Woodwasp Sirex Noctilio Research Articles

Oviposition substrate location by the invasive woodwasp Sirex noctilio: the combined effect of chemical cues emitted by its obligate symbiont Amylostereum areolatum and different host-tree species.

Sirex noctilio is an invasive forest wasp that affects pines and can result in severe economic losses. The use of semiochemicals offers an opportunity to develop sensitive and specific capturing systems to mitigatenegative impacts. Previous research showed that female S. noctilio would use volatiles emitted by its fungal symbiont, Amylostereum areolatum, but little is known about how these modulate behaviour when combined with pine-wood emissions. Our aim was to understand the relevance of fungal volatiles grown on artificial media and wood from two hosts trees, Pinus contorta and Pinus ponderosa, on behavioural and electroantennographic responses of wasp females. Because background odours can modify an insect's response towards resource-indicating semiochemicals, we propose that the behaviour towards the symbiont (resource) will be modulated by host pine emissions (background odours). Olfactometric assays showed that both host species with fungus were attractive when contrasted against air (P. contorta versus Air, χ2 = 12.19, P < 0.001; P. ponderosa versus Air, χ2 = 20.60, P < 0.001) and suggest a clear hierarchy in terms of female preferences towards the tested stimuli, with response highest towards the fungus grown on P. contorta (olfactory preference index: 5.5). Electrophysiological analyses indicate that females detect 62 volatile compounds from the tested sources. Results indicate a strong synergy between symbiont and host semiochemicals, suggesting that the pine species could play a fundamental role in the interaction. Further understanding of the chemical basis of this, could guide the development of specific and attractive lures, in order to maximize attraction of wasps in surveillance programmes. © 2023 Society of Chemical Industry.

Morphology and location of sensilla in the antennae and ovipositor of Sirex noctilio (Hymenoptera: Siricidae)

The woodwasp Sirex noctilio Fabricius is a major quarantine pest that was reported in China in 2013 and mostly damages Pinus sylvestris var. mongolica. Reverse chemical ecology, which uses chemical lures to catch or block insects from mating is the classic way to control forestry pests. This indicates that insect sensilla play a crucial role in detecting external chemical and physical stimuli. Nonetheless, the categorization and distribution of sensilla on the antennae and ovipositor of S. noctilio are insufficiently specific. In this paper, scanning electron microscopy (SEM) was used to observe the ultrastructure of the sensilla of S. noctilio on the antenna and ovipositor. It was found that the types and distribution of sensilla on the antennae of S. noctilio male and female are consistent, and six types of sensilla are found: sensilla trichodea (ST), sensilla chaetica (SC), Böhm bristles (BB), sensilla basiconica (SB), sensilla ampullacea (SA), and contact chemoreceptors (CC). Besides, there are five types of sensilla on the female ovipositor. In addition to ST, SC and BB, two more types of sensilla are also found: sensilla cavity (SCa) and sensilla coeloconica (SCo). Through identification of the morphology and distribution of the sensilla, the functions of different sensilla in the mating and host selection mechanisms of S. noctilio are proposed, thereby establishing a foundation for S. noctilio chemical communication research.

Comparison of Chemosensory Receptor Genes in the Antennae Transcriptomes of Sirex noctilio and Sirex nitobei (Hymenoptera: Siricidae)

