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Abstract Background Culex pipiens sensu stricto (s.s.) is considered the primary vector of Usutu virus and West Nile virus, and consists of two morphologically identical but behaviourally distinct biotypes (Cx. pipiens biotype pipiens and Cx. pipiens biotype molestus) and their hybrids. Both biotypes are expected to differ in their feeding behaviour, and pipiens/molestus hybrids are presumed to display intermediate feeding behaviour. However, the evidence for distinct feeding patterns is scarce, and to date no studies have related differences in feeding patterns to differences in host abundance. Methods Mosquitoes were collected using CO2-baited traps. We collected blood-engorged Cx. pipiens/torrentium specimens from 12 contrasting urban sites, namely six city parks and six residential areas. Blood engorged Cx. pipiens/torrentium mosquitoes were identified to the species and biotype/hybrid level via real-time polymerase chain reaction (PCR). We performed blood meal analysis via PCR and Sanger sequencing. Additionally, avian host communities were surveyed via vocal sounds and/or visual observation. Results We selected 64 blood-engorged Cx. pipiens/torrentium mosquitoes of which we successfully determined the host origin of 55 specimens. Of these, 38 belonged to biotype pipiens, 14 were pipiens/molestus hybrids and the identity of three specimens could not be determined. No blood-engorged biotype molestus or Cx. torrentium specimens were collected. We observed no differences in feeding patterns between biotype pipiens and pipiens/molestus hybrids across different habitats. Avian community composition differed between city parks and residential areas, whereas overall avian abundance did not differ between the two habitat types. Conclusions Our results show the following: (1) Cx. pipiens s.s. feeding patterns did not differ between city parks and residential areas, regardless of whether individuals were identified as biotype pipiens or pipiens/molestus hybrids. (2) We detected differences in host availability between city parks and residential areas. (3) We show that in both urban habitat types, biotype pipiens and pipiens/molestus hybrids fed on both mammalian and avian hosts. This underscores the potential role in arbovirus transmission of biotype pipiens and pipiens/molestus hybrids. Graphical Abstract

Background: Culex pipiens sensu stricto (s.s.) is considered the primary vector of Usutu virus and West Nile virus, and consists of two morphologically identical but behaviourally distinct biotypes (Cx. pipiens biotype pipiens and Cx. pipiens biotype molestus) and their hybrids. Both biotypes are expected to differ in their feeding behaviour, and pipiens/molestus hybrids are presumed to display intermediate feeding behaviour. However, the evidence for distinct feeding patterns is scarce, and to date no studies have related differences in feeding patterns to differences in host abundance. Methods: Mosquitoes were collected using CO2-baited traps. We collected blood-engorged Cx. pipiens/torrentium specimens from 12 contrasting urban sites, namely six city parks and six residential areas. Blood engorged Cx. pipiens/torrentium mosquitoes were identified to the species and biotype/hybrid level via real-time polymerase chain reaction (PCR). We performed blood meal analysis via PCR and Sanger sequencing. Additionally, avian host communities were surveyed via vocal sounds and/or visual observation. Results: We selected 64 blood-engorged Cx. pipiens/torrentium mosquitoes of which we successfully determined the host origin of 55 specimens. Of these, 38 belonged to biotype pipiens, 14 were pipiens/molestus hybrids and the identity of three specimens could not be determined. No blood-engorged biotype molestus or Cx. torrentium specimens were collected. We observed no differences in feeding patterns between biotype pipiens and pipiens/molestus hybrids across different habitats. Avian community composition differed between city parks and residential areas, whereas overall avian abundance did not differ between the two habitat types. Conclusions: Our results show the following: (1) Cx. pipiens s.s. feeding patterns did not differ between city parks and residential areas, regardless of whether individuals were identified as biotype pipiens or pipiens/molestus hybrids. (2) We detected differences in host availability between city parks and residential areas. (3) We show that in both urban habitat types, biotype pipiens and pipiens/molestus hybrids fed on both mammalian and avian hosts. This underscores the potential role in arbovirus transmission of biotype pipiens and pipiens/molestus hybrids. [ABSTRACT FROM AUTHOR]

