Synergistic Effects of Amides from Two <Emphasis Type="Italic">Piper</Emphasis> Species on Generalist and Specialist Herbivores

Plants use a diverse mix of defenses against herbivores, including multiple secondary metabolites, which often affect herbivores synergistically. Chemical defenses also can affect natural enemies of herbivores via limiting herbivore populations or by affecting herbivore resistance to parasitoids. In this study, we performed feeding experiments to examine the synergistic effects of imides and amides (hereafter “amides”) from Piper cenocladum and P. imperiale on specialist (Eois nympha, Geometridae) and generalist (Spodoptera frugiperda, Noctuidae) lepidopteran larvae. Each Piper species has three unique amides, and in each experiment, larvae were fed diets containing different concentrations of single amides or combinations of the three. The amides from P. imperiale had negative synergistic effects on generalist survival and specialist pupal mass, but had no effect on specialist survival. Piper cenocladum amides also acted synergistically to increase mortality caused by parasitoids, and the direct negative effects of mixtures on parasitoid resistance and pupal mass were stronger than indirect effects via changes in growth rate and approximate digestibility. Our results are consistent with plant defense theory that predicts different effects of plant chemistry on generalist versus adapted specialist herbivores. The toxicity of Piper amide mixtures to generalist herbivores are standard bottom-up effects, while specialists experienced the top-down mediated effect of mixtures causing reduced parasitoid resistance and associated decreases in pupal mass.     

Shield Defense of a Larval Tortoise Beetle

Larvae of the folivorous tortoise beetle, Plagiometriona clavata, carry shields formed from feces and exuviae above their bodies. We used an ecologically relevant predatory ant, Formica subsericea, in a bioassay to determine if shields functioned as simple barriers, as previous studies indicated, or whether they were chemical defenses. Shields were necessary for larval survival; shield removal rendered larvae vulnerable. Shields produced by larvae reared on a substitute diet failed to provide protection. Solvent-leached shields also failed to deter ants, indicating the shield had a host-derived chemical component likely located in the feces, not in the exuviae. Solanum dulcamara, the larval host plant, contained free phytol, steroidal glycoalkaloids, and saponins. Shields contained partially deglycosylated metabolites of host steroidal glycoalkaloids and saponins, a suite of fatty acids, and derivatives of phytol, which together formed a deterrent barrier against ant attack. We compared the mobile shield of P. clavata to the stationary shield of another S. dulcamara-feeding leaf beetle, Lema trilinea. Both larval shield defenses were formed from a very similar array of host-derived compounds with deterrent properties. We concluded that convergent patterns of limited chemical transformation and selective incorporation of particular deterrent metabolites in shield defenses of two unrelated taxa represented responses to selection from invertebrate predators.     

Larval exposure to oviposition deterrents alters subsequent oviposition behavior in generalist,Trichoplusia ni and specialist,Plutella xylostella moths

The present study was undertaken to determine the effects of larval feeding experience on subsequent oviposition behavior of the resulting moths. Larvae of the cabbage looper (Trichoplusia ni, Noctuidae) and the diamondback moth (Plutella xylostella, Plutellidae) were exposed to the phenylpropanoid allelochemical trans-anethole (at 100 ppm fw in artificial diet) or the limonoid allelochemical toosendanin (10 ppm sprayed on cabbage leaves). Both compounds had been shown to deter oviposition in naïve moths in previous choice tests. Moths developing from experienced larvae (both sexes) showed a decrease in oviposition deterrence response when given a choice between control and treated leaves, unlike naïve moths. This phenomenon, analogous to habituation to feeding deterrents in lepidopteran larva, occurred irrespective of duration of feeding on the deterrent compound. We also observed that F₁larvae resulting from experienced moths (previously exposed to toosendanin as larvae) grew as well on toosendanin-treated foliage as on control foliage. In contrast, growth of F₁larvae from naïve moths was significantly impaired by toosendanin. These results demonstrate that host-selection behavior in cabbage looper (a generalist) and diamondback moth (a specialist) may be shaped by feeding experience according to Hopkins' Host Selection Principle in addition to chemical legacy.     

