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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.

International audience; 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.

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. Fil: Virla, Eduardo Gabriel. Fundación Miguel Lillo. Dirección de Zoología. Instituto de Entomología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentina Fil: Espinosa, Martin Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentina

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.

Se evaluó, para hembras de Tamarixia triozae de 3 a 12,5 días de edad, el parasitismo y alimentación sobre ninfas N3- N4 -N5 de Bactericera cockerelli en foliólos de tomate (Solanum lycopersicum), así como la proporción sexual y longevidad de los adultos de la generación F1. El parasitismo fue significativamente igual sobre N3 y N5, pero las hembras de mayor edad (10 y 12,5 días) parasitaron más N4 que las jóvenes. Para una misma edad, el parasitismo para T. triozae aumentó con la edad de la ninfa de B. cockerelli cuando eran jóvenes (3-4,5 y 6 días) y no varió cuando tenían de 7,5-12,5 días. El porcentaje de ninfas consumidas fue, generalmente, independiente de la edad de la hembra del parasitoide (máximo de 28 ± 4 para N3 y hembras de 7,5 días) y fue menor al aumentar la edad de la ninfa del huésped. Se obtuvo un número significativamente mayor de machos, en la descendencia de hembras de 12,5 días que parasitaron ninfas N3. Las hembras vivieron más, pero sin diferencias significativas, que los machos. En los ensayos de preferencia con ninfas N3, N4 y N5 de B. cockerelli y foliolos de tomate o chile (Capsicum annuum), no hubo diferencias significativas en parasitismo pero la alimentación de las hembras de T. triozae fue inversamente proporcional a la edad del estadio ninfal ensayado. En conclusión, la combinación de parasitismo y alimentación de las hembras de T. triozae sobre las ninfas de B. cockerelli puede afectar significativamente su dinámica poblacional. Parasitism (proportion of parasitized nymphs) and host-feeding (proportion of consumed nymphs) of Tamarixia triozae females of different ages was evaluated on N3-N4-N5 instars of Bactericera cockerelli on tomato (Solanum lycopersicum) leaflets, together with the sex ratio and longevity of the progeny (F1 generation). Irrespective of the female age, the parasitism rate was not significantly different on N3 and N5 instars, but the oldest females (10 and 12.5 d-old) parasitized significantly more N4 than the youngest ones. Within a female age, the parasitism of T. triozae increased with the age of the nymph when they were young (3-4.5 and 6 d-old) and did not change when they were older (7.5 to 12.5 d-old). Host-feeding was independent of the parasitoid female age (maximum of 28 ± 4 for N3 and 7.5 d-old females) and was lower on older nymphal stages of the host. A significantly higher number of males were only detected in the offspring of 12.5 d-old females that parasitized N3 nymphs. Female longevity was longer, but not statistically significant differences were obtained. In host-feeding preference experiments with three nymphal stages of B. cockerelli (N3-N4-N5) and leaflets of two host plants [tomato and chili pepper (Capsicum annuum)], neither nymphal instars nor plant species had a significant effect on the parasitism rate. However, T. triozae female host-feeding was inversely related to the nymphal instar offered. In conclusion, the combination of T. triozae female parasitism and hostfeeding on B. cockerelli nymphs may significantly affect the population dynamics of this pest.

The parasitoid wasp, Eretmocerus delhiensis (Hymenoptera, Aphelinidae) 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 host-feeding, 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 (Hemiptera, Aleyrodidae) 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 1.4453 h on tomato and 0.5713 and 1.5001 h 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.

International audience; 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.

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.

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.

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 Bouché (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 host-feeding 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.

International audience; 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

The tomato moth, Tuta absoluta (Lepidoptera: Gelechiidae), is a major pest in South America and is at present an important invasive species in the Mediterranean Basin. The larval stadium mines leaves, stems, and fruits, and chemical control is the most used control method in both its original range and the invaded distribution regions. Since current T. absoluta control strategies seem limited, biological control is a prominent tool to be applied abroad. The naturally occurring larval ectoparasitoid in Argentina and Chile Dineulophus phtorimaeae (Hymenoptera: Eulophidae) has been reported to have potential biocontrol efficiency. In this study, the ovigeny strategy of D. phtorimaeae was analyzed throughout the adult female lifetime, and the functional response of females offered a range of 2-15 T. absoluta larvae was measured over a 48-hour period. Mean D. phtorimaeae egg load was 4.15 eggs, and egg production resulted in extremely synovigenic behavior. Meanwhile, a decreasing number of eggs, due to resorption, was found. Proportions of attacked (host-fed and/or parasitized) and only host-fed hosts by the ectoparasitoid were density independent for the tested host range, exhibiting a type I functional response to T. absoluta, with an attack rate of 0.20 host larvae. Meanings of this reproductive strategy in evolutionary time as well as the consequences for augmentative biological control programs are discussed., Centro de Estudios Parasitológicos y de Vectores, Facultad de Ciencias Naturales y Museo

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.