The parasitoid wasp, Eretmocerus delhiensis Mani (Hym., Aphelinidae), is an active ecto-endo and solitary parasitoid in southwestern Iran. To evaluate Er. delhiensis as a biocontrol agent against the greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hem., Aleyrodidae) its host stage preference for parasitism and host-feeding was investigated. In this study, choice (multiple-instar) and no-choice (single-instar) tests were conducted under laboratory standard conditions. The results of both tests indicated that Er. delhiensis fed on and parasitized all T. vaporariorum nymphal instars but preferred the 2nd and 3rd nymphal instars for host-feeding and parasitism, respectively. Moreover, it showed the highest and lowest development times were in the 3rd and 1st nymphal instars, respectively. According to our findings, parasitism of the parasitoid wasp, Er. delhiensis, along with its host-feeding on the nymphal instars of the greenhouse whitefly could prove it to be a good candidate for suppressing the greenhouse whitefly populations. [ABSTRACT FROM AUTHOR]

The parasitism rate and host-feeding rate of Tamarixia radiata (Hymenoptera: Eulophidae), an ectoparasitoid of Diaphorina citri (Hemiptera: Liviidae), were evaluated at 20, 27.5, 30, and 35°C, at 70 ± 5% RH, and 14 h of photo-period. The biological control efficacy of T. radiata was evaluated by linking the age-stage predation rate with the two-sex life table. The net host-feeding rate (C0) by T. radiata was 32.05, 54.40, 17.25, and 1.92 nymphs per female parasitoid at 20, 27.5, 30, and 35°C, respectively. The total net nymphs killing rate (Z0) was 103.02, 223.82, 72.95, and 6.60 nymphs per female parasitoid at 20, 27.5, 30, and 35°C, respectively. Noneffective parasitism rate was observed at 35°C because of high mortality at this temperature. Our results indicated that temperature had meaningful effects on parasitism and host-feeding rate parameters in the laboratory, and may affect biological control efficiency of the parasitoid in the field. The highest host-feeding rate and total biological control efficiency of T. radiata were recorded at 27.5°C. Most importantly, we found that host-feeding activity of the parasitoid is temperature-dependent, and changed across temperature regimes: the host-feeding rate increased as the temperature increased up to 30°C, started to decrease after this temperature and declined to its minimum level at 35°C. This information is valuable for developing biological control and integrated pest management techniques for Asian citrus psyllid management. [ABSTRACT FROM AUTHOR]

BACKGROUND: Yacon (Smallanthus sonchifolius) is a broadleaf host plant suitable for rearing the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Here, the possibility of using yacon as an alternative host plant for production of the parasitoid, Encarsia formosa Gahan, one of the most important natural enemies of whiteflies, was explored. Data on the demographic characteristics, parasitism rate, and host‐feeding rate were collected and analyzed using the TWOSEX‐MSChart, CONSUME‐MSChart, and TIMING‐MSChart computer programs, and then contrasted with comparable data from the more commonly utilized host plant, tobacco. RESULTS: Higher fecundity (F) (190.13 eggs/female) and more oviposition days (Od) (16.60 days) were observed in E. formosa when yacon was used as the host plant for rearing T. vaporariorum, compared with when tobacco was used (F = 150.13 eggs/female, Od = 15.27 days). The intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R0) were significantly higher in E. formosa parasitizing T. vaporariorum reared on yacon compared with those parasitizing tobacco‐reared T. vaporariorum. Furthermore, the net host‐feeding rate (C0 = 40.87 prey/parasitoid), net killing rate (Z0 = 239.73 prey/parasitoid), and finite killing rate (υ = 0.2560/day) for E. formosa on yacon‐reared whiteflies were significantly higher than those from tobacco‐reared whiteflies. CONCLUSION: Our results showed that yacon is more suitable than tobacco as a host plant for mass‐rearing E. formosa for biological control programs to manage whiteflies. An innovative application of the multinomial theorem for calculating the exact probability of bootstrap samples in life table research was also introduced. © 2021 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Lifetime fitness is directly influenced by the decision to use resources for either current or future reproduction. Thus, females should weigh the costs and benefits of each reproductive opportunity and allocate resources accordingly. Here, we explore decision-making and the time spent handling hosts of different instars in the parasitoid Haplogonatopus hernandezae, which uses a single planthopper host to either oviposit (i.e., current reproduction) or feed (i.e., future reproduction). Our results indicate that manipulation time in attacks that led to either oviposition and feeding increased with host instar and size. Consequently, attacks were less successful on older host instars than younger ones. Similarly, attack and handling time during oviposition was greater when manipulating fifth instar nymphs compared to younger ones, but oviposition time was similar. Surprisingly, host grasping by the chelate forelegs differed between oviposition and feeding events, and the specific chelate foreleg morphology of H. hernandezae facilitates the specific grasp of the clypeus and gena of the host. We also link this previously undescribed host grasping and differential handling behavior in this species to the final decision to oviposit or feed. Given the differences in handling time and effort among different host instars, we found that older hosts were more often chosen for consumption than younger hosts, and younger hosts were chosen more often for oviposition. Our study suggests that the tradeoff between current and future benefits is influenced by the investment in handling hosts of different instars, and the assessment of host suitability for successful offspring survival. [ABSTRACT FROM AUTHOR]