The woodwasp Sirex noctilio Fabricius is a worldwide quarantine pest for forestry that mainly harms conifers, especially Pinus species. Sirex nitobei Matsumura, a native species from China and closely related to S. noctilio. Olfaction and gustation play a vital role in the life movements of woodwasps, but the molecular mechanisms of chemoperception in these species remain unclear. We performed a comparative analysis of 41 odorant receptors (ORs), 13 ionotropic receptors (IRs), and 8 gustatory receptors (GRs) of S. noctilio and 43 ORs, 16 IRs, and 10 GRs of S. nitobei. Phylogenetic analysis showed that two species-specific OR subfamilies were identified in each species. In addition to conserved “antennal IRs”, “divergent IRs”, including 7 SnocIRs and 7 SnitIRs, were found. Moreover, a sugar receptor subfamily (SnocGR5 and SnitGR11), a carbon dioxide receptor subfamily (SnocGR2/GR3 and SnitGR3), and a fructose receptor subfamily (SnitGR9) emerged, but bitter receptors were not identified. The tissue-specific expression profiles showed 36 ORs were enriched in the antennae of S. noctilio. Among them, 19 ORs were female-biased, whereas 4 ORs (SnocOR6/15/18/30) were male-biased. In addition, 34 ORs were highly expressed in S. nitobei antennae, of which 22 ORs were female-biased, whereas SnitOR2/18/30 were male-biased. Seven IRs were enriched in the antennae of both species, of which SnocIR4, 6, 10, 11, and 12 were significantly male-biased, while SnitIR4, 6, 10, 11, and 12 were significantly female-biased. Three GRs were highly expressed in the antennae of both species. SnocGR2 and SnocGR6 were also highly expressed in the head and leg, respectively. In the present study, a total 62 and 69 chemosensory receptor genes were identified in the antennal transcriptomes of S. noctilio and S. nitobei, respectively. Although most receptor genes are homologous, there are also some specific receptor genes, suggesting similarities and differences in molecular mechanisms between the two closely related species. OR genes may be involved in different physiological functions by whether they are expressed in olfactory organs, or obvious gender bias. Our results provide a foundation for further investigating the molecular mechanisms of chemoreception in these two closely related woodwasp species, and establishes a starting point for further research on molecular mechanisms of the olfactory system in symphyta woodwasps.

Demography of an invading forest insect reunited with hosts and parasitoids from its native range

The Sirex woodwasp Sirex noctilio Fabricius (Hymenoptera: Siricidae), a widespread invasive pest of pines in the Southern Hemisphere, was first detected in North America in 2004. This study assessed the impacts of life history traits, host resistance and species interactions on the demography of S. noctilio in New York, Pennsylvania and Vermont, then compared key metrics to those found in the native range in Galicia, Spain. Many trees naturally attacked by S. noctilio in North America produced no adult woodwasps, with 5 of 38 infested trees (13%) sampled across six sites yielding 64% of emerging insects. Reproductive success was highest in the introduced host scots pine, Pinus sylvestris, but native red pine, Pinus resinosa, produced larger insects. Sirex noctilio required one or sometimes two years to develop and sex ratios were male biased, 1:2.98 ♀:♂. Body size and fecundity were highly variable, but generally lower than observed in non-native populations in the Southern Hemisphere. Hymenopteran parasitoids killed approximately 20% of S. noctilio larvae and 63% of emerging adults were colonized by the parasitic nematode Deladenus siricidicola, although no nematodes entered eggs. Demographic models suggested that S. noctilio in the northeastern USA have a higher potential for population growth than populations in the native range: estimated finite factor of increase, λ, was 4.17–4.52 (depending on tree species colonized), compared to λ = 1.57 in Spain.

Biologically active cuticular compounds of female Sirex noctilio

AbstractThe Eurasian woodwasp Sirex noctilio Fabricius (Hymenoptera: Siricidae) is a major invasive pest in pine plantations of the Southern Hemisphere. In this study, we aimed to identify pheromone compounds in S. noctilio females, for potential use in lures for pest monitoring and control. An examination of S. noctilio body washes resulted in the identification of a behaviorally active compound, 10‐oxo‐decanoic acid (10‐ODA), that is derived from cuticular hydrocarbons of females. This oxocarboxylic acid is likely produced through oxidative reactions at the cleavage of double bonds of certain female‐produced cuticular dienes. Gas chromatography‐electroantennogram detection (GC‐EAD) analyses showed that only male antennae consistently responded to natural and synthetic 10‐ODA. In olfactometer assays, 10‐ODA alone was attractive to S. noctilio males, although males marginally preferred the combination of 10‐ODA and nonanal, compared with 10‐ODA alone. This suggests pheromonal activity of this compound. However, no wasps were captured in initial field trapping experiments with 10‐ODA and further work is required.

