In the interaction between two ecologically-associated species, the population structure of one species may affect the population structure of the other. Here, we examine the population structures of the aphid Metopeurum fuscoviride, a specialist on tansy Tanacetum vulgare, and its specialist primary hymenopterous parasitoid Lysiphlebus hirticornis, both of which are characterized by multivoltine life histories and a classic metapopulation structure. Samples of the aphid host and the parasitoid were collected from eight sites in and around Jena, Germany, where both insect species co-occur, and then were genotyped using suites of polymorphic microsatellite markers. The host aphid was greatly differentiated in terms of its spatial population genetic patterning, while the parasitoid was, in comparison, only moderately differentiated. There was a positive Mantel test correlation between pairwise shared allele distance (DAS) of the host and parasitoid, i.e. if host subpopulation samples were more similar between two particular sites, so were the parasitoid subpopulation samples. We argue that while the differences in the levels of genetic differentiation are due to the differences in the biology of the species, the correlations between host and parasitoid are indicative of dependence of the parasitoid population structure on that of its aphid host. The parasitoid is genetically tracking behind the aphid host, as can be expected in a classic metapopulation structure where host persistence depends on a delay between host and parasitoid colonization of the patch. The results may also have relevance to the Red Queen hypothesis, whereupon in the ‘arms race’ between parasitoid and its host, the latter ‘attempts’ to evolve away from the former.

Mealybugs are major pests of grapevines worldwide. They cause economic losses by lowering the cosmetic value of fruits, reducing yields, transmitting viruses and resulting in the quarantine or rejection of produce in international trade. Knowledge of the species present in a vineyard is important for the adjustment of management strategies. We surveyed and accurately characterized the mealybugs infesting vineyards in one of the main production areas of Chile; 164 mealybugs were sampled from 26 vineyards in four regions of Chile and identified by DNA sequencing for two markers (cytochrome oxidase I and internal transcribed spacer 2) and morphological examination. Pseudococcus viburni (Signoret) was the most common species, followed by Pseudococcus meridionalis Prado and Pseudococcus cribata González. Molecular variability at the COI and ITS2 loci was observed in both P. viburni and P. cribata. A comparison of haplotypes of P. viburni worldwide provides support for a recent hypothesis that this species is native to South America, a finding with direct consequences for management. Neither Pseudococcus longispinus (Targioni & Tozzetti) nor Planococcus ficus Signoret were found.

The effect of host nutritional quality on spruce budworm (Choristoneura fumiferana (Clemens)) parental and offspring performance was studied using field and laboratory rearing experiments, and foliar chemical analyses. Foliage of balsam fir (Abies balsamea (L.) Mill.), white spruce (Picea glauca (Moench) Voss) and black spruce (P. mariana (Mill.) BSP) was used to rear the parental generation in the field, whereas an artificial diet was used to rear the progeny under laboratory conditions. Important differences in the food quality were provided by the three hosts. Black spruce foliage had higher concentrations of certain monoterpene deterrents and total phenolics, together with stronger seasonal declines in nutrients such as N, P and Mg, compared with the other hosts. We hypothesise that this trend may be related to poor performance and survival of the progeny. Laboratory rearing showed that progeny of parents that fed on black spruce exhibited longer developmental times and greater mortality, and had lower pupal mass than progeny of parents fed on the other hosts. Further, artificial food-fed progeny of insects reared on black spruce reached sixth-instar later, with lower mass, and exhibited higher relative growth rate (RGR) than progeny of parents fed on the other hosts. These results suggest nutritionally-based parental effects. These results also confirmed that the quality of food consumed by the parents can influence the fitness of the next generation.

Knowledge on colonization modes and interplant movement of Nasonovia ribisnigri can contribute to the development of optimal control of this pest. The aim of this study was to determine the spatio-temporal distribution and the mode of spread between adult morphs of Nasonovia ribisnigri, comparing spring and autumn lettuce protected crops. The spatial and temporal pattern was analyzed using the spatial analysis by distance indices (SADIE) methodology and other related displacement indices.

