drosophilae to Drosophila suzukii (Diptera: Drosophilidae) pupae. Our findings indicate that the parasitic behavior of T. drosophilae towards D. suzukii pupae aligns with the Holling II functional response model following exposure to different temperatures. Within the temperature range of 8 °C to -8 °C, lower temperatures correlated decreased instantaneous attack rate of T. drosophilae and an increase in processing time. The search constant Q initially increased and then decreased with declining temperatures. Short-term low-temperature stress negatively impacted the parasitic and searching abilities of T. drosophilae but did not alter its parasitic functional response model. Notably, short-term low-temperature stress had minimal effects on the water content, protein content, and total sugar content of male and female T. drosophilae adults. However, as temperatures decreased, the activities of key enzymes, including GAPDH, SOD, T-AOC, and malondialdehyde (MDA), exhibited an initial increase followed by a decrease. Conversely, the activities of LDH and HOAD decreased, while the activities of CAT and POD increased. Further study on the effect of short-term low temperature on T. drosophilae can provide a research basis for the large-scale production and low-temperature refrigeration technology of T. drosophilae, and provide a scientific basis for its efficient use in the field.

The inappropriate application of imidacloprid destroys the ability of predatory natural enemies to control pests in the food chain: A case study of the feeding behavior of Orius similis on Frankliniella occidentalis

Insecticides are an indispensable and important tool for agricultural production. However, the inappropriate application of insecticides can cause damage to the food chain and ecosystem. Orius similis is an important predatory and natural enemy of Frankliniella occidentalis. Imidacloprid is widely used to control pests, but will inevitably exert adverse effects on O. similis. In order to determine the effect of different imidacloprid treatments on the ability of O. similis to prey on the 2nd-instar nymphs of F. occidentalis, we determined the toxicity and predation of imidacloprid on different stages of O. similis under contact and ingestion treatments. In addition, we used the Holling disc equation to evaluate the ability of O. similis to search and exhibit predatory activity following contact and ingestion treatments. Analysis showed that the highest LC10 and LC20 values for imidacloprid contact and ingestion toxicity treatment were 17.06 mg/L and 23.74 mg/L, respectively. Both imidacloprid treatments led toa reduction in the predatory of O. similis on prey. The functional responses of the 3rd to 5th instar nymphs, along with female and male O. similis adults to the 2nd-instar nymphs of F. occidentalis were consistent with the Holling type II response following contact and ingestion with imidacloprid. However, following imidacloprid treatment, the handing time (Th) of O. similis with single F. occidentalis was prolonged and the instantaneous attack rate (a) was reduced after imidacloprid treatment. The predatory capacity (a/Th) of female O. similis adults when treated with the LC10 concentration of imidacloprid by ingestion was 52.85; this was lower than that of the LC10 concentration of imidacloprid in the contact treatment (57.67). The extent of predation of O. similis on the 2nd-instar nymphs of F. occidentalis was positively correlated with prey density, although the search effect was negatively correlated with prey density. The most extensive search effect was exhibited by adult O. similis females. Simulations with the Hessell-Varley interference model showed that an increase in the number of O. similis would reduce search efficiency regardless of whether they were treated with imidacloprid or not. Thus, O. similis, especially female adults, exhibited strong potential for controlling the 2nd-instar nymphs of F. occidentalis. The toxicity of ingestion following treatment with the same concentration of imidacloprid in O. similis was greater than that of contact treatment. When using O. similis to control F. occidentalis in the field, we should increase the number of female adults released, and prolong the interval between imidacloprid treatment and O. similis exposure. This strategy will improve the control ability of O. similis, coordinate both chemical and biological control, reduce the impact of pesticides on the environment, and improve the efficiency of agricultural production.

Functional response of Neoseiulus californicus (Acari: Phytoseiidae) to Tetranychus urticae (Acari: Tetranychidae) at different temperatures.