Experimental admixture among distinct lineages of Deladenus siricidicola, the biocontrol agent of Sirex noctilio

Deladenus siricidicola is a principal biological control agent used to suppress populations of the globally invasive pine pest, the woodwasp Sirex noctilio. Previous studies have reported low genetic diversity in D. siricidicola populations in biological control programs in the Southern Hemisphere and identified two additional, distinct lineages in North America and Spain. In this study, we tested the ability of these three lineages to interbreed and produce viable offspring. We used microsatellite markers to confirm admixture in offspring. Secondly, we compared growth rates among parental and admixed replicates on four isolates of the Amylostereum areolatum fungus on which nematodes typically feed in their asexual, non-parasitic phase. We show that all the lineages were capable of interbreeding and that admixture was asymmetric (i.e., skewed towards one of the parents). The offspring from one of the crosses showed significant variation in growth rate on different isolates of A. areolatum, compared to the parental isolates, but specifically on the slowest growing fungal isolate. Our results pave the way for the strategic introduction of genetic diversity into biological control programs and also inform expectations of accidental introductions of D. siricidicola into new regions.

Siricid Parasitoids (Hymenoptera: Ichneumonidae) From Eastern White Pine and Associated Pine Species in Southern Appalachia

Siricid Parasitoids (Hymenoptera: Ichneumonidae) From Eastern White Pine and Associated Pine Species in Southern Appalachia

Mongolian pine forest decline by the combinatory effect of European woodwasp and plant pathogenic fungi

Interactions between the decline of Mongolian pine woodlands and fungal communities and invasive pests in northeastern China are poorly understood. In this study, we investigated the fungal communities occurring in three tree samples: the woodwasp Sirex noctilio infested, healthy uninfested and unhealthy uninfested Mongolian pine trees. We analyzed the relationships of the Mongolian pine decline with fungal infection and woodwasp infestation. Twenty-six fungal species were identified from the sampled trees. Each tree sample harbored a fungal endophyte community with a unique structure. Pathogenic fungi richness was four times higher in infested and unhealthy un-infested trees compared to that in healthy uninfested trees. Sphaeropsis sapinea was the most dominant pathogenic fungus in the sampled Mongolian pine trees. The number of S. noctilio was higher than native bark beetles in the declining Mongolian pine trees. The invasion of the woodwasp appeared to be promoted by the fungal infection in the Mongolian pine trees. The incidence of S. noctilio infestation was higher in the fungi infected trees (83.22%) than those without infection (38.72%). S. sapinea population exhibited positive associations with within-tree colonization of S. noctilio and bark beetle. Collectively, these data indicate that the fungal disease may have caused as the initial reason the decline of the Mongolian pine trees, and also provided convenient conditions for the successful colonization of the woodwasp. The woodwasps attack the Mongolian pine trees infected by fungi and accelerated its decline.

Antennal transcriptome analysis of olfactory genes and characterizations of odorant binding proteins in two woodwasps, Sirex noctilio and Sirex nitobei (Hymenoptera: Siricidae)

