Individual Parasitoids Research Articles

Temporal changes in the composition of parasitoid assemblages associated with the invasive chestnut gall wasp

Abstract Invasive alien species pose a challenge to ecosystem stability and crop production, so understanding their interactions with the natural communities they invade is crucial to mitigate negative effects. The oriental chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), is an invasive insect that attacks chestnut trees. It was first recorded in Spain in 2012 and is now presumably present in the majority of chestnut stands in the country. We assessed variation in the abundance of D. kuriphilus galls and the composition of their associated parasitoid community (Hymenoptera: Chalcidoidea) during a 4‐year period (2014–2017) in 12 sampling sites in Catalonia (Spain, northeastern Iberian Peninsula), and identified which species contributed most significantly to the control of D. kuriphilus. The results show that the abundance of individual parasitoid species varied during the study period and that the number of species increased year after year. There was also a transition in the parasitoid community composition across the years. Our data suggest that the joint action of the non‐native parasitoid Torymus sinensis Kamijo and the native T. notatus (Walker) (Hymenoptera: Chalcidoidea: Torymidae) led to the decline of D. kuriphilus until it was no longer considered a pest. Also, the observed pool of parasitoid species ended up being relatively homogeneous across sites over the years, which may be due to the high natural dispersal of these parasitoids (both by active flight and passive wind dispersal).

Assessing Natural Incidence of Resident Pupal Parasitoids on the Drosophila suzukii (Diptera: Drosophilidae) Population in Non-crop Fruits.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), world-renowned as spotted-wing drosophila, is an invasive pest mainly affecting healthy, soft and stone fruit crops throughout Argentinian fruit-growing regions. Natural environments overgrown by exotic feral host plants apparently favour D. suzukii proliferation. This is common in the subtropical northwestern Argentina's berry-producing region. An assemblage of resident parasitoid species has been associated with D. suzukii in crop and non-crop areas of Tucumán, the Argentina's leading berries producer and exporter. Consequently, the hypothesis that the combined action of two pupal parasitoid species, Pachycrepoideus vindemiae Rondani (Hymenoptera: Pteromalidae) and Trichopria anastrephae Lima (Hymenoptera: Diapriidae), occurring in non-crop fruit areas, has a significant impact on D. suzukii natural regulation in such invaded habitats was tested. A survey of D. suzukii puparia from both feral peach [Prunus persica (L.) Batsch] (Rosaceae) and guava (Psydium guajava L.) (Myrtaceae) fallen fruits and soil surrounding them was performed in a wilderness area of Tucumán. Abundance of D. suzukii and associated parasitoids, and parasitism levels were assessed. Whole of 3437 D. suzukii puparia were recovered; 78% and 22% were surveyed from fruits and soil underneath the fruit, respectively. Tested fruits are important D. suzukii multiplying hosts. Both P. vindemiae and T. anastrephae accounted for 99.8% of total parasitoid individuals. Pupal parasitoids contribute to the D. suzukii natural mortality, as they killed a quarter of all puparia. Mostly T. anastrephae foraged on host puparia located in the fruit and P. vindemiae in both microhabitats. This information supports an augmentative biological control strategy in non-crop areas.

What shapes galling insect–parasitoid interaction networks on closely related host plants?

Abstract Ecological networks describe community structure by focusing on how nodes are connected by links (interactions). Related species have higher probabilities of sharing links if interactions depending on phylogeny and/or species are functionally similar; however, if and how this modularity impacts higher trophic levels is still an open question. We aimed to evaluate the effect of different structuring factors on an observed bipartite network of galling insects and associated parasitoids on a system with two closely related and recently diverged plants, where host‐tracking could be underway. We hypothesized that gall structure, galler taxonomy and host plant identity could contribute, from a higher to a lower degree respectively, to network modularity by generating a selective pressure on parasitoids. Samples were collected between May 2015 and June 2017 in the forest areas of Porto Alegre, southern Brazil. Overall, we found 4629 galls of three monophagous and four oligophagous galling species; 664 parasitoid individuals were obtained and classified into 37 morphospecies. We constructed four networks with the collected data by organising nodes according to the tested factors, that is, gall structure, galler taxonomy, host plant identity and gall–plant interaction. All networks were significantly modular, and for three out of four analysed factors (gall structure, galler taxonomy and gall–plant interaction), modularity levels were at least intermediate (at about Q = 0.4). Barriers to or preferences for certain interactions appear to be responses to multiple concomitant factors. However, galler taxonomy and host plant identity are somehow stronger determinants for the parasitoids in terms of attacked hosts.