Trade-offs in Antiherbivore Defenses in Piper cenocladum: Ant Mutualists Versus Plant Secondary Metabolites

Ant–plant mutualisms may provide indirect evidence for costs of antiherbivore defenses when plants demonstrate trade-offs between allocating resources and energy into ant attractants versus chemical defenses. We tested the hypothesis that ecological trade-offs in defenses are present in Piper cenocladum. This plant possesses two distinct defenses: food bodies that attract predatory ants that destory herbivore eggs and amides that deter herbivores. Previous studies have demonstrated that the food bodies in P. cenocladum are an effective defense because the ants deter herbivory by specialist herbivores. Amides in other Piper species have been shown to have toxic qualities, but we tested the additional hypothesis that these amides have an actual defensive function in P. cenocladum. To test for ecological trade-offs between the two putative defenses, fragments of P. cenocladum were examined for the presence of amides both when the plant was producing food bodies and when it was not producing food bodies. Plants with active ant colonies had redundant defenses, producing food bodies and high levels of amides at the same time, but we detected a trade-off in that they had significantly lower levels of amides than did plants with no ants. To test for the defensive value of P. cenocladum amides, we used an ant bioassay and we examined herbivory results from previous experiments with plants that had variable levels of amides. These tests demonstrated that amides are deterrent to omnivorous ants, leaf cutting ants, and orthopterans. In contrast, the resident Pheidole bicornis ants are effective at deterring herbivory by specialist herbivores that oviposit eggs on the plant but not at deterring herbivory by nonresident omnivores. We concluded that although both amides and food body production appear to be costly, redundancy in defenses is necessary to avoid damage by a complex suit of herbivores.     

Similarity of Cuticular Lipids Between a Caterpillar and Its Host Plant: A Way to Make Prey Undetectable for Predatory Ants?

Ithomiine butterflies (Nymphalidae) have long-lived, aposematic, chemically protected adults. However, little is known about the defense mechanisms in larvae and other juvenile stages. We showed that larvae Mechanitis polymnia are defended from ants by a chemical similarity between their cuticular lipids and those of the host plant, Solanum tabacifolium (Solanaceae). This is a novel defense mechanism in phytophagous insects. A field survey during one season showed that larval survivorship was up to 80%, which is high when compared with other juvenile stages. In a laboratory bioassay, live larvae on their host plant were not attacked by the predatory ant Camponotus crassus (Formicidae). Two experiments showed that the similarity between the cuticular lipids of M. polymnia and S. tabacifolium protected the larvae from C. crassus: (a) when the caterpillar was switched from a host plant to a non-host plant, the predation rate increased, and (b) when a palatable larva (Spodoptera frugiperda, Noctuidae) was coated with the cuticular lipids of M. polymnia and placed on S. tabacifolium leaves, it no longer experienced a high predation rate. This defensive mechanism can be defined as chemical camouflage, and may have a double adaptive advantage, namely, protection against predation and a reduction in the cost of sequestering toxic compounds from the host plant.     

Inter- and Intraspecific Comparisons of Antiherbivore Defenses in Three Species of Rainforest Understory Shrubs