BackgroundThe woodwasp Sirex noctilio Fabricius is a major quarantine pest worldwide that was first discovered in China in 2013 and mainly harms Pinus sylvestris var. mongolica Litv.. S. nitobei Matsumura is a native species in China and is closely related to S. noctilio. Recently, the two woodwasps species were found attacking the P. sylvestris var. mongolica Litv in succession. The olfactory system is the foundation of insect behavior. Olfactory genes were identified through antennal transcriptome analysis. The expression profiles odorant binding proteins (OBPs) were analyzed with RT-qPCR.ResultsFrom our transcriptome analysis, 16 OBPs, 7 chemosensory proteins (CSPs), 41 odorant receptors (ORs), 8 gustatory receptors (GRs), 13 ionotropic receptors (IRs), and one sensory neuron membrane protein (SNMP) were identified in S. noctilio, while 15 OBPs, 6 CSPs, 43 ORs, 10 GRs, 16 IRs, and 1 SNMP were identified in S. nitobei. Most of the olfactory genes identified in two species were homologous. However, some species-specific olfactory genes were identified from the antennal transcriptomes, including SnocOBP13, SnocCSP6, SnocOR26, SnocGR2, SnocIR7 in S. noctilio and SnitGR9, SnitGR11, SnitIR17 in S. nitobei. In total, 14 OBPs were expressed primarily in the antennae. SnocOBP9 and SnitOBP9, identified as PBP homologues, were sex-biased expression in two siricid, but with different pattern. SnocOBP11 and SnitOBP11 were highly expressed in antennae and clearly expressed in external genitalia. SnocOBP7 and SnitOBP7 were highly expressed in male genitalia. SnocOBP3 and SnocOBP10 were highly expressed in female genitalia and male heads, while SnitOBP3 and SnitOBP10 did not show obvious tissue bias.ConclusionWe analyzed 86 and 91 olfactory genes from S. noctilio and S. nitobei, respectively. Most of the olfactory genes identified were homologous, but also some species-specific olfactory genes were identified, which indicated the similarities and differences of the molecular mechanisms between the two closely-related species. Different expression in the antennae, external genitals or heads, exhibiting an obvious sex bias, suggested their different role in recognizing sex pheromones or plant volatiles. Species-specific expression for several OBPs genes may suggest that they strengthened or lost their original function during species differentiation, resulting in olfactory differences between the two species.

Genes Identification, Molecular Docking and Dynamics Simulation Analysis of Laccases from Amylostereum areolatum Provides Molecular Basis of Laccase Bound to Lignin.

An obligate mutualistic relationship exists between the fungus Amylostereum areolatum and woodwasp Sirex noctilio. The fungus digests lignin in the host pine, providing essential nutrients for the growing woodwasp larvae. However, the functional properties of this symbiosis are poorly described. In this study, we identified, cloned, and characterized 14 laccase genes from A. areolatum. These genes encoded proteins of 508 to 529 amino acids and contained three typical copper-oxidase domains, necessary to confer laccase activity. Besides, we performed molecular docking and dynamics simulation of the laccase proteins in complex with lignin compounds (monomers, dimers, trimers, and tetramers). AaLac2, AaLac3, AaLac6, AaLac8, and AaLac10 were found that had low binding energies with all lignin model compounds tested and three of them could maintain stability when binding to these compounds. Among these complexes, amino acid residues ALA, GLN, LEU, PHE, PRO, and SER were commonly present. Our study reveals the molecular basis of A. areolatum laccases interacting with lignin, which is essential for understanding how the fungus provides nutrients to S. noctilio. These findings might also provide guidance for the control of S. noctilio by informing the design of enzyme mutants that could reduce the efficiency of lignin degradation.

Sequence data reflect the introduction pathways of the Sirex woodwasp parasitoid, Ibalia leucospoides (Ibaliidae, Hymenoptera)

