Some British species of Anagrus (Hymenoptera: Mymaridae)

Five species of Anagrus , egg parasites of various leafhopper species (Delphacidae and Cicadellidae, Honioptera), were bred for 3–13 generations in laboratory conditions. Biological and niorphological characteristics as well as attempts at crossbreeding were used to recognise the species Anagrus ensijer Debauche and four new. species. A. ensifer occurred in two varieties. The four new species and the two varieties of A. ensifer are described, and a key is given to both sexes.     

Influence of flowering cover crops on Anagrus parasitoids (Hymenoptera: Mymaridae) and Erythroneura leafhoppers (Homoptera: Cicadellidae) in New York vineyards

Abstract 1 We tested the hypothesis that providing nectar‐producing cover crops will enhance the biological control of grape leafhoppers (Erythroneura spp.) by Anagrus wasps in commercial vineyards in New York, U.S.A. 2 We established three cover crops between vine rows in a commercial vineyard: buckwheat (Fagopyrum esculentum (Moench)), clover (Trifolium repens L.) and mowed sod (Dactylis glomerata L.). 3 There was no effect of cover crop on adult Anagrus in 1996, whereas in 1997 adults were more abundant within edge vines with buckwheat compared to vines with clover or sod; adults were more abundant at the vineyard edge, especially early in the season. 4 Parasitism of ‘sentinel’ leafhopper eggs was higher on vines with buckwheat compared to parasitism on vines with clover or sod in 1996; a similar, non‐significant trend, was observed in 1997. 5 Neither the abundance nor the distribution of leafhoppers was influenced by cover crops, although in 1997 there was a trend toward greater numbers of nymphs on edge vines with buckwheat. 6 In a cage experiment, parasitism by Anagrus of leafhopper eggs on grapes was greater when adults had access to flowering buckwheat rather than buckwheat without flowers. 7 In a laboratory study, longevity of female Anagrus was increased when provided with honey or sugar water compared to water only or nothing. 8 Our results suggest that parasitism of grape leafhoppers by Anagrus may be enhanced by providing floral resources within vineyards in New York, although it is unclear whether this will produce meaningful reductions in pest abundance.     

Incidence of Anagrus obscurus (Hymenoptera: Mymaridae) egg parasitism on Calopteryx haemorrhoidalis and Platycnemis pennipes (Odonata: Calopterygidae: Platycnemididae) in Italy

Very little is known about the incidence of egg parasitoids in odonates, perhaps because Odonata eggs are well protected by stems or leaves, sometimes below water. In Central Italy (Pontecorvo, Frosinone Province) two damselflies, Calopteryx haemorrhoidalis and Platycnemis pennipes, occur in high densities. In August 2007 we collected 30 stems of the aquatic plant Potamogeton sp. used as substrate for oviposition and incubated eggs in the laboratory. Most stems (24 for C. haemorrhoidalis and 23 for P. pennipes) contained Odonata eggs. Parasitoids emerged from 12 stems, with a mean parasitism of 2% for C. haemorrhoidalis and 6% for P. pennipes, and a maximum of 14% and 50%, respectively. Furthermore, we observed egg‐laying of 19 females of C. haemorrhoidalis and 11 of P. pennipes, and marked the stems where oviposition was observed. Clutches remained in the river for five days and were then collected and incubated. Parasitoids emerged from 11 of 30 stems, with an average parasitism of 8% for C. haemorrhoidalis and 3% for P. pennipes (maximums of 50% and 29%, respectively). All parasitoids belonged to the family Mymaridae, and were identified as Anagrus (Anagrus) obscurus Förster, 1861, sensu Soyka, 1955 . This is the first time that this species is described as an egg parasitoid of odonates, and that the egg parasitoid of C. haemorrhoidalis and P. pennipes is identified. Our data suggest that egg parasitism might be a significant selective factor for both odonates in the studied locality, affecting female oviposition behavior.     

