Agromyzid Leafminers Research Articles

Thelytokous Diglyphus wani: A more promising biological control agent against agromyzid leafminers than its arrhenotokous counterpart

Diglyphus wani (Hymenoptera: Eulophidae) is a dominant parasitoid that attacks agromyzid leafminers. Two reproductive types occur in D. wani: arrhenotoky (in which virgin females produce only male offspring; and virgin females mate with males to produce bisexual offspring) and thelytoky (in which virgin females produce female offspring). As a potential biological control agent, exploring the differences in the relevant biological parameters of both strains is necessary. In this study, comparisons between the two strains of D. wani were performed by evaluating the life table and host-killing rate. The thelytokous strain exhibited significantly better life table parameters than its arrhenotokous counterpart. Higher values for the intrinsic rate of increase, finite rate of increase, net reproductive rate, and fecundity were found in the thelytokous strain. The thelytokous strain also performed better than the arrhenotokous strain in terms of net parasitism, host-feeding, host-stinging, and total host-killing rates. Thus, populations of the thelytokous strain could grow fast and kill more hosts. In conclusion, the thelytokous strain of D. wani may be the more promising biological agent against agromyzid leafminers compared to its arrhenotokous counterpart. Also, since the thelytokous strain of D. wani is only known to produce females, it should be given priority in future biocontrol applications owing to the cost savings of breeding only females.

Molecular phylogeny and identification of agromyzid leafminers in China, with a focus on the worldwide genus Liriomyza (Diptera: Agromyzidae)

Leaf-mining flies (Diptera: Agromyzidae) are a diverse family of small-bodied insects that feed on living plant tissues as larvae. Various species in this family are considered globally invasive and have caused great agricultural economic losses. In China, economically important vegetable crops have been seriously damaged by these pest insects, especially by species of the genus Liriomyza. However, these species are difficult to differentiate because of their morphological similarities, and the Chinese fauna remains poorly known. To explore the relevant pest species in China and their phylogeny, agromyzid leafminers were collected from 2016 to 2019, and identified based on morphological characteristics and DNA barcodes. In total, 27 species from five genera of Agromyzidae were sampled and identified, including 16 species of Liriomyza. Both mitochondrial and nuclear genes were used to reconstruct their phylogenetic relationships and estimate the divergence time. Highly congruent and well-supported phylogenetic trees were obtained using the Bayesian inference and maximum-likelihood methods. This analysis revealed two main clades in Liriomyza, and clade 2 was inferred to have diverged from clade 1 approximately 27.40 million years ago (95% highest posterior density: 23.03–31.52 million years ago) in the Oligocene. Differences were observed in the distribution patterns and host associations between the Liriomyza clades. Clade 2 species are distributed in cool, high-latitude environments, suggesting that they may have evolved into a cool-adapted lineage.

A new species of Diglyphus Walker (Hymenoptera, Eulophidae) from China, with morphological characterizations and molecular analysis.

Diglyphus Walker, 1844 (Hymenoptera: Eulophidae) is an economically important genus including species acting as biocontrol agents against agromyzid leafminer pests. A new species of Diglyphus, Diglyphusdifasciatus Liu, Hansson & Wan, sp. nov., was discovered during the identification of agromyzid leafminers and their associated parasitoid wasps collected from 2016 to 2022 in China, based on morphological characteristics and molecular analyses of COI, ITS2 and 28S genes. Diglyphusdifasciatus is similar to D.bimaculatus Zhu, LaSalle & Huang, distinguished by two interconnected infuscate vertical bands on the fore wing and the color of the scape. Molecular data support D.difasciatus and D.bimaculatus as two different species. The mean genetic distances between D.difasciatus and D.bimaculatus were 11.33%, 8.62%, and 0.18%, based on the COI, ITS2, and 28S genes, respectively.

A One-Step Multiplex PCR Method to Rapidly Distinguish Two Strains of Diglyphus wani (Hymenoptera: Eulophidae) Against Agromyzid Leafminers.

