Wasp Attack Research Articles

Nociception in Drosophila Larvae.

Nociception is the sensory modality by which animals sense stimuli associated with injury or potential tissue damage. When Drosophila larvae encounter a noxious thermal, chemical, or mechanical stimulus, they perform a stereotyped rolling behavior. These noxious stimuli are detected by polymodal nociceptor neurons that tile the larval epidermis. Although several types of sensory neurons feed into the nociceptive behavioral output, the highly branched class IV multidendritic arborization neurons are the most critical. At the molecular level, Drosophila nociception shares many conserved features with vertebrate nociception, making it a useful organism for medically relevant research in this area. Here, we review three larval assays for nociceptive behavior using mechanical stimuli, optogenetic activation, and the naturalistic stimuli of parasitoid wasp attacks. Together, the assays described have been successfully used by many laboratories in studies of the molecular, cellular, and circuit mechanisms of nociception. In addition, the simple nature of the assays we describe can be useful in teaching laboratories for undergraduate students.

Assaying Nociception Behaviors in Drosophila Larvae During Parasitoid Wasp Attacks.

Nociception in fruit fly (Drosophila melanogaster) larvae is characterized by a stereotyped escape behavior. When a larva encounters a noxious (potentially harmful) stimulus, it responds by curving its body into a c-shape and rolling in a corkscrew-like manner around its long-body axis. This rolling behavior may serve to quickly remove the larva from the source of the noxious stimulus, and is particularly adaptive to escape from a common natural predator of fruit fly larvae: parasitoid wasps (Leptopilina boulardi). L. boulardi completes its life cycle by using fruit fly larvae as hosts for its offspring. Female wasps sting fly larvae with an ovipositor and lay an egg within the larva. The wasp offspring hatches inside the fly larva, consumes the fly tissues during pupation, and eventually emerges from the pupal case as an adult wasp. Fruit fly larvae respond to oviposition attacks by rolling, which causes the long flexible ovipositor to be wound around the larval body like a spool. This dislodges the wasp and allows the larva to attempt to escape by crawling. Rolling behavior is triggered by the activation of sensory neurons (nociceptors) whose function can inform our understanding of the mechanisms of nociception. In this protocol, we describe a simple behavioral assay to test and measure nociceptive responses in Drosophila larvae during oviposition attacks by female parasitoid wasps. First, we discuss parasitoid wasp husbandry and culturing methods in the laboratory. We then describe how to perform the wasp nociception assay on third-instar fruit fly larvae.

Managing ecosystem services in oleaginous forests for bioenergy provision and climate change mitigation

Oleaginous forests provide diverse ecosystem services, including timber, seed yield (a vital feedstock for biodiesel production), and substantial carbon savings. These carbon savings encompass carbon sequestration related to timber growth and carbon savings resulting from substituting fossil fuel with biodiesel. However, oleaginous forests are vulnerable to seed wasp attacks (disservice), which significantly threaten both seed yield and carbon savings. Using an integrated ecological-economic model that includes Faustmann's Land Expectation Value model and a pest damage control model, we aim to understand the intricate relationship among multiple ecosystem services and disservices of oleaginous forests. The results reveal four distinct phases contingent on varying pesticide application rates: the pesticide under-use phase, substitution phase, complementary phase, and over-use phase. Notably, a potential avenue to minimize pest damage is identified during the complementary phase by reducing the optimal rotation age at the expense of decreased carbon sequestration and bioenergy provision, posing a challenge to climate change mitigation. These findings have implications for formulating policies to manage conflicting ecosystem services of energy forests, offering valuable insights into the intersection of sustainable forest management and climate policy.

Urban socioeconomic variation influences the ecology and evolution of trophic interactions.

