Eulophidae (hymenoptera) parasitoids of Phyllonorycter apparella and phyllonorycter populifoliella (Lepidoptera, Gracillariidae), pests of Populus tremula and populus nigra in Ul’yanovsk province, Russia

Parasitoid complexes of two species of the genus Phyllonorycter (Ph. apparella and Ph. populifoliella) reared from 2 plants (Populus tremula and P. nigra) were studied in Ul’yanovsk Province, Russia. Twenty species of parasitoids are new for Ph. apparella and 12 are new for Ph. populifoliella. Minotetrastichus frontalis and Pnigalio agraules are the dominant species for both parasitoid complexes. The highest relative abundance was observed for Ph. apparella on Populus tremula (75%) and for Ph. populifoliella on P. nigra (61%). The parasitoid complexes of Ph. apparella and Ph. populifoliella show high similarity (the Jaccard coefficient is 0.65).     

The Influence of Parasitoids (Hymenoptera,Eulophidae) on Survival of the Lime Leafminer <Emphasis Type="Italic">Phyllonorycter issikii</Emphasis> (Lepidoptera,Gracillariidae) in Udmurtia

The species structure of parasitoids (Hymenoptera, Eulophidae) of the invasive lime leafminer Phyllonorycter issikii (Kumata, 1963) (Lepidoptera, Gracillariidae) was reexamined ten years after the latest survey. The work was carried out in 2015 in three previously selected test plots within the city of Izhevsk. Extremely high survival rates (61.7 to 89%) of the leafminer were observed while the parasitoid complex had a negligible impact on its mortality (0.6 to 1.6%). A slight structural transformation of the parasitoid complex was noted, namely a decrease in the number of dominants and a change of the dominant species. In addition, the species structure of the parasitoids collected in 22 populated localities in Udmurtia was studied in 2016. Five new parasitoids of the lime leafminer were found: Pnigalio pectinicornis (Linnaeus, 1758), Sympiesis acalle Walker, 1848, Chrysocharis amanus Walker, 1839, Ch. pentheus Walker, 1839, and Ch. polyzo Walker, 1839. Two species of parasitoids of Ph. issikii were recognized as new to Udmurtia: Pnigalio agraules (Walker, 1839) and Pediobius saulius (Walker, 1839).     

Parasitoid complexes (Hymenoptera,Eulophidae) of leafminers of the genus <Emphasis Type="Italic">Phyllonorycter</Emphasis> (Lepidoptera,Gracillariidae) in the Middle Volga Basin

The parasitoid complexes of 22 species of the genus Phyllonorycter reared from 20 host plants were studied in the Middle Volga Basin. From a total of 124 host-parasitoid associations analyzed, 88 had been previously unknown. Minotetrastichus frontalis, Sympiesis sericeicornis, Pnigalio soemius, Closterocerus formosus, and S. gordius were the most frequent species. The highest percentage of parasitoids reared was observed in Ph. ulmifoliella (58.6%) and Ph. sylvella (54%), and the lowest one, in Ph. salictella (15%). Ph. corylifoliella (95.7%), Ph. populifoiella (95.5%) and Ph. insignitella (95.5%) had the highest mortality due to parasitoids. The number of endoparasitoid species prevailed over that of ectoparasitoids in the parasitoid complexes of the genus Phyllonorycter, but the number of individuals reared was 4 times greater for ectoparasitoids. The parasitoid complexes were the most similar in Ph. harrisella and Ph. quercifoliella on Quercus robur. The gregarious ectoparasitoid M. frontalis predominated over parasitoids of Phyllonorycter.     

The parasitoid complex (Hymenoptera, Eulophidae) of leafminer flies (Diptera, Agromyzidae) in the middle Volga Basin