The population size of N. ribisnigri was greater in the autumn than in the spring growing seasons due to milder temperatures. The percentage of plants colonized by aphids was higher in spring than in autumn, showing the great dispersal potential of this aphid species independent of their population size. Differential propensity for initial displacement from the central plant was observed between adult morphs in spring, resulting in a greater ability of apterous than alate aphids to spread far away from the source plant. In autumn, both adult morphs showed an initial reduced displacement; however, the number of plants infested (≈20%) with at least one aphid at this initial time (seven days) was similar for both adult morphs and both growing seasons. Analysis of the spatial pattern of both adult morphs revealed a predominantly random distribution for both spring and autumn trials. This pattern was achieved by a prevalent random movement over the area (γ≈0.5). These results highlight the ability of the apterous N. ribisnigri to spread within greenhouse lettuce crops early in the spring, suggesting that detection of the pest by deep visual inspection is required after lettuce emergence.

Climate changes can affect the distribution and intensity of insect infestations through direct effects on their life cycles. Experiments were carried out during three consecutive generations to evaluate the effect of different temperatures (25°C, 28°C, 31°C, 34°C and 37±1°C) on biological traits of the velvetbean caterpillar Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Noctuidae). The insects were fed on artificial diet and reared in environmental chambers set at 14 h photophase. The developmental cycle slowed with the increase in the temperature, within the 25°C to 34°C range. Male and female longevities were reduced with an increase in temperature from 25°C to 28°C. Egg viability was highest at 25°C, and the sex ratio was not influenced by temperature, in the three generations. There was no interactive effect between development time and temperature on pupal weight. The results suggested that the increase in the temperature negatively impacted A. gemmatalis development inside the studied temperature range, indicating a possible future reduction of its occurrence on soybean crops, as a consequence of global warming, mainly considering its impact on tropical countries where this plant is cropped. A. gemmatalis was not able to adapt to higher temperatures in a three-generation interval for the studied temperature range. However, a gradual increase and a longer adaptation period may favor insect selection and consequently adaptation, and must be considered in future studies in this area. Moreover, it is important to consider that global warming might turn cold areas more suitable to A. gemmatalis outbreaks. Therefore, more than a future reduction of A. gemmatalis occurrence due to global warming, we might expect changes regarding its area of occurrence on a global perspective.

The whiteflies Bemisia tabaci Gennadius and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are two of the main pests in tomato crops. Their biological control in Mediterranean IPM systems is based on the predators Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter (Hemiptera: Miridae), as well as on the parasitoids Eretmocerus mundus (Mercet) and Encarsia pergandiella Howard (Hymenoptera: Aphelinidae). These natural enemies may interact with each other and their joint use could interfere with the biological control of those whitefly pests. Analysis of predator-prey interactions under field conditions is therefore essential in order to optimize whitefly control. Species-specific polymerase chain reaction (PCR)-primers were designed to detect DNA fragments of these whiteflies and parasitoids within both predator species in tomato greenhouses. We demonstrated that both predators feed on both whitefly species, as well as on both parasitoids under greenhouse conditions. Prey molecular detection was possible where prey abundance was very low or even where predation was not observed under a microscope. Whitefly DNA detection was positively correlated with adult whitefly abundance in the crop. However, a significant relationship was not observed between parasitoid DNA detection and the abundance of parasitoid pupae, even though the predation rate on parasitoids was high. This unidirectional intraguild predation (predators on parasitoids) could potentially reduce their combined impact on their joint prey/host. Prey molecular detection provided improved detection of prey consumption in greenhouse crops, as well as the possibility to identify which prey species were consumed by each predator species present in the greenhouse, offering a blueprint with wider applicability to other food webs.

We provide a karyological study of 12 species of the genus Pnigalio in an attempt to evaluate the taxonomic utility of karyotypes at the species level. For all species of Pnigalio examined the number of chromosome was 2n=12. Karyotype formulae presented mainly metacentric and submetacentric chromosomes, although a pair of acrocentrics or subtelocentrics, shorter than biarmed chromosomes, was present in some species. The analysis of karyotypes of Pnigalio showed frequent but not general interspecific variability of the chromosome traits. Although most of the studied species revealed concordance between morphological and karyological characters (centromeric index and relative length), two other categories have been identified: morphologically distinct species without reciprocal differences in karyotype structure, and morphologically similar species that strongly differ in chromosomal characters.

