Efficacy of the predator Mallada basalis (Neuroptera: Chrysopidae) on Tetranychus kanzawai and Panonychus citri (Acari: Tetranychidae) at different predator:prey release ratios

We compared population suppression of the phytophagous mites, Tetranychus kanzawai Kishida and Panonychus citri (McGregor), on papaya by second instar larvae of the green lacewing, Mallada basalis (Walker), at various predator:prey release ratios in the laboratory. Initially, we presented M. basalis with mixed age classes of each mite species separately at a density of approximately 30 mites per seedling. After 3 days, predator:prey ratios of 1:30, 1:15, and 1:10 resulted in reductions of T. kanzawai of 66.8%, 82.6%, and 83.3%, respectively, and reductions of P. citri of 41.8%, 75.5%, and 77.2%, respectively. Predation on individual age classes was approximately equal in both species, reinforcing previous findings that this predator does not show a preference among age classes. We next presented M. basalis with mixed populations of the two mite species in which there were equal numbers of each species and the density was as in the single species tests. Total mite reduction with both mite species present was 48.5%, 71.9%, and 74.5% at ratios of 1:30, 1:15, and 1:10, respectively; T. kanzawai was reduced by 50.5%, 77.4%, and 79.5%, respectively, and P. citri was reduced by 44.1%, 60.3%, and 63.2%, respectively. This study suggests that M. basalis has the potential for substantially suppressing populations of both T. kanzawai and P. citri on papaya at a predator:prey ratio of 1:15 or greater. However, evaluation under realistic agricultural settings is needed before specific recommendations about predator release rates can be made.     

Predation potential of <Emphasis Type="Italic">Rhynocoris marginatus</Emphasis> (Hemiptera: Reduviidae) against three mealybug species of agricultural importance

The predation potential of a generalist predator Rhynocoris marginatus (Fab.) (Hemiptera: Reduviidae) against three important mealybug pests of cotton, Phenacoccus solenopsis Tinsley, Maconellicoccus hirsutus Green, and Coccidohystrix insolita Green (Hemiptera: Pseudococcidae) was evaluated under laboratory conditions. The specific objective of the study was to determine the prey capturing time, prey handling time, and prey preference among the three mealybug species for different developmental stages of R. marginatus. The number of prey consumed/predator/24 h by R. marginatus was dependent on the mealybug species and the predator developmental stage. Rhynocoris marginatus showed a decrease in prey capturing time and handling time as the predator grew older. After evaluating the prey stage preference, results indicated that the developmental stages of R. marginatus preferred adult mealybugs over the younger stages. In a choice-test bioassay including the three mealybug species, no significant difference in prey species selection was observed for the various R. marginatus developmental stages. However, the mortality of P. solenopsis was observed to be highest among the mealybugs, followed by M. hirsutus and C. insolita. This supports the idea that R. marginatus can be effectively utilized for the management of one of the most destructive mealybug pests of cotton, P. solenopsis. Results from this study are important for the development of a knowledge-based management program for cotton agroecosystems affected by various mealybug pests.     

Functional response and predation of Nabis kinbergii （Hemiptera. Nabidae） to Plutella xylostella （Lepidoptera. Plutellidae）

The functional response of adult Nabis kinbergii （Hemiptera： Nabidae） to density of diamondback moth Plutella xylostella （Lepidoptera： Plutellidae） was investigated under laboratory conditions. Holling＇ s （1959） type Ⅱ model was found to be a good fit for the observed functional response of this predator. The numbers of P. xylostella consumed increased with temperature from 15℃ to 35℃. The maximum number of prey killed was observed at 35℃, with average of 10.3 and 8.3 forth instar larvae consumed by adult females and males of N. kinbergii, respectively. The predation of N. kinbergii on P. xylostella increased with successive immature stages. The number of prey consumed by predators decreased as the body size of prey increased. An average of 131 eggs or 95 larvae of P. xylostella were killed by a single of female adult in 24 hours at 24＂C. The pupae of P. xylostella were observed to be eaten by fifth instar nymphs and adults N. kinbergiiin numbers of less than an average of 0.7 pupae per predator in 24 hours at 24＂C. Predation preference by N. kinbergii was also investigated. The number of P. xylostella and Myzus persicae killed by female N. kinbergii was not significantly different, but males killed significantly more P. xylostella than M. persicae. Both eggs and larvae of P. xylosteUa were killed in significantly greater number than those of Pieris rapae in the same feeding arena.     

