Chemosensitivity of lobster,Homarus americanus,to secondary plant compounds: Unused receptor capabilities

Chemosensitivity to secondary plant substances was examined electrophysiologically and behaviorally for the lobsterHomarus americanus. Neurophysiological experiments show that some chemoreceptor cells in the antennules (representing the sense of smell) and walking legs (representing the sense of taste) were excited by secondary compounds from plants of marine and terrestrial origin. These compounds include amygdalin, atropine sulfate, bromoform, caffeine,p-coumaric acid, diiodomethane, ferulic acid, heliotropin, phloroglucinol, quinine sulfate, salicin, sinigrin, tannic acid, and tomatine. The possible behavioral function of three of these compounds was tested. Phloroglucinol and ferulic acid had no observable effect on any aspect of feeding behavior at any concentration tested. Tannic acid, which is related to polyphenols found in marine algae, had no observable effect at any concentration tested on orientation to and grasping of food (activities controlled primarily by antennular and leg chemoreceptors, respectively) but did have an inhibitory effect on food ingestion (an activity controlled primarily by mouthpart chemoreceptors). These electrophysiological and behavioral results suggest that potential chemoreceptive information derived from many secondary plant compounds may not be used in feeding behavior. The receptors sensitive to these compounds may represent a common chemical sense as suggested by Dethier (1980). However, at least one compound, tannic acid, that is smelled and tasted by lobsters can function as a feeding inhibitor at the level of the mouthparts.     

Phenolic Metabolites in Leaves of the Invasive Shrub, Lonicera maackii, and Their Potential Phytotoxic and Anti-Herbivore Effects

Lonicera maackii is an invasive shrub in North America for which allelopathic effects toward other plants or herbivores have been suspected. We characterized the major phenolic metabolites present in methanol extracts of L. maackii leaves. In addition, we examined the effects of methanol–water extracts of L. maackii leaves on seed germination of a target plant species and on feeding preference and growth rate of a generalist insect herbivore. A total of 13 individual major and minor compounds were detected in crude leaf extracts by high-performance liquid chromatography coupled to electronspray ionization-tandem mass spectrometry (ESI-MS/MS). Extracts were dominated by two major flavones, apigenin and luteolin, and their glucoside derivatives, apigenin-7-glucoside and luteolin-7-glucoside. Quantities of these compounds, along with chlorogenic acid, varied between two sampling points. Leaf extracts that contained these compounds were inhibitory to seed germination of Arabidopsis thaliana. In addition, treatment of artificial diet with leaf extracts deterred feeding of the generalist herbivore, Spodoptera exigua, in choice experiments but had no effect on growth rate in short-term no-choice bioassays. Purified apigenin tended to deter feeding by S. exigua and inhibited seed germination of A. thaliana. We conclude that leaves of L. maackii contain phenolic compounds, including apigenin and chlorogenic acid, capable of having biological effects on other plants and insects.     

Plant–herbivore–carnivore Interactions in Cotton, <Emphasis Type="Italic">Gossypium hirsutum</Emphasis>: Linking Belowground and Aboveground

Most studies on plant–herbivore interactions focus on either root or shoot herbivory in isolation, but above- and belowground herbivores may interact on a shared host plant. Cotton (Gossypium spp.) produces gossypol and a variety of other gossypol-like terpenoids that exhibit toxicity to a wide range of herbivores and pathogens. Cotton plants also can emit herbivore-induced volatile compounds at the site of damage and systemically on all tissues above the site of damage. As these volatile compounds attract natural enemy species of the herbivore, they are thought to represent an indirect plant defense. Our study quantified gossypol and gossypol-like compounds in cotton plants with foliage feeding (Heliocoverpa zea), root feeding (Meloidogyne incognita), or their combination. Cotton plants with these treatments were studied also with respect to induced local and systemic volatile production and the attraction of the parasitic wasp Microplitis croceipes to those plants. We also evaluated whether foliage or root feeding affected foliar nitrogen levels in cotton. After 48 hr of leaf feeding and 5 wk of root feeding, local and systemic induction of volatiles (known to attract parasitoids such as M. croceipes) occurred with herbivore damage to leaves, and it increased in levels when root herbivory was added. Nevertheless, M. croceipes were equally attracted to plants with both leaf and root damage and leaf damage only. In contrast to previous studies in cotton, production of gossypol and gossypol-like compounds was not induced in leaf and root tissue following foliage or root herbivory, or their combination. We conclude that root feeding by M. incognita has little influence on direct and indirect defenses of Gossypium hirsutum against insect herbivory.     