Plants defend themselves against herbivores and pathogens with a suite of morphological, phenological, biochemical, and biotic defenses, each of which is presumably costly. The best studied are allocation costs that involve trade-offs in investment of resources to defense versus other plant functions. Decreases in growth or reproductive effort are the costs most often associated with antiherbivore defenses, but trade-offs among different defenses may also occur within a single plant species. We examined trade-offs among defenses in closely related tropical rain forest shrubs (Piper cenocladum, P. imperiale, and P. melanocladum) that possess different combinations of three types of defense: ant mutualists, secondary compounds, and leaf toughness. We also examined the effectiveness of different defenses and suites of defenses against the most abundant generalist and specialist Piper herbivores. For all species examined, leaf toughness was the most effective defense, with the toughest species, P. melanocladum, receiving the lowest incidence of total herbivory, and the least tough species, P. imperiale, receiving the highest incidence. Although variation in toughness within each species was substantial, there were no intraspecific relationships between toughness and herbivory. In other Piper studies, chemical and biotic defenses had strong intraspecific negative correlations with herbivory. A wide variety of defensive mechanisms was quantified in the three Piper species studied, ranging from low concentrations of chemical defenses in P. imperiale to a complex suite of defenses in P. cenocladum that includes ant mutualists, secondary metabolites, and moderate toughness. Ecological costs were evident for the array of defensive mechanisms within these Piper species, and the differences in defensive strategies among species may represent evolutionary trade-offs between costly defenses.     

Differential attractiveness of induced odors emitted by eight maize varieties for the parasitoid cotesia marginiventris: is quality or quantity important?

Herbivore-induced plant volatiles can function as indirect defense signals that attract natural enemies of herbivores. Several parasitoids are known to exploit these plant-provided cues to locate their hosts. One such parasitoid is the generalist Cotesia marginiventris, which is, among others, attracted to maize volatiles induced by caterpillar damage. Maize plants can be induced to produce the same blend of attractive volatiles by treating them with regurgitant of Spodoptera species. We collected and analyzed the regurgitant-induced emissions of two plant species (cowpea and maize) and of eight Mexican maize varieties and found significant differences among their volatile emissions, both in terms of total quantity and the quality of the blends. In a Y-tube olfactometer, the odors of the same artificially induced plant species and Mexican varieties were offered in dual choice experiments to naïve mated females of C. marginiventris. Wasps preferred cowpea over maize odor and, in 3 of 12 combinations with the maize varieties, they showed a preference for the odors of one of the varieties. A comparison of the odor collection with results from the behavioral assays indicates that not only the quantity of the volatile emissions, but also the quality composition of the volatile blends is important for attraction of C. marginiventris. The results are discussed in the context of the possibility of breeding crop varieties that are particularly attractive to parasitoids.     

Specific foraging kairomones used by a generalist parasitoid

In general, it is assumed that generalist natural enemies do not innately use specific cues for the location of their host or prey species. This hypothesis was tested using naïve females of the generalist parasitoid Lariophagus distinguendus Förster and two of its hosts, larvae of the lesser grain borer Rhyzopertha dominica (F.) and of the granary weevil Sitophilus granarius L., feeding in wheat grains. In a four-chamber olfactometer, female parasitoids were attracted to volatiles emanating from the feces of both host species. Chemical analysis of the volatiles from the feces of R. dominica revealed the presence of dominicalure 1 and 2, the species specific aggregation pheromones of R. dominica. The main compounds in the volatiles from feces of S. granarius were identified as chemicals related to mites that are associated with hosts of L. distinguendus. Because these mites are not specific for S. granarius but also co-occur with other hosts, the mite chemicals have to be considered as general cues. In bioassays, synthetic dominicalure was attractive to naïve L. distinguendus, explaining the attraction of feces volatiles from R. dominica. Synthetic mite chemicals and sitophilate, the aggregation pheromone of S. granarius, had no effect on naïve parasitoids. It remains to be determined which innate chemical cues from feces of S. granarius are used by L. distinguendus. In contrast to our initial hypothesis, the generalist L. distinguendus is innately using specific cues for foraging. Two ideas are provided to explain this result.     

