Optimal defense strategy against herbivory in plants: Conditions selecting for induced defense, constitutive defense, and no-defense

To examine the conditions selecting for induced defense, constitutive defense, and no-defense, we developed a model of plant defense strategy against herbivory. In the model, a plant consists of two modules between which signal inducing defense compounds can be translocated. We assume three strategies: plants produce defense compounds responding to herbivory (induced defense), they have the compounds beforehand (constitutive defense), and they never produce the compounds (no-defense). We found that no-defense is optimal if the amount of biomass lost due to herbivory is small because of the growth cost of having defense compounds. The constitutive defense is optimal if the amount of biomass lost is not so small and the probability of herbivory is high. If the biomass loss is not so small but the probability of herbivory is low, the induced defense or no-defense is optimal. When the induced defense is optimal, the probability of herbivory necessarily increases in plants once herbivory has occurred. If the probability stays the same, no-defense is optimal. Thus, the behavior of herbivores, i.e., whether they remain around a plant and attack it repeatedly, affects the evolution of the induced defense.     

A novel trade-off of insect diapause affecting a sequestered chemical defense

Diapause allows insects to temporally avoid conditions that are unfavorable for development and reproduction. However, diapause may incur a cost in the form of reduced metabolic energy reserves, reduced potential fecundity, and missed reproductive opportunities. This study investigated a hitherto ignored consequence of diapause: trade-offs involving sequestered chemical defense. We examined the aristolochic acid defenses of diapausing and non-diapausing pipevine swallowtail butterflies, Battus philenor. Pipevine swallowtail larvae acquire these chemical defenses from their host plants. Butterflies that emerge following pupal diapause have significantly less fat, a female fitness correlate, compared to those that do not diapause. However, butterflies emerging from diapaused pupae are more chemically defended compared to those that have not undergone diapause. Furthermore, non-diapausing butterflies are confronted with older, lower quality host plants on which to oviposit. Thus, a trade-off exists where butterflies may have greater energy reserves at the cost of less chemical defense and sub-optimal food resources for their larvae, or have substantially less energetic reserves with the benefit of greater chemical defense and plentiful larval food resources.     

Uptake and metabolism of pyrrolizidine alkaloids in<Emphasis Type="Italic"> Longitarsus</Emphasis> flea beetles (Coleoptera: Chrysomelidae) adapted and non-adapted to alkaloid-containing host plants

Several Longitarsus flea beetle species sequester pyrrolizidine alkaloids acquired from their Asteraceae and Boraginaceae host plants. We carried out feeding and injection experiments using radioactively labeled pyrrolizidine alkaloids to investigate the physiological mechanisms of uptake, metabolism and storage of alkaloids in adult beetles. We examined six Longitarsus species belonging to different phylogenetic clades in a comparative approach. All species that accepted pyrrolizidine alkaloids in a preceding food choice study showed the ability both to store pyrrolizidine alkaloid N-oxides and to metabolize tertiary pyrrolizidine alkaloids into their N-oxides. Regardless of whether the beetles' natural host plants contain pyrrolizidine alkaloids or not, these species were found to possess an oxidizing enzyme. This oxygenase appears to be specific to pyrrolizidine alkaloids: [³H]Atropine and [¹⁴C]nicotine, two alkaloids not related to pyrrolizidine alkaloids, were neither stored nor N-oxidized by any of the tested species. One species, L. australis, that strictly avoids pyrrolizidine alkaloids behaviorally, exhibited a lack of adaptations to pyrrolizidine alkaloids on a physiological level as well. After injection of tertiary [¹⁴C]senecionine, beetles of this species neither N-oxidized nor stored the compounds, in contrast to L. jacobaeae, an adapted species that underwent the same treatment. L. jacobaeae demonstrated the same efficiency in N-oxidation and storage when fed or injected with tertiary [¹⁴C]senecionine.Communicated by G. Heldmaier     

Enemy release but no evolutionary loss of defence in a plant invasion: an inter-continental reciprocal transplant experiment