Functional responses of two chrysopid predators feeding onHelicoverpa armigera (lep.: noctuidae) and aphis gossypii (hom.: aphididae)

Predation onHelicoverpa armigera (Hubner) eggs andAphis gossypii (Glover) nymphs by 3rd instar larvae ofMallada desjardinsi (Navas) andChrysoperla congrua (Walker) was studied under laboratory conditions. Single predators that had been starved for 24 hours were isolated for 1 hour in 9 cm Petri dishes containing prey at densities of 5, 10, 15, 20 and 25 per dish. A type II functional response model gave a satisfactory fit to the data in case ofM. desiardinsi preying onH. armigera. However, with C.congrua, a type III model gave a slightly better fit. ForA. gossypii, functional responses of both predators did not differ from type II, withM. desjardinsi showing a significantly lower search rate and shorter handling time thanC. congrua. Implications of these findings are discussed     

Life table of Xylocoris afer (Hemiptera: Anthocoridae) feeding on eggs of Corcyra cephalonica (Lepidoptera: Pyralidae) and Plutella xylostella (Lepidoptera: Plutellidae)

The aim was to evaluate the biological aspects of Xylocoris afer fed on Corcyra cephalonica and Plutella xylostella eggs. The experiment was conducted with X. afer nymphs aged 12–24?h, one per Petri dish, resulting in a total of 60 nymphs (60 repetitions). On each dish, we placed P. xylostella and C. cephalonica eggs daily, together with a cotton roll moistened with distilled water and conducted daily evaluations. We evaluated the duration, viability, and consumption of nymphal stages, the longevity of males and females, the number of eggs per female, and egg fertility. In addition, the biological data were used to determine the parameters of the fertility life table. The consumption by adults (male and female) of X. afer differed between the preys, the highest consumption was C. cephalonica eggs. Females that consumed eggs of C. cephalonica produced about 90% more eggs and more offspring than those that fed on P. xylostella eggs. Based on our results, it can be inferred that the predator completed its development feeding both on natural prey and the alternative, evidencing the possible potential of X. afer to be used in the biological control of P. xylostella as well as the use of C. cephalonica in mass rearing of this predator under laboratory conditions, aiming its use in applied biological control. However, before being accepted for biological control agent against agricultural pests, various factors should be examined in ecosystem level, as the behavior of predator in different densities of prey.     

黄玛草蛉幼虫对草地贪夜蛾卵和低龄幼虫的捕食能力

【目的】明确本地优势天敌黄玛草蛉Mallada basalis对入侵我国的重大农业害虫草地贪夜蛾Spodoptera frugiperda卵及低龄幼虫的捕食能力和生防潜力。【方法】在实验室条件下采用功能反应模型评价了黄玛草蛉2和3龄幼虫对草地贪夜蛾卵及1和2龄幼虫的捕食能力。【结果】黄玛草蛉幼虫对草地贪夜蛾卵和低龄幼虫的捕食量均随猎物密度的升高而增加,最后趋于捕食饱和状态,而其捕食率随猎物密度的升高而逐步下降,对不同发育阶段的草地贪夜蛾均表现为Ⅱ型功能反应。黄玛草蛉2龄幼虫对草地贪夜蛾卵及1和2龄幼虫的瞬时攻击率a分别为0.150, 0.084和0.094,处理时间Th分别为0.282, 0.333和0.519 h,理论日最大捕食量T/Th分别为85106粒、72072头和46.242头;黄玛草蛉3龄幼虫对草地贪夜蛾卵及1和2龄幼虫的瞬时攻击率分别为2.018, 0.288和0.259,处理时间分别为0.102, 0.311和0.375 h,理论日最大捕食量分别为235294粒、77170头和64000头。【结论】黄玛草蛉2和3龄幼虫对草地贪夜蛾卵和低龄幼虫均具较强的捕食能力,其中黄玛草蛉3龄幼虫比2龄幼虫具有更强的捕食效率。     