Hymenopteran parasitoids generally show a haplo-diploid sex determination system. Haploid males are produced from unfertilized eggs, whereas diploid females develop from fertilized eggs (arrhenotokous). In some cases, diploid females develop from unfertilized eggs (thelytokous). Diglyphus wani (Hymenoptera: Eulophidae) is a biological control agent for agromyzid leafminers and have arrhenotokous and thelytokous strains. However, the morphological characteristics of two strains of D. wani are so similar that it is difficult to accurately distinguish them based on morphology. Here, a rapid molecular identification method was developed based on the mitochondrial gene cytochrome c oxidase I (COI) and one-step multiplex PCR. Two primer combinations, PC1 (Ar-F1/Th-F1/WR2) and PC2 (Ar-F1/Th-F4/WR2), were designed and repeatedly screened to distinguish two strains simultaneously, of which two special forward primers Th-F1/Th-F4 were used for the thelytokous strain and one special forward primer Ar-F1 was used for the arrhenotokous strain. In addition, a common reverse primer, WR2, was used for both strains. The PC1 and PC2 PCR assays were effective in distinguishing the two strains at different developmental stages and field colonies. This method provides a reliable, highly sensitive, and cost-effective tool for the rapid identification of the two strains of D. wani.

The thelytokous strain of the parasitoid Neochrysocharis formosa outperforms the arrhenotokous strain in reproductive capacity and biological control of agromyzid leafminers.

Both arrhenotoky (sexual reproduction of females and asexual reproduction of males) and thelytoky (asexual reproduction of females) occur within the order Hymenoptera. The existence of both thelytokous and arrhenotokous strains within one species provides an opportunity to compare the biocontrol efficiency between two reproductive modes. The parasitoid Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae) has thelytokous and arrhenotokous strains with sympatric distributions. This parasitoid is used to control invasive leafminers through feeding, stinging, and parasitization. To compare the biocontrol efficiency of the two strains, we analyzed life tables and host-killingparameters of these two strains reared on the leafminer Liriomyza sativae Blanchard using the age-stage, two-sex life table and the CONSUME-MSChart software. Our results showed that the intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R0 ) of the thelytokous strain were significantly higher than those of the arrhenotokous strain. The thelytokous females also performed better than the arrhenotokous females for the net host-feeding rate, net host-stinging rate, and net host-killing rate, but not the finite parasitism rate. Conclusively, the finite host-killing rate of the thelytokous strain (0.8720 ± 0.0516) was significantly higher than that of the arrhenotokous strain (0.5914 ± 0.0832). We concluded that thelytokous N. formosa is a better candidate as a biocontrol agent than arrhenotokous N. formosa to control leafminers. Our results shed light on how to choose a better biocontrol agent for integrated pest management (IPM) based on biological control, especially for co-occurring thelytokous and arrhenotokous parasitoids. © 2022 Society of Chemical Industry.

Identification of two leafminer parasitoids (Hymenoptera: Eulophidae),Neochrysocharis formosaandProacriassp. from Australia, with both showing thelytoky and infection byRickettsia

AbstractLiriomyza huidobrensis,L. sativaeandL. trifoliiare polyphagous agromyzid leafminers that have recently arrived in Australia, posing a threat to Australian vegetable and ornamental crops. Adventive and endemic hymenopteran parasitoids of agromyzid leafminers already present in Australia should assist in the management of these invasive agromyzid species.Neochrysocharis formosa(Hymenoptera: Eulophidae: Entedoninae) is an idiobiont endoparasitoid commonly attackingLiriomyzaspp. in many countries, but it has not been formally identified in Australia. This study provides the first confirmed Australian record ofN. formosaas well as an unidentifiedProacriasspecies, another entedonine species. Females of both species were reared from several adventive and endemic agromyzid leafminers in southern Australia. Laboratory cultures of both species established the presence of thelytokous reproduction. DNA barcodes (5′ COI, 3′ COI, ITS1, ITS2, 28S) were used to delineate species boundaries, with the 5′ end of the mitochondrial COI sequences pointing to multiple cryptic lineages amongN. formosa. Additionally, 16S rRNA sequencing indicated that both species were infected with aRickettsiabacterium, which is related to theRickettsiapresent in thelytokous populations ofN. formosain Japan and China. These findings expand records for parasitoids attacking leafminers in Australia and highlight the potential for an endosymbiont to produce thelytokous strains that could provide for more efficient biocontrol agents for augmentative release.