Plant chemical defenses and escape from natural enemies have been postulated to select for dietary specialization in herbivorous insects. In field and laboratory bioassays, we evaluated the effectiveness of intact and chemically modified larval shield defenses of the generalist Chelymorpha alternans and the specialists Acromis sparsa and Stolas plagiata (Chrysomelidae: Cassidinae) against three natural predators, using larvae reared on two morning glory (Convolvulaceae) species. We assessed whether: (1) specialists were better defended than generalists when both were fed and assayed on the same plant; (2) larval shield defenses were chemical, physical, or both; and (3) specialists exploit chemistry better than generalists. Live specialist larvae survived at higher rates than did generalists in predator bioassays with the bug Montina nigripes (Reduviidae), but there were no differences among groups against two species of Azteca ants (Hymenoptera: Dolichoderinae). Solvent leaching by H₂O or MeOH significantly reduced shield efficacy for all species compared to larvae with intact shields. In contrast, freshly killed specialist larvae exhibited significantly lower capture rates and frequencies than the generalists. Although solvent leaching significantly reduced overall shield efficacy for freshly killed larvae of all species, the pattern of leaching effects differed between specialists and generalists, with H₂O-leaching having a greater impact on the specialists. The overall vulnerability of the generalists appears due to lower chemical protection, which is ameliorated by increased escape behaviors, suggesting a selective trade-off between these defensive components. These experiments indicate that shield defenses are essential for larval survival and that specialists are superior at exploiting plant compounds residing in the aqueous fraction. Our results support the hypothesis that diet-specialized herbivorous insects have more effective defenses than generalists when both feed on the same plant due to the differential ability to exploit defensive precursors obtained from the host. The evolution of dietary specialization may therefore confer the advantage of enhanced enemy-free space.     

An evaluation of chemical and physical defenses against fish predation in a suite of seagrass-associated ascidians

The palatability of two solitary and three colonial species of ascidians commonly found in sub-tropical seagrass meadows was evaluated using the abundant, sympatric, omnivorous pinfish Lagodon rhomboides as a model predator. Bite-sized pieces of fresh tissues of both solitary and one of the three colonial ascidian species were unpalatable to fish. Lipophilic and hydrophilic extracts of the three unpalatable species did not cause feeding deterrence indicating that secondary metabolites are not responsible for the lack of palatability. Distaplia bermudensis, the one colonial ascidian that was unpalatable to fish, had a highly acidified outer tunic (pH = 1.5). We tested the ability of acidified agar food pellets (pH = 1.5) to deter pinfish and found that the fish readily ingested acidified pellets. The toughness of the tunic of all five ascidian species was evaluated by measuring the Force (N) required to penetrate the tunic using a penetrometer. Tunic toughness is likely to explain the lack of palatability of the solitary ascidians Styela plicata and Molgula occidentalis as their tunics required a force of > 34 N to penetrate. Tunic toughness may be a particularly effective adaptation for ascidian defense in seagrass habitats where fish with strong crushing jaws, such as those that commonly occur in coral reef systems, are rare.     

Characterization of an algicidal bacterium Brevundimonas J4 and chemical defense of Synechococcus sp. BN60 against bacterium J4

As part of efforts to enhance the strategies explored to eliminate the adverse impacts of cyanobacterial blooms, we isolated an algicidal bacterium, J4, from Lake Taihu. Analysis of 16S rDNA sequence revealed that strain J4 belonged to the genus Brevundimonas. Bacterium J4 exhibited algicidal activity mainly through excretion of extracellular algicidal compounds that were further extracted with methanol and purified by silica gel chromatography and high performance liquid chromatography (HPLC). The compounds showed thermal stability, strong polarity and water solubility in J4 cultures. Study on the algicidal activity of J4 against two dominant cyanobacterial bloom-forming species in Lake Taihu showed that J4 exhibited lower algicidal rate against Synechococcus sp. BN60 (48.6%, t = 6 days) than against Microcystis aeruginosa 9110 (91.8%, t = 6 days). Additionally, rapid reduction in cell density of J4 was observed in co-cultures of Synechococcus sp. BN60 and bacterium J4 but not observed in co-cultures of M. aeruginosa 9110 and bacterium J4 during algicidal process, which was the main reason why the algicidal rate of J4 against BN60 was lower than against 9110. The reduction in cell density of J4 resulted from inducible production of antimicrobial-like compound secreted by Synechococcus sp. BN60 in co-cultures of Synechococcus sp. BN60 and bacterium J4, which reflected a kind of chemical defense from cyanobacteria (BN60) against algicidal bacteria (J4). However, M. aeruginosa 9110 had no chemical defense against J4, suggesting that whether cyanobacterial chemical defense occurs or not between cyanobacteria and algicidal bacteria depends on specific cyanobacteria–algicidal bacteria pairs. These results show that not only one-sided algicidal effect but also two-sided reciprocal inhibition interactions exist between algicidal bacteria and cyanobacteria, indicating the complexity of cyanobacteria–algicidal bacteria interactions in Lake Taihu and the need to take the cyanobacterial defensive responses into consideration when assessing potential use of algicidal bacteria.     