New a species as parasitoid of the apple ermine month Yponomeuta malinellus Zeller, 1838 (Lepidoptera: Yponomeutidae) in the Çoruh Valley, Erzurum Province, Türkiye

The current study aimed to determine parasitoids of Yponomeuta malinellus Zeller, 1838 (Lepidoptera: Yponomeutidae) in apple trees in the Çoruh Valley, Erzurum Province, Türkiye during 2019-2020 summer. The parasitoids associated with Y. malinellus were reared in a laboratory, with a total of 137 individual parasitoids emerging from family Ichneumonidae (Hymenoptera). Among the identified species Trieces facialis (Thomson, 1887), Itoplectis tunetana (Schmiedeknecht, 1914) and Pimpla turionellae (Linnaeus, 1758) were determined as pupal parasitoid. Of these, Trieces facialis has been obtained from Y. malinellus our country first time and also is new for the Turkish Ichneumonidae fauna. In this study of the Çoruh Valley, the mean parasitism rate was %27.4.

Protein Deficient Diets: Cascade Effects on a Lepidopteran Pest and Its Parasitoid Wasp

Abstract The nutritional quality of herbivorous insects’ food can not only directly affect the herbivorous insects themselves, but can also indirectly affect their parasitoids. To investigate these cascading, multi-trophic effects, we reared cabbage looper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), on artificial diets (8.1, 11.5, 16.75, 25.5, 34.25, and 43 g protein/liter diet) to assess how diet protein content affected the development of this common pest and its suitability as a host for the gregarious parasitoid, Cotesia vanessae (Reinhard) (Hymenoptera: Braconidae). Nonparasitized caterpillars experienced increased mortality when reared on 8.1 g protein/liter diet, and slower development and reduced pupal mass when reared on ≤16.75 g protein/liter diet. Host diet did not affect the percentage of hosts with parasitoid emergence nor the mass of individual parasitoids. However, parasitoid broods emerging from caterpillars reared on ≤25.5 g protein/liter diet were smaller and those reared on ≤16.75 g protein/liter diet exhibited prolonged development. The consequences of host diet on these latter F1 parasitoids did not affect their reproductive fitness. Caterpillars compensated for nutrient stress, induced by either low quality diet or parasitism, by increasing the amount of diet that they consumed. These collective results demonstrate the plasticity of host-parasitoid systems. Compensatory feeding allows the host caterpillar to moderate the consequences of low quality diets, which may subsequently affect the F1 parasitoids developing within the host, but not necessarily affect the F2 parasitoid generation.

Reproduction of Ooencyrtus submetallicus (Hymenoptera: Encyrtidae) in egg densities of Euschistus heros (Hemiptera: Pentatomidae)

Abstract Knowledge about the ideal host ratio per female parasitoid reared in glass tubes is important for obtaining descendants with better biological quality. The study aimed to evaluate the reproduction of Ooencyrtus submetallicus (Hymenoptera: Encyrtidae) females in egg densities of Euschistus heros (Hemiptera: Pentatomidae) to find the most adequate relationship between parasitoids and hosts aiming at the parasitoid multiplication. The experiment was conducted with E. heros eggs at densities (parasitoid:host) of 1:3, 1:6, 1:9, 1:12, 1:15, or 1:18 with 24 hours of parasitism by O. submetallicus. The parasitoid females and the egg carton were placed in glass tubes and kept in a climate-controlled chamber. The percentage of parasitism was affected by the nonparasitised eggs. The emergence of adult parasitoids, number of parasitised eggs, number of individual parasitoids emerging per egg, the length of the parasitoids’ posterior tibiae, and the parasitoids’ longevity, life cycle, and sex ratio were not affected by the different densities of nonparasitised eggs subjected to treatments. Ooencyrtus submetallicus parasitised and developed in E. heros eggs in all evaluated densities, with 1:6 presenting the best combination of parasitoid and host.