As urbanization expands, it is becoming increasingly important to understand how anthropogenic activity is affecting ecological and evolutionary processes. Few studies have examined how human social patterns within cities can modify eco-evolutionary dynamics. We tested how socioeconomic variation corresponds with changes in trophic interactions and natural selection on prey phenotypes using the classic interaction between goldenrod gall flies (Eurosta solidaginis) and their natural enemies: birds, beetles, and parasitoid wasps. We sampled galls from 84 sites across neighbourhoods with varying socioeconomic levels, and quantified the frequency of predation/parasitism on flies and natural selection by each enemy. We found that bird predation was higher in the highest income neighbourhoods, increasing the strength of selection for smaller galls. Wasp and beetle attack, but not their strength of selection, increased in lower income neighbourhoods. We show that socioeconomic variation in cities can have strong unintended consequences for the ecology and evolution of trophic interactions.

Neotropical songbird chick predation by an invasive wasp, the German yellowjacket (Vespula germanica)

AbstractSocial wasps (Family: Vespidae) are opportunistic and generalist feeders, which can occasionally feed on live vertebrates. The German yellowjacket (Vespula germanica) is native to Eurasia and Northern Africa, and has invaded many countries around the world, producing several environmental, economic and social impacts. Here we report the first video‐recorded evidence that this wasp species preys on chicks. Over six breeding seasons, we studied the parental care behaviour of the Chilean Elaenia (Elaenia chilensis), a long‐distance migratory bird that breeds in the Andean‐Patagonian Forest. We filmed 59 nests when chicks were 2–3 and 10–11 days old, and recorded in a nest containing two 10‐day‐old nestlings the predation of one of them by German yellowjackets. The other chick was found alive on the ground, indicating that it escaped from the wasps. Parents did not defend offspring against wasp attacks. The rarity of this observation may suggest either that this insect is not yet a significant nest predator or that it is difficult to obtain a record of predation by wasps, because birds may remove dead nestlings from the nests (i.e. nest sanitation). Although Chilean Elaenia is not threatened, 41% of bird species in the Andean‐Patagonian Forest are endemic, and this new nest predator may potentially become a threat to the conservation of any of those species, which deserves further research. Hence, to evaluate the German yellowjacket impact on bird populations, it is imperative to conduct videotaped nest monitoring in order to remove the masking effect of nest sanitation on predator identity, which will allow to determine how much this wasp contributes to nest failure in the invaded zone of the Neotropical region.

Fundamental limits of parasitoid-driven host population suppression: Implications for biological control.

Parasitoid wasps are increasingly being used to control insect pest populations, where the pest is the host species parasitized by the wasp. Here we use the discrete-time formalism of the Nicholson-Bailey model to investigate a fundamental question-are there limits to parasitoid-driven suppression of the host population density while still ensuring a stable coexistence of both species? Our model formulation imposes an intrinsic self-limitation in the host's growth resulting in a carrying capacity in the absence of the parasitoid. Different versions of the model are considered with parasitism occurring at a developmental stage that is before, during, or after the growth-limiting stage. For example, the host's growth limitation may occur at its larval stage due to intraspecific competition, while the wasps attack either the host egg, larval or pupal stage. For slow-growing hosts, models with parasitism occurring at different life stages are identical in terms of their host suppression dynamics but have contrasting differences for fast-growing hosts. In the latter case, our analysis reveals that wasp parasitism occurring after host growth limitation yields the lowest pest population density conditioned on stable host-parasitoid coexistence. For ecologically relevant parameter regimes we estimate this host suppression to be roughly 10-20% of the parasitoid-free carrying capacity. We further expand the models to consider a fraction of hosts protected from parasitism (i.e., a host refuge). Our results show that for a given host reproduction rate there exists a critical value of protected host fraction beyond which, the system dynamics are stable even for high levels of parasitism that drive the host to arbitrary low population densities. In summary, our systematic analysis sheds key insights into the combined effects of density-dependence in host growth and parasitism refuge in stabilizing the host-parasitoid population dynamics with important implications for biological control.