A serious sugarcane pest, Dasylepida ishigakiensis, remains in the soil during most of its life cycle except for a short period for mating. Mating disruption by an artificial release of the sex pheromone (R)-2-butanol (R2B), therefore, may be a feasible method to control this pest. We examined the effects of artificial release of R2B and its related compounds, (S)-2-butanol (S2B) and the racemic 2-butanol (rac-2B), on the mating success of this beetle both in the laboratory and in the field. In flight tunnel experiments, almost all males orientated towards a R2B-releasing source and 40% of them landed on the source. When the atmosphere was permeated with R2B, the frequency of males landing on the model was significantly reduced. Both rac-2B and S2B were less effective, but substantial reduction in landing success by males was achieved at higher rac-2B concentrations. R2B released from polyethylene dispensers in sugarcane plots greatly reduced not only the proportion of females mated with males but also the number of males caught by R2B-baited traps, indicating that male mate-searching behaviour was strongly affected by the released R2B. Similar inhibitory effects on male behaviour were also observed when tube- or rope-type dispensers released high rac-2B concentrations in the field. These results indicate that it would be highly possible to control D. ishigakiensis through the disruption of the sexual communication by releasing either synthetic R2B or rac-2B.

Wetlands have traditionally been associated with harbouring mosquitoes, a well-known nuisance and vectors of diseases. Within mosquito life cycle, oviposition is a determinant event by shaping their individual fitness and vectorial capacity. The study was conducted in one of the main temperate wetlands in South America. We used Generalized Linear Models to study the relation between temperature, precipitation, tidal regime, land use, microenvironment, and the occurrence of floodwater (Ochlerotatus and Psorophora spp.) and raft-laying (Culex and Uranotaenia spp.) mosquitoes using temporary pools as larval habitats. Pool occurrence was negatively associated with temperature, and positively related to precipitation and high tides. As regards the land use, it was lowest in domestic areas and plantations, intermediate in secondary forests, and highest in marshes. Each oviposition strategy was best modelled as a function of different environmental factors. The occurrence of floodwater mosquitoes was positively associated with high cumulative precipitation and low tide records. Raft-laying mosquitoes were related to low temperature records, while the effect of flooding varied with the land use. In view of these results, physical (water inputs and movement), chemical, and biological (egg and larval flushing, and predatory interactions) considerations are given to provide insight in the oviposition patterns of mosquitoes occurring in this complex wetland. We finally propose the generation of a tidal flow as a control measure against floodwater mosquitoes, which are the most anthropophilic in the study area.

Pesticide resistance monitoring includes resistance detection and subsequent documentation/ measurement. Resistance detection would require at least one (≥1) resistant individual(s) to be present in a sample to initiate management strategies. Resistance documentation, on the other hand, would attempt to get an estimate of the entire population (≥90%) of the resistant individuals. A computer simulation model was used to compare the efficiency of simple random and systematic sampling plans to detect resistant individuals and to document their frequencies when the resistant individuals were randomly or patchily distributed. A patchy dispersion pattern of resistant individuals influenced the sampling efficiency of systematic sampling plans while the efficiency of random sampling was independent of such patchiness. When resistant individuals were randomly distributed, sample sizes required to detect at least one resistant individual (resistance detection) with a probability of 0.95 were 300 (1%) and 50 (10% and 20%); whereas, when resistant individuals were patchily distributed, using systematic sampling, sample sizes required for such detection were 6000 (1%), 600 (10%) and 300 (20%). Sample sizes of 900 and 400 would be required to detect ≥90% of resistant individuals (resistance documentation) with a probability of 0.95 when resistant individuals were randomly dispersed and present at a frequency of 10% and 20%, respectively; whereas, when resistant individuals were patchily distributed, using systematic sampling, a sample size of 3000 and 1500, respectively, was necessary. Small sample sizes either underestimated or overestimated the resistance frequency. A simple random sampling plan is, therefore, recommended for insecticide resistance detection and subsequent documentation.