Capsella bursa-pastoris Is a Key Overwintering Plant for Aphids in the Mediterranean Region

Simple SummaryReservoir plants are crucial for overwintering pests and their biological control agents. A long-term survey revealed that Capsella bursa-pastoris is a significant host plant, especially for aphids as well as their parasitoids and hyperparasitoids. Twenty-five aphids and eleven parasitoid species were identified on this weed. Myzus persicae and Aphis gossypii were the most commonly recorded aphid species, and Binodoxys angelicae the most frequent parasitoid. Additionally, the monthly distribution of the aphids, parasitoids, and hyperparasitoids showed that C. bursa pastoris fills the host plant gap in the absence of crops. Trophic relations within the community and the importance of C. bursa pastoris were also analyzed in this study.The reproduction of aphids depends to a great extent on their host plants, an integration that impacts on the successful expansion of overwintering populations. Therefore, a survey was conducted to evaluate the globally distributed Capsella bursa-pastoris as an overwintering host of economically important aphid species, their parasitoids and hyperparasitoids in the southern and western regions of Turkey from November to March in 2006 to 2013. During this survey, 395 samples of C. bursa-pastoris were collected with 25 aphid species recorded. Among aphids that feed on this host, Myzus persicae, Aphis gossypii, Rhopalosiphum padi, Aphis fabae, Aphis craccivora, Lipaphis erysimi, and Brevicoryne brassicae were the most frequently recorded. In total, 10,761 individual parasitoids were identified. Binodoxys angelicae, Aphidius colemani, Aphidius matricariae, Diaeretiella rapae, Ephedrus persicae, and Lysiphlebus confusus were the most abundant aphidiines that emerged from the aphids collected from C. bursa-pastoris. Alloxysta spp. (Hymenoptera: Cynipoidea), Chalcidoidea (unidentified at genus level), and Dendrocerus spp. (Hymenoptera: Ceraphronoidea) were identified as hyperparasitoids on the parasitoids. These findings indicate that C. bursa-pastoris is a key non-agricultural plant that significantly contributes to the overwintering of numerous aphids and their parasitoids, which should be given serious consideration when biological control strategies are designed.

Successful biological control of the ambermarked birch leafminer, Profenusa thomsoni (Hymenoptera: Tenthredinidae), in Anchorage, Alaska: Status 15 years after release of Lathrolestes thomsoni (Hymenoptera: Ichneumonidae)

In Anchorage, Alaska, larvae of the invasive ambermarked birch leafminer (AMBLM), Profenusa thomsoni Konow (Hymenoptera: Tenthredinidae), are parasitized in leafmines by Lathrolestes thomsoni Reshchikov and L. soperi Reshchikov (Hymenoptera: Ichneumonidae). The first species was introduced to Alaska from Alberta and the Northwest Territories of Canada beginning in 2004 after it was noted to be associated with the collapse of an outbreak of AMBLM in Alberta. The second species, L. soperi, was described in 2010 after it was found attacking AMBLM larvae in mines in Anchorage. In previous studies, we documented that after the release of L. thomsoni in Anchorage, AMBLM densities declined from 70% leaves mined in 2006, to 19% in 2011, and that parasitism of AMBLM larvae in mines by the two Lathrolestes species combined rose from 8% in 2006 to 32% in 2011. Here we conduct another post-release survey and find that the percentage of leaves mined has been reduced even further to 9%, and that parasitism rates by the Lathrolestes species have reached 70% in 2019. We then used DNA sequencing to determine the relative dominance of the two species of Lathrolestes by dissecting out individual parasitoid eggs or larvae from 249 parasitized AMBLM larvae collected in August 2019. In total, 207 parasitoid eggs or larvae were successfully sequenced and identified from 200 leafminer larvae, of which seven were supernumerary larvae in four host larvae. DNA sequencing indicated that of AMBLM larvae that were parasitized, 71% (n = 142) were parasitized by L. thomsoni, and 29% (n = 58) were parasitized by L. soperi. AMBLM now appears to be at non-pest densities at most sites in Anchorage, with the majority of biological control services provided by the introduced L. thomsoni.