Functional response and mutual interference of Peristenus spretus (Hymenoptera: Braconidae), a parasitoid of Apolygus lucorum (Heteroptera: Miridae)

Peristenus spretus Chen & van Achterberg (Hymenoptera: Braconidae) is a solitary endoparasitoid, which is considered for augmentative biological control of Apolygus lucorum Meyer-Dür (Heteroptera: Miridae) in Chinese cotton fields. Since the association of P. spretus with A. lucorum was only recently discovered, the biology of the parasitoid remains unknown. In order to understand its reproductive biology, the mutual interference and functional response of P. spretus were investigated by altering either the parasitoid or the host density while keeping the other constant. In both experiments, the effects of parasitoid and host densities on parasitism, superparasitism, progeny production and sex ratio were assessed. P. spretus exhibited a Holling type II functional response to changing host densities, indicating that parasitism increases with increasing host density until the parasitoid reaches its maximum reproductive capacity. The model suggested that a single P. spretus female could parasitise a maximum of 88 nymphs per day or four nymphs per hour. Increasing the wasp-nymph ratio from 1:10 to 1:80 significantly increased the offspring production more than fivefold from ±5.8 to ±35.6; further increasing the host densities (above 80 nymphs) did not significantly increase offspring production. Strong mutual interference of foraging P. spretus females occurred only at high parasitoid densities. Parasitoids foraging alone produced an average progeny of 33.4, whereas parasitoids foraging in groups of 16 produced only 2.6. The optimal wasp-nymph ratio for mass-rearing P. spretus is 4:100, given that resources of parasitoids and nymphs are unlimited.     

Occurrence of different development time patterns induced by photoperiod in Anagrus atomus (Hymenoptera: Mymaridae), an egg parasitoid of Empoasca vitis (Homoptera: Cicadellidae)

The wasp Anagrus atomus L. parasitizes eggs of the cicadellid Empoasca vitis (Göthe) on grapevines during the vegetative season. In vineyards, abundant parasitoid emergence occurs in the autumn as a result of a developmental delay in part of the A. atomus population. In this context, physiological times required by the parasitoid to develop in E. vitis eggs are recorded during the summer. In early summer, all individuals develop fully, with physiological times in agreement with those reported in the literature. From early August onwards, an increasing proportion of parasitoids show a delay in development involving pre‐imaginal stages. Under transmission microscopy, larvae of A. atomus inside the eggs of E. vitis can be clearly differentiated as ‘light’ and ‘dark’ types, which are associated with normal and delayed development, respectively. The decreasing photoperiod as autumn approaches appears to promote the retardation of growth. This phenomenon can be considered a typical case of risk spreading because, when the availability of E. vitis eggs in vineyards is high (i.e. in early summer), A. atomus shows (i) only a normal developmental pattern that allows a faster population increase, whereas (ii) when E. vitis egg availability begins to be scarce (i.e. from mid summer), an increasing proportion of individuals having delayed development provides better fitness because it allows the parasitoid to synchronize its life history with leafhopper species that lay overwintering eggs on plants other than grapevines.     

Long-distance dispersal by a parasitoid (Anagrus delicatus,Mymaridae) and its host

Summary We demonstrate that an egg parasitoid, Anagrus delicatus (Mymaridae, Hymenoptera) and its host, Prokelesia marginata (Delphacidae, Homoptera) regularly disperse 1 km or more in a north Florida saltmarsh. Anagrus delicatus were caught on yellow sticky traps on offshore islets and oyster bars throughout the spring, summer, and fall, whereas P. marginata were caught during one pulse in the spring. Parasitism rates were higher on offshore islets than at mainland sites, even though egg densities were higher at the mainland sites. The majority of parasitoids caught offshore were females. Long-distance dispersal by A. delicatus may be a cause of inverse density-dependent or density-independent spatial patterns of parasitism and may represent a risk-spreading strategy.     

