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1.
We investigated the dual effects of bacterial infections and diseased cassava plants on the fitness and biology of the Bemisia tabaci infesting cassava in Africa. Isofemale B. tabaci colonies of sub-Saharan Africa 1-subgroup 3 (SSA1-SG3), infected with two secondary endosymbiotic bacteria Arsenophonus and Rickettsia (AR+) and those free of AR infections (AR?), were compared for fitness parameters on healthy and East African cassava mosaic virus-Uganda variant (EACMV-UG)-infected cassava plants. The whitefly fecundity and nymph development was not affected by bacterial infections or the infection of cassava by the virus. However, emergence of adults from nymphs was 50 and 17% higher by AR? on healthy and virus-infected plants, respectively, than AR+ flies. Development time of adults also was 10 days longer in AR+ than AR?. The whiteflies were further compared for acquisition and retention of EACMV-UG. Higher proportion of AR? acquired (91.8%) and retained (87.6%) the virus than AR+ (71.8, 61.2%, respectively). Similarly, the AR? flies retained higher quantities of virus (~ninefold more) than AR+. These results indicated that bacteria-free whiteflies were superior and better transmitters of EACMV-UG, as they had higher adult emergence, quicker life cycle and better virus retention abilities than those infected with bacteria.  相似文献   

2.
The cotton whitefly, Bemisia tabaci (Genn.) (Hom., Aleyrodidae) is increasingly a very important pest on many vegetables, field crops and ornamental plants. Therefore, controlling of this pest is still needed especially under glasshouse conditions. The specialist whiteflies’ predator, Serangium parcesetosum Sicard (Col., Coccinellidae) appears to have a great potential for the cotton whitefly control. In this study, the dynamic changes in B. tabaci populations in glasshouse cabins in response to S. parcesetosum were monitored. B. tabaci were introduced to cotton plants in three cabins in average of 50 adults per plant. One and two weeks later, adult females and males of S. parcesetosum were introduced at a rate of one female and one male per plant in the first and second cabins, respectively. The third cabin was considered as a control. The results showed that the mean number of whiteflies in the control cabin was found significantly higher than that of either when S. parcesetosum was introduced 1 or 2 weeks after the infestation with the whitefly. Also, the mean number of B. tabaci was significantly higher when the predator was introduced 2 weeks rather than 1 week after B. tabaci infestation. The maximum mean weekly number of whiteflies/plant was 192.3 in the second week, whereas it was 294.6 in the third week and 1136.4 in the fifth week, in first, second and control cabins, respectively. In the last experimental week, the mean weekly numbers were 74.7, 122.9 and 684.7 whiteflies/plant in the three cabins, respectively. S. parcesetosum has been successfully fed, reproduced and established its population on B. tabaci on cotton plants. The mean weekly number of the predatory individuals increased gradually with the progress of the experimental time. The results demonstrated that the maximum reduction percentage in B. tabaci population was 90.7 and 86.5% in the fifth week after B. tabaci infestation, when the predator was introduced 1 and 2 weeks after the infestation with the whiteflies, respectively. Nevertheless, it is speculated that an earlier release of S. parcesetosum would be more effective in the biological control of B. tabaci.  相似文献   

3.
The phenology and natural enemies of Nemolecanium graniformis (Wunn) (Homoptera: Coccidae) in infesting Abies cephalonica, were studied in Greece during 1998?–?1999. This oviparous species develops one generation per year in Central Greece (Attica) and overwinters as 2nd instar nymph. Young adult females appear by the end of July, and the first instar nymphs by the middle of August. By the middle of October, the whole population of the scale is recorded as 2nd instar nymphs. The parasitoids Coccophagus lycimnia (Walker), Coccophagus Westwood sp., Aphycoides Mercet sp. and the predator Exochomus quadripustulatus L. (Coleoptera: Coccinellidae), were observed as natural enemies of the scale. The average fecundity of N. graniformis was 188.4 eggs.  相似文献   