High temperatures do not decrease biocontrol potential for the host-killing parasitoid Neochrysocharis formosa (Hymenoptera: Eulophidae) on agromyzid leafminers

Temperature, as a critical abiotic factor, might influence the effectiveness of biological control by parasitoids in host-parasitoid systems. In this study, Neochrysocharis formosa (Westwood), a larval endoparasitoid, is used to investigate the efficacy of biological control on a vegetable agriculture pest, Liriomyza sativae Blanchard, reared on kidney bean (Phaseolus vulgaris L.), at four constant temperatures (26, 29, 32, and 35°C) under laboratory conditions. Our results show that high temperatures (29, 32, and 35°C) do not significantly affect lifetime host-killing events of female adults by increased daily host-killing events compared to temperature of 26°C, although their lifespans decrease with an increase in temperatures. Each life-history trait of female adults (lifespan, parasitism, stinging, or non-reproductive host-killing events) present a linear relation with temperatures and host-feeding events, respectively. Our findings contribute to a better understanding of biocontrol efficacy of parasitoid N. formosa against agromyzid leafminers at high-temperature seasons or environments.

Community Structure and Diversity of Hymenopteran Parasitoids of Chromatomyia horticola (Diptera: Agromyzidae) in Different Habitats in Changchun, China.

The community structure and diversity of hymenopteran parasitoids of the agromyzid leafminer Chromatomyia horticola (Diptera: Agromyzidae) were studied in agricultural, urban, and natural habitats in Changchun, Northeast China. In agricultural habitats, a total of 3,380 individuals and 19 species were collected, and the dominant species were Diglyphus isaea (Walker) (Hymenoptera: Eulophidae) (71.15%) and Chrysocharis pentheus (Walker) (Hymenoptera: Eulophidae) (12.10%). In urban habitats, a total of 5,996 individuals and 21 species were collected. There were three dominant species, C. pentheus (26.68%), Chrysocharis phryne (Walker) (Hymenoptera: Eulophidae) (22.18%), and D. isaea (22.13%). In natural habitats, a total of 1,566 individuals and 26 species were collected. There were three dominant species, C. pentheus (30.52%), D. isaea (15.52%), and Pediobius metallicus (Nees) (Hymenoptera: Eulophidae) (12.26%). The diversity indices of the parasitoid community in urban and natural habitats were higher than that in agricultural habitats, and the richness index in natural habitats was higher than that in agricultural and urban habitats. These results suggest that there are differences in the community composition and dynamics of parasitoids in different habitats. Hymenopteran parasitoids of C. horticola are less abundant in natural habitats; however, species richness is greater, and can be used as a species reserve for biological control.

Multiple Data Demonstrate That Bacteria Regulating Reproduction Could Be Not the Cause for the Thelytoky of Diglyphus wani (Hymenoptera: Eulophidae).