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae) threatens California's citrus industry because of its ability to transmit the bacterium, Candidatus Liberibacter asiaticus, associated with huanglongbing (HLB). To reduce the risk of HLB spread, an area-wide management strategy was established to control D. citri in both conventional and organic commercial citrus. In addition, releases of the parasitoid Tamarixia radiata Waterston (Hymenoptera: Eulophidae) as a classical biological control agent have been conducted in certain urban areas of California to improve control of D. citri . The objectives of this study were to document the residual efficacy of organic insecticides against D. citri nymphs, compare the efficacy of multiple applications of the organic spinosad relative to a single application of the non-organic insecticide fenpropathrin, and estimate the non-target effect of selected foliar insecticides on T. radiata . Spinosad + oil showed greater residual control of D. citri nymphs compared to pyrethrins + oil. The effects of organic insecticides were short lived; by 10 d post treatment there was no detectable effect. Fenpropathrin provided significantly longer control of D. citri nymphs and the efficacy of two or more applications of spinosad was comparable to one application of fenpropathrin. Of the organic insecticides, spinosad + oil resulted in the greatest non-target effects on T. radiata and pyrethrins, pyrethrins + oil, and oil alone had the least severe effects on T. radiata . This study provides important information regarding the residual control of D. citri by organic insecticides and their compatibility with the biological control agent T. radiata . [ABSTRACT FROM AUTHOR]

BACKGROUND: Bottom-up and top-down forces are major components of biological control against pests in an agro-ecosystem. Understanding the multi-trophic interactions between plants and secondary consumers would help optimize pest control strategies. We manipulated nitrogen and/or water inputs to tomato plants (Solanum lycopersicum) to test whether these manipulations could trigger bottom-up effects on the parasitoid Necremnus tutae via host (Tuta absoluta) and/or non-host (Bemisia tabaci) exposures, and compared the control efficacy of N. tutae on T. absoluta in the presence and absence of B. tabaci. RESULTS: The results showed no cascading effects of plant nitrogen and/or water inputs on N. tutae via either host or non-host exposure. The bottom-up force was mitigated by chewing or sap-feeding insect consumers at the second energy level. By contrast, the top-down force on T. absoluta from parasitoids was enhanced by an additionally provided non-host, which could produce alternative food sources extending N. tutae longevity and enhancing the fitness of its offspring. CONCLUSION: Our results provided evidence for the combination of bottom-up and top-down approaches in tomato integrated pest management programs. [ABSTRACT FROM AUTHOR]

An appraisal of the regulatory role of natural enemies on target pests requires the identification of the mechanisms/traits that enhance the ability of an organism to control the density of its prey/host. After stinging herbivore hosts with their ovipositor, hymenopteran parasitoids tend to reject them without ovipositing or host-feeding. Termed pseudoparasitism, the frequency and consequences of this type of attack (hereafter oversting) have been largely disregarded in the hymenopteran parasitoid literature. We choose the parasitoids Aphytis melinus and A. chrysomphali and their common host Aonidiella aurantii as a model system to study this behavior. Using field and laboratory observations, we showed that overstinging is a common behavior in the wild. Under controlled conditions, overstinging occurred more frequently than host-feeding, a behavioral trait that is used to evaluate the potential of parasitoids as biological control agents. Oversting reduced the fecundity and survival of the herbivore host. When we compared between parasitoid species that attack the same host species, the virulence and frequency of this behavior depended on parasitoid species. These results demonstrate that overstinging should be incorporated in the models of host-parasitoid interactions to analyze population dynamics as well as in the future selection of parasitoids for biological control. [ABSTRACT FROM AUTHOR]

Sexual cannibalism is a phenomenon registered in a wide variety of invertebrates. The Dryinidae are exclusive parasitoids of the suborders Cicadomorpha and Fulgoromorpha. Their ecology and biology are generally little known. In this communication, we studied biological traits of Gonatopus chilensis, reporting two novel facts for dryinid species: occasionally the virgin females were re-mated by the same male, and after mating, occasionally young females captured the male and devoured their gaster. This is the first record of sexual cannibalism for the Dryinidae and, as far as we know, for the Order Hymenoptera. [ABSTRACT FROM AUTHOR]