Taxonomic identification and biological traits ofPlatystethynium triclavatum(Donev & Huber, 2002), comb. n. (Hymenoptera, Mymaridae), a newly recorded egg parasitoid of the Italian endemic pestBarbitistes vicetinus(Orthoptera, Tettigoniidae)

The little known fairyfly (Hymenoptera, Mymaridae),Platystethynium(Platystethynium)triclavatum(Donev & Huber, 2002), comb. n. fromPseudocleruchusDonev & Huber, 2002, is newly recorded as an egg parasitoid ofBarbitistes vicetinusGalvagni & Fontana, 1993 (Orthoptera, Tettigoniidae). This bush-cricket is endemic to northeastern Italy (mainly Euganean Hills of Veneto Region), where it has recently become an economically significant agricultural and forest pest. Data on discovery, distribution, and some remarkable biological traits of this gregarious egg parasitoid are presented. Its identification and availability of many well-preserved fresh specimens have made possible to re-definePseudocleruchusDonev & Huber, 2002 syn. n., with type and the only described speciesPseudocleruchus triclavatusDonev & Huber, 2002, as a synonym ofPlatystethyniumOgloblin, 1946 and its nominate subgenus,P. (Platystethynium), and also to describe the brachypterous male ofP. (Platystethynium)triclavatum. It is the first known male for the entire genus. Enlarged mandibles of the megacephalous males are used to chew holes in the hard chorion of the host egg, allowing fully winged females, whose mandibles are strongly reduced and do not cross over, to emerge after mating with the males inside it. Up to 136 individual parasitoids (about 77 on average) can hatch from a single egg ofB. vicetinus, with their sex ratio being strongly female biased (80–97% females per egg).

Partial bivoltinism in a gregarious endoparasitoid: larval diapause as influenced by season and sharing a host

AbstractThe yearly timing of the life cycle of a parasitoid is a key element of its life‐history strategy. I examine here factors influencing the expression of partial bivoltinism in Tetrastichus julis Walker (Hymenoptera: Eulophidae), a specialist parasitoid introduced to North America to attack its univoltine host, the cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae). The varying tendency was assessed of individuals of this gregarious larval parasitoid to either emerge as adults in the same summer they mature, or to enter diapause to emerge the following year. Parasitized hosts were obtained by rearing cereal leaf beetles collected as mature larvae from grain fields in northern Utah (western USA) throughout the growing seasons in 2013 and 2014. Cocoons spun by these beetles were held to determine patterns over the spring and summer in the tendency of the parasitoid to forgo larval diapause. A high percentage (nearly 90% in 2013) of parasitoid individuals were found to forgo diapause and emerge in the same summer from earliest maturing hosts. This percentage rapidly declined to 20% or less of individuals forgoing diapause and emerging from cocoons as the summer advanced. The percentage of parasitoid individuals forgoing diapause increased significantly at a given time of season (early or late) as the number of conspecifics with which an individual shared a host larva increased. These results may reflect a trade‐off for individual parasitoids in which greater success in finding – and ovipositing in – host larvae the following spring vs. in summer, is countered by reduced survivorship in diapausing over the winter vs. emerging in the same summer in which the parasitoid matures. Expression of partial bivoltinism of T. julis, as affected strongly by both season and within‐host density, results in high rates of parasitism of cereal leaf beetles both early and late in the season.

Tipe penggunaan lahan memengaruhi keanekaragaman dan komposisi hymenopteran parasitoid di Jambi

Hymenoptera merupakan salah satu dari empat ordo serangga terbesar di dunia yang salah satu perannya adalah sebagai musuh alami (parasitoid, predator). Konversi lahan dapat memengaruhi keanekaragaman dan komposisi hymenopteran parasitoid dan peran ekologisnya. Penelitian ini bertujuan untuk memelajari pengaruh tipe penggunaan lahan terhadap keanekaragaman dan komposisi dari hymenopteran parasitoid di Jambi. Penelitian diakukan pada berbagai tipe penggunaan lahan di lanskap Hutan Harapan dan Taman Nasional Bukit Duabelas (TNBD), Provinsi Jambi meliputi hutan, hutan karet, perkebunan kelapa sawit, dan perkebunan karet. Pengambilan sampel serangga dilakukan dari bulan Maret sampai September 2013, dengan teknik pengasapan (fogging). Sebanyak 14.258 individu hymenopteran parasitoid yang terdiri atas 30 famili diperoleh dari seluruh lokasi penelitian. Famili Encyrtidae, Bracondae, Aphelinidae, Eulophidae, Scelionidae, Ceraphronidae, dan Platigasteridae merupakan famili yang ditemukan dengan kelimpahan tinggi. Tipe penggunaan lahan kelapa sawit ditemukan memiliki komposisi parasitoid berbeda dibandingkan dengan tipe penggunaan lahan lainnya, sedangkan tipe penggunaan lahan hutan dan hutan karet memiliki komposisi spesies yang tinggi. Hasil penelitian ini menunjukkan bahwa tipe penggunaan lahan mempengaruhi keanekaragaman dan komposisi spesies hymenopteran parasitoid.