Simple SummaryIn Hymenoptera, some species have two reproduction modes, that is, arrhenotokous and thelytokous parthenogenesis. Although arrhenotoky is common, the thelytoky is not rare. Thelytoky in Hymenopteran species has several causes and is generally induced by bacteria. Here, we examined a thelytokous Chalcidoidea parasitoid, Diglyphus wani, which was recently reported to be a dominant parasitoid attacking agromyzid leafminers. In this study, we aimed to combine multiple methods to explore whether endosymbionts induce thelytokous D. wani. Our findings revealed that the thelytoky of D. wani was not to be associated with the actual presence of the endosymbionts. Thus, Diglyphus wani is the second reported eulophid parasitoid for which thelytoky is not linked with the presence of endosymbionts.In Hymenoptera parasitoids, the reproductive mode is arrhenotoky, while a few species reproduce by thelytoky. The thelytoky of Hymenoptera parasitoids is generally genetically determined by the parasitoids themselves or induced by bacteria, including Wolbachia, Cardinium, and Rickettsia. Diglyphus wani (Hymenoptera: Eulophidae), a recently reported thelytokous species is a main parasitoid attacking agromyzid leafminers. To assess whether endosymbionts induce thelytoky in D. wani, we performed universal PCR detection and sequenced the V3-V4 region of 16S ribosomal RNA gene. In addition, bacteria were removed through high-temperature and antibiotic treatments, and the localized bacteria were detected using FISH. Based on general PCR detection, Wolbachia, Cardinium, Rickettsia, Arsenophonus, Spiroplasma, and Microsporidia were absent in laboratory and field individuals of thelytokous D. wani. Furthermore, 16S rRNA gene sequencing revealed that the dominant endosymbionts in thelytokous D. wani were not reproductive manipulators. High-temperature and antibiotic treatment for five consecutive generations cannot reverse the thelytokous pattern of D. wani, and no male offspring were produced. Moreover, no bacterial spots were found in the ovaries of D. wani. Thus, it is considered that the thelytoky of D. wani does not result in the presence of endosymbionts. This species is thus the second reported eulophid parasitoid whose thelytoky appears not to be associated with endosymbionts.

Morphological and molecular identification of arrhenotokous strain of Diglyphuswani (Hymenoptera, Eulophidae) found in China as a control agent against agromyzid leafminers.

Diglyphus species are ecologically and economically important on agromyzid leafminers. In 2018, a thelytokous species, Diglyphuswani Liu, Zhu & Yefremova, was firstly reported and described. Subsequently, the arrhenotokous D.wani were discovered in Yunnan and Guizhou Provinces of China. We compared the morphological characteristics of thelytokous and arrhenotokous strains. However, the females of two strains had a strongly similar morphology and showed subtle differences in fore- and hind-wings. The difference was that forewing of arrhenotokous female was with denser setae overall, showing that costal cell with 2 ~ 4 rows of setae on dorsal surface and the setae of basal cell with 15 ~ 21 hairs and forewing of thelytokous female was with two rows of setae on dorsal surface and basal cell with 10 ~ 15 hairs generally. The setation beneath the marginal vein of the hind-wing of arrhenotokous female is denser than the same area of thelytokous female. To explore the genetic divergence between thelytokous and arrhenotokous strains of D.wani, the mitochondrial and nuclear gene were applied and sequenced. The polygenic analyses revealed that two strains can be distinguished by COI, ITS1 and ITS2. The mean sequence divergence between the two strains was 0.052, 0.010 and 0.007, respectively. Nevertheless, the 28S gene was unfeasible due to its containing a sharing haplotype between different strains. The two strains of D.wani are dominant parasitoids against agromyzid leafminers and such effective discernible foundation provides future in-depth studies on biological characteristics, along with insight into field application of two strains of D.wani.

A molecular method for biomonitoring of an exotic plant-pest: Leafmining for environmental DNA.

Understanding how invasive species respond to novel environments is limited by a lack of sensitivity and throughput in conventional biomonitoring methods. Arthropods in particular are often difficult to monitor due to their small size, rapid lifecycles, and/or visual similarities with co-occurring species. This is true for the agromyzid leafminer fly, Liriomyza sativae, a global pest of vegetable and nursery industries that has recently established in Australia. A robust method based on environmental DNA (eDNA) was developed exploiting traces of DNA left inside "empty" leaf mines, which are straightforward to collect and persist longer in the environment than the fly. This extends the window of possible diagnosis to at least 28days after a leaf mine becomes empty. The test allowed for visually indistinguishable leafmining damage caused by L.sativae to be genetically differentiated from that of other flies. Field application resulted in the identification of new local plant hosts for L.sativae, including widely distributed weeds and common garden crops, which has important implications for the pest's ability to spread. Moreover, the test confirmed the presence of a previously unknown population of L.sativae on an island in the Torres Strait. The developed eDNA method is likely to become an important tool for L.sativae and other leafmining species of biosecurity significance, which, historically, have been difficult to detect, diagnose and monitor. More generally, eDNA is emerging as a highly sensitive and labour-efficient surveillance tool for difficult to survey species to improve outcomes for agricultural industries, global health, and the environment.