Sexual cannibalism is a phenomenon that has been reported in a wide variety of invertebrate predators. In arthropods, it has been documented mostly in arachnids. The Dryinidae, a small cosmopolitan family of aculeate hymenopterans, are exclusively parasitic of the hemipteran suborders Cicadomorpha and Fulgoromorpha. They include some species that have been successfully employed in biological control programs. The ecology and biology of the Dryinidae is generally little known. In this short communication, studying biological traits of Gonatopus chilensis, a parasitoid of planthoppers, we report two novel facts for dryinid species: occasionally virgin females were re-mated by the same male, and after mating, occasionally young females caught the male and devoured its gaster. This is the first record of sexual cannibalism for the family Dryinidae and, to our knowledge, for the order Hymenoptera. [ABSTRACT FROM AUTHOR]

The parasitoid wasp, Eretmocerus delhiensis Mani is a thelytokous and syn-ovigenic parasitoid. To evaluate E. delhiensis as a biocontrol agent in greenhouse, the killing efficiency of this parasitoid by parasitism and hostfeeding, were studied. Killing efficiency can be compared by estimation of functional response parameters. Laboratory experiments were performed in controllable conditions to evaluate the functional response of E. delhiensis at eight densities (2, 4, 8, 16, 32, 64, 100, and 120 third nymphal stage) of Trialeurodes vaporariorum Westwood on two hosts including; tomato and prickly lettuce. The maximum likelihood estimates from regression logistic analysis revealed type II functional response for two host plants and the type of functional response was not affected by host plant. Roger's model was used to fit the data. The attack rate (a) for E. delhiensis was 0.0286 and 0.0144 per hour on tomato and 0.0434 and 0.0170 per hour on prickly lettuce for parasitism and host feeding, respectively. Furthermore, estimated handling times (Th) were 0.4911 and 1.4453h on tomato and 0.5713 and 1.5001h on prickly lettuce for parasitism and host feeding, respectively. Based on 95% confidence interval, functional response parameters were significantly different between the host plants solely in parasitism. Results of this study opens new insight in the host parasitoid interactions, subsequently needs further investigation before utilizing it for management and reduction of greenhouse whitefly. [ABSTRACT FROM AUTHOR]

Pseudavga flavicoxa, a solitary koinobiont ectoparasitoid of Bucculatrix thoracella, attacks host larvae early rather than late in their final instar, subsequent development of the parasitoid then occurring within the host cocoon. This paper supplements an earlier contribution outlining other aspects of its biology and taxonomy. The host is stung repeatedly, both into the thoracic region and elsewhere on its body, causing temporary paralysis and also enabling host-feeding, which preceded oviposition in all observed cases. Stung hosts then intercepted without oviposition occurring recovered and (like parasitized hosts) resumed feeding and then constructed a cocoon, but suffered developmental arrest as a prepupa. The egg is invariably laid onto the arthrodial membrane between the first and second thoracic segments, to which it is glued. This site is first prepared by the female by a to-and-fro motion involving contact by the lower valves of the ovipositor, which are somewhat blade-like and sharp-edged. It is unclear whether dried traces of a 'glue', presumably originally liquid, subsequently seen at this site were of host origin resulting from a small wound or arose as a secretion from the female wasp, but the former is suggested. The egg was seen to issue from the extreme base of the ovipositor, at most guided onto the prepared patch by the parted lower valves. Although clearly partly plurivoltine, P. flavicoxa is remarkably long-lived as an adult, both sexes being easily kept alive under semi-natural conditions (Edinburgh, U.K.) during the late summer and autumn, males for 8 weeks and females for up to 20, despite their small size (ca 2.2-2.4 mm long). Dissection of gravid females showed that each of the 4 ovarioles carried just one mature egg at a time, with submature eggs remaining only poorly developed until the mature egg was expended. [ABSTRACT FROM AUTHOR]