AbstractThe parasitoid wasp Ibalia leucospoides is native to the northern hemisphere and has been introduced to the southern hemisphere as a biological control agent for the invasive woodwasp Sirex noctilio. Two subspecies of the parasitoid, Ibalia leucospoides leucospoides (Palearctic distribution) and Ibalia leucospoides ensiger (Nearctic distribution), were introduced and are reported to have hybridized. Despite extensive records of the numbers and origins of the wasps imported into the southern hemisphere, nothing is known regarding their current population diversity. We investigated the genetic variation of I. leucospoides in its native and introduced ranges using mitochondrial (COI) and nuclear (ITS) markers. Mitochondrial DNA diversity in the introduced range was limited, with only five haplotypes, although sequence divergence between these haplotypes was high. Similarly, the ITS rDNA sequences revealed multiple clades present in the introduced range. These results reflect introductions from a wide geographical range but where genetic bottlenecks have possibly reduced the genetic diversity. The data further reflect the origin of the I. leucospoides populations in South America and South Africa from New Zealand or Australia. We found no evidence of hybridization between the two subspecies of the parasitoid in its introduced range, and no evidence that I. leucospoides ensiger has established outside its native range.

Trapping success and flight behavior of two parasitoid species of the woodwasp Sirex noctilio

Classical biological control relies on the deliberate introduction of natural enemies to reduce pest populations below damage thresholds. Knowledge on key aspects of the behavior of antagonists and their population densities through time can be important to increase the efficiency of control programs. The woodwasp Sirex noctilio is a global threat to pine forests and biological control can be based, among other agents on two parasitoids, Ibalia leucospoides and Megarhyssa nortoni, with variable success. Currently no sensitive and standardized monitoring method exists for these control agents and little is known on their behavior, such as their vertical flight-distribution. Our aims were: firstly, assess the efficiency in capturing the parasitoids of four methods (two passive traps based on flight-path interception or caging previously-attacked trees to retain emerging insects, and two active traps baited with pine volatiles), and secondly establish the parasitoids vertical flight distribution. Ibalia leucospoides (females) was captured by all methods but intercept panel traps registered the highest captured individuals when accounting for effort. Conversely M. nortoni did not respond to baited traps, and low numbers were recorded in passive traps. Males of both species flew higher than females of I. leucospoides. Intercept traps baited with pine volatiles could be used to monitor I. leucospoides, but M. nortoni is not captured in these traps. We suggest that both species could be monitored by passively trapping insects at the moment of emergence from previously-infested trees. Further research is needed, especially on the chemical ecology of both species, to further develop inexpensive and standardized monitoring methods.

Local antagonism and resource partitioning between two invasive pine plantation pests

AbstractThe woodwasp Sirex noctilio Fabricius, native to Eurasia and North Africa, regularly co‐occurs with a North American origin Pissodes sp. on Pinus trees in South Africa. The nature of this co‐occurrence and potential impacts on either of the species is unknown. Using structured sampling, we investigated the pattern and degree of co‐occurrence of S. noctilio and Pissodes sp. in six sites in P. patula plantations in South Africa aiming to better understand the potential for interactions and population‐level feedbacks. We compared density, adult body size and within‐tree distribution of both insect species in trees where they co‐occurred or occurred singly. Sirex noctilio and Pissodes sp. co‐occurred on 68.0 ± 3.8% of infested trees (range 55–80%). Both insect species were more abundant in trees where they occurred alone relative to co‐inhabited trees. The within‐tree distribution of S. noctilio did not differ in the presence of Pissodes sp.; however, in the presence of S. noctilio, Pissodes sp. were more frequent in the bottom than the middle tree section where S. noctilio was at higher density and this could be an indication of resource partitioning. Body size of S. noctilio and Pissodes sp. was not influenced by co‐occurrence. The results obtained in the present study suggest a broad overlap for both insects in preference for stressed trees in similar states of decline, as well as moderate antagonism between the species leading to lower emergence of both species in shared trees. The influence of S. noctilio on Pissodes sp. population densities may still be a net positive at a landscape scale because Pissodes sp. prefers declining or recently dead trees that are readily created by S. noctilio via attacks on healthy trees.

The Draft Genome of Deladenus siricidicola.

The nematode Deladenus siricidicola is used as biological control agent against the invasive woodwasp Sirex noctilio, a serious invasive pest of Pinus plantations globally. The draft genome of this ecologically and economically important entomoparasitic nematode was determined.