Variation in sex ratio of the leafminerPhytomyza plantaginisGoureau (Diptera: Agromyzidae) from Australia

AbstractParthenogenetic reproduction has only previously been demonstrated in two species of agromyzid leafminer flies (Diptera: Agromyzidae), both from the genusPhytomyza. The plantain leafminer,Phytomyza plantaginis, is Palaearctic in origin, and bisexual populations have been observed in this region. However, historically, only females had been collected in the Australasian, Nearctic, Neotropical and Oceanian regions. Here, we show that southern Australian samples of this species fromPlantagospp. can be composed of both parthenogenic and bisexual populations. In sites around Melbourne, males were present, although the sex ratio was female biased, with females comprising 75% of sampled individuals. In contrast, males were absent from collections in western and northern Victoria, Australian Capital Territory, New South Wales and Western Australia. FemaleP. plantaginisflies were reared from threePlantagohost plants (Plantago lanceolata,Plantago majorandPlantago coronopus), although females were particularly common fromPl. lanceolata. Insect cages set up with leafminers from sites where only females occurred produced only females, while cages with leafminers from sites where males occurred produced both sexes and mating was observed. Individuals from all populations were infected byWolbachiaendosymbionts, suggesting that the presence/absence ofWolbachiais not directly responsible for the parthenogenesis. However, there was an association between a mtDNA variant (PP.02) and sexual reproduction, in that this variant was absent in areas where only females were collected but present in all males and some females from areas with sexual populations. The mechanism responsible for parthenogenesis inP. plantaginisremains unknown but is linked to maternal factors.

Interactions between Diglyphus isaea and Neochrysocharis formosa (Hymenoptera: Eulophidae), two parasitoids of agromyzid leafminers

When two parasitoids exploit a common host simultaneously, competitive interactions between them usually occur, and are more complex among host-killing species. Diglyphus isaea (Walker) and Neochrysocharis formosa (Westwood) are larval parasitoids of agromyzid leafminers. They have widespread distributions and share the same host resources when sympatric. In this study, interactions between these two parasitoids and different parasitoid release modes were investigated. Parasitoids were exposed to leaves infested with late second to early third instar Liriomyza sativae at two different host densities in Petri dishes. The total death rate of N. formosa released alone was density-dependent. And release modes also impacted the total death rate of parasitoids at a high host density. However, the oviposition number of D. isaea was significantly greater than that of N. formosa when they coexisted. In addition, host-feeding proportions were greatest among three host-killing behaviors: parasitism, host feeding and host stinging. These results contribute to a further understanding of parasitoids’ host-killing strategies.

Life history and biocontrol potential of the first female-producing parthenogenetic species of Diglyphus (Hymenoptera: Eulophidae) against agromyzid leafminers

Diglyphus species are dominant biocontrol agents for suppressing outbreaks of agromyzid leafminers in fields. In July 2015, we collected a new thelytokous species of Diglyphus in Qinghai, China. The wasp is here named as D. wani Liu, Zhu & Yefremova sp. nov., based on morphological and molecular analyses. The life history and biocontrol potential of the wasp were studied in the laboratory and by providing Liriomyza sativae larvae. The intrinsic rate of increase, finite rate of increase, and mean generation time were 0.2373 d−1, 1.2678 d−1, and 15.9 d, respectively. The wasps showed three types of host-killing behaviour, namely parasitism, host feeding and host stinging, resulting in 47.6, 94.4 and 3.4 host larvae killed per wasp over a lifetime, respectively. The finite total host-killing rate was 1.0071 and the wasp showed strong synovigeny. The wasp may be a crucial biocontrol agent against agromyzid leafminers.