To develop a bank plant system for the biological control of vegetable aphids, we used wheat, Triticum aestivum L., as a host plant to rear the English grain aphid, Sitobion avenae Fabricius, as an alternative host for rearing the parasitoid Aphelinus asychis Walker. A. asychis reared from S. avenae were allowed to parasitize second instar Myzus persicae nymphs feeding on chili pepper and cabbage plants. We compared the life history and life table parameters of A. asychis , including development time, pupal mortality, sex ratio, longevity, fecundity and host-feeding of the F 1 generation. The data were analyzed using the age-stage, two-sex life table method. We found that the parasitoids reared from S. avenae could successfully parasitize and host-feed M. persicae on chili pepper and cabbage, but they performed differently when the aphids on the two host plants were offered. The parasitoids had a shorter developmental duration, higher proportion of female progeny, longer longevity, higher fecundity and feeding rate when parasitizing the aphids on chili pepper than on cabbage. Based on the life table parameters, the including intrinsic rate of increase ( r ), net reproductive rate ( R 0 ) and net aphid killing rate ( Z 0 ), A. asychis reared from S. avenae performed better as a biological control agent of M. persicae on chili pepper than on cabbage. [ABSTRACT FROM AUTHOR]

Metabolic rate is a positive function of body weight, a rule valid for most organisms and the basis of several theories of metabolic ecology. For adult insects, however, the diversity of relationships between body mass and respiration remains unexplained. The aim of this study is to relate the respiratory metabolism of a parasitoid with body weight and foraging activity. We compared the metabolic rate of groups of starving and host-fed females of the parasitoid Eupelmus vuilleti recorded with respirometry for 7 days, corresponding to the mean lifetime of starving females and over half of the lifetime of foraging females. The dynamics of carbohydrate, lipid and protein in the body of foraging females were quantified with biochemical techniques. Body mass and all body nutrients declined sharply from the first day onwards. By contrast, the CO 2 produced and the O 2 consumed increased steadily. Starving females showed the opposite trend, identifying foraging as the reason for the respiration increase of feeding females. Two complementary physiological processes explain the unexpected relationship between increasing metabolic rate and declining body weight. First, host hemolymph is a highly unbalanced food, and the excess nutrients (protein and carbohydrate) need to be voided, partially through excretion and partially through respiration. Second, a foraging young female produces eggs at an increasing rate during the first half of its lifetime, a process that also increases respiration. We posit that the time-varying metabolic rate contributions of the feeding and reproductive processes supplements the contribution of the structural mass and lead to the observed trend. We extend our explanations to other insect groups and discuss the potential for unification using Dynamic Energy Budget theory. [ABSTRACT FROM AUTHOR]

During the last few years following the invasion of European tomato crops by the invasive South American tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), several indigenous larval parasitoid species were recorded as natural enemies of this pest. Necremnus cf. artynes (Walker) and to a lesser extent Stenomesius sp. nr. japonicus (Ashmead) (Hymenoptera: Eulophidae) have been frequently reported attacking T. absoluta in tomato greenhouses in Europe and they are considered as possible biocontrol agents. Few biological data are available on these two species, notably when they parasitize T. absoluta. Therefore, the present study documents their biology when parasitizing T. absoluta, and provides scientific bases for potential development of biological control programs relying on larval ectoparasitoids in invaded areas. We demonstrated the ability of the two parasitoid species to reproduce on T. absoluta as host on tomato plants. On average, N. cf. artynes female parasitized 28.5 larvae and killed 26.2 larvae during its life time whereas S. sp. nr. japonicus female was more long-lived and consequently more efficient; it parasitized 144.3 larvae and killed 90.1 larvae. In a second step, we also explored the effect of T. absoluta larvae instar on parasitism by S. sp. nr. japonicus and subsequent development of the parasitoid offspring. Best results were obtained with the third larvae instar with a higher number of offspring produced, bigger individuals and a higher proportion of females. Our results support the hypothesis that the two species are good candidates for biological control programs targeting T. absoluta in Europe. [ABSTRACT FROM AUTHOR]

The augmentative releases of mass-reared Aphytis spp. (Hymenoptera: Aphelinidae) parasitoids are widely used against armored scales. The nutritional status and the initial egg load of Aphytis spp. females are key to their success as biological control agents. For these reasons, this work focuses on the study of providing a protein feed to Aphytis lingnanensis (Compere) and A. melinus DeBach to improve the egg load before their release. The addition of protein to a honey diet during the first 2 d after the adult parasitoid emergence increased the initial egg load in both species of parasitoids by more than five eggs. Furthermore, the addition of protein increased the total number of eggs laid by A. lingnanensis on oleander scale, Aspidiotus nerii Bouche´ (Hemiptera: Diaspididae). In contrast, this effect was not observed on A. melinus probably because A. nerii is considered a suboptimal host for this parasitoid. The hostfeeding activities of the two Aphytis species were differentially affected by the addition of protein to their diets. These results may have direct implications for augmentative biological control programs, especially during transportation from insectaries to the field, a period of time when parasitoids are deprived of hosts. [ABSTRACT FROM AUTHOR]