The defense hypothesis of elemental hyperaccumulation: status,challenges and new directions

Elemental hyperaccumulation may have several functions, including plant defense against natural enemies. A total of 34 studies, including 72 experimental tests, have been conducted to date. At least some tests have demonstrated defense by hyperaccumulated As, Cd, Ni, Se and Zn, but relatively few plant taxa and natural enemies have been investigated. Defense by hyperaccumulated Ni has been shown for most leaf/root chewing herbivores and pathogens tested (20 of 26 tests) but not for herbivores of other feeding modes (1 of 8 tests). Most tests (5 of 6) using Ni concentrations below accumulator levels found no defensive effect, and the single test using plants in the accumulator range also found no effect. For Zn, mixed results have been reported for both hyperaccumulator (3 of 6 tests showed defense) and accumulator levels (3 of 4 tests showed defense). These tests have focused exclusively on leaf chewing/scraping herbivores: no herbivores of other feeding modes, or pathogens, have been tested. Both hyperaccumulator and accumulator concentrations of Se generally have shown defensive effects (12 of 14 tests). Most (75%) of these positive results used plants with accumulator Se concentrations. The three tests of Cd showed defensive effects in two cases, one for hyperaccumulator and one for sub-accumulator Cd concentrations. Arsenic has been tested only once, and was found effective against a leaf-chewing herbivore at a concentration much less than the hyperaccumulator level. Defense studies have used a variety of experimental approaches, including choice and no-choice experiments as well as experiments that use artificial diet or growth media. Investigations of hyperaccumulation as a defense against natural enemies have led to two emerging questions. First, what is the minimum concentration of an element sufficient for defense? Evidence suggests that plants other than hyperaccumulators (such as accumulators) may be defended by elements against some natural enemies. Second, do the effects of an element combine with the effects of organic defensive compounds in plants to produce enhanced joint defensive effects? Recent investigation of this “joint effects hypothesis,” using Ni and secondary plant compounds in artificial insect diet, has demonstrated joint effects. Initial answers to both these questions suggest that defensive effects of elements in plants are more widespread than previously believed. These results also suggest an evolutionary pathway by which elemental hyperaccumulation may have evolved from accumulation. In this “defensive enhancement” scenario, defensive benefits of elevated levels of elements may have led to stepwise increases in element concentrations that further magnified these benefits. This series of steps could have led to increased accumulation, and ultimately hyperaccumulation, of elements by plants.     

Indirect plant defense against insect herbivores: a review

Plants respond to herbivore attack by launching 2 types of defenses: direct defense and indirect defense. Direct defense includes all plant traits that increase the resistance of host plants to insect herbivores by affecting the physiology and/or behavior of the attackers. Indirect defense includes all traits that by themselves do not have significant direct impact on the attacking herbivores, but can attract natural enemies of the herbivores and thus reduce plant loss. When plants recognize herbivore‐associated elicitors, they produce and release a blend of volatiles that can attract predators, parasites, and other natural enemies. Known herbivore‐associated elicitors include fatty acid–amino acid conjugates, sulfur‐containing fatty acids, fragments of cell walls, peptides, esters, and enzymes. Identified plant volatiles include terpenes, nitrogenous compounds, and indoles. In addition, constitive traits including extrafloral nectars, food bodies, and domatia can be further induced to higher levels and attract natural enemies as well as provide food and shelter to carnivores. A better understanding of indirect plant defense at global and componential levels via advanced high throughput technologies may lead to utilization of indirect defense in suppression of herbivore damage to plants.     