Biodiversity of the natural enemies of aphids (Hemiptera: Aphididae) in Northwest Turkey

In the present study, the natural enemies of aphids (Hemiptera: Aphididae) and their host plants including herbaceous plants, shrubs and trees were analysed to reveal their biodiversity and disclose tritrophic associations in different habitats of the South Marmara region of northwest Turkey. As a result of field surveys, 58 natural enemy species associated with 43 aphids on 58 different host plants were identified in the region between March of 2017 and November of 2018. In 173 tritrophic natural enemy-aphid-host plant interactions including association records new for Europe and Turkey, there were 21 representatives of the family Coccinellidae (Coleoptera), 14 of the family Syrphidae (Diptera) and 15 of the subfamily Aphidiinae (Hymenoptera), as well as eight other generalist natural enemies. In these interactions, a total of 37 aphid-natural enemy associations–including 19 associations of Acyrthosiphon pisum (Harris) with natural enemies, 16 associations of Therioaphis trifolii (Monell) with natural enemies and two associations of Aphis craccivora Koch with natural enemies–were detected on Medicago sativa L. during the sampling period. Similarly, 12 associations of Myzus cerasi (Fabricius) with natural enemies were revealed on Prunus avium (L.), along with five associations of Brevicoryne brassicae (Linnaeus) with natural enemies (including mostly parasitoid individuals) on Brassica oleracea L. Also in the study, reduviids of the species Zelus renardii (Kolenati) are reported for the first time as new potential aphid biocontrol agents in Turkey. The results of field surveys show that the natural enemies of aphids have high biodiversity, which should be considered in the management of biological pest control.

Phenotypic matching in ovipositor size in the parasitoid Galeopsomyia sp. (Hymenoptera, Eulophidae) attacking different gall inducers

ABSTRACT Parasitoid ovipositor size importantly affects host choice; those attacking exposed hosts usually have shorter ovipositors compared to those needing drilling deeper through substrates such as plant tissue and gall tissue. Most studies treat this theme at the interspecific level, and the aim of this work was to test for intraspecific variation and phenotypic matching in ovipositor size for Galeopsomyia sp. attacking galls. Galls were sampled from Guapira opposita(Nyctaginaceae), a host plant to five species of Bruggmannia gallers (Diptera, Cecidomyiidae) in southern Brazil: Bruggmannia elongata, B. robusta, B. acaudata, and two undescribed species of Bruggmannia (sp. 1 and sp. 2). On forest transects, all galls from the 30 first galled plants found were sampled and kept in sealed plastic bags until parasitoid emergence. A total of 15 samples were done along two years. We measured galler last instar larvae length and gall thickness for each galling species, and ovipositor length for all Galeopsomyia sp. individuals emerging from the galls. There were no differences in larval length among galler species. However, Bruggmannia sp. 1 and sp. 2 galls were significantly thicker than those of B. acaudata, and the latter thicker than both B. elongata and B. robusta galls. Wasp ovipositor size differed significantly between those coming from Bruggmannia sp. 1 and sp. 2 galls relative to all others. Host extended phenotype size is thus fundamental to determine parasitoid size, but in this case host (larval) size does not change among species, although gall thickness was different. Thicker galls were attacked by larger parasitoids with longer ovipositors, denoting phenotypic matching. Thicker galls appear to be selecting larger parasitoid individuals, which in the long run can lead to important evolutionary change as well.

WITHDRAWN

The document associated with this DOI has been withdrawn.