Induction of Plant Volatiles by Herbivores with Different Feeding Habits and the Effects of Induced Defenses on Host-Plant Selection by Thrips

Induced plant responses to attack by chewing insects have been intensively studied, but little is known about plant responses to nonchewing insects or to attack by multiple herbivores with different feeding habits. We examined volatile emissions by tobacco, Nicotiana tabacum, in response to feeding by the piercing–sucking insect western flower thrips (WFT), Frankliniella occidentalis, the chewing herbivore Heliothis virescens, and both herbivores simultaneously. In addition, we examined the effects of herbivore-induced plant defenses on host-plant selection by WFT. Plants responded to thrips feeding by consistently releasing five compounds. Simultaneous feeding by WFT and H. virescens elicited the same 11 compounds emitted in response to caterpillar feeding alone; however, two compounds, α-humulene and caryophyllene oxide, were produced in greater amounts in response to simultaneous herbivory. In choice tests, thrips consistently preferred uninduced plants over all other treatments and preferred plants damaged by caterpillars and those treated with caterpillar saliva over those treated with caterpillar regurgitant. The results are consistent with a previous finding that caterpillar regurgitant induces the release of significantly more volatile nicotine than plants damaged by caterpillars or plants treated with caterpillar saliva. A repellent effect of nicotine on WFT was confirmed by encircling unwounded plants with septa releasing volatile nicotine. Our results provide the first direct evidence that thrips feeding induces volatile responses and indicates that simultaneous herbivory by insects with different feeding habits can alter volatile emissions. In addition, the findings demonstrate that induced plant responses influence host-plant selection by WFT and suggest that the induction of volatile nicotine may play a role in this process.     

The Effects of Ants on the Entomophagous Butterfly Caterpillar Feniseca tarquinius, and the Putative Role of Chemical Camouflage in the Feniseca–Ant Interaction

Butterfly caterpillars in the lycaenid subfamily Miletinae are predators of ant-tended Homoptera, yet they lack specialized secretory and call-production organs crucial to ant association in other lycaenids. Here, we address the question of how miletine caterpillars have invaded the ant–Homoptera symbiosis through a study of the only New World miletine, Feniseca tarquinius, a predator of the wooly aphid Prociphilus tesselatus. Previous interpretations have suggested that F. tarquinius and other miletine caterpillars avoid ant aggression by concealing themselves under silken webs. In contrast, our field data indicate that F. tarquinius caterpillars are less likely to be concealed in the presence of the ants Camponotus pennsylvanicus and Formica obscuriventris than in the absence of ants, although caterpillar and ant behaviors vary between years. Chemical analysis and behavioral assays suggest that chemical camouflage, not physical concealment, is responsible for the ants’ failure to detect and remove F. tarquinius caterpillars from aphid colonies. Analyses by gas chromatography indicate that the cuticular lipid composition of caterpillars are similar to that of their aphid prey, although it varies with prey species. Behavioral assays confirm that solvent extracts of F. tarquinius caterpillars and P. tesselatus aphids evoke similar behavioral responses in C. pennsylvanicus ants. Chemical camouflage is well known in social parasites of ants, but the present study represents one of a few documented cases where chemical deceit is important to interactions with ants outside the nest.     

Phenolic Compounds in Red Oak and Sugar Maple Leaves Have Prooxidant Activities in the Midgut Fluids of <Emphasis Type="Italic">Malacosoma disstria</Emphasis> and <Emphasis Type="Italic">Orgyia leucostigma</Emphasis> Caterpillars