Insect parasitoids develop at the expense of other organisms called hosts. Host quality is thus important for parasitoid development and survival. The number of offspring a parasitoid female produce thus depend on her capacity to localize hosts and to determine their qualities. In competition, when hosts become scarce, they are expected to adjust their oviposition strategies in order to maximize their fitness. The main goal of this work is to study the oviposition strategies of a solitary parasitoid, Anisopteromalus calandrae, under intraspecific competition conditions. In solitary species, partly because of lethal larval fights, only one adult can emerged from a given host, whatever the number of eggs initially laid on it. We were thus interested in larval fights by investigating biotic factors affecting their outcomes. Our results show that, in this species, females are better competitors in larval fights. Moreover, the latter the second individual is laid after the first, the more the probability he would be eliminated will be high. Consequently, parasitoid females are able to discriminate the different categories of hosts they are confronted to. Firstly, the choice between parasitized and unparasitized hosts depends on the strategy they employed toward them, that is whether the host is used for oviposition or directly to feed on. Moreover, these strategies are directly linked to the females' physiological state (age, nutritive reserve...). Secondly, when females are confronted to already parasitized hosts, they preferentially select those recently parasitized, i.e., on which their offsprings have the better probability to win the competition. This discrimination is based on modifications of the host's cuticular profile with time after parasitism. Moreover, when eggs present on hosts have reached a certain development stage, females are able to assess their sex. They thus have a tendency to lay more male eggs when female eggs are already laid in the vicinity. Nevertheless, they avoid laying them directly on hosts parasitized by a female egg, because males would have few probabilities to win the competition. Adaptive aspects of these strategies and mechanisms involved are discussed.; Les insectes parasitoïdes effectuent leur développement aux dépens d'un autre organisme, un hôte. La qualité des hôtes va directement influencer le développement et la survie des parasitoïdes. Le nombre de descendants produits par les femelles dépend donc de leur capacité à localiser les hôtes et à déterminer leur qualité. Aussi, lorsqu'elles sont en situation de compétition et que les hôtes en question se trouvent être en quantité limitée, elles devront adapter leurs stratégies de ponte de manière à maximiser leur succès reproducteur. L'objectif de cette thèse est d'étudier les stratégies de ponte des femelles d'une espèce de parasitoïde solitaire, Anisopteromalus calandrae en situation de compétition intraspécifique. Chez les espèces solitaires, en partie à cause de combats larvaires mortels, un seul adulte pourra émerger d'un hôte donné, et ce, quel que soit le nombre d'oeufs initialement pondus. Nous nous sommes intéressés à ces combats en étudiant les facteurs biotiques pouvant affecter leur issue. Chez cette espèce, les larves femelles sont de meilleures compétitrices que ne le sont les mâles. Plus l'intervalle de temps entre deux pontes augmente, plus le deuxième individu pondu risque de se faire éliminer. Ainsi, chez cette espèce, les femelles sont capables de distinguer les différentes catégories d'hôtes auxquelles elles sont confrontées. Premièrement, le choix entre hôtes parasités et non parasités dépend de la stratégie de la femelle, à savoir si elle les utilise pour la ponte ou pour se nourrir. Cette stratégie est elle-même modulée par son état physiologique (âge, réserves nutritives...). Deuxièmement, lorsque les femelles sont confrontées à des hôtes déjà parasités, elles pondent préférentiellement sur ceux récemment parasités, hôtes sur lesquels leurs descendants ont la plus grande probabilité de survivre. L'origine de cette discrimination est dûe à l'évolution du profil cuticulaire de l'hôte au cours du temps après parasitisme. De plus, lorsque les oeufs présents sur les hôtes parasités ont atteint un certain stade de développement, les femelles sont capables de reconnaitre leur sexe. Elles vont ainsi avoir tendance à pondre plus de mâles lorsque des oeufs femelles sont déjà pondus. Toutefois, elles évitent de les pondre directement sur des hôtes déjà parasités par un oeuf femelle, les mâles ayant peu de chances de remporter le combat. L'aspect adaptatif de ces stratégies ainsi que les mécanismes sous-jacents sont discutés.

In insects reproductive success is strongly determined by the nutritional resources available to females and by the allocation rules of these nutrients in the organism. By carrying out a detailed physiological investigation of the host-feeding in two ectoparasitoid synovigenic, we have identified and quantified resources obtained by the parasitoid and tested the effects of these nutrients on female life-history traits. We followed the incorporation of the ingested nutrients into each individual egg laid over the average life span and confirmed a direct link between host-feeding and fecundity. Our results showed that the two major sugars obtained by the parasitoid during host-feeding, trehalose and sucrose, are entirely responsible for the increased longevity observed in host-fed females. To conclude, host-feeding enables females to sustain reproduction as well as maintenance.; Chez les insectes, le succès reproducteur est intimement lié aux ressources nutritives dont dispose la femelle ainsi qu'à leur allocation au sein de l'organisme. Grâce à une étude physiologique détaillée du nourrissage sur l'hôte chez deux ectoparasitoïdes synovigéniques nous avons identifié et quantifié les nutriments obtenus lors du nourrissage sur l'hôte et testé leurs effets sur les traits d'histoire de vie des femelles. Nous avons ainsi prouvé que les parasitoïdes consomment l'hémolymphe de leur hôte lors du nourrissage sur l'hôte. Nous avons également démontré qu'il existe un lien direct entre nourrissage sur l'hôte et fécondité. Nos résultats montrent également que les principaux sucres obtenus au cours du nourrissage sur l'hôte, le tréhalose et le saccharose, sont responsables de l'augmentation de survie observée suite au nourrissage. Le nourrissage sur l'hôte permet donc aux femelles d'assurer les dépenses métaboliques liées aussi bien à la maintenance qu'à la fécondité.