Palatability of Macroalgae that Use Different Types of Chemical Defenses

This study compared algal palatability and chemical defenses from subtropical green algae that may use different types of defense systems that deter feeding by the rock-boring sea urchin Echinometra lucunter. The potential defense systems present include (1) the terpenoid caulerpenyne and its activated products from Caulerpa spp., and (2) dimethylsulfoniopropionate (DMSP)-related defenses in Ulva spp. Secondary metabolites from these chemical groups have been shown to deter feeding by various marine herbivores, including tropical and temperate sea urchins. Live algal multiple-choice feeding assays and assays incorporating algal extracts or isolated metabolites into an artificial diet were conducted. Several green algae, including Ulva lactuca, Caulerpa prolifera, and Cladophora sp., were unpalatable. Nonpolar extracts from U. lactuca deterred feeding, whereas nonpolar extracts from C. prolifera had no effect on feeding. Polar extracts from both species stimulated feeding. Caulerpenyne deterred feeding at approximately 4% dry mass; however, dimethyl sulfide and acrylic acid had no effect at natural and elevated concentrations. E. lucunter is more tolerant than other sea urchins to DMSP-related defenses and less tolerant to caulerpenyne than many reef fish. Understanding the chemical defenses of the algae tested in this study is important because they, and related species, frequently are invasive or form blooms, and can significantly modify marine ecosystems.     

Allelopathic effects ofPolygonum aviculare L. I. Vegetational patterning

Polygonum aviculare was observed to spread rapidly into heavy stands ofCynodon dactylon (L.) Pers. resulting in death of the latter. This indicated a strong interference againstCynodon dactylon. Measurements of selected soil minerals and physical factors indicated that competition was probably not the chief cause of that interference. Soil collected under deadPolygonum was very inhibitory to all test species exceptSporobolus pyramidatus (Lam.) Hitchc., suggesting the presence of inhibitory compounds. Tops and roots ofPolygonum, root exudates, and leachate of the tops inhibited seed germination and seedling growth of most test species. Therefore, allelopathy apeared to be the dominant component of the interference, with competition probably accentuating its effects.Polygonum aviculare was inhibitory toGossypium barbadense L. andSorghum bicolor (L.) Moench, indicating that allelopathy is an important component of the interference byPolygonum against crop yields.     

Lespedeza phenolics andPenstemon alkaloids: Effects on digestion efficiencies and growth of voles

Lespedeza cuneata contains high levels of phenolics and is a common food plant of the meadow vole (Microtus pennsylvanicus);Penstemon digitalis contains substantial quantities of alkaloids and is a common food plant of meadow voles and prairie voles (M. ochrogaster). We investigated the palatability of these plants and the effects of their secondary compounds on the digestion efficiencies and growth of both species of voles. Voles ate very little of either plant when alternative food was present. Phenolics and alkaloids were extracted from the plants, incorporated into separate artificial diets, and fed to weanling voles for three weeks.Lespedeza phenolics reduced the growth of meadow voles but not prairie voles throughout the feeding trial. These compounds disrupted digestion, reducing protein digestibility by more than half.Penstemon alkaloids lowered only the initial growth rates of prairie voles and had no significant effect on meadow voles. Prairie voles tended to increase food consumption rates on bothLespedeza andPenstemon diets. This response offset some of the decrease in digested protein intake in the first case, and offset the increased metabolic cost of processing the diet in the latter case. Our results indicate that althoughLespedeza phenolics andPenstemon alkaloids do influence consumption and digestibility of artificial diets, they do not greatly reduce the performance (i.e., growth or survival) of voles when consumed at levels generally observed for wild voles. However, these compounds probably do place an upper limit on the amount of freshLespedeza andPenstemon that can be consumed and contribute to the generalist feeding strategy of voles.     

Allelochemics and nutritional indices for larch sawfly,Pristiphora erichsonii (Hartig): A specialist feeding onLarix spp.