Developmental changes in red-eyed treefrog embryo behavior increase escape-hatching success in wasp attacks

Developmental changes in red-eyed treefrog embryo behavior increase escape-hatching success in wasp attacks

History matters: Thermal environment before but not during wasp attack determines the efficiency of symbiont-mediated protection.

The outcome of natural enemy attack in insects is commonly impacted by the presence of defensive microbial symbionts residing within the host. The thermal environment is a factor known to affect symbiont-mediated traits in insects. Lower temperatures, for instance, have been shown to reduce Spiroplasma-mediated protection in Drosophila. Our understanding of protective symbiosis requires a deeper understanding of environment-symbiont-protection links. Here, we dissect the effect of the thermal environment on Spiroplasma-mediated protection against Leptopilina boulardi in Drosophila melanogaster by examining the effect of temperature before, during and after wasp attack on fly survival and wasp success. We observed that the developmental temperature of the mothers of attacked larvae, but not the temperature of the attacked larvae themselves during or after wasp attack, strongly determines the protective influence of Spiroplasma. Cooler maternal environments were associated with weaker Spiroplasma protection of their progeny. The effect of developmental temperature on Spiroplasma-mediated protection is probably mediated by a reduction in Spiroplasma titre. These results indicate that historical thermal environment is a stronger determinant of protection than current environment. Furthermore, protection is a character with transgenerational nongenetic variation probably to produce complex short-term responses to selection. In addition, the cool sensitivity of the Spiroplasma-Drosophila symbioses contrasts with the more common failure of symbioses at elevated temperatures, indicating a need to understand the mechanistic basis of low temperature sensitivity on this symbiosis.

The impact of the Asian chestnut gall wasp (Dryocosmus kuriphilus) on chestnut tree growth may be mediated by site resources

IntroductionThe Asian chestnut gall wasp (Dryocosmus kuriphilus) is a major pest of chestnut trees worldwide, seriously affecting chestnut cultivation. Information concerning the effects of gall wasp attack on diameter growth of chestnut trees is currently scarce and limited to coppice stands and to use of the growth of a non-target control species (unaffected by the pest) for reference purposes. The effects of the pest on widely-spaced plantations (grown at a much lower density than chestnut coppices) and the use of explicitly-observed annual infestation rate data remain to be explored.MethodsIn the present study, we analyzed the impact of the chestnut gall wasp on the diameter growth of chestnut trees, using data from 16 experimental plots established in widely-spaced plantations located in good quality sites. Two of the plots are in plantations where a susceptible hybrid chestnut clone and a chestnut clone resistant to the gall wasp coexist, whereas the remaining 14 plots are in Castanea sativa plantations where the level of gall wasp infestation varies across trees and years. The plots were surveyed to determine the diameter growth of the trees and the level of infestation during 5 years (2017–2021).ResultsThe infestation level corresponding to the theoretical damage threshold was surpassed inmost plots during the study period. Nevertheless, there were no differences in the growth of attacked and unaffected plants in the two plots planted with hybrid clones with contrasting susceptibility to the gall wasp. The attack had a modest effect in C. sativa plots, with a mean reduction in annual basal area increment of 9.9%.DiscussionThese findings apparently contradict previous reports of a marked reduction in radial growth of chestnut coppice trees due to gall wasp attack. The difference in findings may be related to increased compensation for herbivory with increasing levels of resources (especially light) in the plantations under study, which were less dense than previously studied stands. The study outcomes add to existing knowledge on the impact of chestnut gall wasp on wood formation and may have implications regarding planting site recommendations and subsequent stand management.

Parasitoid Wasp Culturing and Assay to Study Parasitoid-induced Reproductive Modifications in Drosophila.