The frequency of superparasitism and its effects on the quality of laboratory-reared Spalangia cameroni (Hymenoptera: Pteromalidae) parasitoids were investigated under laboratory conditions. Numerous variables were measured, such as the number of ‘ovip holes’ per host as a measure of superparasitism. Adult emergence and sex ratio, as well as female size, emergence ability from soil and longevity were also measured. Finally, an assessment was made of fertility and survival of adult parasitoids emerging from the medfly Ceratitis capitata (Diptera: Tephritidae) pupae with different levels of superparasitism. A high frequency and prevalence of superparasitism under laboratory rearing conditions was observed. The number of ‘ovip holes’ per host ranged from one to 17, with an average (±SD) of 2.8±3.4. Sex ratios became increasingly female-biased with increasing levels of superparasitism, although overall levels of wasp emergence (male, female) declined. Nevertheless, no relationship was discerned between female size and level of superparasitism. The ‘emergence ability from the soil’ was higher in those parasitoids that emerged from strongly superparasitized hosts, but not related to the type of substrate in which the host pupae were buried. The level of superparasitism did not have a significant effect on the longevity, fertility and survival of female parasitoids. Our results support the hypothesis that superparasitism in S. cameroni might be adaptive, since attributes such as ‘emergence ability from the soil’, longevity, fertility and survival were not affected by the level of superparasitism or the presumably detrimental effects derived from physical combats among conspecific larvae. Our findings are relevant to recommendations for rearing S. cameroni for biological control releases, as well as shedding light on superparasitism under both laboratory and field conditions.

Organisms differ greatly in dispersal ability, and landscapes differ in amenability to an organism's movement. Thus, landscape structure and heterogeneity can affect genetic composition of populations. While many agricultural pests are known for their ability to disperse rapidly, it is unclear how fast and over what spatial scale insect pests might respond to the temporally dynamic agricultural landscapes they inhabit. We used population genetic analyses of a severe crop pest, a member of the Bemisia tabaci (Hemiptera: Sternorrhyncha: Aleyrodoidea: Aleyrodidea) cryptic species complex known as Middle East-Asia Minor 1 (commonly known as biotype B), to estimate spatial and temporal genetic diversity over four months of the 2006–2007 summer growing season. We examined 559 individuals from eight sites, which were scored for eight microsatellite loci. Temporal genetic structure greatly exceeded spatial structure. There was significant temporal change in local genetic composition from the beginning to the end of the season accompanied by heterozygote deficits and inbreeding. This temporal structure suggests entire cohorts of pests can occupy a large and variable agricultural landscape but are rapidly replaced. These rapid genetic fluctuations reinforce the concept that agricultural landscapes are dynamic mosaics in time and space and may contribute to better decisions for pest and insecticide resistance management.

Mealybugs (Hemiptera: Pseudococcidae) are common invasive pests in Europe, causing major problems on crops and ornamental plants. However, very few data are available concerning the mealybug fauna of southern Europe. This lack of data and the difficulty of identifying mealybugs morphologically by traditional techniques currently limit the perspectives for efficient specific pest management. The aim of this study was to provide multi-criterion characterization of mealybugs surveyed in eastern Spain in order to facilitate their routine identification through DNA sequencing or the use of derived species-specific molecular tools. We characterised 33 mealybug populations infesting crops and ornamental plants in eastern Spain, using a combination of molecular and morphological techniques, including the sequencing of the universal barcode DNA region cytochrome c oxidase subunit I (COI). This characterisation has led to the identification of ten species and provides sequence data for three previously unsequenced species, contributing to the phylogenetic knowledge of the family Pseudococcidae. In addition, the intraspecific variations found in the populations of five mealybug species provide insight into their invasion history.