Nutritional indices for larch sawfly,Pristiphora erichsonii (Hartig), larvae fed single and tufted needles of fourLarix spp. are reported. Larvae offered only single needles ofL. lancina, L. russica, andL. decidua had lower relative growth rates than larvae fed tufted needles of the same species. There was no significant reduction in larval growth for larvae fedL. kaempferi single needles as compared to tufted needles. Abietic acid-treated foliage reduced consumption but did not lower relative growth rate. These findings are discussed with respect to the mechanism of preferential feeding of the larch sawfly and current hypotheses of host plant herbivore interaction.Research supported by the School of Natural Resources, College of Agricultural and Life Sciences, University of Wisconsin—Madison under a grant from the McIntire-Stennis Program, Project 2243.     

Effects of secondary metabolites from marine algae on feeding by the sea urchin,Lytechinus variegatus

A bioassay was developed to test the hypothesis that secondary metabolites from marine algae affect feeding by sea urchins. During experiments measuring chemoreception and gustation, feeding by the regular sea urchin,Lytechinus variegatus (Lamarck), was inhibited by extracts from the green marine alga,Caulerpa prolifera (Forsskal) Lamouroux andCymopolia barbata (Linneaus) Lamouroux. Cymopol, a monoterpene-bromohydroquinone component ofC. barbata, was partially responsible for the inhibited feeding observed in tests of theCymopolia crude extract. Caulerpenyne, an oxygenated sesquiterpene fromC. prolifera, was responsible for all of the urchin feeding inhibition observed in tests of theC. prolifera crude extract. Feeding was not affected by: (1) extracts from several otherCaulerpa species includingC. mexicana (Sonder) J. Agardh,C. ashmaedii Harvey,C. racemosa v.macrophysa (Kutzing) Taylor, andC. racemosa v.laetevirens (Montagne) Weber-van Bosse; (2) caulerpin, an indole-containing pigment isolated from all of theCaulerpa species exceptC. mexicana; and (3) an extract from the red marine alga,Gracilaria foliifera v.angustissima (Harvey) Taylor, which has no known secondary metabolites. Feeding inhibition was independent of the test diameter which correlated with the reproductive state of the urchins. Feeding inhibition was also independent of the starvation periods between experiments, and the temperature and salinity in ranges tolerated byL. variegatus obtained from the Florida Gulf Coast. The data strongly suggest that at least one alga,Caulerpa prolifera, is chemically defended against a dominant omnivore in its community.     

Relationship Between Chemical Functional Groups on Eucalyptus Secondary Metabolites and their Effectiveness as Marsupial Antifeedants

Eucalyptus displays strong intraspecific variation in resistance to browsing by marsupial folivores that can be attributed to variation in the concentration and type of diformylphloroglucinol compounds (DFPCs) in the foliage. In this study, we ask which functional groups of diformylphloroglucinol compounds determine their effectiveness in deterring feeding. We used a simple and highly deterrent compound, jensenone, as a model DFPC and compared its activity to structural variants that differ in the types of functional groups on the phloroglucinol molecule. Torquatone, a naturally occurring compound in the steam volatile fraction of Eucalyptus torquata foliage, has neither the aldehyde nor phenol groups that are believed to contribute to the antifeedant actions of jensenone. From the naturally occurring compounds we have synthesized two intermediates, a capped phenol/free aldehyde compound (acetyl-jensenone) and a free phenol/no aldehyde compound (demethyl-torquatone). Addition of jensenone and acetyl-jensenone to diets of common ringtail possums (Pseudocheirus peregrinus) substantially reduced their food intakes. Torquatone showed less activity, and there was little reduction in food intake when demethyl-torquatone was added to the diet. We conclude that at least the aldehyde groups attached to the aromatic nucleus are important in determining whether these compounds deter feeding by common ringtail possums, whereas the phenol groups may play only a minor role.     

The role of leaf lipids in food selection by larvae of the tobacco hornworm,Manduca sexta