Droughts drive outbreak dynamics of an invasive forest insect on an exotic host

Insect outbreaks are among the most important biotic disturbances in forest ecosystems and can exert immense economic and ecological impacts. Understanding the spatio-temporal patterns of eruptive insects can provide insights into the mechanisms driving their dynamics and help predict future responses under climate change. The aims of this study were to analyze the spatio-temporal patterns of outbreaks of the woodwasp Sirex noctilio –a major invasive pest of pines– in an invaded region of South America, to assess the relative importance of density-dependent and density-independent mechanisms on population dynamics, and to identify the primary factors that influence the magnitude of outbreaks. We used tree ring and insect sampling data of more than 1000 trees to reconstruct S. noctilio outbreaks in 29 pine stands across Patagonia-Argentina over a 16-year period. We found marked spatial synchrony in S. noctilio outbreaks at a regional scale. Rates of tree mortality from S. noctilio were influenced by both density-dependent and density-independent factors. The occurrence of S. noctilio outbreaks are triggered by an abrupt increase in drought, which likely increases the availability of susceptible host trees. The damage caused by the outbreaks is determined by stand level variables, closely related with tree stress. Rates of tree mortality decreased over time due to negative density-dependence in S. noctilio populations, likely due to the loss of suitable resources over time. Depicting mechanisms of large-scale tree mortality in ecosystems provides insights to the drivers of forest outbreaks and other factors such as responses to a changing climate.

Biocontrol of Sirex noctilio by the parasitic nematode Deladenus siricidicola: A five season field study in southern Chile.

In 2001, the woodwasp Sirex noctilio was detected in Pinus radiata plantations in the Biobio region of southern Chile. Subsequently, an intense biological control program using the female sterilizing nematode Deladenus siricidicola was implemented in 2010. During five seasons between 2012 and 2017, we studied the parasitism of D. siricidicola nematode and its effect on woodwasp populations and infestation of P. radiata in different locations within the Biobio region. Parasitism was assessed by dissecting adult females of S. noctilio obtained from infested P. radiata logs. The total population of S. noctilio was determined by the emergence of individuals from the same logs. The level of damage caused by the S. noctilio pest was determined by establishing plots in stands of P. radiata at an intensity of 1 plot every 5 ha-1. During the study period, parasitism of S. noctilio by the nematode D. siricidicola increased from 29.6% in 2012 to 93.1% in 2016, while pest population decreased 3.4% in the same time period. Infestation increased from 0.3 to 11,6% of trees between 2012 and 2015, but subsequently decreased to 5.9% by 2017. We confirmed establishment of the nematode in the region under study and its natural dispersion to non-inoculated areas. Finally, we determined that the effect of inoculation age (antiquity) on parasitism levels reached 90% after three years of inoculation.

Detecção da vespa-da-madeira em Pinus taeda no estado de São Paulo, Brasil

ABSTRACT: The woodwasp Sirex noctilio (Fabricius) (Hymenoptera: Siricidae) is one of the main pests of Pinus plantations in South America. The aim of this study is to report the occurrence of S. noctilio in Pinus taeda in Botucatu, São Paulo, Brazil. The surveys were carried out in the arboretum of Faculdade de Ciências Agronômicas (FCA) da Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), campus Botucatu, SP where six species of Pinus are distributed in blocks of 100 trees. Resin beads were observed on the trunks and stems of Pinus species. In post-flight evaluation it was reported that 8.77% of P. taeda trees showed symptoms of oviposition by S. noctilio. A female S. noctilio was found performing oviposition. Sirex noctilio is present in Botucatu, increasing the geographical distribution of the pest in São Paulo State.