Phenolic compounds are generally believed to be key components of the oxidative defenses of plants against pathogens and herbivores. However, phenolic oxidation in the gut fluids of insect herbivores has rarely been demonstrated, and some phenolics could act as antioxidants rather than prooxidants. We compared the overall activities of the phenolic compounds in red oak (Quercus rubra) and sugar maple (Acer saccharum) leaves in the midgut fluids of two caterpillar species, Malacosoma disstria (phenolic-sensitive) and Orgyia leucostigma (phenolic-tolerant). Three hypotheses were examined: (1) ingested sugar maple leaves produce higher levels of semiquinone radicals (from phenolic oxidation) in caterpillar midgut fluids than do red oak leaves; (2) O. leucostigma maintains lower levels of phenolic oxidation in its midgut fluids than does M. disstria; and (3) phenolic compounds in tree leaves have overall prooxidant activities in the midgut fluids of caterpillars. Sugar maple leaves had significantly lower ascorbate:phenolic ratios than did red oak leaves, suggesting that phenolics in maple would oxidize more readily than those in oak. As expected, semiquinone radicals were at higher steady-state levels in the midgut fluids of both caterpillar species when they fed on sugar maple than on red oak, consistent with the first hypothesis. Higher semiquinone radical levels were also found in M. disstria than in O. leucostigma, consistent with the second hypothesis. Finally, semiquinone radical formation was positively associated with two markers of oxidation (protein carbonyls and total peroxides). These results suggest that the complex mixtures of phenolics in red oak and sugar maple leaves have overall prooxidant activities in the midgut fluids of M. disstria and O. leucostigma caterpillars. We conclude that the oxidative defenses of trees vary substantially between species, with those in sugar maple leaves being especially active, even in phenolic-tolerant herbivore species.     

A Novel Function of the Triterpene Squalene in a Tritrophic System

Changes in apple leaf chemistry after infestation by leafminers and their effect on both host location and host habitat location of the generalist parasitoid Pholetesor bicolor were investigated. Chemical analysis of leaf solvent extracts from healthy and leafminer-damaged leaves revealed that herbivory increased the amount of the triterpene squalene (C₃₀H₅₀), whereas quantities of all other identified compounds were similar in both plant treatments. To assess the response of parasitoids to host location cues, contact bioassays were conducted with naïve females. Results showed that parasitoids performed a characteristic ovipositional probing more often on the mine-damaged than on the healthy leaf. This behavior was triggered by a hexane extract of the mine-damaged leaf, but not by a healthy leaf extract. A synthetic mixture of the compounds identified in the extract triggered a similar response. A mixture devoid of squalene was not active, whereas squalene alone elicited the probing behavior. To assess the use of the identified compounds in habitat location, Y-tube olfactometer experiments were conducted with naïve and experienced females. Results showed that squalene is not involved in habitat location and has no priming effect on P. bicolor. While other triterpenes are known to mediate habitat location of parasitoids, this is the first report in which a plant triterpene is shown to mediate host location of a parasitoid. The biological and ecological functions of squalene on all three trophic levels are discussed.     

Defensive role ofAllium sulfur compounds for leek mothAcrolepiopsis assectella Z. (Lepidoptera) against generalist predators

It has been shown previously that sulfur volatiles produced byAllium plants affect the behavior of their specialist phytophages and of their specialist entomophages. The action of these compounds in protecting the leek mothAcrolepiopsis assectella against generalist entomophages was studied in comparison to the proposed original defensive role of these compounds against generalist herbivorous insects. Two ants species,Formica selysi andF. fusca, were used as generalist predators. Six behavioral criteria of the predatory behavior of the ants were studied in presence of the last-instar caterpillars (C₅). C₅ reared on artificial diets with or without leek components were tested, as well as C₅ soaked in frass of leek-reared caterpillars or disulfide solutions. In addition, the response of the ants to pure chemicals found in leek was studied using honey solutions with or without sulfur compounds. The sulfur allelochemicals ofAllium plants have a negative action on predatory ants. Interestingly, the nonvolatile precursors of sulfur volatiles ofAllium plants seem to have a protective role for their phytophagous insects against generalist entomophages.     