In this study, we present cytogenetic data regarding 66 Myzus persicae strains collected in different regions of Italy. Together with the most common 2n = 12 karyotype, the results showed different chromosomal rearrangements: 2n = 12 with A1–3 reciprocal translocation, 2n = 13 with A1–3 reciprocal translocation and A3 fission, 2n = 13 with A3 fission, 2n = 13 with A4 fission, 2n = 14 with X and A3 fissions. A 2n = 12–13 chromosomal mosaicism has also been observed. Chromosomal aberrations (and in particular all strains showing A1–3 reciprocal translocation) are especially frequent in strains collected on tobacco plants, and we suggest that a clastogenic effect of nicotine, further benefited by the holocentric nature of aphid chromosomes, could be at the basis of the observed phenomenon.

A laboratory study was carried out to assess the potential prey-mediated effects of Cry3Bb1-expressing Bt maize on the fitness and predatory ability of Atheta coriaria Kraatz (Coleoptera: Staphylinidae), using Tetranychus urticae Koch (Acari: Tetranychidae) as prey. The concentration of Cry3Bb1 toxin through the trophic chain significantly decreased from Bt maize (21.7 μg g−1 FW) to mites (5.6 μg g−1 FW) and then to A. coriaria adults (1.4 μg g−1 FW), but not from mites to A. coriaria L1–L3 larvae (4.1–4.6 μg g−1 FW). Interestingly, the toxin levels detected in A. coriaria larvae represent more than 20% of the concentration found in Bt maize, and the toxin was detected up to 48 h after exposure. To our knowledge, this is the highest level of exposure ever reported in a predatory beetle to the Cry3Bb1 protein. When A. coriaria larvae were reared on Bt-fed mites, Bt-free mites or rearing food, no significant differences among treatments were observed in development, morphological measurements of sclerotized structures and body weight. Moreover, no negative effects on reproductive parameters were reported in adults feeding on Bt-fed prey after 30 days of treatment, and survival was not affected after 60 days of exposure. Similarly, predatory ability and prey consumption of A. coriaria larvae and adults were not affected by exposure to the toxin. All together, these results indicate a lack of adverse effects on A. coriaria, a species commonly used as a biological control agent. The use of A. coriaria as a surrogate species for risk assessment of GM crops that express insecticidal proteins is discussed.

Resource diversity is critical to fitness in many insect species, and may determine the coexistence of competitive species and the function of ecosystems. Plant material provides the nutritional base for numerous aquatic systems, yet the consequences of diversity of plant material have not been studied in aquatic container systems important for the production of mosquitoes. To address how diversity in leaf detritus affects container-inhabiting mosquitoes, we examined how leaf species affect competition between two container inhabiting mosquito larvae, Aedes aegypti and Aedes albopictus, that co-occur in many parts of the world. We tested the hypotheses that leaf species changes the outcome of intra- and interspecific competition between these mosquito species, and that combinations of leaf species affect competition in a manner not predictable based upon the response to each leaf species alone (i.e. the response to leaf combinations is non-additive). We find support for our first hypothesis that leaf species can affect competition, evidence that, in general, leaf combination alters competitive interactions, and no support that leaf combination impacts interspecific competition differently than intraspecific competition. We conclude that combinations of leaves increase mosquito production non-additively such that combinations of leaves act synergistically, in general, and result in higher total yield of adult mosquitoes in most cases, although certain leaf combinations for A. albopictus are antagonistic. We also conclude that leaf diversity does not have a different effect on interspecific competition between A. aegypti and A. albopictus, relative to intraspecific competition for each mosquito.

Walking speeds were calculated for nine clones of the peach potato aphid Myzus persicae collected from three countries along a latitudinal cline of its European distribution from Sweden to Spain (Sweden, UK and Spain), and the effects of collection origin and intra and intergenerational acclimation were investigated. Walking speeds declined with decreasing temperature, with maximum performance at temperatures closest to acclimation temperature (fastest median walking speed of 5.8 cm min–1 was recorded for clone UK 3, collected from the UK, at 25°C after acclimating to 25°C for one generation). Following acclimation at both 20°C and 25°C, walking ceased (as indicated by median walking speeds of 0.0 cm min–1) at temperatures as high as 7.5°C and 12.5°C. However, acclimation at 10°C enabled mobility to occur to temperatures as low as 0°C. There was no relationship between mobility and latitude of collection, suggesting that large scale mixing of aphids may occur across Europe. However, clonal variation was suggested, with clone UK 3 outperforming the majority of other clones across all temperatures at which mobility was maintained following acclimation at 10°C for one and three generations and at 25°C for one generation. The Scandinavian clones consistently outperformed their temperate and Mediterranean counterparts at the majority of temperatures following acclimation for three generations at 25°C.