Disarming the paradox of sublethal plant defense against insects: Trirhabda virgata larval development time and leaf tissue loss on Solidago altissima

Although the fitness benefits of traits that kill herbivores are obvious, the contention that sublethal antiperformance traits have evolved as plant defenses has proved more controversial. Traits that slow herbivore development seem particularly paradoxical, given the common assumption that a protracted feeding period will lead to greater total consumption. Whereas this assumption is superficially reasonable, there is very little evolutionarily relevant evidence to suggest that plants on which larval development is slower actually lose more tissue. For the assumption underlying the sublethal‐defense paradox to be valid, plant traits that affect larval development time and tissue loss must be positively correlated genetically within natural plant populations. In this study, we examined the relationship between larval development time of the beetle Trirhabda virgata LeConte (Coleoptera: Chrysomelidae) and plant tissue loss by its host plant Solidago altissima L. (Asteraceae). Plant genets on which the larval development time was longer ended up losing less leaf area than plant genets that allowed quicker larval development. This negative genetic correlation contradicts the common assumption that greater sublethal resistance leads to increased tissue loss. Combined with other hypothesized benefits of sublethal resistance, this result suggests that antiperformance traits may constitute a more potent form of resistance than is generally acknowledged.     

Relationships between leaf age and the food quality of cottonwood foliage for the gypsy moth,Lymantria dispar

Summary The cottonwood tree, Populus deltoides, continues to produce leaves late into the growing season, exposing midseason herbivores to leaves of a wide range of maturity. Gypsy moth larvae preferred and grew best on the oldest cottonwood leaves and suffered higher mortality and 85% less growth when fed young, expanding leaves. Concentration of phenolics in the youngest leaves was 3 times that in the oldest leaves and was negatively correlated with caterpillar growth rate. The active phenolics were not identified; tannin was present but its concentration changed more with season than leaf age.     

Occurrence and impact of the parasitic mite Linobia coccinellae on its host beetle Chrysomela populi: implications for its potential as a biological control agent

Due to social demands with regard to sustainability and ecological considerations, an aim of current research in short-rotation coppices (SRC) is to find effective candidates for biological control of pest species. The great red poplar leaf beetle, Chrysomela populi L. (Coleoptera: Chrysomelidae), is one of the most harmful pests in the SRC. The endoparasitic mite Linobia coccinellae (Scopoli) (Acari: Astigmata, Hemisarcoptidae) lives under the elytra of C. populi and feeds on the beetles' hemolymph. The population dynamics of the mites and their impact on the fecundity and longevity of female beetles were examined in two experiments. To study the occurrence of the mites, beetles were collected from two poplar SRC sites in Germany on three dates. Infestation rates of collected male and female C. populi individuals increased over the course of the year and reached 78–97% in the last survey. Females were parasitized more often than males at any time. For the second part of the study, beetles were reared under laboratory conditions to study the development of the mites and their impact on the hosts. For this purpose, half of the females were actively seeded with five adult females of L. coccinellae and the other half was used as a control. There was no significant impact on longevity or reproductive traits of the beetles. Despite the high rates of infestation, it appears that the mites do not have a serious effect on female beetles. Thus L. coccinellae, by itself, is not an effective biological control agent against C. populi. However, it remains to be investigated whether the mites increase the beetles' susceptibility to other biotic and abiotic factors, and so may contribute to an integrated pest management regime with multiple antagonists.     

Rank and colony defense against conspecifics in a facultatively eusocial hover wasp

An important benefit of social living is increased capacityfor defense. Highly eusocial species have often evolved a fightingcaste for this purpose, but many facultatively eusocial insectsand cooperatively breeding vertebrates lack morphological castesand the decision to defend or not can depend on costs and benefitsto each individual. Defense by subordinates in a social groupcan be regarded as a form of helping, and helping input oftenvaries among subordinates of different age or size. Severalhypotheses attempt to explain variation in helping effort, includingthe effects of relatedness and differences in the costs of helping.Evidence for these hypotheses is mixed and often lacks dataon the rank of subordinates, an important determinant of expectedfuture fitness. We examined individual variation in propensityto defend the nest against conspecifics in the tropical hairy-facedhover wasp Liostenogaster flavolineata. Prior to experimentation,we determined the positions of all wasps in the age-based queueto inherit the single egg-laying position in each L. flavolineatagroup. Two approaches were then used: observations of defenseagainst natural intrusions by conspecifics and experimentaltrials where wasps were presented attached to a wire. Higherranks were more likely to defend the nest than lower ranks,opposite to the pattern previously documented for another formof helping: foraging effort. Possible explanations for thisresult are that higher ranked females are better defenders andthat they suffer a larger decrease in expected future fitnesswhen an intruder usurps their position in the inheritance queue.     