Interpopulation variation of hibernal-aestival-diapause in the egg parasitoid wasp Anagrus takeyanus: adaptation to seasonal host-plant alternation of the tingid host, Stephanitis takeyai

The egg parasitoid wasp, Anagrus takeyanus Gordh & Dunbar (Hymenoptera: Mymaridae), is one of the few natural enemies of the andromeda lace bug, Stephanitis takeyai Drake & Maa (Heteroptera: Tingidae). Studying this wasp in two habitats, I found that at Kyoto, where the bug alternates its host plants seasonally, most wasp individuals in the overwintering eggs of the bug entered summer diapause immediately after winter diapause. However, at Nara, where the bug does not alternate its host plant, the wasp proved to have no summer diapause. Changes in the parasitization rate between generations differed at the two study sites. In Kyoto, the overwintered generation suffered the highest parasitism among the three generations of the year. In contrast, the first and second generations suffered higher parasitization rates in Nara. This difference in level of parasitization between the two study sites corresponded to the different diapause regime of the wasp and the seasonal population trends of the lace bug. Laboratory experiments showed that short photoperiod in combination with low temperature could terminate the long diapause at the time the non-aestivating individuals terminate winter diapause. As a life cycle without host plant alternation is likely to be an ancestral character of the bug, the aestivation of the wasp is thought to have been appended to overwintering as an adaptation to the evolution of seasonal host plant alternation in the lace bug.     

应用巢式PCR-DGGE技术分析稻虱缨小蜂体内Wolbachia的多样性

以采集自中国杭州和菲律宾的稻虱缨小蜂Anagrus nilaparvatae为研究对象,采用巢式PCR扩增Wolbachia的16S rDNA和wsp基因片段,并用DGGE分析稻虱缨小蜂体内Wolbachia的多样性.基于16S rDNA基因的分析结果准确地检测到稻虱缨小蜂体内细菌主要是Acinetobacter sp...     

Local augmentation efficiency of Anaphes nitens (Hymenoptera,Mymaridae), the egg parasitoid of Gonipterus platensis (Coleoptera,Curculionidae)

The efficiency of local augmentation releases of the egg parasitoid Anaphes nitens to control the Eucalyptus snout‐beetle Gonipterus platensis was tested in Eucalyptus globulus plantations in Galicia (NW Spain). On May–June 2006, at two localities of Pontevedra province, the release of host egg capsules parasitized by A. nitens at a potential rate of 300 adults/ha was compared with a release density of 900 adults/ha, and a control group of eucalypts not subjected to augmentation. Parasitism rate after 1–2 weeks did not significantly increase over the control plots at both localities. The high release rate did not ensure a higher crop protection and therefore could be not economically justified. On March–April 2017, at four localities of Pontevedra province, the test was replicated by releasing 300 parasitoids/ha. Parasitism level did significantly increase over the control just in one locality. Augmentation of A. nitens at small scale generally failed to achieve a higher protection from the pest, possibly due to the large extension of the E. globulus plantations, the magnitude of the G. platensis population and the fluctuations of the established parasitoid population, whose density is in turn affected by host egg availability and density‐dependent dispersal.     

Egg-laying experience and acceptance of parasitized hosts by the parasitoid,Leptopilina heterotoma (Hymenoptera: Eucoilidae)

The influence of egg-laying experience on the response of females of the eucoilid parasitoid,Leptopilina heterotoma, to parasitized and unparasitizedDrosophila melanogaster host larvae was examined under more controlled conditions than those used in past studies. In laboratory assays, we precisely manipulated both the number of eggs laid by females and the kind of larvae (parasitized versus unparasitized) in which the eggs were laid. We found that the tendency to avoid laying eggs in parasitized hosts depended markedly on whether or not eggs had been laid previously, but depended little on whether those eggs had been laid in parasitized or unparasitized hosts. The observed effect of general egg-laying experience on avoidance of parasitized hosts may reflect responses to either changes in the wasp's internal state (perhaps, changes in egg load) or changes in the wasp's neural representation of the external environment (such as those presumed to occur during learning). In light of these results, we offer a tentative reinterpretation of several earlier studies.     