Effects of Ingested Secondary Metabolites on the Immune Response of a Polyphagous Caterpillar <Emphasis Type="Italic">Grammia incorrupta</Emphasis>

We considered the effects of plant secondary metabolites on the immune response, a key physiological defense of herbivores against pathogens and parasitoids. We tested the effect of host plant species and ingested iridoid glycosides on the immune response of the grazing, polyphagous caterpillar, Grammia incorrupta (Arctiidae). Individuals of G. incorrupta were fed either one of three plant diets with varying secondary metabolites, or an artificial diet with high or low concentrations of iridoid glycosides. An immune challenge was presented, followed by measurement of the encapsulation response. We failed to detect a significant difference in the immune response of G. incorrupta feeding on diets with varying concentrations of iridoid glycosides, or feeding on different host plants. However, the immune response was lower in caterpillars consuming the artificial diet compared to those consuming the plant diets. When caterpillar performance was measured, pupal weights were lower when caterpillars ingested high concentrations of iridoid glycosides due to a decrease in feeding efficiency. Overall, individuals of G. incorrupta that consumed different plant diets exhibited a high immune response with low variation. We conclude that the immune response of G. incorrupta is adapted to feeding on a variety of plants, which may contribute to the maintenance of this caterpillar’s polyphagous habit.     

Larval Beetles Form a Defense from Recycled Host-Plant Chemicals Discharged as Fecal Wastes

Larvae of the leaf-feeding beetles Neolema sexpunctata and Lema trilinea carry feces on their backs that form shields. We used the generalist predatory ant, Formica subsericea, in a bioassay to determine whether shields were a physical barrier or functioned as a chemical defense. Fecal shields protected both species against ant attack. Larvae of both species reared on lettuce produced fecal shields that failed to deter ants. Commelina communis, N. sexpunctata's host, lacks noxious secondary compounds but is rich in phytol and fatty acids, metabolites of which become incorporated into the fecal defense. In contrast, the host plant of L. trilinea, Solanum dulcamara, contains steroidal glycoalkaloids and saponins, whose partially deglycosylated metabolites, together with fatty acids, appear in Lema feces. Both beetle species make modifications to host-derived precursors before incorporating the metabolites into shields. Synthetic chemicals identified as shield metabolites were deterrent when applied to baits. This study provides experimental evidence that herbivorous beetles form a chemical defense by the elimination of both primary and secondary host-derived compounds. The use of host-derived compounds in waste-based defenses may be a more widely employed strategy than was hitherto recognized, especially in instances where host plants lack elaborate secondary compounds.     

The Chlorophyll Catabolite,Pheophorbide <Emphasis Type="Italic">a</Emphasis>, Confers Predation Resistance in a Larval Tortoise Beetle Shield Defense

Larval insect herbivores feeding externally on leaves are vulnerable to numerous and varied enemies. Larvae of the Neotropical herbivore, Chelymorpha alternans (Chrysomelidae:Cassidinae), possess shields made of cast skins and feces, which can be aimed and waved at attacking enemies. Prior work with C. alternans feeding on Merremia umbellata (Convolvulaceae) showed that shields offered protection from generalist predators, and polar compounds were implicated. This study used a ubiquitous ant predator, Azteca lacrymosa, in field bioassays to determine the chemical constitution of the defense. We confirmed that intact shields do protect larvae and that methanol-water leaching significantly reduced shield effectiveness. Liquid chromatography-mass spectrometry (LC-MS) of the methanolic shield extract revealed two peaks at 20.18 min and 21.97 min, both with a molecular ion at m/z 593.4, and a strong UV absorption around 409 nm, suggesting a porphyrin-type compound. LC-MS analysis of a commercial standard confirmed pheophorbide a (Pha) identity. C. alternans shields contained more than 100 μg Pha per shield. Shields leached with methanol-water did not deter ants. Methanol-water-leached shields enhanced with 3 μg of Pha were more deterrent than larvae with solvent-leached shields, while those with 5 μg additional Pha provided slightly less deterrence than larvae with intact shields. Solvent-leached shields with 10 μg added Pha were comparable to intact shields, even though the Pha concentration was less than 10% of its natural concentration. Our findings are the first to assign an ecological role for a chlorophyll catabolite as a deterrent in an insect defense.     