The role of leaf lipids in food plant selection by larvae ofManduca sexta was investigated by measuring preference responses in a two-choice preference test using glass fiber filter paper disks laced with extract (test) or water (control). The larvae respond to the petroleum ether extract of whole leaves of the host-plantLycopersicon esculentum (tomato) extract in a concentration-dependent manner. At natural concentration it is the most strongly stimulating extract or compound yet tested using the disk test. This response is affected by food plant experience of the larvae, suggesting stimulation by plant-specific compounds in the extract. The extract contains volatile compounds that attract the larvae. In contrast, it does not promote continued feeding on an agar-cellulose diet that incorporates the extract. Also stimulating are the extracts of leaf surfaces of two hosts,L. esculentum andSolanum pseudocapsicum, and two acceptable nonhosts,Brassicae napus andVigna sinensis, indicating the presence of nonpolar feeding stimulants at the leaf surface. However, similar leaf-surface extracts of the unacceptable plantCanna generalis were inactive, although the surface extraction process renders this plant acceptable. Leaf-surface extracts ofL. esculentum, S. pseudocapsicum, andB. napus evoke feeding responses that are qualitatively comparable to those of their corresponding leaves. However, no such parallel is found for surface extracts ofV. sinensis andC. generalis. Thus, nonpolar compounds at the leaf surface of host and some acceptable non-host-plant species strongly stimulate feeding and hence must play an important role in food selection by the tobacco hornworm.     

Chemical aspects of host-plant specificity in threeLarrea-feeding grasshoppers

The host-selection behavior of three species of grasshopper feeding on creosote bush,Larrea tridentata, in southern California was investigated. The species wereBootettix argentatus, which is monophagous;Ligurotettix coquilletti, oligophagous; andCibolacris parviceps, polyphagous. The monophagous species is stimulated to bite by nordihydroguaiaretic acid (NDGA), a compound that is characteristic of the host plant and that may comprise up to 10% of the dry weight of the leaf. Host specificity ofB. argentatus is enhanced by deterrent responses to compounds present in the surface waxes of all non-host-plant species. Both the oligophagous and polyphagous species are deterred by NDGA at naturally occurring concentrations. Their association withLarrea is probably based on tolerance of the plant chemicals rather than on dependence on specific chemicals. Factors other than the chemistry of the plant probably also contribute to the specificity ofB. argentatus andL. coquilletti.     

Phlorotannin-protein interactions

Tannins are one of the most broadly distributed types of plant secondary compounds, and have been the focal point for many studies of plant/herbivore interactions. Tannins interact strongly with proteins, so that the fate and effects of ingested tannins are in part dependent on the mode of interaction of the tannin with dietary and endogenous proteins in an herbivore's gut. We investigated the factors affecting the precipitation of proteins by phlorotannins from three species of marine brown algae:Carpophyllum maschalocarpum, Ecklonia radiata, andLobophora variegata. Phlorotannins were precipitated by proteins in a pH-dependent and concentration-dependent fashion. Precipitation also varied as a function of the presence of reducing agent, the type of phlorotannin or protein used, and the presence of organic solvents such as hydrogen bond inhibitors. Of particular significance was the ability of some phlorotannins to oxidize and form covalent bonds with some proteins. In contrast, under similar experimental conditions three types of terrestrial tannins (procyanidins, profisetinidins, and gallotannins) apparently did not form covalent complexes with proteins. Our results suggest several ways in which the biological activity of phlorotannins may vary as a function of the properties of the gut environment of marine herbivores. Moreover, we identify specific structural characteristics of phlorotannins which affect their tendency to oxidize, and thus, their potential effects on marine herbivores.     

Comparison of three methods for quantifying brown algal polyphenolic compounds

Three methods of quantifying total phenolic compounds in marine brown algae were compared for their ability to measure accurately known concentrations of phloroglucinol in the presence of a protein, bovine serum albumin (BSA). These methods were: (1) a Folin-Ciocalteu assay for compounds dissolved in 80% methanol, (2) a Folin-Ciocalteu assay for compounds dissolved in 75% methanol-25% trichloroacetic acid, and (3) an assay in which polyvinylpolypyrrolidone (PVPP) was used to remove phenolic compounds in order to quantify nonphenolic, Folin-Ciocalteu-reactive materials. The Folin-Ciocalteu assay used with compounds dissolved in 80% methanol was the method that produced the most consistent results. It was also the assay in which the presence of proteins interfered least with the measurements of phloroglucinol and the assay that was easiest to conduct. The presence of TCA decreased the pH of the extracting solution and increased the amounts of proteins in solution. These proteins later interfered with the Folin-Ciocalteu reaction. TCA effectively bound proteins when protein concentrations were low but not when protein concentrations were high. The amount of phloroglucinol removed by PVPP varied widely and was dependent on phloroglucinol concentration, making this an unreliable method for quantifying phenolic concentrations. The Folin-Ciocalteu assay will measure some nonphenolic substances when brown algae are extracted in 80% methanol; however, inFucus gardneri, nonphenolic substances were at most 5% of the material quantified by the assay.     