As a prerequisite for area-wide application of the sterile insect technique in an area encompassing northern Argentina and southern Brazil, prezygotic and postzygotic reproductive compatibility among three geographically distant populations in the area was tested. In field cages, sexually mature adults of each population were found to be sexually compatible, mating duration was not affected by fly origin and there was no clear evidence of spatial partition of mating location. In the laboratory, homotypic and heterotypic crosses for all possible combinations displayed similar levels of fertility and yielded F1 adults without distortion of the sex ratio. Finally, F1 hybrid and parental adults produced equally viable F2 eggs. Put together, our results and those from earlier studies suggest that a large area, ranging from Buenos Aires to the surroundings of São Paulo, could be managed using a single A. fraterculus mass-reared strain. At the northern margin of this area, two A. fraterculus morphotypes appear to coexist in sympatry. We delineate future research to further delimit the distribution of the aff1 morphotype (Argentina-southern Brazil) and to gain insight into evolutionary patterns producing divergence and radiation of tropical fruit fly species.

Aphids perform a series of behaviours to assess feeding suitability and, hence, to select a plant. Little information, however, is available on such behaviour after aphids have settled on a plant. Observation of probing behaviour over an extended period of time can improve our understanding of insect-plant interactions and is instrumental in the study of crop resistance. Here, we assessed the influence of aphid age and plant resistance level on aphid behaviour. An electrical penetration graph (EPG) technique was implemented to monitor the behaviour of potato aphid, Macrosiphum euphorbiae, alates on potato, Solanum tuberosum, and on both a susceptible and a resistant genotype of a wild Solanum species, S. chomatophilum. The behaviour was measured at daily intervals for the first seven days following adult emergence. The results indicated independent and interacting effects of aphid age and plant genotype on probing behaviour. Some behavioural discrepancies between susceptible and resistant genotypes were only observed after the first day, thus highlighting the limits of punctual one-day behavioural studies to assess plant resistance mechanisms. Our work supports the hypothesis that aphids continuously adapt their behaviour to the plant characteristics.

The preference-performance hypothesis has principally considered insect herbivores with aboveground lifecycles, although the hypothesis could be equally relevant to insects with life stages occurring both aboveground and belowground. Moreover, most studies have focussed on either laboratory or field experiments, with little attempt to relate the two. In this study, the preference-performance hypothesis was examined in an aboveground-belowground context in the laboratory using the vine weevil (Otiorhynchus sulcatus (F.)) (Coleoptera: Curculionidae) and two cultivars of red raspberry (Rubus idaeus), Glen Rosa and Glen Ample. A two-year field study (2008–2009) was also undertaken to characterise the population dynamics of adult weevils on the two raspberry cultivars. Larval performance (abundance and mass) differed significantly between Glen Rosa and Glen Ample, with Glen Rosa resulting in 26% larger but 56% fewer larvae compared to Glen Ample. Larval abundances were significantly and positively correlated with root nitrogen and magnesium concentrations, but negatively correlated with root iron. However, concentrations of these minerals were not significantly different in the two cultivars. Adult weevils did not preferentially select either of the two cultivars for egg laying (laying 3.08 and 2.80 eggs per day on Glen Ample and Glen Rosa, respectively), suggesting that there was no strong preference-performance relationship between adult vine weevils and their belowground offspring. Field populations of adult vine weevils were significantly higher on Glen Ample than Glen Rosa, which may reflect the higher larval survival on Glen Ample observed in laboratory experiments.