In nature, parasitoid wasp infections are a major cause of insect mortality. Parasitoid wasps attack a vast range of insect species to lay their eggs. As a defense, insects evolved survival strategies to protect themselves from parasitoid infection. While a growing number of studies reported both host defensive tactics and parasitoid counter-offensives, we emphasize that this parasite-host relationship presents a unique ecological and evolutionary relevant model that is often challenging to replicate in a laboratory. Although maintaining parasitoid wasp cultures in the laboratory requires meticulous planning and can be labor intensive, a diverse set of wasp species that target many different insect types can be maintained in similar culture conditions. Here, we describe the protocol for culturing parasitoid wasp species on Drosophila larvae and pupae in laboratory conditions. We also detail an egg-laying assay to assess the reproductive modification of Drosophila females in response to parasitoid wasps. This behavioral study is relatively simple and easily adaptable to study environmental or genetic influences on egg-laying, a readout for female germline development. Neither the parasitoid culture conditions or the behavioral assay require special supplies or equipment, making them a powerful and versatile approach in research or teaching laboratory settings. Graphical abstract.

Rapid divergence in independent aspects of the compatibility phenotype in a Spiroplasma-Drosophila interaction.

Heritable symbionts represent important components of the biology, ecology and evolution of their arthropod hosts. Particular microbial taxa have become common across arthropods as a consequence of their ability to establish in new host species. For a host shift to occur, the symbiont must be exposed to a novel host and then be compatible: it must not cause excess pathology, must have good vertical transmission and must possess a drive phenotype that enables spread. Here we investigate the lability of compatibility to symbiosis with Spiroplasma. We used transinfection to establish the protective Spiroplasma symbiont from Drosophila hydei in two closely related novel hosts, Drosophila simulans and Drosophila melanogaster. The Spiroplasma had contrasting compatibility in the two species, exhibiting pathology and low vertical transmission but delivering protection from wasp attack in D. melanogaster but being asymptomatic and transmitted with high efficiency but with lower protection in D. simulans. Further work indicated that pathological interactions occurred in two other members of the melanogaster species group, such that D. simulans was unusual in being able to carry the symbiont without damage. The differing compatibility of the symbiont with these closely related host species emphasizes the rapidity with which host-symbiont compatibility evolves, despite compatibility itself not being subject to direct selection. Further, the requirement to fit three independent components of compatibility (pathology, transmission, protection) is probably to be a major feature limiting the rate of host shifts that will likely impact on the utility of Spiroplasma in pest and vector control. Moving forward, the variation between sibling species pairs provides an opportunity to identify the mechanisms behind variable compatibility, which will drive hypotheses as to the evolutionary drivers of compatibility variation.

Contrast in Post-Chill Eclosion Time Strategies Between Two Specialist Braconid Wasps (Hymenoptera: Braconidae) Attacking Rhagoletis Flies (Diptera: Tephritidae) in Western North America.

Parasitoids comprise a speciose insect group, displaying a wide array of life history strategies. In the Pacific Northwest of the United States, the tephritid fruit flies Rhagoletis tabellaria (Fitch) and Rhagoletis indifferens Curran infest red osier dogwood, Cornus sericea L. (Cornaceae), and bitter cherry, Prunus emarginata (Douglas ex Hooker) Eaton (Rosaceae), respectively. The flies are parasitized by different braconid wasps at different life stages; Utetes tabellariae (Fischer) oviposits into R. tabellaria eggs, whereas Diachasma muliebre (Muesebeck) oviposits into R. indifferens larvae feeding in cherries. Because Rhagoletis only have one major generation a year and the wasps attack temporally distinct fly life stages, we predicted that eclosion times of U. tabellariae should more closely follow that of its host than the larval-attacking D. muliebre. As predicted, U. tabellariae eclosed on average 6.0-12.5 d later than R. tabellaria, whereas D. muliebre eclosed on average 32.1 d after R. indifferens. Unexpectedly, however, longer chill duration differentially affected the systems; longer overwinters minimally influenced eclosion times of R. tabellaria and U. tabellariae but caused earlier eclosion of both R. indifferens and D. muliebre. Results imply that in temperate regions, diapause timing in braconid wasps evolves in response to both host life stage attacked and fly eclosion characteristics, possibly reflecting differential effects of winter on host plant fruiting phenology. Differences in phenological sensitivity of the lower host plant trophic level to variation in environmental conditions may have cascading effects, sequentially and differentially affecting eclosion times in higher frugivore (fly) and parasitoid (wasp) trophic levels.