Responses of Episyrphus balteatus DeGeer (Diptera: Syrphidae) in relation to prey density and predator size

Laboratory experiments were conducted to determine the functional and numerical responses of the aphidophagous hover fly Episyrphus balteatus DeGeer (Diptera: Syrphidae) to different densities of 4th instar black bean aphids, Aphis fabae Scopoli (Homoptera: Aphididae), on broad bean, Vicia faba L. (Fabaceae). Two different-sized larvae of predators were tested in different densities of similar-sized prey to determine whether functional response parameters depended on the body sizes of predator and prey. In numerical response experiments, gravid E. balteatus females were exposed individually to different densities of 4th instars of A. fabae on cut sections of the broad bean plant, V. faba L. Logistic regression suggested a type II functional response for both larval sizes of E. balteatus. The searching efficiency (a) of the larger larvae was higher than that of the smaller ones. Prey consumption was higher, and handling time (T_h) was lower for larger larvae than smaller ones. The theoretical maximum number of A. fabae nymphs eaten by the different-sized larvae was 125 and 269 nymphs per day. Larger E. balteatus larvae are more efficient predators for aphid management strategies. The reproductive numerical response, in terms of the number of eggs laid, increased curvilinearly with increasing prey density, but the proportion of eggs laid (egg number/prey density) decreased as the initial density of prey increased.     

Predatory behaviour of Podisus nigrispinus (Heteroptera: Pentatomidae) on different densities of Anticarsia gemmatalis (Lepidoptera: Noctuidae) larvae

The functional response of the predatory bug Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) feeding on its prey, Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae), was studied in a greenhouse compartment. Each cage enclosed three soybean plants plus two, four, six, eight, 10, 12 or 14 prey larvae. One adult predator was released and kept inside the cages for 24h. The predation rate of adult male P. nigrispinus was highest at densities of eight or more A. gemmatalis larvae with a handling time of 5.76h and an attack rate of 0.68h^?1. Adult females had higher predation rates on plants with 10 or more A. gemmatalis larvae, with a handling time of 3.84h and an attack rate of 0.65h^?1. The maximum number of larvae consumed by males and females of this predator were 4.1 and 6.0 per day, respectively, in groups of three plants. The results suggest that P. nigrispinus may be used in biological control programmes against A. gemmatalis in soybean fields.     

黄玛草蛉对两种蚜虫的捕食效能

实验室条件下研究了黄玛草蛉2龄与3龄幼虫对甘蓝蚜以及玉米蚜成虫的捕食功能反应。结果表明:黄玛草蛉2龄与3龄幼虫对2种蚜虫的捕食量均随着猎物密度的增加而增加,寻找效应随着猎物密度的增加而减小。不同龄期幼虫对2种蚜虫的捕食功能反应均符合HollingⅡ模型,黄玛草蛉2龄与3龄幼虫对玉米蚜最大理论日捕食量分别为120.48头、185.18头;黄玛草蛉2龄与3龄幼虫对甘蓝蚜最大理论日捕食量分别为60.60头、86.95头。在相同猎物种类下,黄玛草蛉3龄幼虫对2种蚜虫的捕食量均高于黄玛草蛉2龄幼虫;在相同猎物密度下,黄玛草蛉2龄幼虫与3龄幼虫对玉米蚜的捕食量均高于甘蓝蚜。     