Parasitoid complexes of fifteen species of Agromyzidae reared from 20 host plants were studied: Agromyza nana Meigen, Aulagromyza populi (Kalt.), Amauromyza sp. n. aff. insularis, Calycomyza humeralis (von Roser), Chromatomyia horticola (Goureau), Liriomyza eupatoriana Spencer, L. demeijerei Hering, L. dracunculi Hering, L. strigata (Meigen), L. soror Hendel, L. tanaceti de Meijere, L. taraxaci Hering, Ophiomyia quinta Spencer (recorded for the first time for the Palaearctic), Phytomyza petoei Hering, and Ph. griffithsi Spencer. A total of 38 host-parasitoid associations were analyzed, 31 of them were previously unrecorded. During this research, 17 Eulophidae parasitoid species (Cirrospilus viticola (Rondani), Chrysocharis pubicornis (Zetterstedt), Ch. viridis Nees, Ch. crassiscapus (Thomson), Closterocerus trifasciatus Westwood, Diglyphus crassinervis Erdös, D. chabrias (Walker), D. isaea Walker, D. poppoea Walker, D. pusztensis (Erdös, Novicky), Minotetrastichus frontalis (Nees), Neochrysocharis aratus (Walker), N. formosa (Westwood), Pnigalio pectinicornis (Linnaeus), P. soemius (Walker), Pediobius metallicus (Nees), and P. cassidae Erdös) were found. New parasitoids were recorded for Ch. horticola, A. nana, and Ph. petoei. The number of ectoparasitoid species was 1.25 times as great as that of endoparasitoids in the complexes, whereas the number of reared specimens of ectoparasitoids was 1.7 times as great as that of endoparasitoids. The dominant species of the parasitoid complexes of Agromyzidae were D. isaea (28.4%), Pediobius metallicus (14.5%), N. formosa (13.7%), and Pnigalio soemius (12.7%).     

A 3 year field survey of the natural enemies of the horse-chestnut leaf miner <Emphasis Type="Italic">Cameraria ohridella</Emphasis> in Lombardy,Italy

A survey to inventory the natural enemies of the horse-chestnut leafmining moth, Cameraria ohridella Deschka and Dimic (Lepidoptera, Gracillariidae) and to evaluate their relative abundance, was conducted from 2001 through 2003 in Lombardy, northern Italy. Two predators and 10 parasitoids were found during the 3-year survey. An increasing number of parasitoid species associated with the leafminer was detected (4 species in 2001, 5 in the 2002 and 10 in 2003). Eulophidae (Hymenoptera: Chalcidoidea) were most represented: Minotetrastichus frontalis Nees, Closterocerus trifasciatus Westwood, Pnigalio pectinicornis L., Pnigalio agraules Walker, Pediobius saulius Walker, Chrysocharis pentheus Walker, Cirrospilus talitzkii Bouek, Sympiesis sericeicornis Nees, Baryscapus nigroviolaceus (Nees). Only one Ichneumonidae (Hymenoptera: Ichneumonoidea) was found during 2003: Itoplectis alternans (Grav.).     

Ecological and morphological characteristics of endoparasitoids on Elcysma westwoodii (Vollenhoven) (Lepidoptera: Zygaenidae)

Six species of insect endoparasitoids were identified from Elcysma westwoodii, which is the most damaging lepidopteran pest of Prunus yedoensis. From Hymenoptera, two species were identified: a species in Braconidae and Charops striatus in Ichneumonidae. From Diptera, there were four species in Tachinidae: Compsilura concinnata, Exorista sp., Pales sp. and Tachinidae spp. The parasitic ratio was 4.86% (45 of 926 larvae). The hymenopterans were parasitic on 31 individuals of E. westwoodii (68.9%) and the dipterans were parasitic on 14 individuals (31.1%). It was found that parasitoids from the larvae of E. westwoodii were all either endoparasitoids or larval parasitoids. However, Exorista sp. of Tachinidae was found to be either a larval parasitoid or larval-pupal parasitoid. Additionally, all the identified parasitoids were solitary parasitoids, as only one parasite occurred in a larva of E. westwoodii. Because the larva of E. westwoodii eats and molts after it is parasitized, all the parasitoids were identified as koinobionts. There were no big differences in morphological characteristics and life histories between C. striatus and C. concinnata. However, for Exorista sp. and Pales sp., males took 3–5 days longer to emerge from their pupae and had remarkably longer body lengths than females.     

The parasitoid complex (Hymenoptera, Eulophidae) of the leafminer Phyllonorycter issikii (Kumata) (Lepidoptera, Gracillariidae) from the Middle Volga Basin

In the Middle Volga Basin, Phyllonorycter issikii, an invasive species new to Europe, is attacked by many native parasitoids of the family Eulophidae (the percentages of infestation are given in parentheses): Sympiesis gordius (42), Minotetrastichus frontalis (20), Chrysocharis laomedon (11), Pnigalio soemius (10), S. sericeicornis (8), Apanteles sp. (4), Hissopus geniculatus (4), Entedon sp. (0.4), Aprostocetus sp., Cirrospilus lyncus, C. diallus, C. viticola, and Pteromalidae (0.2). Six species of parasitoids: Aprostocetus sp., C. lyncus (Walker 1838), C. diallus (Walker 1838), C. viticola (Rondani 1877), H. geniculatus (Hartig 1838), and Apanteles sp. (Braconidae), are recorded for the first time. The number of ectoparasitoids is 5.5 times that of endoparasitoids. The second generation of Ph. issikii is reduced by 22% due to parasitoids, and its propagation rate also decreases. However, the climate warming may level the pressure of parasitoids and promote development of the third generation in Ph. issikii.     