Density-dependent parasitism of Delphacodes kuscheli eggs by Anagrus flaveolus: Influence of egg patchiness and density

Many herbivorous insects display a marked tendency to aggregate and previous work has shown that the parasitoids likely to be more effective for pest control programs are those that concentrate their attacks on denser host patches. However, as herbivore density changes different spatial patterns usually emerge in their distribution. In Tucumán province, Argentina the mymarid Anagrus flaveolus is a native egg parasitoid of Delphacodes kuscheli, which oviposits endophitic eggs and is the only demonstrated vector of the MRCV virus that seriously affects maize (Zea mays). Winter is the critical period for maize colonization from oat (Avena sativa) crops where D. kuscheli overwinters. We analyzed, under field conditions and during the winter critical period, percentage parasitism by A. flaveolus when host patch density increases following two different patterns: an increase in the batch size, and an increase in the number of infested plants with similar mean batch size. In order to generate a heterogeneous egg patchiness, 144 oat plants were arranged in 36 groups of four plants each, and four types of groups were created by placing one, two, three or four infested plants per group. Each group was characterized by the number of infested plants as well as by the number of eggs. If one, two, three or all four plants were infested, the group was denominated G1, G2, G3 or G4, respectively. Considering only G1, the number of eggs per group increased only if the batch size increased. On the other hand, considering all G1, G2, G3 and G4 groups, the increase in patch density from G1 to G4, was essentially due to an increase in the number of infested plants. The groups were symmetrically distributed in the field in a homogeneous 200-m² area (the position of each group was randomly assigned), and allowed for oviposition for 48 h since A. flaveolus only attacks eggs that have three or less days of development. We found that almost all infected plants were parasitized by A. flaveolus but parasitism never surpassed 64% of the available eggs, suggesting that the parasitoid selectively attacks eggs inserted in particular places of the oat plant, and/or never saturates a batch. We also found that parasitism was spatially direct density dependent when only G1 was considered, as well as when G1, G2, G3 and G4 were considered together. In the first case, an increase in the number of eggs in a group of four plants represents an increase in the batch size, and higher batch size received higher parasitism. In the second case, it represents an increase in the number of infested plants, and higher patch density received higher parasitism. Although the proportion of infected plants parasitized was similar, infected plants with similar number of eggs received higher parasitism when placed in denser groups (G3 and G4) than when placed in the less dense groups (G1 and G2). Behavioral mechanisms leading to a restriction on re-dispersal, like an area-restricted search behavior, as well as supernormal stimulus of contiguous host egg batches in certain places that may require a higher threshold before mutual interference has an effect, could be explained these results.     

Identification of egg parasitoids of rice leafhoppers and planthoppers (Hemiptera: Cicadellidae and Delphacidae) of economic importance in Taiwan,part 1: Mymaridae (Hymenoptera)

Fairyfly egg parasitoids (Hymenoptera: Mymaridae) of rice leafhoppers and planthoppers (Hemiptera: Cicadellidae and Delphacidae) known from Taiwan are identified taxonomically, keyed, and illustrated. Their host associations are determined by rearings using sentinel eggs of mainly four key pest species. The previously published records of such egg parasitoids in Taiwan are critically analyzed in the unfortunate absence of almost any voucher specimens. Three species of Mymaridae are shown to be the predominant egg parasitoids of one leafhopper and three planthopper major pests of rice in Taiwan: Anagrus (Anagrus) incarnatus Haliday of the green rice leafhopper Nephotettix cincticeps (Uhler) and the delphacids Laodelphax striatella (Fallén) (small brown planthopper), Nilaparvata lugens (Stål) (brown planthopper), and Sogatella furcifera (Horváth) (whitebacked planthopper), as well as Gonatocerus aegyptiacus Soyka and Mymar taprobanicum Ward of N. cincticeps. The zig-zag leafhopper Maiestas dorsalis (Motschulsky), which is also common in paddy fields, is newly recorded as a host for A. incarnatus, G. aegyptiacus, Lymaenon litoralis (Haliday), and M. taprobanicum. Additional new records of some other Mymaridae in Taiwan, mostly from the rice field agroecosystems, are indicated. Litus assamensis Rehmat and Anis, syn. nov. from India, is synonymized with L. sutil Triapitsyn and Berezovskiy from Thailand, which is also newly recorded from Taiwan.     