Environmental factors like temperature have a great impact on the predation potential of biological control agents. In the present study, the functional response of the predatory mite Neoseiulus californicus (Acari: Phytoseiidae) to the pest mite Tetranychus urticae (Acari: Tetranychidae) at moderate to high temperatures under laboratory conditions was determined. The study aimed to understand the prey-predator interaction under different temperatures and prey densities. Five constant temperatures (24 °C, 27 °C, 30 °C, 33 °C, and 36 °C), and thirteen prey densities (4, 5, 8, 10, 12, 15, 16, 20, 24, 25, 30, 32, and 40) of each stage (adult, nymph, larvae, and egg stage) were employed in the experiment. Observations were made 24 h after the start of each experiment. Results revealed that the predatory mites showed type II functional response to adult females of T. urticae, whereas type I to other stages (nymphs, larvae, and eggs) of T. urticae. The predation capability of adult predatory mites on T. urticae was significant at 24-36 °C. The instantaneous attack rate (a) of N. californicus increased and the handling time (Th) decreased with an increase in temperature. The maximum attack rate was recorded at 36 °C (1.28) for the egg stage. The longest handling time was (0.78) for the larval stage of T. urticae at 30 °C. Daily consumption increased with increasing prey density. Maximum daily consumption was observed at 33 °C (30.00) at the prey density of 40. Searching efficiency decreased with the increase in prey density but was found to increase with the rise in temperature. N. californicus was found to be voracious on the larval and egg stages. Conclusively, the incorporation of N. californicus at earlier stages (larvae and eggs) of T. urticae would be beneficial under warm conditions because managing a pest at its initial stage will save the crop from major losses. The results presented in this study at various temperatures will be helpful in different areas with different temperature extremes. The results of the functional response can also be applied to mass rearing, quality testing, and integrated pest management programmes.

How the plant probiotic bacteria and herbivore-induced plant volatiles (HIPVs) alter functional response of Phytoseiulus persimilis (Phytoseiidae) on the two-spotted spider mite

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the economically most important pests on different crops worldwide. Its management programs are normally conducted based on the usage of chemical acaricides. However, considering the side effects of acaricides and rapid resistance development, releasing the predator mite, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae), is an alternative method for the control of T. urticae. In this study, the effects of plant probiotic bacteria; Bacillus pumilus INR7 (Bacillales: Bacillaceae) and Bacillus velezensis Fol (Bacillales: Bacillaceae), and herbivore-induced plant volatiles (HIPVs) (methyl jasmonate, methyl salicylate, Indole and 3-pentanol) were investigated on the functional response of P. persimilis to T. urticae eggs laid on attached leaves of kidney bean under laboratory conditions (25 ± 1 °C, 65 ± 5% RH and a photoperiod of 16:8h L:D). Densities of 2, 5, 10, 20, 30, 40, 50 and 60 prey in 10 replications were offered to the 1-day-old adult female individuals of P. persimilis during a 24-h period. The results of logistic regression analyses showed a type II functional response on all treatments. The Rogers model was used to estimate the instantaneous attack rate (a) and handling time (T<sub>h</sub>). The instantaneous attack rate had no significant difference among treatments. The handling time on B. velezensis (0.3540 ± 0.0716 h) and methyl salicylate (0.3593 ± 0.0842 h) was significantly lower than in other treatments. These results suggest that methyl salicylate and B. velezensis may have a positive effect on the foraging behavior of P. persimilis against T. urticae.

Predatory Ability of Harmonia axyridis (Coleoptera: Coccinellidae) and Orius sauteri (Hemiptera: Anthocoridae) for Suppression of Fall Armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae)

The lepidopteran pest, Spodoptera frugiperda (JE Smith), spread rapidly after its first detection in China and has caused significant yield loss to maize production in the southwestern part of the country. Although natural enemies of S. frugiperda are present in the field, biological control using naturally distributed predators is ineffective because their underlying populations are too low. To enhance our understanding of the potential role of natural enemies in regulating this invasive pest, functional response experiments were conducted to quantify the response of two predators, Orius sauteri (Poppius) (Hemiptera: Anthocoridae) and Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), in terms of consumption of S. frugiperda. Experimental results revealed that the predatory effects of nymphs of O. sauteri and H. axyridis on the eggs and larvae of S. frugiperda fitted Holling's Type II functional response model. Importantly, the theoretical maximum number of prey consumed per day (Na-max), the instantaneous attack rate (a') and the handling time (Th) of O. sauteri nymphs on S. frugiperda eggs were 15.19, 0.7444 and 0.049 d, respectively; and the parameters on first instar larvae of S. frugiperda were 700.24, 0.5602 and 0.0008 d, respectively. These data contrast to those of H. axyridis, where the Na-max, a' and Th of adults on eggs of S. frugiperda were 130.73, 1.1112 and 0.085 d, respectively, and on the first instar larvae of S. frugiperda were 1401.1, 0.8407 and 0.0006 d, respectively. These results revealed that H. axyridis is a highly voracious predator of the eggs and young larvae of S. frugiperda and O. sauteri could also be used as biocontrol agent of this pest. Our work provides a theoretical framework for the application of natural enemies to control S. frugiperda in the field. Further research is required to strategize conservation biological control approaches in the field to increase populations of these predators and enhance the suppression of S. frugiperda.