Parasitoids of chickpea leafminer Liriomyza cicerina (Diptera: Agromyzidae) and their parasitism rate on chickpea fields in North Tunisia

In recent years, as a consequence of climatic changes, the leafminer Liriomyza cicerina had emerged as a serious pest in chickpea crops causing considerable damage in Tunisia. Thus, the search of control methods is necessary. The aim of this research was to monitor and identify the naturally occurring parasitoids of the chickpea leafminer Liriomyza cicerina in insecticide-free chickpea-growing areas located in North-Western Tunisia. Chickpea leaves with mines were weekly sampled from Beja and Kef sites during 2016 and 2017 and kept to observe and count emerging leafminer and parasitoid adults in the laboratory. Results revealed that L. cicerina parasitoids complex species included three hymenopteran parasitoids namely Opius monilicornis (Fisher, 1962) (Braconidae); Diglyphus isaea (Walker, 1838) (Eulophidae) and Diaulinopsis arenaria (Erdös, 1951) (Eulophidae). These parasitoids were identified and recorded for the first time in Tunisia on L. cicerina with parasitism rate varied between 13% and 52.5%. The most common species was O. monilicornis. The correlation between infestation rate on chickpea plants and number of emerged three parasitoids was calculated revealing high significant and positive correlations. The diversity index (H′) was also calculated. The three parasitoids were found in two sites Beja and Kef; while the diversity differed during the developmental stage of chickpea crops.     

Eulophid wasps (Hymenoptera, Eulophidae), parasitoids of leaf-mining moths (Lepidoptera: Gracillariidae, Nepticulidae, Tischeriidae) on the English oak in the Middle Volga Area

Data on the parasitoid eulophid complexes reared from 6 species of leaf mining moths damaging the oak in the Middle Volga Area are reported. The reared eulophids belong to three subfamilies: Eulophinae (8 species from 6 genera): Cirrospilus diallus Walker, C. viticola (Rondani), Euplectrus liparidis Ferrière, Hyssopus geniculatus (Hartig), Sympiesis gordius (Walker), Pnigalio rotundiventris (Erdös), P. soemius (Walker), Rhicnopelte crassicornis (Nees); Entedoninae (11 species from 4 genera): Chrysocharis laomedon (Walker), Ch. prodice (Walker), Ch. pubens Delucchi, Ch. submutica Graham, Closterocerus formosus Westwood, Neochrysocharis aratus (Walker), Pediobius cassidae Erdös, P. flaviscapus (Thomson), P. metallicus (Nees), P. pyrgo Walker; and Tetrastichinae (3 species from 3 genera): Aprostocetus sp., Minotetrastichus frontalis (Nees), and Sigmophora brevicornis (Panzer). The most abundant of the moth parasitoids are M. frontalis and Ch. laomedon, while Tischeria ekebladella has the greatest number of parasitoids. The ectoparasitoids/endoparasitoids ratio in the number of species is 2: 1, and in the number of individuals reared, 1.76: 1. Thus, the host density is regulated primarily by the ectoparasitoids.     

Quantitative food webs of lepidopteran leafminers and their parasitoids in a Japanese deciduous forest