Lactoferrin: Role in iron homeostasis and host defense against microbial infection

The transferrin family of non-heme iron binding glycoproteins are believed to play a central role in iron metabolism and have been implicated in iron transport, cellular iron delivery and control of the level of free iron in external secretions. Lactoferrin (LF) is a member of this family that is widely localized in external fluids including milk and mucosal secretions, in addition to being a prominent component of the secondary granules of neutrophils. Although structurally related to transferrin, LF appears to have a broader functional role mediated by both iron dependent and iron independent mechanisms. In this review, we will focus on our current understanding on the role of LF in regulating iron homeostasis and its role in host protection against microbial infection at the mucosal surface. In addition, recent insights obtained from analyzing the phenotypic consequences of LF ablation in lactoferrin knockout mice (LFKO), which challenge the long held dogma that LF is required for intestinal iron absorption in the neonate, are summarized.     

Lack of rapid monoterpene turnover in rooted plants: implications for theories of plant chemical defense

Summary Evidence for the rapid metabolic turnover of leaf monoterpenes is a significant component of theories regarding the evolution and metabolic cost of plant chemical defenses. We re-examined whether monoterpenes are continuously synthesized and lost in intact peppermint plants, and demonstrate that the rapid monoterpene turnover previously observed using detached stems does not occur in intact plants. The apparent artifactual nature of rapid monoterpene turnover in peppermint suggests that a re-evaluation of the rates of metabolic turnover of plant defenses is needed before accurate hypotheses regarding the cost of plant chemical defense can be proposed.     

Native species vulnerability to introduced predators: testing an inducible defense and a refuge from predation

To manage the impacts of biological invasions, it is important to determine the mechanisms responsible for the effects invasive species have on native populations. When predation by an invader is the mechanism causing declines in a native population, protecting the native species will involve elucidating the factors that affect native vulnerability. To examine those factors, this study measured how a native species responded to an introduced predator, and whether the native response could result in a refuge from predation. Predation by the green crab, Carcinus maenas, has contributed to the decline in numbers of native soft-shell clams, Mya arenaria, and efforts to eradicate crabs have proven futile. We tested how crab foraging affected clam burrowing, and how depth in the sediment affected clam survival. Clams responded to crab foraging by burrowing deeper in the sediment. Clams at shallow depths were more vulnerable to predation by crabs. Results suggest soft-shell clam burrowing is an inducible defense in response to green crab predation because burrowing deeper results in a potential refuge from predation by crabs. For restoring the native clam populations, tents could exclude crabs and protect clams, but when tents must be removed, exposing the clams to cues from foraging crabs should induce the clams to burrow deeper and decrease vulnerability. In general, by exposing potential native prey to cues from introduced predators, we can test how the natives respond, identify whether the response results in a potential refuge, and evaluate the risks to native species survival in invaded communities.     

Romaine lettuce latex deters feeding of banded cucumber beetle: a vehicle for deployment of biochemical defenses

Latex is widely found among plant species and is known to play a defensive role against certain herbivores. Two romaine lettuce, Lactuca sativa L. (Asteraceae) cultivars, 'Valmaine' (resistant) and 'Tall Guzmaine' (susceptible), were selected to study the potential of latex as a defense mechanism against the banded cucumber beetle, Diabrotica balteata LeConte (Coleoptera: Chrysomelidae). Latex from Valmaine strongly inhibited feeding of adult D. balteata compared to latex from Tall Guzmaine when applied to the surface of artificial diet. Beetles consumed significantly less diet from disks treated with Valmaine latex than they consumed from diet treated with Tall Guzmaine latex, in both choice and no-choice tests. In a choice test involving diet disks treated with Valmaine latex from young leaves vs. disks treated with latex from mature leaves, the beetles consumed significantly less diet treated with latex from young leaves. No significant difference in diet consumption was found between diets treated with latex from young and mature leaves of Tall Guzmaine in choice tests. Three solvents of differing polarity (water, methanol, and methylene chloride) were tested to extract deterrent compounds from latex; Valmaine latex extracted with water:methanol (20:80) strongly inhibited beetle feeding when applied to the surface of artificial diet. In no-choice tests, fewer beetles were observed feeding on diet treated with water:methanol (20:80) extract of Valmaine latex than on diet treated with a similar extract of Tall Guzmaine latex, resulting in significantly less consumption of the diet treated with the Valmaine latex extract. These studies suggest that moderately polar chemicals within latex may account for resistance in Valmaine to D. balteata.     