Functional response of adult Cheyletus malaccensis (Acari: Cheyletidae) to different developmental stages of Aleuroglyphus ovatus (Acari: Acaridae)

Cheyletus malaccensis is an important natural enemy of stored pests. In the study, the functional response of C. malaccensis against Aleuroglyphus ovatus was investigated under five constant temperatures of 16, 20, 24, 28 and 32 °C. The results showed that the functional response of adult C. malaccensis to different stages of A. ovatus was conformed to Holling II. Under the temperature between 16 and 32 °C, C. malaccensis females consumed more larvae and nymphs, followed by male and females of A. ovatus. While male C. malaccensis merely consumed larvae and nymphs of prey. Adult C. malaccensis ate few eggs of A. ovatus. The daily consumption and instantaneous attack rate (a/Th) increased with the temperature increasing from 16 °C to 32 °C while the peak was at 28 °C. The maximum daily consumption for larva and a/Th of female C. malaccensis are 135.1 and 110.7, respectively. Cheyletus malaccensis showed positive preference to larvae and nymphs, while negative preference to adults and eggs of A. ovatus. Because of the competition and interference among predators, the predation efficiency decreased with the density of predator increasing, and the interference coefficient (m) was 0.485 at 28 °C. These results could be helpful to provide theoretical basis and practical instructions for the biological control of A. ovatus by C. malaccensis.

Predation of Aphis craccivora (Hemiptera: Aphididae) by Orius sauteri (Hemiptera: Anthocoridae) Under Different Temperatures

Aphids are important agricultural pests because of their feeding and, for many species, their ability to transmit plant pathogenic viruses. Orius sauteri (Poppius) (Hemiptera: Anthocoridae) is an important predator in northern China of many aphid species, including Aphis craccivora (Koch) (Hemiptera: Aphididae). We measured the functional response and intraspecific competition of O. sauteri under different densities of A. craccivora at several constant temperatures. Predation of O. sauteri on A. craccivora conformed to Holling's type II functional response at all temperatures tested. The predation capability of O. sauteri showed a significant correlation with temperature. The predation capacity of O. sauteri was highest at 25°C, at which temperature we found the highest instantaneous attack rate (a = 0.8711), the theoretical maximum number of aphids captured (181.36), and the shortest handling time (Th = 0.0055). Predation by O. sauteri increased progressively with temperature from 15 to 25°C, but then decreased at 30°C. Intraspecific competition of O. sauteri increased positively with predator density under all temperatures examined. Our results indicate O. sauteri has significant potential for use as a biocontrol agent, under a wide range of temperatures. The inverse density-dependent predation and intraspecific competition of O. sauteri suggests that to obtain the greatest degree of pest suppression, releases of O. sauteri should begin early in the cropping season and numbers released should take prey density into consideration.

Life history and functional response to prey density of the flower bug Orius sauteri attacking the fungivorous sciarid fly Lycoriella pleuroti

Seldom have natural enemies been quantified in their ability to control fungivorous arthropods, despite the severe losses they can cause in production of edible fungus. Here, we evaluated the omnivorous predator Orius sauteri (Poppius) when preying on eggs and larvae of the fungivorous sciarid fly Lycoriella pleuroti (Yang et Zhang) and compared against a microencapsulated artificial diet. We also estimated the predation ability of O. sauteri feeding on different densities of L. pleuroti larvae and eggs. The results indicated that O. sauteri successfully oviposit on a mushroom substrate. Moreover, both L. pleuroti eggs and larvae were capable of supporting O. sauteri populations. A type II functional response was observed for both males and females of the predator. Further, moderate values for parameter a′ (instantaneous attack rate) and greatly reduced Th (handling time) revealed a high potential for O. sauteri in suppressing outbreaks of L. pleuroti. This is the first report of a generalist predator feeding and developing within an edible mushroom-pest system. O. sauteri is a prime candidate for testing as a biological control agent, either in inoculative or in inundative release, for targeted suppression of the fungivorous sciarid L. pleuroti.