Quantitative food webs were constructed to explore the community structure of leaf-mining moths in the family Gracillariidae and their parasitoid wasps in a deciduous forest in Hokkaido, Japan. A whole food web was constructed from data collected from June to October 2001. In the web, 16 leafminer species on seven tree species were attacked by 58 species of hymenopteran parasitoid; 376 links between leafminers and parasitoids were observed. Leafminers were specialist herbivores, but most parasitoids were generalists. Five webs were constructed for the seasonal prevalence of leafminers over the one-year period to reveal the temporal dynamics in community structure. Among the seasonal webs, the first web in June was distinctive because two tree species, Japanese umbrella tree Magnolia obovata and Japanese magnolia M. kobus, supported the community. Second to fourth webs from July to September were dominated by the leafminer species on Japanese oak Quercus crispula, and the fifth web was marked by that on Carpinus cordata. The extent of potential apparent competition among leafminers was evaluated using quantitative parasitoid overlap diagrams. These diagrams suggested that abundant host species are likely to have large indirect effects on less abundant species. Moreover, the potential for apparent competition between leafminer species inhabiting different host tree species can occur, although leafminers sharing the same tree species are prone to interact via shared parasitoids. In this system, particular leafminer species, acting as potential sources of apparent competition, can affect other species as sinks, and control whole-community dynamics. Directed apparent competition may potentially occur around oak trees.     

Laboratory rearing and biological parameters of the eulophid Pnigalio agraules,a parasitoid of Cameraria ohridella

Predators as well as parasitoids native to Europe accept the exotic horse chestnut leafminer, Cameraria ohridella Deschka and Dimi? 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.     

Indigenous parasitoids (Hym., Chalcidoidea) of Phyllocnistis citrella Stainton (Lep., Gracillariidae) in Jaguariúna, São Paulo State, Brazil: preliminary results

Abstract: The citrus leafminer, Phyllocnistis citrella Stainton, is native to Asia and was detected for the first time in Brazil in 1996. The objectives of this study were to conduct a survey of parasitoids attacking citrus leafminer in Jaguariúna, one of the citrus production regions of São Paulo State, Brazil, and to determine whether indigenous species were providing effective control of this pest species. The collections of new leaves were made weekly at citrus groves in Jaguariúna from October 1996 to October 1997. Of the six indigenous parasitoids which were found, Galeopsomyia fausta LaSalle was the most abundant parasitoid of P. citrella in this region, accounting for more than 90% of the specimens collected. Thus, this species is a serious candidate for biological control of the citrus leafminer in this region of Brazil. Other species collected were Horismenus sp., Cirrospilus 'sp. C', Elasmus sp., Eupelmus sp. and Conura (Ceratosmicra) sp. The mean percentage of parasitism was 39.28% (6.19−86.21%) in unsprayed orchards and 21.38% (1.33−56.63%) in orchards that were occasionally treated with fungicides, acaricides and insecticides Temik and Dipterex.     

Discovery of false coconut scale (Aspidiotus rigidus) and three of its primary parasitoids in Việt Nam,and likely species origins

The false coconut scale, Aspidiotus rigidus Reyne (Hemiptera: Diaspididae), is a serious pest of coconut in the Indonesian and Philippine archipelagos. Field surveys in Viêt Nam in 2015–2018 discovered A. rigidus (a new country record). Also found were three of its primary hymenopteran parasitoids: an unidentified ectoparasitic Aphytis species (Aphelinidae) and two endoparasitoids, Comperiella calauanica (Encyrtidae) and Pteroptrix parvipennis (Aphelinidae). Aphytis sp. was the commonest parasitoid; the average level of parasitism of A. rigidus found in six surveys was 46%, in immatures of both sexes and adult females. Comperiella calauanica was recorded in three surveys, with an average parasitism level of 54% in adult female A. rigidus. It was also found attacking Aspidiotus destructor Signoret. Pteroptrix parvipennis was recorded in 47% of second instar A. rigidus in one survey. In molecular phylogenies based on 28S and COI genes, Pteroptrix parvipennis grouped with species of Encarsia. Although A. rigidus occurs in the largest coconut-growing areas in Việt Nam, incidence of the scale is low, and no outbreaks have been recorded. Its parasitoids therefore have potential for use as biological control agents in areas where the scale is problematic. The low incidence of A. rigidus in Việt Nam and the presence of the three parasitoid species there suggests that the scale and these parasitoids originated in Indochina.     