Defensive behavior of the invasive alien hornet, Vespa velutina, against color, hair and auditory stimuli of potential aggressors

BackgroundDuring recent years, invasion of the yellow-legged hornet (Vespa velutina) has occurred in Europe, Korea and Japan, and stinging accidents often occur as some V. velutina nests are in places where humans can reach them. Misleading information regarding precautionary measures for mitigating wasp attacks has only exacerbated the situation. In this study, we sought to identify appropriate countermeasures by analyzing wasp defensive behavior, with a focus on color, hair and auditory stimuli.MethodsDefensive behavior was analyzed using video recordings by creating an experimental frame to attach experimental bundles to nine V. velutina nests in Daegu and Gyeongbuk, South Korea. For the color experiment, eight-color and single-color tests were conducted with bundles of eight colors (black, brown, yellow, green, orange, gray, red and white), and the difference in defensive behavior was tested between black hair/hairless and green hair/black hairless configurations.ResultsWhen presented simultaneously with bundles of eight different colors, V. velutina showed the greatest and the longest defensive behavior against the black bundle, followed by brown. A similar response was observed in single-color tests. Furthermore, there was no significant difference in the defensive behavior against black hair and black hairless, but the duration of defensive behavior was longer for black hair. A comparison between green hair and black hairless stimuli indicated that wasps are more sensitive to color than to hair texture. Vespa velutina showed no discernible responses when exposed to selected auditory stimuli (human conversation and loud music). Dark colors and dark hair are characteristic features of potential predators, to which wasps are evolutionarily predisposed, and are accordingly likely to provoke strong defensive responses. The results of this study provide scientifically credible information that can be used to base appropriate precautionary measures against wasp attacks.

Defensive behavior of the invasive alien hornet Vespa velutina nigrithorax against potential human aggressors

AbstractIn areas where wasps are common, many wasp sting incidents occur. However, guidance on the correct response to wasp attacks remains lacking. In this study, behavioral response experiments were conducted with the aim of minimizing damage from group wasp attacks. The study species was Vespa velutina, which frequently causes wasp sting injuries in the southern regions of South Korea. Results demonstrated that worker wasps showed defensive behavior when a person approached within 3 m of the nest, and the attack rate was higher when the person conducted a large arm swing. When a person walked away after touching a nest, the number of workers attacking did not significantly decrease until they reached 5 m, this reduced to less than half when the person reached 10 m. Approximately 1.3 workers attacked even up to 300 m. However, when the person ran, the number of workers attacking was almost one or less after 10 m. Therefore, it is best to escape quickly to at least 10 m to reduce injury from group attacks. When wasps attacked, even if the person crouched, the attack did not decrease. Our recommended defensive behavior when wasps attack unexpectedly is that victims should turn their face in the opposite direction to the nest or the wasps, protect their face with their hands and arms, lean forward and run away rapidly to minimize injury. Wearing a wide brim hat was very effective, preventing about 75% of stings to the head, so this is also recommended.

Thermal sensitivity of the Spiroplasma-Drosophila hydei protective symbiosis: The best of climes, the worst of climes.