Influence of temperature on the functional response of the predatory bug, Anthocoris minki pistaciae (Hemiptera: Anthocoridae), a predator of Agonoscena pistaciae (Hemiptera: Psyllidae)

AbstractThe common pistachio psylla, Agonoscena pistaciae Burckhardt and Lauterer (Hemiptera: Psyllidae), is one of the most destructive pests of cultivated pistachio trees in Iran. A locally available anthocorid predator, Anthocoris minki pistaciae Wagner (Hemiptera: Anthocoridae) was evaluated as a biological agent candidate for the control of this pest. The functional response of this predatory bug was investigated at temperatures of 20, 25, 27.5, and 30 °C, relative humidity of 50–60%, photoperiod L:D of 16:8 h and at densities of 2, 4, 8, 20, 40, 60, 80, and 100 nymphs of A. pistaciae during a 24-h period. A type II functional response model was fitted at all tested temperatures. The results indicated that the instantaneous attack rate for the predatory bug ranged from 0.15 to 0.36 nymphs per hour and estimated handling times were 0.41, 0.35, 0.42, and 0.27 h at 20, 25, 27.5, and 30 °C, respectively. Based on asymptotic 95% confidence intervals, searching efficiency didn’t differ significantly from 2...

Estimating the Odds of Relapsing Event

Adopting the life table techniques this paper proposed and presents a statistical method for estimating probabilities and odds that a randomly selected subject or patient in a population is afflicted by spasm of a recurring or relapsing event or disease over a specified time period. Estimates of conditional probabilities that a randomly selected subject would experience and not experienced the relapsing event or illness at some time period given that the same patients has experienced and not experienced an attack by the relapsing event or illness at a previous time period are provided. Also provided are estimates of the number of patients expected to suffer or not to suffer the next attack of the relapsing illness within a specified time period no matter how spasmodic the attacks are. Similarly, provided are estimates of the number of subjects or patients expected to experience and not experience the relapsing event at a subsequent time period given that these same patients had early experienced and not experienced the same relapsing event or disease at a previous time period no matter short these time period. The proposed method is illustrated with some hypothetical data under the assumption that the relapsing event or disease has a known and given instantaneous attack rate in the population.

Effect of Temperature on Functional Response ofAphidius gifuensis(Hymenoptera: Braconidae) ParasitizingMyzus persicae(Hemiptera: Aphididae)

Abstract Aphidius gifuensis Ashmead (Hymenoptera: Braconidae) is a common parasitoid of aphids including the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). To maximize the use of A. gifuensis for biological control of M. persicae, the functional response of A. gifuensis using M. persicae as a host was determined at 4 constant temperatures (15, 20, 25, and 30 °C) and 20 host densities (5, 10, 15, increased incrementally by 5, to a maximum of 100) on a 6-leaf sweet pepper plant (30 cm in height) over a 24 h period. Roger's random parasitoid equation (RRPE) and Holling's disc equation (HDE) were used to fit the data. The results showed that functional responses at all temperatures were type II, and the instantaneous attack rate (a) in both models increased as temperature increased from 15 to 25 °C and then decreased at 30 °C. The highest instantaneous attack rate (a) for A. gifuensis was at 25 °C for the 2 models, 1.3203 ± 0.0415 d-1 for HDE and 4.295e+03 d-1 for RRPE. The handling time (...