Do Enemies of Herbivores Influence Plant Growth and Chemistry? Evidence from a Seminatural Experiment

It is predicted that enemies of insect herbivores may influence the effects of herbivores on their host plants by affecting the choice of plant genotypes. To examine the effect of predators, we conducted two experiments, each with a different caterpillar species (Junonia coenia and Pyrrharctia isabella). Under seminatural conditions, we provided a choice between two genotypes of plantain (Plantago lanceolata) with different levels of iridoid glycosides and used Podisus maculiventris stinkbugs as predators. There were four treatments: no herbivores and no predators, low density of herbivores and no predators, high density of herbivores and no predators, and high density of herbivores plus predators. The caterpillars had little effect on plant growth but did influence the iridoid glycoside concentration. For the Junonia experiment, the concentration of iridoid glycosides was less for plots with a low density of caterpillars (with no predators) compared to the other treatments of caterpillar density. In the Pyrrharctia experiment, catalpol was induced by a high density of caterpillars (with no predators). There were no increases in total iridoid glycosides associated with either herbivore species. The presence of predators had no effect on plant growth or total iridoid glycoside pattern. The lack of effect by predators seems to reflect the relatively large variation in iridoid glycoside concentration among leaf ages, and the herbivores ability to respond to that variation, such that the difference in iridoid glycoside concentrations in the plant genotypes was less important.     

The Scent of Ant Brood: Caste Differences in Surface Hydrocarbons of Formica exsecta Pupae

Chemical communication is common across all organisms. Insects in particular use predominantly chemical stimuli in assessing their environment and recognizing their social counterparts. One of the chemical stimuli used for recognition in social insects, such as ants, is the suite of long-chain, cuticular hydrocarbons. In addition to providing waterproofing, these surface hydrocarbons serve as a signature mixture, which ants can perceive, and use to distinguish between strangers and colony mates, and to determine caste, sex, and reproductive status of another individual. They can be both environmentally and endogenously acquired. The surface chemistry of adult workers has been studied extensively in ants, yet the pupal stage has rarely been considered. Here we characterized the surface chemistry of pupae of Formica exsecta, and examine differences among sexes, castes (reproductive vs. worker), and types of sample (developing individual vs. cocoon envelope). We found quantitative and qualitative differences among both castes and types of sample, but male and female reproductives did not differ in their surface chemistry. We also found that the pupal surface chemistry was more complex than that of adult workers in this species. These results improve our understanding of the information on which ants base recognition, and highlights the diversity of surface chemistry in social insects across developmental stages.

     

Newly Hatched Neonate Larvae Can Glycosylate: The Fate of Betula pubescens Bud Flavonoids in First Instar Epirrita autumnata

Betula pubescens bud flavonoid aglycones reportedly have negative effects on the performance of first instar Epirrita autumnata and, thus, may defend birch leaves from larval defoliation. We hypothesized that the detrimental effects of these lipophilic flavonoids on larvae are due to their high levels in birch buds and/or the inability of naïve neonates to glycosylate them, which we have shown to occur in fifth instars. To test the latter hypothesis, we investigated the biochemical transformation of bud flavonoids in first instar E. autumnata. We found that newly hatched larvae have the ability to glycosylate birch bud/leaf flavonoid aglycones into corresponding glycosides. Moreover, we suggest that glycosylation may depend upon the chemical character of the aglycone and is an important factor in the performance of first instars.     

Antifungal Diketopiperazines from Symbiotic Fungus of Fungus-Growing Ant Cyphomyrmex minutus

The attine fungus Tyridiomyces formicarum, the symbiont of the fungus-growing ant Cyphomyrmex minutus, produces several antifungal diketopiperazines. This represents the first identification of antifungal compounds from an attine symbiont and contradicts previous suggestions that attine fungi do not produce metabolites with antifungal activity. T. formicarum probably produces antifungal compounds in defense (1) against other fungi that invade the gardens and escape the weeding activity of the ants, or (2) against ant-pathogenic fungi that could harm the host ants. Fungi cultivated by fungus-growing ants may represent a rich source of additional bioactive metabolites.