Potential of the predatory mite Phytoseius finitimus (Acari: Phytoseiidae) to feed and reproduce on greenhouse pests

Phytoseiid mites of the genus Phytoseius are natural enemies of tetranychid and eriophyid herbivorous mites mostly found on hairy plants where they feed on prey, as well as on pollen. Nevertheless, the nutritional ecology and the role of these predators in biological pest control are only rarely addressed. In the present study, we evaluated the potential of Phytoseius finitimus to feed and reproduce on three major greenhouse pests, the two-spotted spider mite, the greenhouse whitefly and the western flower thrips. Additionally, we estimated the effect of cattail pollen when provided to the predator alone or in mixed diets with prey. Contrary to thrips larvae, both spider mite larvae and whitefly crawlers sustained the development of P. finitimus. In addition, females consumed more spider mite eggs and larvae, as well as whitefly crawlers than thrips larvae, but laid eggs when feeding on all prey. When provided alone, cattail pollen sustained the development and reproduction of the predator. The addition of pollen in mixed diets with prey reduced prey consumption, though it increased the predator’s egg production. We discuss the implications of our findings for biological pest control.     

Predation of the apefly,Spalgis epius (Lepidoptera: Lycaenidae) on citrus mealybug,Planococcus citri (Hemiptera: Pseudococcidae)

The citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae) is a serious pest of economically important crops worldwide. The apefly, Spalgis epius (Westwood) (Lepidoptera: Lycaenidae) is a potential predator of various species of mealybugs. Earlier investigation on its daily preying capacity and preference for prey stages on P. citri is incomplete. Hence, a study was conducted to find out the daily prey consumption ability and preference for prey stages by different larval instars of S. epius reared on P. citri in the laboratory. Through the 8-day developmental period with four larval instars, the daily prey consumption of S. epius increased from the first to the seventh day and decreased on the eighth day prior to the prepupal stage. Generally, there was a significant difference in the prey consumption on different days. When the prey stages were offered separately, the first to fourth instar larva of S. epius consumed, respectively, a mean of 199.6, 722.6, 1908.8, and 4625.6 eggs or 21.5, 77.0, 168.5, and 670.5 nymphs or 3.2, 7.2, 16.0, and 35.1 adults of P. citri. When an S. epius larva was fed on P. citri eggs, nymphs and adults separately, it consumed a mean of 7456.7 eggs, 937.6 nymphs, or 62.3 adults during its entire development. When the prey stages were offered all together, a single S. epius larva consumed 2618.4 eggs, 170.4 nymphs, and 39.7 adults of P. citri throughout its entire development. The study revealed that S. epius is a voracious predator of P. citri and thus could be utilized as a major biological control agent.     

Predatory Potential of Euseius alatus (Phytoseiidae) on Different Life Stages of Oligonychus ilicis (Tetranychidae) on Coffee Leaves Under Laboratory Conditions

This study evaluated the predatory capacity of Euseius alatus (DeLeon) as a biological control agent of the pest mite Oligonychus ilicis (McGregor) on coffee leaves under laboratory conditions, using arenas containing 25 O. ilicis per coffee (Coffea arabica) leaf to one specimen of each stage of the predator mite. The functional response and oviposition rate of adult females of E. alatus were evaluated on coffee leaf arenas and offered from 1 to 125 immature stages of O. ilicis per arena. The number of preys killed and the number of eggs laid by the predator were evaluated every 24 h during 8 days. The preys consumed were daily replaced. Male and female adults of E. alatus were the most efficient in killing all developmental stages of O. ilicis. Larvae and nymphs of O. ilicis were the most consumed by all stages of the predatory mite. The functional response and oviposition rates of E. alatus increased as the prey density increased, with a positive and highly significant correlation. Regression analysis suggested a type II functional response, with a maximum predation of 22 O. ilicis/arena and a maximum oviposition rate of 1.7 eggs/day at a density of 70 O. ilicis/arena.     