4.
The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has recently invaded Mediterranean countries and is a major pest in tomato crops. Trichogrammatid oophagous parasitoids have shown promising potential for controlling the pest before the yield decreases in the greenhouse. In protected tomato crops (greenhouse), mirid predators are commonly used for biological control of whiteflies and they also prey on T. absoluta. These predators do not attack Trichogramma adults but they may partially decrease the overall impact of parasitoids on T. absoluta if intraguild predation (IGP) occurs on parasitized eggs. Under laboratory conditions, we tested if the mirid predator Macrolophus pygmaeus shows preference between parasitized and unparasitized T. absoluta eggs. We also tested if the predator reduces the number of parasitized eggs on caged tomato plants (microcosms) and assessed the efficacy of natural enemies used alone or together in limiting T. absoluta populations. We found that IGP is inflicted on the parasitoid Trichogramma achaeae by M. pygmaeus and that the risk of IGP depends on the developmental stage of T. achaeae inside the egg because the larva is at risk mostly early in its development (when parasitized egg is still yellow). In addition, we observed that non-consumptive events, likely probing of the predator on parasitized eggs, may induce mortality in parasitoid offspring without actual feeding on parasitized eggs. However, both IGP and non-consumptive events decreased when the predator was not confined with parasitized eggs in small arenas. Despite negative effects of the predator to the parasitoid, results demonstrate that adding Trichogramma parasitoids may significantly increase the level of control of the pest over what could be attained when only the mirid predator M. pygmaeus is present on tomato. Implications of results are discussed regarding potential of these natural enemies for biological control of T. absoluta in greenhouse tomato crops.  相似文献   

5.
The utilization of olfactory responses of predators and ­parasitoids to the allelochemicals emitted by phytophagous arthropods and their host plants is becoming more important in biological pest control. The effects of three weed ­species, i.?e. wormwood Artemisia vulgaris L., tansy Tanacetum vulgare L. and stinging nettle Urtica dioica L., which were planted as accompanying vegetations into a lettuce field, were examined for the predatory species Coccinella septempunctata L., Adalia bipunctata (L.), Propylea quatuordecimpunctata (L.) (Coleoptera, Coccinellidae) and Chrysoperla carnea (Steph.) (Neuroptera, Chrysopidae), as well as for aphids during the summer of 2000. The presence of weeds significantly increased the density of adults and larvae of the predators on the lettuce plants in relation to the control (lettuce field without weeds). However, the differences remained smaller for eggs and pupae. C. septempunctata tended to be the most abundant species, followed by P. quatuordecimpunctata. Remarkable differences among the attractiveness levels of the weeds in the 3 treatments were not observed. The increased populations of predators were accompanied by significantly reduced infestation rates with aphids in the treatments in relation to the control. Myzus persicae Sulzer was in general the most abundant aphid species followed by Nasonovia ribisnigri Mosley and Macrosiphum euphorbiae Thomas. The results of the present study are discussed with respect to the management of agroecosystems and the use of weeds in biological control.  相似文献   