Infestation caused by the Agromyzid Leafminer Liriomyza trifolii of Bean Crops in Kafr EL–Shiekh, Egypt

Infestation caused by the Agromyzid Leafminer Liriomyza trifolii of Bean Crops in Kafr EL–Shiekh, Egypt

Life history and life table of the host-feeding parasitoid Hemiptarsenus varicornis (Hymenoptera: Eulophidae)

Hemiptarsenus varicornis (Girault), a destructive host-feeding wasp, is an important biocontrol agent/larval ectoparasitoid of agromyzid leafminers worldwide. In the present study, the life history and life table of H. varicornis reared with Liriomyza trifolii (Burgess) were studied at a constant 27 °C. The developmental durations of female and male eggs, larvae, prepupae, pupae and total immature wasps were 1.00 and 1.00, 2.57 and 2.62, 0.45 and 0.37, 3.88 and 3.52, and 7.90 and 7.52 days, respectively. This wasp showed three types of host-killing behavior: reproductive parasitization (parasitism), non-reproductive host feeding (host feeding), and host stinging without oviposition or feeding (host stinging), resulting in 133.9, 303.8, and 84.2, respectively, killed host larvae. We confirm that H. varicornis is a strong synovigenic parasitoid, with an ovigeny index of 0.003. The number of host-feeding events was strongly correlated with parasitism, host-stinging events, longevity and total host mortality. The intrinsic rate of increase, the finite rate of increase, the net reproductive rate, the gross reproduction rate, and the mean length of a generation of H. varicornis were 0.3011/day, 1.3624/day, 66.22 offspring/individual, 168.33 offspring/individual, and 13.56 days, respectively. These results could contribute to a better understanding of the biocontrol efficiency of this destructive host feeder.

緑肥作物ハゼリソウにおけるハモグリバエ類（ハエ目：ハモグリバエ科）の土着寄生蜂相とネギハモグリバエ防除のためのバンカープランツおよびインセクタリープランツとしての利用の可能性

Phacelia tanacetifolia Bentham is known worldwide as a kind of insectary plant and is used in Japan as a green manure crop before Welsh onion planting. To explore the possibility of using P. tanacetifolia as a banker plant or an insectary plant for parasitoids of Liriomyza chinensis Kato, we investigated the seasonal abundance of agromyzid leafminers and their hymenopterous parasitoids on infested leaves and blooming flowers of P. tanacetifolia collected in Chiba Pref., Japan, in 2009, 2010, and 2012. We also investigated longevity increase in Diglyphus isaea（Walker）adults with a blooming P. tanacetifolia plant in the laboratory. Almost all agromyzid leafminers reared from leaves were Chromatomyia horticola（Goureau）. Twenty-one parasitoid species including seven species reported from L. chinensis mines by different authors in Japan were reared from leaves, and nine species including eight species reared from leaves were caught on flowers. The most abundant parasitoid species was D. isaea. In this study, Diglyphus crassinervis Erdös was reared from C. horticola for the first time in Japan. The longevity of D. isaea adults provided with a blooming plant and water was about 18 days at 24°C with a 16L : 8D photoperiod. The log-rank test, used to compare survival curves from the 2 treatments; with and without blooming P. tanacetifolia plant, showed a statistically significant difference between treatments. These results suggest that P. tanacetifolia has potential as a banker plant or insectary plant for parasitoids to control L. chinensis in Welsh onion fields.