Functional response of Euseius concordis to densities of different developmental stages of the cassava green mite

Both prey density and developmental stage of pests and natural enemies are known to influence the effectiveness of biological control. However, little is known about the interaction between prey density and population structure on predation and fecundity of generalist predatory mites. Here, we evaluated the functional response (number of prey eaten by predator in relation to prey density) of adult females and nymphs of the generalist predatory mite Euseius concordis to densities of different developmental stages of the cassava green mite Mononychellus tanajoa, as well as the fecundity of adult females of the predator. We further assessed the instantaneous rate of increase, based on fecundity and mortality, of E. concordis fed on eggs, immatures and adults of M. tanajoa. Overall, nymphs and adults of E. concordis feeding on eggs, immatures and females of M. tanajoa had a type III functional response curve suggesting that the predator increased prey consumption rate as prey density increased. Both nymphs and adult females of the predator consumed more eggs than immatures of M. tanajoa from the density of 20 items per leaf disc onwards, revealing an interaction between prey density and developmental stage in the predatory activity of E. concordis. In addition, population growth rate was higher when the predator fed on eggs and immatures in comparison with females. Altogether our results suggest that E. concordis may be a good candidate for the biological control of M. tanajoa populations. However, the efficiency of E. concordis as a biological control agent of M. tanajoa is contingent on prey density and population structure.     

Prey stage preference and feeding behaviour ofOligota kashmirica benefica (Coleoptera: Staphylinidae), an insect predator of the spider miteTetranychus urticae (Acari: Tetranychidae)

We studied the prey stage preference and feeding behaviour of the first to third instar larvae and adult females ofOligota kashmirica benefica Naomi (Coleoptera: Staphylinidae), a predator of the spider miteTetranychus urticae Koch (red form) (Acari: Tetranychidae), on leaves of the kudzu vine (Pueraria lobata (Wild.) Ohwi (Leguminosae)) under laboratory conditions. The number of mites eaten increased with the growth of predator larvae. Third instar larvae preyed on all stages of spider mite, whereas first instar larvae preyed mainly on immobile stages (eggs and quiescent stages). The predator larvae showed two types of foraging behaviour (active searching and ambush behaviour) when targeting the mobile stages (larval nymph and adult stages of prey). Although no difference was found in the number of prey consumed by adult females and third instar larvae of the predator, the adult females mainly attacked and consumed the immobile stages.     

Potential for integrated control of Culex quinquefasciatus (Diptera: Culicidae) using larvicides and guppies

Acute toxicity tests were carried out to determine the effect of three larvicides, spinosad, pirimiphos methyl, and chlorpyrifos, on Culex quinquefasciatus Say, Anopheles gambiae s.s. Giles (Diptera: Culicidae), and guppies, Poecilia reticulata Peters (Pisces: Poeciliidae). Thereafter, larvae of Cx. quinquefasciatus were introduced to P. reticulata in containers of different volumes with low concentrations of each larvicide at established predator to prey densities of 1–35; 5–70 and 10–350 (fish to larvae) respectively. The experiment was replicated six times, and the larval consumption was counted after 24 h. Spinosad and pirimiphos methyl were significantly toxic to Cx. quinquefasciatus, the less susceptible mosquito species. Guppy consumption of Culex larvae was highest at a predator to prey density 5–70. Feeding activity of guppies increased in the spinosad treatment at 49 μg L⁻¹ compared to control and the synthetic larvicides. The synthetic larvicides generally reduced consumption of larvae except for the lowest concentration of pirimiphos methyl which increased it at the highest predator to prey density in a 3 L container. The highest percentage of Culex larvae was consumed by fish in the presence of spinosad at 49 μg L⁻¹ and a predator to prey density of 5–70 in 0.5 L plastic containers. Thus, predator to prey density, container size, type and concentration of larvicide are all important factors to be considered in integrated management of mosquito larvae.     