6.
The output of inspection resulted in the following common predators:Orius laevigatus Fieb.,Orius albidipennis Reut. (Hem., Anthocoridae);Chrysoperla carnea Steph. (Neur., Chrysopidae);Coccinella undecimpunctata L.,Scymnus syriacus Mars,Scymnus interruptus Goeze (Col., Coccinellidae). It was found that the 6 insect species appeared on the cotton plants during the last week of April or the first week of May. The population increased gradually during May and the first two weeks of June then decreased during the second two weeks of June and the first week of July.Orius spp. constitutes more than 50% of the inspected species. Data show that application of kelthane-S and methomyl against mites and aphids slightly reduced the population of these predators, percent reduction ranged between 10.6–17.9%. The same species previously inspected during the early season were found during the second half of the season, exceptC. undecimpunetata.
Zusammenfassung Die Untersuchungen umfaßten folgende 6 Predatoren-Arten:Orius laevigatus Fieb.,O. albidipennis Reut. (Hem., Anthocoridae), —Chrysoperla carnea Steph. (Neur., Chrysopidae),—Coccinella undecimpunctata L.,Scymnus syriacus Marsh.,S. interruptus Goeze (Col., Coccinellidae). Es wurde festgestellt, daß diese 6 Insektenarten auf den Baumwolle-Pflanzen während der letzten April- oder ersten Mai-Woche erschienen. Ihre Populationen wuchsen während des Mai bis Mitte Juni und verringerten sich danach bis Ende Juni, Anfang Juli.Orius spp. machte mehr als 50% der Gesamt-Predatorenpopulation aus. Die Daten zeigen, daß die Anwendung von Kelthane-S und Methomyl gegen Milben und Blattläuse die Predatoren-Population um 10,6–17,9% reduzierte. Die gleichen Predatoren-Arten wie in der Frühsaison wurden auch in der Spätsaison festgestellt, mit Ausnahme vonC. undecimpunctata, der in der Spätsaison fehlte.
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7.
Studies were conducted in cucumber fields to evaluate the standard and reduced dosage rates of 5 insecticides for control the cotton whiteflyBemisia tabaci (Genn.) and melon aphidAphis gossypii Glov. and effect of insecticide application on associated parasites and predators. Eggs of whitefly appeared to be less susceptibility to all treatments (max. 66% reduction) than larval and pupal stages. Populations of larval and pupal stages of whitefly were significantly reduced in all treated plots. For example (larvae on day 10 after treatment with ethiofencarb, diafenthiuron, and chlorpyrifos methyl 67, 50, and 68% pupae 68, 69, and 75%). Two aphelinid parasitoids,Eretmocerus mundus Mercet andProspaltella lutea Masi, were the most primary important parasitoids of the whitefly pupae in all test plots. Percent parasitism, in most treated plots, were slightly affected as a result of insecticide application. However, all tested insecticides and dosage rates caused severe suppression of emergence of adult parasitoids. Moreover, longevity of adult parasitoids were highly decreased. Populations of the melon aphid were extremely reduced, especially by ethiofencarb and diafenthiuron. Populations of predator species (Chrysopa carnea Steph.,Coccinella undecimpunctata Reiche andSyrphus spp.) were reduced in all treated plots. However, ethiofencarb applied at rates as low as 208.4g a.i./1001 provided equally effective aphid control and conserved numbers of insect predators in the treated plots. Also, the prothiofos and chlorpyrifos methyl applications at rates as low as 166.7 g a.i./1001 kept aphid numbers below than those in control and caused a smaller reduction in the combined populations of insect predators.  相似文献   

8.
We examined the effects of nonhost plant diversity and predators on the potato leafhopper, Empoasca fabae (Harris), the pea aphid, Acyrthosiphon pisum (Harris), and their primary host plant, alfalfa, Medicago sativa L. Potato leafhopper intensity (i.e., leafhoppers/alfalfa stem density) and plant damage (i.e., hopperburn) were significantly greater in alfalfa mono- than in polycultures of alfalfa mixed with nonhost plant species. There was no significant effect of nonhost plant diversity on pea aphid intensity or on predator abundance. Predator:prey ratios were higher in poly- than in monoculture. One predator, Nabis sp., was selected for further study. A microcosm experiment indicated that Nabis is an effective predator of both herbivores, and suggested that nonhost plant diversity may enhance the predation of leafhoppers by Nabis. These results suggest that nonhost plant diversity and Nabis limit leafhopper populations and protect alfalfa from herbivory. The potential for nonhost plants to increase herbivore movement and vulnerability to predation is discussed.  相似文献   

9.
Orius laevigatus is a generalist predator that is widely used in augmentative strategies against the key pest of sweet pepper, Frankliniella occidentalis. Despite being a zoophytophagous predator, the phytophagous behavior of O. laevigatus has not been previously explored in depth nor has the impact of phytophagy on plant physiology. Here, the hierarchical significance of O. laevigatus feeding on sweet pepper is compared with other behaviors. O. laevigatus spends the majority of its time (38%) feeding on apical meristems and apical fresh leaves, which were also preferred residence locations. Here, the phytophagous feeding behavior of O. laevigatus on sweet pepper is shown to trigger defensive responses in the plant. These O. laevigatus plant-induced defenses are then shown to contribute to the repellence or attraction of pests or natural enemies, respectively. Specifically, O. laevigatus-punctured sweet pepper plants induce repellency for the whitefly Bemisia tabaci and the thrips species F. occidentalis. In contrast, the whitefly parasitoid Encarsia formosa was significantly attracted to O. laevigatus-punctured plants. The plant responses to O. laevigatus punctures include the release of an altered blend of volatiles and activation of the jasmonic acid and salicylic acid signalling pathways. These results highlight an interesting facet to the biology of O. laevigatus, in which the ability of the predator to induce defensive responses in sweet pepper plants may serve to improve the biological control of both thrips and whiteflies.  相似文献   