Parasitism of different larval stages of Cameraria ohridella

About 20 species of parasitic Hymenoptera havebeen reported from the horse chestnutleafminer, Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae). Generally,parasitism is low compared to other closelyrelated leafminers and the parasitism levelvaries considerably. Among other reasons,parasitism rates depend on the developmentalstage of the moth and therefore vary with thesampling date. In the current study,investigations on the parasitism of the moth'sfirst generation were carried out in order todetermine which preimaginal stages areparasitized by the most abundant parasiticwasps. Minotetrastichus frontalis (Nees),Pnigalio agraules (Walker) and Chrysocharis nephereus (Walker) (allHymenoptera: Eulophidae) developed as larval orpupal parasitoids and preferred later larvalinstars of the moth. Egg parasitism did notoccur. Overall, the last two of the six larvalinstars (the spinning instars) of the leafminersuffered the heaviest attack. In concordancewith the fairly low parasitism rates, theeffect of the four most abundant chalcidoids onthe leafminer population was negligible, havingno significant influence on the mortality ofC. ohridella. Although the speciescomposition of the parasitoid complex of C. ohridella shows similarities with thesituation found in other closely relatedleafmining moths, it is unlikely that thenaturally occurring chalcidoids will be able toprevent the horse chestnut leafminer fromdeveloping epidemic population densities in thenear future.     

The Distributions of Parasitoids (Hymenoptera) of Anastrepha Fruit Flies (Diptera: Tephritidae) along an Altitudinal Gradient in Veracruz, Mexico

In the state of Veracruz, Mexico, fruits from 38 sites at various altitudes were collected monthly over a period of 2 years, and the tephritid fruit flies of the genus Anastrepha and associated parasitoids that emerged from these fruits were identified and counted. Of the 26 species of fruits that contained Anastrepha larvae, 18 species also contained a total of 10 species of Anastrepha parasitoids. These consisted of 4 native and 1 exotic species of opiine braconid larval–pupal parasitoids, 2 native species of eucoilid larval–pupal parasitoids, 1 exotic species of eulophid larval–pupal parasitoid, 1 exotic species of pteromalid pupal parasitoid, and 1 native species of diapriid pupal parasitoid. Overall parasitism (including flies from fruit species that bore no parasitoids) was 6% and was greatest, 16%, at 600–800 m in altitude. The relative contributions of individual parasitoid species to overall parasitism were frequently influenced by both the altitude (and correlated changes in temperature and precipitation) and the species of plant in which the Anastrepha larvae were found. This was particularly the case among the more abundant and widespread Braconidae. To distinguish the role of altitude from that of the distributions of the host plants, these braconids were examined in 4 individual species of fruit that grew over a broad range of altitudes. In guava (Psidium guajava L.) and “jobo” (Spondias mombin L.) the parasitoid Doryctobracon areolatus (Szepligeti) was relatively more common at low altitudes. Its congener, Doryctobracon crawfordi (Viereck), was relatively more abundant at high altitudes in sour orange (Citrus aurantium L.). Utetes anastrephae (Viereck) became relatively more common at higher altitudes in S. mombin, whereas Diachasmimorpha longicaudata (Ashmead) tended to become relatively rare at the highest altitudes in C. aurantium, but increased at high altitudes in P. guajava compared to other braconids. Different altitudinal patterns of abundance in different fruits suggests the importance of both biotic and abiotic factors in parasitoid distributions. We discuss the effect of an expanding agricultural frontier on parasitoid abundance and relate our findings to the design of a fruit fly biological control program that tailors mass releases to parasitoid climate preferences.     

Native parasitoids and their potential to control the invasive leafminer, Cameraria ohridella DESCH. & DIM. (Lep.: Gracillariidae)

In spite of the fact that since the end of the eighties, the horse chestnut leafminer, Cameraria ohridella, has established itself throughout Europe, native predators such as ants and birds are not attuned to this neozoic species. In contrast, several parasitic wasp species already started to exploit the invasive horse chestnut leafminer, but until now parasitation rates are quite low, mainly because of asynchrony in the lifecycles of parasitoids and host. Only the removal of leaf litter, in which pupae hibernate, is at the moment a strategy to reduce the infestation level in the next year. Unfortunately, not only hibernating horse chestnut leafminers but also parasitoids are removed, and important resources for biocontrol are unused. In the current study, we investigated the potential efficiency of the horse chestnut leafminer parasitoid complex extracted from leaf litter in defined environments. Parasitoids were released at different densities to investigate density dependence in parasitation rates.Although seven different species were released in our experiments, only Pnigalio agraules turned out to be responsible for biocontrol of C. ohridella. We recorded parasitation rates of up to 35%. Overall, parasitation rates were independent of the leafminer density but increased fourfold if ten times more parasitoid individuals were released. Unfortunately, none of the parasitoid species could be established in the experimental units in the long run. Results are compared to other parasitoid-leafminer systems, and promotion of horse chestnut leafminer parasitoids to support natural selection and biological control of the horse chestnut leafminer is discussed.     