The effect of prey size and prey density on the functional response,survival, growth and development of a predatory pentatomid bug,Podisus maculiventris say

Two experiments on the nymphal predation of Podisus maculiventris were conducted using Spodoptera litura larvae as prey. First experiment: The predator nymphs divided into three groups were reared individually from second instar to adult in a small vessel. Each nymph in the groups 1, 2 and 3 was allowed to attack the serially growing larvae (these were supplied at the rate of one per day) from 3-, 5- and 7-day old after hatching, respectively. The first prey used for the group 1 was so small that it was not only insufficient to satiate the predator but also was difficult to be searched out. But these disadvantages were soon recuperated due to the rapid growth of the prey and all nymphs could survive to adults. The survival rate of third and fourth instar nymphs in the group 3 was severely affected by vigorous counterattack of older prey larvae. Second experiment: The predator nymphs were individually reared either in a small vessel or in a large one at various rates of food supply (the prey larvae of 7-day old were used). The functional response curves obtained for each instar of the predator took a saturation type within a certain range of the prey density. The saturation level specific to each instar was generally higher for the predator reared in the large vessel than in the small one. The functional response of fourth and fifth instar nymphs was accelerated at a high prey density, viz. 16 larvae per vessel. Even at the low rate of food supply, viz. one larva per day per predator, the predator nymphs could survive to adults, but the size of resultant adults were abnormally small.     

Efficiency of four heteroptera as predators ofAphis gossypii andMacrosiphum euphorbiae (Hom.: Aphididae)

Predation rate and nymphal development time were determined for four predatory bugs (Dicyphus tamaninii Wagner andMacrolophus caliginosus Wagner [Het.:Miridae],Orius laevigatus (Fieber) andO. majusculus (Reuter) [Het.:Anthocoridae], on cucumber withAphis gossypii Glover (Hom.:APhididae) as prey and for both mirids also on tomato withMacrosiphum euphorbiae (Thomas) as prey. All four predator species were able to achieve adulthood feeding on both aphids. The developmental period ofD. tamaninii nymphs was the longest and the shortest was forO. majusculus. During nymphal developmentD. tamaninii consumed greater numbers of both aphids thanM. caliginosus, whileOrius’ consumption ofA. gossypii was intermediate. Average daily predation was higher forD. tamaninii than forM. caliginosus, but was not different from bothOrius species. FemaleD. tamaninii exhibited a typical type-II functional response when preying on varying densities ofA. gossypii nymphs.     

Life table and efficacy of Mallada desjardinsi (Chrysopidae: Neuroptera), an important predator of tea red spider mite, Oligonychus coffeae (Acari: Tetranychidae)

Green lacewing, Mallada desjardinsi Navas, is an important predator of red spider mite, Oligonychus coffeae infesting tea. Life history, life table and efficacy of M. desjardinsi were determined using red spider mite as prey under laboratory conditions. Duration of development of M. desjardinsi recorded was 5.1, 13.8 and 13 days for eggs, larvae and pupae respectively, with an average of 31.9 days from egg to adult emergence. After a mean pre oviposition period of 7.1 days, a single female laid an average of 252.6 eggs in its life time. Adult longevity of the male was recorded as 39.6 days while the females lived longer (58.2 days). The life table of M. desjardinsi was characterized by an intrinsic rate of increase (r) of 0.096 day, net reproductive rate (R ₀ ) of 153.19 eggs/female, gross reproduction rate (∑mx) of 167.28 eggs/female, generation time (T) of 52.47 days, doubling time of 7.22 days and finite rate of increase(λ) of 1.1 day. The optimum predator–prey ratios were 1:50 and 1:33 under laboratory conditions however, 1:33 and 1:25 ratios were effective in green house conditions. The results of the study can be considered as a first step towards the utilization of this predator in an IPM program for the management of red spider mite infesting tea.     