10.
Studies onAltica quercetorum Foud. (Coleopt., Chrysomelidae) during an outbreak 1992 – 1995 in Serbia For about 10 years the oak flea beetle,Altica quercetorum Foud. has shown outbreaks at numerous localities in Central and South Serbia. Our observations revealed that the pest preferred mixed stands of sessile and Turkey oaks under nearer preference of the first named oak. Defoliation was caused by the adult insects in early spring, followed by leaf skeletonizing by larvae. In September the adults of the new generation started their secondary feeding. Also a threefold defoliation partly took place during the mass occurrence, in the course of one vegatation period. Outbreaks of this size are new for Serbia. Our researches between 1992 and 1995 deal with the bionomy, gradation and economic importance. The following predators and parasitoids were recorded:Zicrona coerulea L. (Hem., Pentatomidae),Oenopia impustulata L. (Col., Coccinellidae),Microctonus sp. (Hym., Braconidae),Mesochorus palus Schw. (Hym., Ichneumonidae), andMedina luctuosa Meig. (Dipt., Tachinidae).  相似文献   

11.

Habitat management improves biological control by increasing the abundance and fitness of natural enemies through the provision of floral resources along field edges or between crops. Among the natural enemies reliant on flower resources, green lacewings often stand out due to their abundance, predation capacity and polyphagy. We evaluated the impact of tailored flower strips on the enhancement of natural enemies, especially green lacewings, in three organic cabbage (Brassica oleracea) farms in Southern Sweden. Insects were sampled from the flower strips, and cabbage pests and predators were visually recorded in the crop. In a laboratory assay, the pollen feeding preferences of Chrysoperla carnea (Stephens, 1836) were evaluated in a dual-choice test. The pollen consumed by the Chrysopidae was extracted from laboratory and field specimens, then quantified and identified. Flower strips were found to attract predators and parasitoids, whose abundance increased as flowers bloomed. Cabbage plants next to the flower strips showed lower pest infestation as compared to cabbage plant control, although no significant differences were observed in the number of predators. Chrysopidae used flower strips as feeding, reproduction and shelter sites and mainly consumed pollen from Phacelia tanacetifolia Benth. Under laboratory conditions, C. carnea showed a preference for P. tanacetifolia and Coriandrum sativum L. pollen over Borago officinalis L. and Fagopyrum esculentum Moench. We show that tailored flower strips could be an efficient tool for enhancing beneficial arthropods and should be considered in integrated pest management for cabbage crops.

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12.

The multicolored Asian ladybeetle, Harmonia axyridis Pallas (Col, Coccinellidae), is recognized as one of the most invasive insects in the world. It has reduced the native coccinellids populations in several areas, and it is considered a threat for biodiversity at large. A significant trait, favoring its invasiveness and its dominance over indigenous ladybeetles, is intraguild predation (IGP). IGP has advantageous adaptive value for individuals: removing competitors and potential predators, and providing an alternative nutritive resource when main resources are scarce. IGP can be affected by several factors, but little is known about the effect of pesticides on this behavior. Previous research demonstrated that the invasive Asian ladybeetle is highly susceptible to the reduced-risk insecticide novaluron, a chitin synthesis inhibitor, whereas the North American indigenous competitor, Coleomegilla maculata DeGeer (Col, Coccinellidae), is not. Our study explores the adaptive value of IGP for each of the two coccinellids after preying on each other’s larvae, which were previously treated with insecticide. Our first hypothesis is that the invasive ladybeetle, susceptible to the insecticide, should lose the adaptive value of IGP. Our second hypothesis is that the adaptive value of IGP for the invasive predator will recover over time, because of neutralization of the insecticide by the intraguild prey. The results confirm both hypotheses and show that an insecticide can completely remove the adaptive value of IGP for the invader, while the adaptive value of IGP does not change for the indigenous ladybeetle. Moreover, the study demonstrates that if the intraguild prey (non-susceptible to the insecticide) undergoes molt after being exposed to the insecticide, the adaptive value for the intraguild predator is restored.