The relationship between variable host grouping and functional responses among parasitoids of Antispila nysaefoliella (Lepidoptera: Heliozelidae)

Our study investigated the importance of variability in the parasitoid community as a source of selection on host group size using a field population of the tupelo leafminer, Antispila nysaefoliella Clemens, which specializes on tupelo, Nyssa sylvatica Marsh. Larvae were collected from leaves with variable numbers of larvae and screened for parasitism using polymerase chain reaction of mitochondrial cytochrome oxidase I using markers designed specifically for amplifying parasitoid DNA while excluding host DNA. This method of selective PCR was effective for detecting the presence and identifying species of immature stages of three hymenopteran superfamilies: Chalcidoidea, Ichneumonoidea and Platygastroidea, which represented 83.4%, 16.0% and 0.6% of the total detectable parasitism, respectively. Our resulting sequences were then calibrated with sequences from identified adult parasitoids that had been either reared or field‐captured. A cluster analysis revealed 10 distinct clades that showed differences in attack patterns with respect to host traits and season. Total parasitism followed an inverse density‐dependent or density‐independent pattern with respect to host density (number per leaf). However, when parasitoid taxa were considered separately, one clade, which could be a cryptic species of Pnigalio maculipes Crawford (Chalcidoidea: Eulophidae), was found to increase its per leaf attack rate with host density. Our results suggest that parasitoid community composition and differences among species in their attack strategies can play a large role in determining the adaptive advantage of host grouping.     

Food web structure of aphids and their parasitoids in Belgian fruit agroecosystems

Community structures of aphids and their parasitoids were studied in fruit crop habitats of eastern Belgium in 2014 and 2015. Quantitative food webs of these insects were constructed separately for each year, and divided into subwebs on three host‐plant categories, fruit crop plants, non‐crop woody and shrub plants and non‐crop herbaceous plants. The webs were analyzed using the standard food web statistics designed for binary data. During the whole study period, 78 plant species were recorded as host plants of 71 aphid species, from which 48 parasitoid species emerged. The community structure, aphid / parasitoid species‐richness ratio and trophic link number varied between the two years, whereas the realized connectance between parasitoids and aphids was relatively constant. A new plant–aphid–parasitoid association for Europe was recorded. Dominant parasitoid species in the study sites were Ephedrus persicae, Binodoxys angelicae and Praon volucre: the first species was frequently observed on non‐crop trees and shrubs, but the other two on non‐crop herbaceous plants. The potential influence, through indirect interactions, of parasitoids on aphid communities was assessed with quantitative parasitoid‐overlap diagrams. Symmetrical links were uncommon, and abundant aphid species seemed to have large indirect effects on less abundant species. These results show that trophic indirect interactions through parasitoids may govern aphid populations in fruit crop habitats with various non‐crop plants, implying the importance for landscape management and biological control of aphid pests in fruit agroecosystems.     

Effects of parasitoid community structure upon the population dynamics of the honeysuckle leafminer,Chromatomyia suikazurae (Diptera: Agromyzidae)

Population dynamics of a leafminer,Chromatomyia suikazurae (Agromyzidae, Diptera) and its parasitoid community were studied for ten years at seven natural populations along an altitudinal gradient in Japan. This species which mines leaves of a forest shrub,Lonicera gracilipes (Caprifoliaceae), was attacked by 25 hymenopterous parasitoid species. Annually, the parasitoid community structure varied less within a population than among populations. The seven parasitoid communities were clustered into three groups corresponding to the altitudinal gradient: (a) lowland communities dominated by late-attacking, generalist pupal idiobiont eulophids and with highest species diversity, (b) hillside communities dominated by an early-attacking, specialist larval-pupal koinobiont braconid and (c) highland communities dominated by an early-attacking, generalist larval idiobiont eulophid. Annual changes of the host larval densities among the local populations were largely synchronous rather than cyclic. Among these populations, host density levels and mortality patterns greatly varied. By analyzing these inter-populational differences of host mortality patterns, the following conclusions were drawn: (1) The host mortality patterns were determined by the host utilization patterns of the locally dominant species. (2) The host pupal mortality but not larval mortality was related to species diversity but not to species richness itself of each parasitoid community. (3) Density dependence was detected only in pupal mortality at a lowland population dominated by late-attacking pupal parasitoids. These results suggest that interspecific interactions of parasitoids add additive effects to host population dynamics dissimilarly among local populations with different parasitoid communities.