南方小花蝽在不同空间及笼罩条件下对西花蓟马的控制作用

在室内研究了5种空间异质条件下南方小花蝽对西花蓟马的捕食作用，并研究了笼罩条件下4种比例释放南方小花蝽对西花蓟马的控制效果。结果表明，不同空间异质下，南方小花蝽对西花蓟马的功能反应均符合Holling Ⅱ圆盘方程；以瞬时攻击率和寻找效应为评价指标，发现南方小花蝽在小容器中的瞬时攻击率（<em>a</em>’）最高，为0.9204，寻找效应最好；在大容器且空间异质最复杂的处理中的瞬时攻击率（<em>a</em>’）最低，为0.6303，寻找效应最差。在笼罩条件下，以3：120和6：120比例释放南方小花蝽和西花蓟马，其控制效果差；以9：120的比例释放，5周后对西花蓟马成虫和若虫的控制效果分别达到74.70%和81.01%；以15：120比例释放，5周后对西花蓟马成虫和若虫的控制效果分别达到95.71%和89.02%。结果显示空间越小或异质性越简单，越利于南方小花蝽捕食西花蓟马。若实际生产中采用9：120的益害比例释放南方小花蝽，既可以达到对西花蓟马较好的控制效果，又相对节约成本。

Functional Response ofGonatocerus ashmeadiand the “New Association” ParasitoidG. tuberculifemurAttacking Eggs ofHomalodisca vitripennis

The functional response of two egg parasitoids, Gonatocerus tuberculifemur (Ogloblin) and G. ashmeadi Girault (Hymenoptera: Mymaridae), to varying densities of Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) eggs was studied in the laboratory. G. tuberculifemur showed a type II functional response where parasitism increased at a decreasing rate as host egg density increased from 5 to 40, reaching an asymptote of an upper limit of 9.3 host eggs within the 1-h exposure period. The instantaneous attack rate and handling time as estimated by the random predator equation were 2.28/h and 0.10 h, respectively. In contrast, G. ashmeadi showed a type I functional response where the number of hosts attacked followed a constant linear increase regardless of host density to an upper limit of 11.5 host eggs within the 1-h exposure period. Female G. ashmeadi parasitized on average 4.3 and 3.5 more eggs per hour when presented with 10 and 20 H. vitripennis eggs, respectively, compared with G. tuberculifemur. When 5 or 40 H. vitripennis eggs were offered, there was no significant difference in parasitism rates between parasitoid species. Percentage of female offspring was significantly higher (5%) for G. ashmeadi compared with G. tuberculifemur. Under the experimental conditions used in these evaluations, results suggest that G. tuberculifemur is an inferior parasitoid to G. ashmeadi.

Temperature-dependent functional response of Scolothrips longicornis (Thysanoptera: Thripidae) preying on Tetranychus urticae

Environmental variables like temperature are important factors that affect the efficiency of biological control agents in greenhouse crops. This study examined the effect of temperature on the functional response of an acarophagous thrips Scolothrips longicornis Priesner to different densities of two spotted spider mite, Tetranychus urticae Koch in laboratory conditions. Five constant temperatures (15, 20, 26, 30, and 35 °C) and seven prey densities (2, 4, 8, 16, 32, 64, and 128) were used in the experiments. At each temperature, 2 to 128 adult of T. urticaue were exposed to a female S. longicornis for a 24 h period. The results indicated that the predatory thrips exhibited type II functional response to different densities of T. urticae at all examined temperatures. Temperature had significant effect on the predation capacity of the adult thrips over the range of 15–35 °C. Instantaneous attack rate ( a) of the predator increased linearly with increasing temperature from 15 to 35 °C. At 35 °C, the highest instantaneous attack rate was estimated to be 0.0579 day − 1 using the Holling model and 0.1480 day − 1 using Rogers model. The estimated value of handling time ( T h) using both Holling and Rogers models decreased linearly with increasing temperature from 15 to 35 °C. Scolothrips longicornis achieved higher predation at higher temperature (16.1 preys/day at 35 °C). This observation suggested that S. longicornis may be more effective for biological control of two spotted spider mite in warmer conditions.