Keanekaragaman parasitoid dan predator kutu lak (Laccifer lacca Kerr) di KPH Probolinggo Perum Perhutani Unit II, Jawa Timur

Kutu lak (Laccifer lacca Kerr) (Homoptera: Kerriidae) merupakan serangga yang hidup secara parasitik pada tanaman inangnya. Serangga tersebut menghasilkan resin alami yang kompak dan tebal, yang menempel pada cabang tanaman tempat hidupnya yang biasa disebut lak. Lak cabang merupakan resin alami dari hasil sekresi serangga L. lacca berupa lapisan tebal lak yang membungkus ranting-ranting tanaman inang. Serangan parasitoid dan predator terhadap kutu lak berdampak langsung pada penurunan produktivitas lak. Penelitian ini bertujuan untuk mengidentifikasi parasitoid dan predator yang menyerang kutu lak, dan menghitung tingkat parasitisasi di BKPH Kabuaran dan Taman, KPH Probolinggo, Perum Perhutani Unit II Jawa Timur. Sampel lak cabang diambil dari BKPH Kabuaran dan Taman masing-masing sebanyak 200 sampel lak cabang. Masing-masing lak cabang dimasukkan ke dalam tabung reaksi. Pengamatan parasitoid yang keluar dari lak cabang dilakukan dalam tabung reaksi. Famili parasitoid yang dominan ditemukan, yaitu Aphelinidae, Encyrtidae, dan Eulophidae. Predator yang ditemukan pada kutu lak terdiri atas Famili Lathridiidae (Coleoptera), Cosmopterigidae, dan Noctuidae (Lepidoptera), Nabidae (Hemiptera), serta Chrysopidae (Neuroptera). Jumlah kumulatif parasitoid di lapangan lebih banyak (5.900 individu) dibandingkan dengan di gudang (5.263 individu). Pertambahan individu parasitoid tertinggi dari lapangan dan gudang terjadi pada pengamatan hari ke-7 sampai hari ke-17. Tingkat parasitisasi kutu lak di lapangan dan gudang tergolong tinggi dengan nilai rata-rata sebesar 93% dan 96%. Dapat disimpulkan bahwa kutu lak yang berasal dari lapangan maupun gudang mengalami serangan parasitoid yang sangat tinggi.

The composition of the egg-parasitoid guild of the golden egg bug, Phyllomorpha laciniata (Heteroptera: Coreidae), in Spain

The golden egg bug (Phyllomorpha laciniata (Villers)) is a phytophagous insect with an unusual reproductive system. Females use the bodies of conspecifics, both males and females, as oviposition substrates. In addition, a varying fraction of the eggs is laid on the food plant. Egg carrying on conspecifics increases offspring survival. Predators and, especially, hymenopteran parasitoids are themain cause of egg mortality. So far, only the wasp Gryon bolivari (Giard) (Hymenoptera: Scelionidae) has been reported as an egg parasitoid of P. laciniata in several Mediterranean populations. In this study, three new egg-parasitoid species are recorded from P. laciniata: the primary solitary parasitoids Gryon monspeliense (Picard) and Telenomus sp. (Hymenoptera: Scelionidae), and the facultative hyperparasitoid Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae). All of these parasitoids have been reared from host eggs being carried by conspecific bugs. We discuss the taxonomy and biology of the individual parasitoid species, as well as ecological and evolutionary aspects of the interactions in this host-parasitoid system.

Decaying Organic Matter Does Not Remove Sublethal Effects of Imidacloprid on Mating in Spalangia endius (Hymenoptera: Pteromalidae), a Parasitoid of Filth Flies.

Both the parasitoid wasp Spalangia endius Walker and the insecticide imidacloprid are used to control house flies. A recent study found that negative sublethal effects of imidacloprid on killing flies and on offspring production by this parasitoid wasp are eliminated when females have the opportunity to crawl through decaying matter. An enzyme-linked immunosorbent assay showed that the presence of decaying matter reduces the amount of pesticide on their bodies. This study examined whether this was also true for sublethal effects on mating. S. endius were exposed to a realistic concentration of imidacloprid that induces very low mortality. Then, individual parasitoids were allowed to burrow through decaying organic matter or not, followed by mating tests in the absence of decaying matter. Even after 24 h with the decaying matter, copulation for both males and females that had previously been exposed to imidacloprid was delayed compared with no-pesticide controls. Furthermore, for pesticide-exposed males, subsequently burrowing through media made copulation even more delayed than if they were not exposed to media. For pesticide-exposed females, subsequently burrowing through media neither increased or decreased the negative effect of the pesticide exposure. Together with other studies, these results reinforce that use of S. endius and use of imidacloprid are incompatible, even at much lower than recommended concentration, unless application is sufficiently separated in place and time.