Lonicera Implexa Leaves Bearing Naturally Laid Eggs of the Specialist Herbivore Euphydryas Aurinia have Dramatically Greater Concentrations of Iridoid Glycosides than other Leaves

We tested in the field the hypothesis that the specialist butterfly Euphydryas aurinia (Lepidoptera: Nymphalidae, Melitaeinae) lays eggs on leaves of Lonicera implexa (Caprifoliaceae) plants with greater iridoid concentrations. We conducted our investigations in a Mediterranean site by analyzing leaves with and without naturally laid egg clusters. There were no significant differences in iridoid glycoside concentrations between leaves from plants that did not receive eggs and the unused leaves from plants receiving eggs, a fact that would seem to indicate that E. aurinia butterflies do not choose plants for oviposition by their iridoid content. However, the leaves of L. implexa that bore egg clusters had dramatically greater (over 15-fold) concentrations of iridoid glycosides than the directly opposite leaves on the same plant. These huge foliar concentrations of iridoids (15% leaf dry weight) may provide specialist herbivores with compounds that they either sequester for their own defense or use as a means of avoiding competition for food from generalist herbivores. Nevertheless, it may still be possible that these high concentrations are detrimental to the herbivore, even if the herbivore is a specialist feeder on the plant.     

Effects of birch phenolics on a grazing and a browsing mammal: A comparison of hares

Mountain hares (Lepus timidus L.) commonly have high proportions of birch (Betula spp.) in their winter diets, whereas European hares (Lepus europaeus) do not. The effects of a birch extract added to laboratory diets offered to mountain hares and European hares on the digestibility and sodium balance were measured. The extract added contained total phenolics equivalent in amount to that occurring in diets containing 0, 40, 60 and 80% dry matter of birch twigs. Increasing dietary phenolic concentration led to reduced voluntary food intake and apparent protein digestibility in both hare species. No effects on apparent dry matter digestibility were observed. The highest concentration of birch extract caused severe sodium losses via the urine by European hares but not by mountain hares. The effects of the birch extract within the digestive system appear to be similar in the two hare species, whereas the mountain hare appears to be better adapted to the toxic effects that disrupted sodium balance in the European hare. These preliminary results suggest that detoxification rather than digestive abilityper se may contribute to different mammalian herbivores' feeding strategies.     

Olfactory recognition of nonhosts aspen and birch by conifer bark beetlesTomicus piniperda andHylurgops palliatus

The field response ofTomicus piniperda (L.) andHylurgops palliatus (Gyll.) (Coleoptera: Scolytidae) to the attractant ethanol in combination with volatile wood constituents released from the nonhost tree speciesPopulus tremula L. (Salicaceae) andBetula pendula Roth (Betulaceae) was studied using flight barrier traps. The attraction of both species decreased when aspen or birch wood was added to the ethanol bait. The same was true forRhizophagus depressus (F.) (Coleoptera: Rhizophagidae), a predatory species associated with conifer bark beetles.Glischrochilus quadripunctatus (L-),Epuraea bickhardti St.-Claire Deville,E. unicolor (Oliv.) (Coleoptera: Nitidulidae), andRhizophagus parvutus (Payk.) (Coleoptera: Rhizophagidae) were caught in higher numbers in traps baited with both ethanol and wood of aspen or birch than in traps baited with ethanol alone. In a separate experiment, landings ofT. piniperda andH. palliatus on nonhosts (black plastic tubes) were demonstrated with sticky traps.     

Systemically Induced Plant Volatiles Emitted at the Time of “Danger”

Feeding by Pieris brassicae caterpillars on the lower leaves of Brussels sprouts (Brassica oleracea var. gemmifera) plants triggers the release of volatiles from upper leaves. The volatiles are attractive for a natural antagonist of the herbivore, the parasitoid Cotesia glomerata. Parasitoids are attracted only if additional damage is inflicted on the systemically induced upper leaves and only after at least three days of herbivore feeding on the lower leaves. Upon termination of caterpillar feeding, the systemic signal is emitted for a maximum of one more day. Systemic induction did not occur at low levels of herbivore infestation. Systemically induced leaves emitted green leaf volatiles, cyclic monoterpenoids, and sesquiterpenes. GC-MS profiles of systemically induced and herbivore-infested leaves did not differ for most compounds, although herbivore infested plants did emit higher amounts of green leaf volatiles. Emission of systemically induced volatiles in Brussels sprouts might function as an induced defense that is activated only when needed, i.e., at the time of caterpillar attack. This way, plants may adopt a flexible management of inducible defensive resources to minimize costs of defense and to maximize fitness in response to unpredictable herbivore attack.     