Symbionts mediate oviposition behaviour in invasive and native woodwasps

Abstract Globalization leads to the introduction of invasive species that are often accompanied by associated microorganisms, and this can lead to homogenization of both introduced hosts and microbes with the native biota. One such example is the invasive Eurasian woodwasp Sirex noctilio, which inoculates pines with an obligate nutritional mutualist, the white rot fungus Amylostereum areolatum. Although S. noctilio has been previously introduced outside of its native range, its arrival in North America was the first time that it was introduced to communities hosting native Sirex species and Amylostereum strains. We conducted experiments aiming to investigate acceptance versus avoidance of native and non‐native Amylostereum strains and species during ovipositor drilling by females of S. noctilio and a native congener, Sirex nigricornis. Sirex noctilio preferred wood without prior fungal emplacement, whereas S. nigricornis preferred wood inoculated with one of the strains of Amylostereum that putatively invaded with S. noctilio. Drilling and presumed oviposition by both woodwasp species were highly aggregated. Based on the responses of these two Sirex species to the fungal strains and species included in the present study, the invasive S. noctilio would continue its present symbiont associations, whereas the native S. nigricornis would partly use the strain of fungal symbiont putatively introduced with S. noctilio.

Morphology of Male and Female Antennal Sensilla of Ibalia leucospoides ensiger (Hymenoptera: Ibaliidae)

Since the early 1900s, the Eurasian woodwasp (Sirex noctilio F.; Hymenoptera: Siricidae), a pest of pine (Pinus spp.; Pinales: Pinaceae) trees, has been introduced to various regions in Southern Hemisphere and North America. Among the most effective biocontrol agents of S. noctilio are hymenopteran parasitoids that parasitize various life-stages of woodwasps. Little is known about how these parasitoids locate their host in the wood, but presumably do so through chemolocation using antennae. We examined the external antennal morphology of Ibalia leucospoides ensiger (Norton) (Hymenoptera: Ibaliidae), a major parasitoid of native siricids in North America. Males were found to have two more antennal flagellomeres (13) than females (11), although the total antennal length was similar. The first flagellomere of the male has a distinctive excavated region. Using scanning electron microscopy, we identified seven types of antennal sensilla on male and female I. l. ensiger including campaniform, chaetica (types 1 and 3), coeloconic, fluted basiconica (FB), pits (PI), and placodea. There were no differences in the total number of antennal sensilla between male or female I. l. ensiger. However, females had greater numbers of chaetica type 1 and FB, whereas males had more sensilla placodea. Sensilla were unevenly distributed along the antennae of both males and females. Chaetica type 1 was the most numerous sensillum followed by FB, placodea, and PI. We present analyses of the morphology of the antennae of each sex of I. l. ensiger, and discuss possible function of each sensilla-type and how they may mediate mate location and oviposition activities.

Sex, life history and morphology drive individual variation in flight performance of an insect parasitoid

1. The movement of organisms can be driven by multiple factors and has implications for fitness and the spatial distribution of populations. Insects spend a large proportion of their adult lives foraging by flying for resources; however, their capability and motivation to move can vary across individuals.2. The aims of this study were to examine interindividual and sex differences in flight performance and flight characteristics, using a flight mill bioassay, in Megarhyssa nortoni (Hymenoptera; Ichneumonidae), a parasitoid of the invasive woodwasp Sirex noctilio (Hymenoptera: Siricidae), one of the most important pests of pine afforestation worldwide. We also assessed the influence of morphological traits in combination with sex on flight and explored the cost of flight on longevity and mass loss.3. The results show a difference between sexes in flight characteristics and performance. Females show greater total distance flown than males, and have a better capacity to undergo sustained flight. Sexual size dimorphism was also found and it was noted that size positively affects distances travelled. Females have a longer life span than males, yet no differences were noted in longevity within sex between individuals that did not fly and those that flew. Age did not influence flight performance of females or impacted on post‐flight longevity. Females lost less body mass than males even after flying longer distances.4. These results suggest that sex‐specific behaviours probably govern flight abilities together with (and not only because of) morphological traits. The paper discusses sex‐specific life‐history strategies in parasitoids and their implications for biocontrol programmes.