The outcome of natural enemy attack in insects is commonly influenced by the presence of protective symbionts in the host. The degree to which protection functions in natural populations, however, will depend on the robustness of the phenotype and symbiosis to variation in the abiotic environment. We studied the impact of a key environmental parameter-temperature-on the efficacy of the protective effect of the symbiont Spiroplasma on its host Drosophila hydei, against attack by the parasitoid wasp Leptopilina heterotoma. In addition, we investigated the thermal sensitivity of the symbiont's vertical transmission, which may be a key determinant of the ability of the symbiont to persist. We found that vertical transmission was more robust than previously considered, with Spiroplasma being maintained at 25°C, at 18°C and with 18/15°C diurnal cycles, with rates of segregational loss only increasing at 15°C. Protection against wasp attack was ablated before symbiont transmission was lost, with the symbiont failing to rescue the fly host at 18°C. We conclude that the presence of a protective symbiosis in natural populations cannot be simply inferred from the presence of a symbiont whose protective capacity has been tested under narrow controlled conditions. More broadly, we argue that the thermal environment is likely to represent an important determinant of the evolutionary ecology of defensive symbioses in natural environments, potentially driving seasonal, latitudinal and altitudinal variation in symbiont frequency.

Does Drosophila sechellia escape parasitoid attack by feeding on a toxic resource?

Host shifts can drastically change the selective pressures that animals experience from their environment. Drosophila sechellia is a species restricted to the Seychelles islands, where it specializes on the fruit Morinda citrifolia (noni). This fruit is known to be toxic to closely related Drosophila species, including D. melanogaster and D. simulans, releasing D. sechellia from interspecific competition when breeding on this substrate. Previously, we showed that larvae of D. sechellia are unable to mount an effective immunological response against wasp attack, while larvae of closely-related species can defend themselves from parasitoid attack by melanotic encapsulation. We hypothesized that this inability constitutes a trait loss due to a reduced risk of parasitoid attack in noni. Here we present a lab experiment and field survey aimed to test the hypothesis that specialization on noni has released D. sechellia from the antagonistic interaction with its larval parasitoids. Our results from the lab experiment suggest that noni may be harmful to parasitoid wasps. Our results from the field survey indicate that D. sechellia was found in ripe noni, whereas another Drosophila species, D. malerkotliana, was present in unripe and overripe stages. Parasitic wasps of the species Leptopilina boulardi emerged from overripe noni, where D. malerkotliana was the most abundant host, but not from ripe noni. These results indicate that the specialization of D. sechellia on noni has indeed drastically altered its ecological interactions, leading to a relaxation in the selection pressure to maintain parasitoid resistance.

How much does the host matter to the parasitoid? Distribution of Eurytoma (Hymenoptera, Chalcidoidea) species amongst two locally co-occurring gall-inducing hosts in the genus Diplolepis (Hymenoptera, Cynipidae)

AbstractGall wasps in the cynipid genus Diplolepis Geoffroy (Hymenoptera: Cynipidae) attack various species of native and introduced roses in Canada. Although gall forms are diverse, gall wasps are parasitised by highly concordant complexes of parasitoids and inquilines. Many species of gall wasps attack the same host plants and develop over the same periods in the season, suggesting that opportunistic parasitoids may be exploiting a range of hosts rather than specialising. We sampled larvae of Eurytoma Illiger (Hymenoptera: Cynipidae) from galls of D. variabilis (Bassett) and D. rosaefolii (Cockerell), gall inducers that develop fairly synchronously late in the growing season on leaves of Rosa woodsii Lindl. (Rosaceae) in the Okanagan Valley of central British Columbia, Canada. Galls were sampled at five different sites along a gradient from the north end of the valley to the Canada–United States border, a distance of 100 km. We extracted DNA, then amplified and sequenced the cytochrome b segment for each Eurytoma larva. We identified two well-supported clades that were differentiated by neither sampling location nor host. Instead, at least two species of Eurytoma, E. imminuta Bugbee and E. longavena Bugbee, exist at these localities, and both exploit at least two of the Diplolepis hosts found at these sites.

Timing alters how a heat shock affects a host-parasitoid interaction.