An integrative approach to species discrimination in the Anagrus atomus group sensu stricto (Hymenoptera: Mymaridae), with a description of a new species

Egg parasitoids of the genus Anagrus Haliday (Hymenoptera: Mymaridae) are natural enemies of many pests around the world. We used an integrative approach to characterize some species belonging to the Anagrus atomus group, using specimens reared from leafhoppers infesting some Lamiaceae. Starting from morphological identifications based on available keys, we carried out a multi-locus genetic characterization using phylogenetic and species delimitation analyses, and integrated it with biological and morphometric evidence. This approach revealed the existence of a new species, A. nepetellae sp. nov., here described along with its phenological traits. The approach also allowed us to characterize the expected taxonomic stability of other putative species within the group. We propose two new species groups called the atomus group sensu stricto and the vilis group, with the goal of streamlining the taxonomy of the atomus group. We also present a key for the identification of females of the European species of the atomus group sensu stricto. Some specimens show heterozygosity in 28S-D2 sequences, suggesting hybridization between A. atomus and A. nepetellae, which, if it is common between other species as well, could partly explain the taxonomic problems in the genus Anagrus. DNA sequencing of specimens reared by the same biofactory at different times suggests involuntary contamination leading to the displacement of a laboratory strain of A. atomus by A. nepetellae, which may have resulted from undetected partial reproductive compatibility.http://zoobank.org/urn:lsid:zoobank.org:pub:DFCD7654-5AA5-4E4F-AE48-24377BAACEFE     

Host-searching behavior ofVenturia canescens (Grav.) (Hymenoptera: Ichneumonidae): Superparasitism

The foraging behavior ofVenturia canescens, a solitary endoparasitoid of lepidopteran larvae, was investigated in the laboratory. FemaleVenturia canescens with a larger number of mature eggs to lay were found to have higher levels of superparasitism (measured as numbers of eggs laid per parasitized host). Increased parasitoid density was found to result in reduced levels of superparasitism by host-deprived (i.e.,undepleted) wasps. Females which had been allowed access to hosts before the experiment (depleted wasps) laid fewer eggs per parasitized host than undepleted wasps, although there was no significant difference in the levels of superparasitism among the depletion periods of 1, 2, 5, and 7 h. It was also found that an egg which was encountered less than 15 min after oviposition was much less likely to be avoided than one which was encountered after more than 15 min had elapsed.     

Comparison of oviposition behavior of a solitary and a gregarious parasitoid (Hymenoptera: Mymaridae)

Anaphes victus Huber andAnaphes listronoti Huber (Hymenoptera: Mymaridae) are respectively solitary and gregarious egg parasitoids of the carrot weevil,Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae). We made detailed ethograms of the oviposition behavior on unparasitized and parasitized hosts for the two species. We then compared the behavior of virgin and mated females for the oviposition of male and female progenies. The two species did not always oviposit after insertion of the ovipositor, but these punctures without oviposition could be readily differentiated from oviposition.A. victus oviposited only once by puncture, whileA. listronoti deposited one to three eggs during the same sequence. The variability of the duration of the various components was generally lower for a given female than between females. Two components, the abdominal vibrations and the pause, were significantly shorter in ovipositions that resulted in male progency for the two species. However, an important overlap in duration prevents using these differences to sex the progeny at oviposition. Virgin females of both species, although capable of producing only males, exhibited both behaviors. Parasitized hosts were recognized through internal and external markings that were used in host discrimination.     

Adaptive self- and conspecific superparasitism in the solitary parasitoid Leptopilina heterotoma (Hymenoptera: Eucoilidae)