During the years after the invasion of Western Palaearctic tomato crops by the South American tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), several indigenous generalist parasitoids have been recorded on this new host. Among these, Bracon nigricans Szépligeti (Hymenoptera: Braconidae) is widely distributed in the Palaearctic region, and has been frequently recovered from South American tomato leafminer. However, most of the available data on this species deal with taxonomic aspects and its recovery in faunistic surveys. The current study documents the biology of B. nigricans on South American tomato leafminer, and provides a scientific basis for its inclusion in South American tomato leafminer management programs in Afro-Eurasia. We studied several B. nigricans life-history traits relevant to juvenile development and reproduction by females. B. nigricans proved to be an idiobiont and a synovigenic ectoparasitoid of mature South American tomato leafminer larvae. Several B. nigricans reproductive traits were influenced by the age of the mothers; on average, the progeny had a slightly male-biased sex ratio (60% males) and a low rate of successful development (≈37%). Adult females lived 42.8 d and produced an average of 29.8 offspring. These biological parameters yielded an intrinsic rate of increase of 0.052. Females showed behavioral plasticity in host use, as initial host paralysis was followed by host-feeding, oviposition, or host rejection, with a consequent high mortality rate among hosts exposed to parasitism. Although further field studies are needed, these data, obtained in laboratory conditions, suggest that B. nigricans should be considered as a potential biological control agent of in newly invaded areas of the Palaearctic region. [ABSTRACT FROM AUTHOR]

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The occurrence of sub-optimal temperatures during development of immature parasitoids can have important consequences on adult fitness. We investigated the impact of different regimes of low temperature on emergence, differential mortality, longevity and fecundity in Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae). The host-feeding behaviour of adult females was also measured as an indicator of energy reserve at emergence. Acclimation of 30 days at 10 °C or 24 days at 13 °C allowed T. brassicae immatures to develop with a lower mortality than those exposed directly at 5 °C. Longevity and fecundity of females decreased at a lower rate with acclimation at 10 °C suggesting that acclimation at 13 °C may have depleted the energy reserves of individuals more than acclimation at 10 °C. Short photoperiod exposure during the maternal generation had no effect on progeny's fitness. We found no difference among the treatments in females' host-feeding behaviours, in differential mortality at emergence, in female's mobility and in F1 sex ratio. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the reproductive biology and functional response of Dineulophus phtorimaeae to tomato moth Tuta absoluta. The study also analyzed the ovigeny strategy of Dinelophus phtorimaeae throughout the adult female lifetime. It showed that phtorimaeae egg load was 4.15 eggs, and egg production led to extremely synovigenic behavior.

Host exploitation behavior in two hyperparasitoids, Lysibia nana and Gelis agilis, was compared in single cocoon clusters of their primary parasitoid host, Cotesia glomerata. L. nana reproduces sexually, is fully winged, does not host-feed and matures eggs quite rapidly after eclosion, whereas G. agilis possesses opposite traits. Cohorts of individual hyperparasitoid females of differing age and physiological state were given access to single cocoon clusters of C . glomerata that also varied in age. These results reveal that the reproductive biology of L. nana is well matched to exploit cocoon broods in C. glomerata, suggesting strong a co-evolutionary history with this host. By contrast, G. agilis is much less efficient at exploiting host cocoons and is probably a generalist species that attacks other hosts in nature. [ABSTRACT FROM AUTHOR]

Abstract: When parasitoid females encounter a host, they can either lay an egg and thus invest in current reproduction or feed on the host and thus invest in future reproduction. However, hosts could have different values according to their parasitized status. Whereas already parasitized hosts represent poor quality for egg-laying, they could have a high nutritive value for feeding. Moreover, the optimal strategy adopted generally depends on the females’ physiological state. In this study, the impact of the females’ physiological state on their reproductive strategies was investigated in the solitary parasitoid Anisopteromalus calandrae. We analysed how their age and diet influenced (i) the use of hosts (feeding vs. oviposition) and (ii) host selection (previously parasitized vs. unparasitized). Our results show that both age and diet influence the reproductive strategy of A. calandrae females: old females fed with the poorer diet laid fewer eggs and made more host-feeding than others. Females also showed a preference for already parasitized hosts for feeding. This strategy cannot be explained by the nutritive value of haemolymph, as parasitized hosts carry fewer lipids. However, as parasitized hosts are also paralyzed, it could be less costly to feed on them than on unparasitized hosts. [Copyright &y& Elsevier]