Assessing temporal dynamics of predation and effectiveness of caterpillar visual defense using sawfly larval color and resting posture as a model

Caterpillars (Lepidoptera and Symphyta larvae) employ diverse visual defensive tactics, and effectiveness of such tactics may be highly dynamic across time due to seasonal changes in the predator assemblages and their preferences. However, this has rarely been studied especially in tropical regions. Here we assessed temporal changes in the defensive value of caterpillar color and shape, using six types of plasticine dummy caterpillars: three colors (green, black, and white) × two shapes (curled and straight). These dummy caterpillars were deployed five times over different seasons in tropical forests of Xishuangbanna (China) and, as a comparison, twice in a temperate forest of Hirosaki (Japan). The colors and shapes of dummy caterpillars simulate visual traits of black sawfly larvae which take the curled resting posture in tropical rainforests of Xishuangbanna, apparently masquerading excrements commonly found on plants, while in Hirosaki there is no black-curled sawfly larvae and few excrements on plants. We found no significant effects of caterpillar colors or shapes on predation in Hirosaki. In contrast, black and curled caterpillars received significantly lower predation by birds in Xishuangbanna constantly across time. However, we were unable to provide evidence that the black-curled sawfly larvae are masquerading as excrements. Shapes of the dummy caterpillars also affected the predation by ants and parasitoid wasps at certain times. This is the first report on ecological function of the curled posture of sawfly larvae, and we demonstrated the importance to assess the temporal dynamics of predation and effectiveness of defensive tactics in tropical forests.     

Associational effects and the maintenance of polymorphism in plant defense against herbivores: review and evidence

Many plant species have evolved defense traits against herbivores. Associational effects (AEs) refer to a kind of apparent interaction where the herbivory risk to a focal plant species depends on the composition of other plant species in a neighborhood. Despite ample evidence for AEs between different plant species, this point of view has rarely been applied to polymorphism in defense traits within a plant species. The purpose of this review is to highlight an overlooked role of conspecific AEs in maintaining polymorphism in antiherbivore defense. First, I present a general review of AE between plant species and its role in the coexistence of plant species. This viewpoint of AE can be applied to genetic polymorphism within a plant species, as it causes frequency‐ and density‐dependent herbivory between multiple plant types. Second, I introduce a case study of conspecific AEs in the trichome‐producing (hairy) and glabrous plants of Arabidopsis halleri subsp. gemmifera. Laboratory and semi‐field experiments illustrated that AEs against the brassica leaf beetle Phaedon brassicae mediate a minority advantage in defense and fitness between hairy and glabrous plants. Combined with a statistical modeling approach, field observation revealed that conspecific AEs can maintain the trichome dimorphism via negative frequency‐dependent selection in a plant population. Finally, I discuss spatial and temporal scales at which AEs contribute to shaping genetic variation in antiherbivore defense in a plant metapopulation. Based on the review and evidence, I suggest that AEs play a key role in the maintenance of genetic variation within a plant species.     

Hyperparasitoid defense strategies against spiders: the role of chemical and morphological protection

The aphid endohyperparasitoid Alloxysta brevis(Thomson) (Hymenoptera: Charipidae) applies defensive chemicals stored in mandibular gland reservoirs against attacking ants. Alloxystines can be divided into species capable of exploiting ant-attended resources and into species exclusively reared from unattended aphid-parasitoid systems. Mandibular secretions are found in species of both groups, with little variation in chemical composition. We show that the mandibular gland secretion does not only protect against ant attacks but acts as an overall defense agent against generalist predators like spiders. The protective success differed with the spider species. The web-building spider Agelena labyrinthica(Clerck) (Araneae: Agelinidae) killed 57% of attacked A. brevisfemales, but sucked out only 8%. The smaller free-hunting jumping spider Salticus scenicus(Clerck) (Araneae: Salticidae) failed in overwhelming or severely injuring A. brevis. The pattern of interactions showed striking similarities with interactions between A. brevisand the ant Lasius niger(Hymenoptera: Formicidae). Primary parasitoids which are lacking chemical defense and sufficient morphological protection suffered significantly higher mortality due to spider predation. Our results indicate that – additional to chemical defense- parasitoid survival depends on the specific morphological resistance against grip pressure during capture, and on the predator – prey size relationship.