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13.
Morphological characteristics of immature developmental stages of Rhyzobius lophanthae Blaisdell (Col.: Coccinellidae), predator of scale insects of the family Diaspididae (Homoptera), are described. Data about the morphology of eggs, the four larval instars, and the pupa is presented. Larval instars are described in more detail: size of head capsule, length of tibia, distribution of dorsal and lateral setae of abdomen segments for each larval instar is reported. Distribution of spiracles is also given. Study on the biology concerns the influence of prey on the duration of instar periods. The diaspidids Aspidiotus nerii and Aonidiella aurantii were used as food. The mean duration of the developmental period from egg to adult was 27.1 days, and no mortality was observed (0?%) when A. nerii was used as prey. The respective numbers when the prey was A. aurantii were 48.8 days and 84?%.  相似文献   

14.
During 1996 and 1997, populations of aphids and whiteflies and their parasites were studied in plastic greenhouses under a chemical control program and in those free of pesticides. In the greenhouses free of pesticides, the parasite A. colemani destroyed 14.7?% of the aphids. B. tabaci had no effect on the cucumbers during the spring cultivation. However, it attacked the autumn cultivation. The parasite E. mundus killed 30?% of these nymphs. The parasite A. colemani parasitized up to 10?% of aphids on tomato plants in greenhouses free of chemical pesticides. The parasite E. mundus killed 15.7?% of whitefly nymphs. In greenhouses under a chemical pesticides program, aphids and whiteflies were found on the plants at the end of the plantation season, after the pesticide spraying had stopped. Although the pest population was low, the parasite A. colemani parasitized 8?% of the aphid population. Whiteflies were not found on tomato plants in greenhouses under extensive pesticides use.  相似文献   

15.
We used standard isolation protocols to explore the endophytic fungal communities in three tissue types of two dominant orchids (Bulbophyllum neilgherrense and Vanda testacea) of the Kaiga forest ofthe Western Ghats. We surface sterilized and assessed 90 segments ofeach orchid for the occurrence and diversity of endophytic fungal taxa.The 118 fungal isolates were obtained from root, bulb and leaves of B.neilgherrense, consisting of 17 anamorphic taxa (range, 10 15 taxa) with 1.3 fungal taxa per segment (range, 1.2 1.4 taxa). Four taxa (Aspergillus flavus, A. niger, Penicillium sp. and morpho sp. 1) belonged to the coregroup (11.1% 32.2%). The relative abundance of A. flavus and morpho sp.1 was more than 10%. A total of 130 fungal isolates from roots, stems and leaves of V. testacea yielded 20 anamorphic taxa (range, 11 15 taxa)with 1.4 fungal taxa per segment (range, 1.4 1.5 taxa). Aspergillus flavus,A. niger, A. ochraceus, Gliocladium viride, Penicillium sp. and morphosp. 1 belonged to the core group. Relative abundance exceeded 10% for A. flavus, A. niger, and morpho sp. 1. The Simpson and Shannon diversity indices were higher in leaf than root or bulb/stem of both orchids.Jaccard’s similarity coefficient was higher between root and leaf in both orchids (56.3% 60%) than between other pairs. Our study revealed thatthe endophytic fungal assemblage and diversity of B. neilgherrense and V.testacea of Kaiga forest of the Western Ghats were relatively similar between orchids and their tissues.  相似文献   

16.
The particle film technology based on processed kaolin sprays has been recently introduced for the control of the olive fruit fly Bactrocera oleae (Rossi), the key pest of olive groves. A 3-year field experiment was conducted from 2005 to 2007 at Villarejo de Salvanés, Spain to assess the efficacy of a kaolin-based product (Surround WP) for controlling B. oleae and two other olive insect pests: the olive black scale Saissetia oleae (Olivier) and the olive psyllid Euphyllura olivina (Costa). The effects of Surround WP on the arthropod community of olive trees and on natural enemies were also evaluated. In a high olive fruit fly pressure year (2007), Surround WP sprays significantly reduced the incidence of B. oleae and that of S. oleae. However, Surround WP treatments did not have any effect on E. olivina populations. Both the abundance and the diversity of arthropods were reduced by Surround WP treatment. The principal response curve (PRC) analysis revealed a significant deleterious effect of Surround WP on the natural enemy arthropod community of the olive grove. The most affected taxa were the following: the coccinellids Scymnus mediterraneus Iablokoff-Khnzorian, Stethorus punctillum Weise and Hyperaspis reppensis (Hbst.); the mirid Brachynotocoris ferreri n. sp. Baena (in litteris); different species of Orius and the families of Philodromidae, Scelionidae, Pteromalidae, Chrysopidae and Aphelinidae. Processed kaolin is proposed as an alternative to chemical control of the olive fruit fly. However, the effect of processed kaolin treatments on natural enemies should be taken into account in a rational pest control programme.  相似文献   