Temperature-dependent functional response of two aphid parasitoids, Aphidius colemani and Aphidius matricariae (Hymenoptera: Aphidiidae), on the cotton aphid

The functional response of two aphid parasitoids, Aphidius colemani Viereck and Aphidius matricariae (Haliday) (Hymenoptera: Aphidiidae), on the cotton aphid, Aphis gossypii Glover (Homoptera: Aphididae), was examined. Five constant temperatures (10, 15, 20, 25, and 30°C) and six host densities (2, 4, 8, 16, 32, and 64) were used during a 24-h period. At each temperature, 2–64 third-instar nymphs of A.gossypii were exposed to individual wasp mating pairs. A type II functional response model for both parasitoid wasps was fit separately for each temperature. The results showed that instantaneous attack rate (a) in A.colemani increased linearly as the temperature increases from 10 to 30°C, but in A.matricariae, (a) increased almost linearly with temperature to reach a maximum at 25°C, and then decreased at 30°C, displaying an asymmetrical dome-shaped pattern. The highest instantaneous attack rate for A.colemani and A.matricariae were calculated 0.940 ± 0.144 day−1 at 30°C and 0.687 ± 0.157 day−1 at 25°C, respectively. Handling time (Th) for A.colemani was inversely proportional to temperature and ranged from 0.093 ± 0.026 day at 10°C to 0.032 ± 0.004 day at 30°C, but in A.matricariae, (Th) was between 0.078 ± 0.015 day at 10°C and 0.036 ± 0.014 day at 20°C. A.colemani achieved higher parasitism rate than A. matricariae at higher temperatures. This observation suggests that A.colemani maybe more effective for biological control of the cotton aphid during warmer periods.

Parasitism of the glassy-winged sharpshooter, Homalodisca coagulata (Homoptera: Cicadellidae): Functional response and superparasitism by Gonatocerus ashmeadi (Hymenoptera: Mymaridae)

Abstract The functional response by the egg parasitoid, Gonatocerus ashmeadi, and superparasitism of Homalodisca coagulata eggs were found to be related to host age and density when studied under laboratory conditions. Several aspects relating to parasitism of 1-, 3-, 5-, 7-, 9-day-old H. coagulata eggs were measured under varied densities ranging from 1:1 to 1:60 parasitoid to host ratios. The functional response for the parasitoid to host eggs of all age groups closely fit the Type II model that describes responses to changing densities. The instantaneous attack rate and handling time of the parasitoid were similar for H. coagulata eggs of various ages. The number of host eggs parasitized varies significantly with host density and age, but not when analyzed by a host age × density interaction. However, host age and density, as well as the host age × density interaction, contribute significantly to the differences found in length of the development time of G. ashmeadi within host eggs. This parasitoid showed a significantly greater tendency toward superparasitism at parasitoid-to-host ratios ⩽10:100. The maximum number of parasitoid eggs found in a single host egg was 18. The frequencies of superparasitism for G. ashmeadi display a random distribution over all observed host densities. Our results also suggest G. ashmeadi eliminates the supernumerary parasitoids through physiological suppression.

Functional Response of an Ambush Predator: Chaoborus americanus Predation on Daphnia pulex

Estimations of invertebrate predation parameters usually rely on behavioral observations and on feeding rates in single, arbitrary prey densities. In this study, predation parameters were estimated directly from functional response data. This type of analysis relies on many prey densities and therefore should lead to more widely applicable parameter values. Functional response curves of third—and fourth—instar Chaoborus americanus preying on five size—classes of Daphnia pulex in the laboratory were examined. Data for each size—class were fitted to Rogers' random predator equation, a modification of Holling's type II functional response equation. The data fit the model well. The parameters a' (instantaneous attack rate) and Th (handling time) were calculated for each prey size from these curves. Attack rate reached a maximum, indicating highest vulnerability, at an intermediate size. Deduced handling times were greater than simple observation would suggest and were highly correlated with prey dry mass, suggesting digestion as the primary component. Results of mixed—size—class experiments were compared to predictions based on the parameters from single—size—class experiments. The ratio of predation—caused mortality rates for prey size—classes was consistent with the predictions, suggesting that no active behavioral selection was occurring. Feeding rates in mixed—sized—class experiments were underestimated when experiments were run a month later than the single—size—class experiments during the 1st yr of this study. However, when single— and mixed—size—class experiments were run simultaneously during the 2nd yr, predictions were very close to observed feeding rates. This indicates the possibility that predator age and seasonal physiological changes affect functional response parameters. Attack rate increased with temperature, probably due to increased encounter rates as Daphnia swimming speed increased. Handling time decreased with increased temperature, probably due to increased digestive rate. The biological significance of Holling's parameters and those of other more behaviorally based models is discussed.