Predators as well as parasitoids native to Europe accept the exotic horse chestnut leafminer, Cameraria ohridella Deschka and Dimić 1986 (Lepidoptera: Gracillariidae), either as prey or as host. However, the influence of these antagonists on the populations of the pest insect is so far very low. Therefore, efforts to develop an integrated pest management system against C. ohridella should include methods which foster the natural enemy complex. In the present study we developed a laboratory rearing method and investigated several biological parameters of Pnigalio agraules (Walker 1839) (Hymenoptera: Eulophidae), a dominant species in the horse chestnut leafminer’s parasitoid complex in many European regions. This native parasitoid satisfies three basic requirements for successful use as a biocontrol agent with regard to C. ohridella. The parasitoid’s fecundity, longevity and the speed of juvenile development by far exceeds that of the leafminer, enabling the parasitoid population to increase faster than that of the host. Furthermore, our results show that the impact of this species on C. ohridella populations has been previously underestimated, because non-reproductive killing (i.e. host-feeding and host-stinging) of the hosts, resulting in considerable larval mortality of the leafminer, has not been quantitatively assessed. However, naturally occurring parasitoid populations have negligible impact on C. ohridella populations. Further studies, including experimental releases of P. agraules, are necessary to understand the constraints limiting the parasitoid’s performance in the field and to assess the potential benefits of releases for the control of C. ohridella. [ABSTRACT FROM AUTHOR]

Abstract: Effective parasitoid production or mass-rearing is one of the key components in practicing biological control with parasitoids. Selection of host species for rearing parasitoids is a major approach to improve the production efficiency. The stone leek leafminer Liriomyza chinensis (Kato) is a destructive pest of onion crops in many Asian countries, which is difficult to control with chemicals. The present study examined whether the production of Neochrysocharis okazakii Kamijo, a promising native biological agent of L. chinensis, could be effective if kidney bean-Liriomyza trifolii (Burgess) system was used as an alternative rearing procedure. The suitability of L. chinensis and L. trifolii as hosts of N. okazakii was investigated in the laboratory. Neochrysocharis okazakii completed its development on both two host species, and the total development time was similar on these hosts. Longevity of N. okazakii females provided with L. chinensis was longer than those on L. trifolii. There were no significant differences in fecundity and offspring sex ratio when females had been provided with these two host species. The adult parasitoids emerged from L. chinensis were significantly larger than those from L. trifolii. However, the intrinsic rate of increase was higher, and mean generation time was lower, for L. trifolii than L. chinensis. Thus, mean net reproductive rate (Ro) was higher when L. trifolii was used as host. Although the two host species were equally suitable as host for N. okazakii, our findings suggested that L. trifolii and kidney bean is an ideal system for N. okazakii production. [Copyright &y& Elsevier]

Abstract: Pnigalio soemius (Walker) (Hymenoptera: Eulophidae) is a polyphagous ectoparasitoid of late instars of leafminer larvae belonging to different orders of insects and gall-forming sawflies. Its life history was studied in the laboratory on Cosmopterix pulchrimella Chambers (Lepidoptera: Cosmopterigidae) reared on its natural host Parietaria diffusa M. & K. P. soemius development was shortest at 30°C and increased as temperature decreased with an average maximum of 134.8 days at 10°C. The lower theoretical threshold was 8.8°C for both males and females; the optimum developmental temperature and the upper lethal threshold were 28.9 and 35.1°C, respectively, for males and 28.6 and 34.6°C for females. Longevity of fed females and males at 25°C±1, 60±10% relative humidity and 12L:12D averaged 42.5 and 32.3 days, respectively. Females provided with males started oviposition on average 2.2 days after emergence and continued ovipositing for 43.0 days after emergence. Each female laid an average of 131.5 eggs and killed an average of 122.2 C. pulchrimella larvae by host-feeding and host-stinging without oviposition. Unmated females produced only male progeny. Offspring sex ratio (males/females) of females provided with males throughout their life was 2.76. Superparasitism averaged 4.1%. The intrinsic rate of increase (r m) of P. soemius was 0.114, while its kill rate (k m) was 0.377. The importance of host-feeding and host-stinging behavior of P. soemius females on C. pulchrimella populations and its influence on biological control is discussed. [Copyright &y& Elsevier]