17.
Damages caused by the larvae of Byturus tomentosus (Coleoptera: Byturidae) are a big problem of European raspberry production. Under integrated pest management conditions in Switzerland, B. tomentosus is controlled by chemical-synthetic insecticides. In organic production, no corresponding insecticides are permitted. White sticky traps (type Rebell® bianco) are used for monitoring purposes. Can glue-traps also be used for mass-trapping and damage control? In this study, the attractiveness for adult B. tomentosus of one yellow and several white glue-traps was compared by counting the trapped individuals. Trapped beneficial insects like honey bees, Coccinellidae, Syrphidae and Chrysopidae were also counted. The contamination of the traps caused by other non-target arthropods was measured by a computer-assisted method. The white sticky trap type Rebell bianco was the most attractive for B. tomentosus. The attractiveness for the beneficials was relatively low, except when too much glue was applied on the traps, then the attractiveness for honey bees increased significantly. In this study, traps, which were placed in high densities (17 traps per 100 m2), significantly decreased the damages caused by larvae by around 40%. The trapping method does not cause any residuals of pesticides on the fruits or soil. Therefore, the trapping method could be an alternative to control B. tomentosus, especially in organic production.  相似文献   

18.
The objective of this study was to investigate the potential resistance mechanisms to Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) B biotype, in eight Cucurbita pepo varieties. Attractivity, oviposition preference, and nymphal development were evaluated under greenhouse and laboratory conditions. Variety Bianca was the least attractive to adult whiteflies in multi-choice tests. The whiteflies showed oviposition nonpreference (antixenosis) for Novita Plus, Bianca and Sandy in multi-choice test, and similar results were observed in no-choice tests with varieties Bianca, Novita, Caserta Cac and Sandy. Sandy expressed high antibiosis levels against whitefly nymphs, leading to 63.9% mortality. The high level of resistance in variety Sandy can serve as base for genetic improvement of C. pepo focusing on the development of resistant varieties to B. tabaci B biotype.  相似文献   

19.
Although Quercus liaotungensis forest is an important component of Loess Plateau forest ecosystems, little is known about the ectomycorrhizal fungal (EMF) symbiosis of Q. liaotungensis in this ecosystem. Here we investigated EMF communities of Q. liaotungensis along three successional stands on the central Loess Plateau (Yan’an, China): a seedling stand (1 to 3-year-old seedlings under a Populus davidiana forest stand), a young tree stand (20 to 30-year-old Q. liaotungensis forest stand), and a mature tree stand (50 to 70-year-old Q. liaotungensis forest stand). In each stand, the Q. liaotungensis roots were sampled, then EMF communities were examined on the basis of EMF morphotyping, PCR–RFLP, and DNA sequencing. In total, 70 EMF species were observed, and the total richness of estimated species exceeded 100 EMF species. The EMF community was composed of a few common taxa (approx. 7 %) and many rare taxa (approx. 61 %). EMF richness in young and mature trees was higher than in seedlings. EMF communities of young and mature trees were more similar than those of seedlings and trees. Nonmetric multidimensional scaling ordinations of the EMF community revealed more separation among Q. liaotungensis of different age. This study provides preliminary insight into the taxonomic diversity of EMF of Q. liaotungensis along different successional stands on the Loess Plateau.  相似文献   

20.
Larvae of the common green lacewing, Chrysoperla carnea (Stephens) (Neuroptera :Chrysopidae) were fed with different densities of Hyalopterus pruni (Geoffer) (Homoptera: Aphididae) in Petri dishes under laboratory conditions. Functional response, developmental time, mortality rate and fecundity of the predator were measured. Treatments were carried out at 25±1°C, 65±5% RH and a 16L:8D photoperiod in a controlled temperature cabinet. Prey was given at densities of 5, 10, 20, 40, 80, 160 and 250 aphids per larva per day and the number of consumed prey, developmental time and mortality rate of the predator were recorded daily. Larvae of C. carnea responded to increasing prey densities with increasing food consumption and older larval stages displayed a higher rate of predation than younger ones. The behaviour of each of the three larval stages matched Hollings type II functional response. Larvae were able to complete their development in each of the seven prey densities, although increased prey densities reduced developmental time and mortality rate. Increased prey consumption in immature stages resulted in a higher net reproduction rate (R 0) and the intrinsic rate of increase (r m) of adult females.  相似文献   

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