Quantifying Temporal Variation in the Benefits of Aphid Honeydew for Biological Control of Alfalfa Weevil (Coleoptera: Curculionidae).

Sugar feeding by biological control agents, such as parasitoid wasps, may enhance their ability to control crop pests, although its importance is likely to vary greatly through space and time. Here we quantified temporal variation in the potential importance of sugar resources associated with honeydew secreted by the pea aphid (Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae)) in determining levels of parasitism of the alfalfa weevil (Hypera postica (Gyllenhal) (Coleoptera: Curculionidae)) by its dominant parasitoid, Bathyplectes curculionis (Thomson) (Hymenoptera: Ichneumonidae) across irrigated alfalfa fields in Montana, United States over 5 yr. A positive association between parasitism of H. postica and A. pisum densities at the across-site scale was observed in 2 of 5 yr, with parasitism increasing twofold to fourfold over gradients in A. pisum density. The relationship was strongest in the 2 yr of lowest parasitoid relative to host densities, when increases in per capita effects of individual parasitoids would be expected to be particularly important. Acyrthosiphon pisum densities were at their lowest in these same years, suggesting that they may generally be sufficiently abundant that parasitoids are not limited by sugars in most years. This conclusion is supported by results of anthrone tests which revealed a high level of sugar-fed parasitoids (>50%) in a year of high aphid abundance. More studies, such as this one, that explore the frequency with which increasing sugar resource availability actually enhances parasitism levels in the field will be critical to gauge the broader potential of sugar resource addition (e.g., through flowering strips, banker plants or sugar sprays) to bolster biological control.

No evidence of strong host resource segregation by phorid parasitoids of leaf-cutting ants

Resource segregation by species is a cornerstone ecological concept that may result from several processes such as interspecific competition, and can help structuring communities, in particular parasitoid communities. Phorid parasitoid flies that use ants as hosts usually employ one host per individual parasitoid, and thus the pressure for segregating the host resource should be high. At a particular community, these parasitoids might segregate resources by temporal differences in activity patterns, using different host species or nests from those available. Even if parasitoid species coexist on the same nest, they can take advantage of worker polymorphism and task division, searching for ants performing different tasks at different microsites of the same nest. Here we evaluated the segregation of parasitoid species in these hypothesized axes using leaf-cutting ant phorid parasitoids as a model system. We analyzed temporal data collected at two localities with contrasting host species richness; and compared parasitoid co-occurrence at the different niche axis. For most of the hypothesized niche axes tested we found either no departures from random expectations or significantly more niche overlap than expected by chance, ruling out the existence of biologically relevant host resource segregation in this system. However, there was evidence of segregation for some species, since one parasitoid species was only found in winter and another species showed a negative correlation of its abundance over nests with other two species. Furthermore, we found that several species were flexible in host use; Atta phorids varied in average host sizes preferred, whereas Acromyrmex phorids that were generalists were able to use different host species or microsites for host location. From an applied perspective, these results are encouraging when selecting species for the control of leaf-cutting ants because parasitoids coexistence seems to be unaffected by their overlap in niche dimensions.

A study on five sampling methods of parasitic hymenopterans in rice ecosystem

For insect diversity studies to be of value, the sampling methods employed must produce samples representative of the community or taxon selected for the investigation. However, as yet, few evaluations on the variability and effectiveness of sampling methods have been undertaken. The survey was carried out in the rice fields during 2015-16 in Paddy Breeding Station, Tamil Nadu Agricultural University, Coimbatore. From this study a total of 1,019 parasitoid individuals were collected. Among six different collection methods employed for sampling hymenopteran parasitoids in rice ecosystem, the yellow pan trap at ground level was found to be the most effective method in trapping the parasitoids (27.2 ± 2.56 parasitoids per day) followed by sweep net method (12.1 ± 1.03 parasitoids per day). The next best sampling method is yellow pan trap erected at canopy level which recorded a mean of 9.2 ± 2.26 parasitoids per day. The other three traps viz., malaise trap, suction trap and light trap were found to collect less number (<1.5) of parasitoids per day.