Paucity of data on host-feeding patterns and behavior of 43 mosquito species that are reported as suspected West Nile virus (WN) vectors has limited full evaluation of their vectorial capacity. Recent studies addressing this issue need additional confirmation and should also be expanded to include collections of species or subpopulations attracted to humans. We used 4 types of collection methods to collect mosquitoes, including omnidirectional Fay-Prince traps, Centers for Disease Control-type light traps, gravid traps, and human-landing collections. Mosquitoes were collected during 2 full WN transmission seasons in 2001 and 2002, at 9 different sites across Delaware. We collected from various habitats, including salt marshes, brackish water areas, woodlands, a tire dump, a racetrack, and a mushroom farm. Blood-meal analyses were performed on parous mosquitoes by using a sandwich-type enzyme-linked immunosorbent assay. We tested primarily for 5 common host species, including rabbits, dogs, deer, horses, and chickens. We obtained substantial host-feeding data from 8 mosquito species. The most mammalophilic species were Anopheles quadrimaculatus, Coquillettidia perturbans, and Aedes albopictus, whereas the most ornithophilic species was Culex pipiens. Aedes albopictus was the most anthropophilic species, whereas Ae. vexans and Cq. perturbans exhibited relatively low attraction to humans. Culex salinarius was the species with the most diverse host-feeding activity. Based on feeding behavior, Cx. pipiens and Cx. salinarius appear to be the most likely bridge vectors. Other species may have opportunities to be bridge vectors under special circumstances, as discussed in the paper. [ABSTRACT FROM AUTHOR]

Models of host handling decisions and physiologically structured host-parasitoid population dynamics make diverging assumptions, untested as of this writing, about the allocation rules of nutrients to survival and reproduction. Our aim. is to develop a data- rich multidimensional dynamical budget of nutrient acquisition and allocation in survival and reproduction in the host-feeding, synovigenic bruchid ectoparasitoid Eupelmus vuilietti (Hymenoptera: Eupelmidae) over the entire lifetime of the animal in order to address the above questions. We quantified sugar, glycogen. protein, and lipid reserves of single females at birth and death and their daily maintenance needs. We recorded each host-feeding and oviposition event over entire lifetimes and quantified the amounts acquired and invested in eggs using microcolorimetric techniques. We then built two nutrient budgets. with and without hosts, encompassing 20 measured biochemical parameters and tested their predictions using time of death. Carbohydrate reserves are burned at a high rate for maintenance and can he used to predict lifetime in absence of hosts. The model without hosts is adequate, but the one with hosts is not, as it predicts a continuous increase of proteins from the massive host-feeding intake, contrasting with the observed decline. A good prediction of time of death could be achieved in that model by assuming that the large amounts of ingested proteins and carbohydrates from host-feeding are used for maintenance, thereby enabling females to spare lipids for reproduction. We tested this assumption in a treatment with hosts and supplemental sugars. in which the maximal number of produced eggs is expected to be almost exclusively a function of lipids when other nutrients can be obtained to cover maintenance costs. Our results enable us to discriminate between competing hypotheses about nutrient allocation in models of parasitoid behavior and host-parasitoid population dynamics. They show that E. vuilletti is both a capital breeder for lipids and an income breeder for sugars. implying that this dichotomy is best superseded by a multidimensional and dynamical approach to nutrient acquisition and allocation. [ABSTRACT FROM AUTHOR]

Understanding behavioural decisions relative to host use for feeding or reproduction by foraging parasitoids requires not only the study of metabolic pathways followed by nutrients, but also the quantification of lifetime fitness gains of each alternative behaviour. By using a combination of observational and manipulative approaches, the lifetime host-feeding gains are measured both in terms of fecundity and longevity in the parasitoid Eupelmus vuilletti. Host-feeding increases both egg production and longevity. The increase in fecundity is mainly determined by the amount of lipids obtained whereas the lifespan extension is mainly determined by carbohydrates. Proteins obtained through host-feeding have been implicated previously in egg production by parasitoids but protein intake has no effect on fecundity and longevity in E. vuilletti. The amount of nutrients gained through host-feeding and invested in eggs is variable and changes over the lifetime of the animal. Therefore, lifetime feeding gains are best understood through the construction of dynamical budgets running over the entire lifespan of an insect. [ABSTRACT FROM AUTHOR]