Correlation Between Climatic Factors And Leafminer (Insecta: Agromyzidae) Infestation On Three Vegetable Crops In Chittagong, Bangladesh

Present study deals with the impact of climatic factors (temperature, humidity and wind speed) on agromyzid leafminers infestation in three cultivated crops viz. Tomato, French bean and Cowpea. Correlation studies showed that there was significantly positive relation of temperature, whereas wind speed showed negative relation to agromyzid infestation on cultivated crops. But there was no significant relation with humidity. Temperature influenced infestation rate as 18.70 ± 4.12, 16.01 ± 15.85 and 9.38 ± 9.10 % for Tomato, French bean and Cowpea respectively.
 Asiat. Soc. Bangladesh, Sci. 41(1): 1-5, June 2015

DNA-based identifications reveal multiple introductions of the vegetable leafminer Liriomyza sativae (Diptera: Agromyzidae) into the Torres Strait Islands and Papua New Guinea.

Leafmining flies (Diptera: Agromyzidae) can be serious economic pests of horticultural crops. Some genera such as Liriomyza are particularly problematic with numerous species, some of which are highly polyphagous (wide host range), which can only be confidently identified morphologically from adult males. In our study, DNA barcoding was employed to establish new locality records of the vegetable leafminer fly, Liriomyza sativae, from the islands of Torres Strait (Queensland, Australia) and the central highlands of Papua New Guinea (PNG). These records represent significant range extensions of this highly invasive plant pest. Specimens of immature leafminers (from leaf mines) were collected over a 5-year period during routine plant health surveys in ethanol or on FTA® filter paper cards, both methods proved effective at preserving and transporting insect DNA under tropical conditions, with FTA cards possessing some additional logistical benefits. Specimens were identified through sequencing two sections of the cytochrome oxidase I gene and the utility of each was assessed for the identification of species and intra-specific genetic lineages. Our study indicates that multiple haplotypes of L. sativae occur in PNG, while a different haplotype is present in the Torres Strait, with genetic regionalization between these areas apart from a single possible instance - one haplotype 'S.7' appears to be common between these two regions - interestingly this has also been the most common haplotype detected in previous studies of invasive L. sativae populations. The DNA barcoding methods employed here not only identified multiple introductions of L. sativae, but also appear generally applicable to the identification of other agromyzid leafminers (Phytomyzinae and Agromyzinae) and should decrease the likelihood of potentially co-amplifying internal hymenopteran parasitoids. Currently, L. sativae is still not recorded from the Australian mainland; however, further sampling of leafminer flies from Northern Australia and surrounding areas is required, as surveillance for possible Liriomyza incursions, as well as to characterize endemic species with which Liriomyza species might be confused.

Comparing Immature Development and Life History Traits in Two Coexisting Host-Feeding Parasitoids, Diglyphus isaea and Neochrysocharis formosa (Hymenoptera: Eulophidae)

Coexisting natural enemies that share a common host resource in the same guild usually exhibit variation in their life history traits, due to their need to share a similar ecological niche. In this study, we compared the immature development times and adult life history traits of two coexisting, host-feeding parasitoids, Diglyphus isaea Walker and Neochrysocharis formosa Westwood (Hymenoptera: Eulophidae), of which both attack larvae of the same agromyzid leafminers. These two species are both synovigenic, idiobiont parasitoids, whose adults consume host fluids (“host feeding”) and lay anhydropic eggs. Of the two, D. isaea has a larger body but little or no initial egg load, and engages in similar lifetime host-feeding events. However, it achieves higher fecundity, longer adult longevity, and higher host suppression ability than N. formosa, which has a smaller body and higher initial egg load. Although D. isaea engages in similar lifetime host-feeding events with N. formosa, all of its gains in life history traits per host-feeding event of D. isaea were larger than those of N. formosa. The age-specific fecundity and host mortality curves of N. formosa were more skewed in early life than those of D. isaea. In addition, the ovigeny index of N. formosa was negatively correlated to body size. Our results confirmed that two coexisting parasitoids, which share the same host resource, show different immature development patterns and life history traits, suggesting that different resource allocation mode could be a general rule of coexisting species sharing the same habitat or host.