Abiotic factors' effects on species are now well-studied, yet they are still often difficult to predict, especially for strongly interacting species. If these altered abiotic factors and species interactions occur as discrete events in time, such complications may occur because of the events' relative timing. One such discrete abiotic factor is the short-duration, large magnitude increase in temperature called a heat shock. This study investigates how the timing of heat shocks affects the successful attack and reproduction of a parasitoid wasp (Aphidius ervi) attacking its host, the pea aphid (Acyrthosiphon pisum). We tested three relative timings: 1) heat shock before the wasp attacks hosts, 2) heat shock while the wasp is foraging, and 3) heat shock after the wasp has attacked hosts. In each scenario we compared wasp mummy production (pupal stage) with and without a heat shock. Our results showed that a heat shock had the largest effect when it occurred while wasps actively foraged, with fewer mummies produced when exposed to a heat shock compared to the no heat shock control. Follow-up behavioral tests suggest this was caused by wasps becoming inactive during heat shocks. In contrast, when heat shocks were applied three days before or after foraging, we found no difference in mummy production between the heat shock treatment and no heat shock control. These results show the potential importance of timing when considering the ramifications of an altered abiotic factor, especially with relatively discrete abiotic events and interactions.

BIOLOGY, ECOLOGY AND CONTROL OF THE PLUM SEED WASP [EURYTOMA SCHREINERI SCHREINER (HYMENOPTERA: EURYTOMIDAE)

The plum seed wasp, Eurytoma schreineri Schr. is a new pest on plum trees in Bulgaria. It is a serious pest for plums in northeastern Bulgaria. This wasp attacks the fruits of various plum cultivars. Damage by E. schreineri on plums ranges from 26-92%. The damage percent depends upon bioecological conditions and on the susceptibility of the plum varieties. Late-flowering cultivars are the most sensitive, where the attack can reach up to 90-92% of Stanley cultivar. This is univoltine and overwinters as a fully developed larva within stones of the fallow fruit under the plum trees. During the spring, usually in early May, the adults go out of the fallen mummified fruits and after mating the females oviposit inside the newly formed plum fruit. The egg is inserted into the endosperm of the fruit before the formation of the stone. Incubation lasts about 20-22 days, and hatch begins about the time that the plum seed embryo becomes visible. Larva development is completed by the end of June or early July, then the larvae enter diapause and remain in this state for 1-3 winters. Locally penetrating insecticides, applied when the larvae begin to hatch, provide a significant degree of larval control.

Symbiont-mediated protection varies with wasp genotype in the Drosophila melanogaster\u2013Spiroplasma interaction

The ability of an insect to survive attack by natural enemies can be modulated by the presence of defensive symbionts. Study of aphid–symbiont–enemy interactions has indicated that protection may depend on the interplay of symbiont, host and attacking parasite genotypes. However, the importance of these interactions is poorly understood outside of this model system. Here, we study interactions within a Drosophila model system, in which Spiroplasma protect their host against parasitoid wasps and nematodes. We examine whether the strength of protection conferred by Spiroplasma to its host, Drosophila melanogaster varies with strain of attacking Leptopilina heterotoma wasp. We perform this analysis in the presence and absence of ethanol, an environmental factor that also impacts the outcome of parasitism. We observed that Spiroplasma killed all strains of wasp. However, the protection produced by Spiroplasma following wasp attack depended on wasp strain. A composite measure of protection, including both the chance of the fly surviving attack and the relative fecundity/fertility of the survivors, varied from a <4% positive effect of the symbiont following attack of the fly host by the Lh14 strain of wasp to 21% for the Lh-Fr strain in the absence of ethanol. We also observed that environmental ethanol altered the pattern of protection against wasp strains. These data indicate that the dynamics of the Spiroplasma–Drosophila–wasp tripartite interaction depend upon the genetic diversity within the attacking wasp population, and that prediction of symbiont dynamics in natural systems will thus require analysis across natural enemy genotypes and levels of environmental ethanol.