Allelopathic effects ofPolygonum aviculare L.

We previously reported thatPolygonum aviculare has a strong allelopathic action againstCynodon dactylon (L.) Pers. and other test species. Moreover, we found that several phenolic compounds appeared to be important allelochemics in this activity. We have now isolated other potential inhibitors fromP. aviculare residues and soil underPolygonum stands, and none of these occurred in soil underC. dactylon stands. GC-MS analysis revealed that these additional inhibitors are long-chain fatty acids with 14–22 carbons. Nine were identified inP. aviculare residues and seven in soil underP. aviculare. Sodium salts of all the identified fatty acids inhibited seedling growth ofC. dactylon and at least some test strains of the nitrogen-fixing bacteria,Azotobacter andRhizobium.     

Effects of phenolic acids on germination and early growth of herbaceous woodland plants

Four herbaceous plant species from woodland (clearings),Deschampsia flexuosa, Scrophularia nodosa, Senecio sylvaticus, andChamaenerion angustifolium, were tested for their sensitivity to phenolic acids. Seven commonly occurring phenolic compounds were used in a germination experiment in concentrations ranging from 0.01 to 10 mM, i.e., salicylic,p-hydroxybenzoic, syringic, caffeic, vanillic,p-coumaric, and ferulic acids. Germination was delayed rather than inhibited. Radicle elongation was strongly affected; at lower concentrations stimulatory effects were observed, whereas at high concentrations radicle elongation was severely reduced. Salicylic acid was the most effective phenolic compound, whereas caffeic acid caused no effects. Early growth was studied in more detail in a second experiment withDeschampsia flexuosa andSenecio sylvaticus and the phenolic acids, ferulic and p-coumaric acid. Primary root length, number and length of secondary roots, and dry weight were stimulated at 0.01 mM but were inhibited at 10 mM of both compounds. The results are discussed in view of the allelopathic relations between trees and herbaceous understory vegetation.     

Plant Cyanogenesis of <Emphasis Type="Italic">Phaseolus lunatus</Emphasis> and its Relevance for Herbivore–Plant Interaction: The Importance of Quantitative Data

Quantitative experimental results on the antiherbivorous effect of cyanogenesis are rare. In our analyses, we distinguished between the total amount of cyanide-containing compounds stored in a given tissue [cyanogenic potential (HCNp)] and the capacity for release of HCN per unit time (HCNc) from these cyanogenic precursors as a reaction to herbivory. We analyzed the impact of these cyanogenic features on herbivorous insects using different accessions of lima beans (Phaseolus lunatus L.) with different cyanogenic characteristics in their leaves and fourth instars of the generalist herbivore Schistocerca gregaria Forskål (Orthoptera, Acrididae). Young leaves exhibit a higher HCNp and HCNc than mature leaves. This ontogenetic variability of cyanogenesis was valid for all accessions studied. In no-choice bioassays, feeding of S. gregaria was reduced on high cyanogenic lima beans compared with low cyanogenic beans. A HCNp of about 15 μmol cyanide/g leaf (fresh weight) with a corresponding HCNc of about 1 μmol HCN released from leaf material within the first 10 min after complete tissue disintegration appears to be a threshold at which the first repellent effects on S. gregaria were observed. The repellent effect of cyanogenesis increased above these thresholds of HCNp and HCNc. No repellent action of cyanogenesis was observed on plants with lower HCNp and HCNc. These low cyanogenic accessions of P. lunatus were consumed extensively—with dramatic consequences for the herbivore. After consumption, locusts showed severe symptoms of intoxication. Choice assays confirmed the feeding preference of locusts for low over high cyanogenic leaf material of P. lunatus. The bioassays revealed total losses of HCN between 90 and 99% related to the estimated amount of ingested cyanide-containing compounds by the locusts. This general finding was independent of the cyanogenic status (high or low) of the leaf material.