One of the foraging decisions facing parasitoids is whetherto accept (superparasitize) or reject hosts that have alreadybeen parasitized. An important distinction is whether the hosthas been parasitized by the female parasitoid herself or bya conspecific. In solitary parasitoids, the pay-off from anegg laid in the latter host type (conspecific superparasitism)is the probability that the second egg wins the competitionfor the host and results in an offspring. The pay-off from anegg laid in the former type (self-superparasitism) increaseswith an increasing probability that another female will superparasitizethe host in the near future. When this probability equals one,self-superparasitism and conspecific superparasitism have thesame payoff. However, conspecific superparasitism will generallyhave a higher pay-off than self-superparasitism. It will thereforebe beneficial for a female parasitoid to be able to distinguishbetween a host she parasitized and one parasitized by a conspecific.The degree of benefit depends on the probability of conspecificsuperparasitism in the near future. Using an optimal diet model,I show that when a parasitoid encounters a patch containinga mixture of unparasitized and already-parasitized hosts, afemale that can distinguish between the two types of parasitizedhosts gains more offspring than a female without this ability.However, when parasitoids search a patch together with conspecifics,it is adaptive to self-superparasitize, and the pay-off fromthis ability may be negligible. It is therefore predicted thatwhen a female parasitoid searches a partially depleted patchalone, it will reject the hosts parasitized by itself more frequentlythan hosts parasitized by conspecifics. In contrast, femaleparasitoids searching together are predicted to accept hoststhat they parasitized themselves much more often. The resultsshow that the solitary parasitoid Leptopilina heterotoma (Hymenoptera:Eucoilidae) is able to distinguish between hosts that it parasitizedand hosts parasitized by conspecifics. The predictions of themodel are met in a second experiment that shows that L. heterotomaself-superparasitizes when the probability of conspecific superparasitismis high.     

Egg load and adaptive superparasitism in Anaphes nitens, an egg parasitoid of the Eucalyptus snout-beetle Gonipterus scutellatus

We studied egg production and the occurrence of adaptive superparasitism in Anaphes nitens, an egg parasitoid of the Eucalyptus snout beetle Gonipterus scutellatus. First, we determined whether A. nitens females were synovigenic or pro‐ovigenic. Newly emerged females were allowed to lay eggs alone during 3 days on six fresh egg capsules. A first group of females (n = 25) were killed by freezing and the remaining females (n = 21) were maintained during two extra days with food, but without hosts. Their fecundity was measured by dissection of host eggs and females’ ovarioles. We found that the second group of females increased their fecundity by about 20%, suggesting they were weakly synovigenic. To test for the occurrence of adaptive superparasitism in relation to competitors’ density, we compared the oviposition behaviour of females kept alone, in pairs, or in groups of four during patch visit. Results indicated that the females superparasited significantly more often in this last treatment. Synovigeny and the ability to modulate the use of superparasitism could be mentioned as important attributes that allow A. nitens to efficiently control the pest population.     

Biology of Anagrus atomus (Hymenoptera: Mymaridae), an egg parasitoid of the grape leafhopper Arboridia kermanshah (Homoptera: Cicadellidae)

Biology, morphology and oviposition behavior of Anagrus atomus (Linnaeus), an egg parasitoid of the grape leafhopper Arboridia kermanshah Dlabola in Isfahan, Iran, were investigated. Adults were smaller than those so far reported from other regions. Females continuously drummed on plant surfaces with their antennae to search for host eggs. Parasitoid eggs hatched 2–3 days after oviposition, and A. atomus had two larval instars. First instar larvae were sacciform and immobile. Second instar larvae appeared 4 days after oviposition and were very active, and doubled their body length. The prepupal and pupal stages lasted for 1 and 5–6 days, respectively. Adult emergence began 16 days after oviposition, and peaked on day 17.     

稻田飞虱卵寄生蜂群落结构和动态的初步研究

报道了广东省四会市大沙镇稻田中褐飞虱Nilaparvata lugens卵期寄生蜂的结构和动态。该群落由缨小蜂科和赤眼蜂科的6个属、共19种卵寄生蜂组成。其中,稻虱缨小蜂Anagrus nilaparvatae、长管稻虱缨小蜂A. longitubulosus和拟稻虱缨小蜂A. paranilaparvatae是群落中的优势种群,它们对控制褐飞虱种群卵期的存活率起主要作用。6个属在群落中的优势地位相对稳定,但不同物种包括优势种类在群落中的地位并不稳定。早、晚稻前期,群落的寄生蜂数量与稻田褐飞虱数量正相关;中期,寄生蜂数量在一定的范围内波动;后期,其数量先上升,然后急剧下降。水稻生长前、中和后期,寄生蜂对褐飞虱卵的平均寄生率分别约为76%,70%和50%。