Harmonia axyridis (Coleoptera: Coccinellidae) Exhibits No Preference between Bt and Non-Bt Maize Fed Spodoptera frugiperda (Lepidoptera: Noctuidae)

A recent shift in managing insect resistance to genetically engineered (GE) maize consists of mixing non-GE seed with GE seed known as “refuge in a bag”, which increases the likelihood of predators encountering both prey fed Bt and prey fed non-Bt maize. We therefore conducted laboratory choice-test feeding studies to determine if a predator, Harmonia axyridis, shows any preference between prey fed Bt and non-Bt maize leaves. The prey species was Spodoptera frugiperda, which were fed Bt maize (MON-810), expressing the single Cry1Ab protein, or non-Bt maize. The predators were third instar larvae and female adults of H. axyridis. Individual predators were offered Bt and non-Bt fed prey larvae that had fed for 24, 48 or 72 h. Ten and 15 larvae of each prey type were offered to third instar and adult predators, respectively. Observations of arenas were conducted at 1, 2, 3, 6, 15 and 24 h after the start of the experiment to determine the number and type of prey eaten by each individual predator. Prey larvae that fed on non-Bt leaves were significantly larger than larvae fed Bt leaves. Both predator stages had eaten nearly all the prey by the end of the experiment. However, in all combinations of predator stage and prey age, the number of each prey type consumed did not differ significantly. ELISA measurements confirmed the presence of Cry1Ab in leaf tissue (23–33 µg/g dry weight) and S. frugiperda (2.1–2.2 µg/g), while mean concentrations in H. axyridis were very low (0.01–0.2 µg/g). These results confirm the predatory status of H. axyridis on S. frugiperda and that both H. axyridis adults and larvae show no preference between prey types. The lack of preference between Bt-fed and non-Bt-fed prey should act in favor of insect resistance management strategies using mixtures of GE and non-GE maize seed.     

Transport and kinetics of diflubenzuron and pyriproxyfen in the beet armywormSpodoptera exigua and its predatorPodisus maculiventris

Transport and retention of the insect growth regulators (IGRs) diflubenzuron and pyriproxyfen in larvae of the beet armywormSpodoptera exigua (Hübner) and in nymphs of the predatory bugPodisus maculiventris (Say) were investigated. In a first experiment, the retention of orally administered [¹⁴C]radiolabeled isotopes of both compounds in fifth-instar larvae of the beet armyworm was studied. Rate of excretion of both IGRs inS. exigua caterpillars was high, with a 50% excretion time of approximately 6 h after intake. In a second experiment, the transport of the compounds from prey to predator and their retention inside the predator were studied. Fifthinstar nymphs ofP. maculiventris were allowed to feed on caterpillars that had been given contaminated food. For both diflubenzuron and pyriproxyfen, more than 80% of the amount of radiolabel applied was recovered in consumed prey. Low levels of radioactivity (c. 3% of the applied amount of radiolabel) were also found in the fluid regurgitated by the prey larvae when attacked by the predatory bugs. Relatively small amounts of radiolabel (c. 8 and 15% of the amount orally applied to the prey for diflubenzuron and pyriproxyfen, respectively) were ingested byP. maculiventris nymphs when feeding on beet armyworm caterpillars. The data suggest that the predators did not use gut content as food. The pattern of excretion in nymphs ofP. maculiventris differed between compounds. For diflubenzuron, there was a drastic decrease of radioactivity inside the predator body of around 40% within the first 6 h and then the level of retained radiolabel remained stable at 3–4% up to 72 h. For pyriproxyfen, a slow decrease of radioactivity inside the body was observed and at 72 h only 2% of the applied quantity was detected. Results of this study are discussed in relation to the findings from previous studies on the toxicity of both IGRs toP. maculiventris.