Isolation of 8-hydroxygeraniol-8-O-β-d-glucoside,a probable intermediate in biosynthesis of iridoid monoterpenes,from defensive secretions ofPlagiodera versicolora andGastrophysa viridula (Coleoptera: Chrysomelidae)

8-Hydroxygeraniol and its 8-O--d-glucoside have been found as trace components in the defensive secretions ofPlagiodera versicolora andGastrophysa viridula larvae. This discovery supports the hypothesis that the evolution of the utilization of plant precursors by some chrysomelid species was favored by the plesiomorphic occurrence of a-glucosidase and an oxidase in the defensive secretion of iridoid-producing species.     

Defensive secretions of three species ofAcilius (Coleoptera: Dytiscidae) and their seasonal variations as determined by high-pressure liquid chromatography

A rapid, sensitive, stable, and quantitative high-pressure liquid chromatographic technique was developed for the analysis of defensive secretions obtained from the pygidial and prothoracic glands of dytiscids. Methods were developed for both normal phase (Porasil) and reverse phase (Bondapak C₁₈) columns. The applicability of this technique was demonstrated when defensive compounds ofAcilius semiculcatus, A. sylvanus andA. mediatus were isolated, identified, and quantitated. No major differences were found in the composition of the defensive secretions between the three species. The seasonal defensive titer ofA. semisulcatus was determined from June through October 1977. The pygidial defensive agents (benzoic acid,p-hydroxybenzaldehyde, and methylp-hydroxybenzoate varied from 9.0 to 67.8 g and exhibited a maximum in July, and a steroid from the prothoracic gland varied from 7.1 to 33.2 g and was maximum in October.     

Chemistry and Defensive Efficacy of Secretion of Burrowing Bug (Sehirus cinctus cinctus)

Adult Sehirus cinctus cinctus emit a volatile secretion from their metathoracic scent glands when tactually stimulated. We identified the volatile components by gas chromatography, high-performance liquid chromatography, and mass spectrometry. The secretion of both sexes contained (1R)-(+)--pinene, (1S)-(–)--pinene, -myrcene, (R)-(+)-limonene, and -terpinolene. Two additional compounds were found in only female secretions: (E)-2-hexenyl acetate and (E)-2-octenal. We also tested the defensive capability of this insect by offering it to various predators. Anoles, starlings, and a killdeer rejected S. c. cinctus after an initial sampling. These findings suggest that the secretion plays a defensive role.     

Pentatomid natural products

In addition to the primarily defensive metathoracic glands, adult Pentatomoidea possess a pair of active exocrine glands that open between the III and IV abdominal tergites. In the southern green stink bug,Nezara viridula, and other phytophagous species examined, the glands are small (< 10 g secretion/individual) and of approximately equal size in both sexes. In some, but not all, of the predaceous pentatomids (Asopinae), the III-IV dorsal abdominal glands are small in females (< 10 g secretion/individual) and extremely large in males (>500 g secretion/individual). Using a GC-MS system, the secretion from both males and females ofN. viridula (Pentatominae) was found to contain (E)-2-hexenal, hexanal, 1-hexanol, andn-tridecane. Females contained about three times moren-tridecane than males. The capacious glands ofPodisus maculiventris (Asopinae) males produce (E)-2-hexenal, benzyl alcohol, -terpineol, linalool, terpinen-4-ol, andcis-piperitol. The composition of the previously unanalyzed secretions from the adult III-IV dorsal abdominal glands is compared and contrasted to that of secretions from the metathoricic gland, and the role of coexisting exocrine glands in adult Heteroptera is discussed.     

Inhibition of Fungal Spore Germination by Nasutitermes: Evidence for a Possible Antiseptic Role of Soldier Defensive Secretions

The antifungal property of two of the principal components of the terpenoid frontal gland secretions of nasute termite soldiers was studied by incubating spore suspensions of the fungus Metarhizium anisopliae with -pinene and limonene singly or in combination at different concentrations. In vitro assays showed that these substances reduced spore germination through direct and indirect (vapor) contact. To determine if the frontal gland secretions protected termites from fungal infection in vivo, the effect of M. anisopliae on the time course of survival of Nasutitermes costalis and N. nigriceps was studied by exposing termites to either a 4.3 × 10⁷ spores/ml or a control sporeless suspension. The caste composition of experimental groups was manipulated to create mixed-caste subcolonies and monocaste groups. Relative to Coptotermes formosanus, a species that relies on the mechanical defenses of soldiers, N. costalis and N. nigriceps were less susceptible to fungal infection. Spore-exposed N. costalis and N. nigriceps termites had 1.2 times the hazard ratio of death of controls, while the hazard ratio of death of spore-exposed C. formosanus was 11.4 times that of controls. Although the lower susceptibility to infection in Nasutitermes may be explained in part by the antifungal properties of -pinene and limonene, group composition also played a major role in the survival of spore-exposed termites. Mixed-caste and soldier monocaste groups had 3.4 and 4.7 times the hazard ratio of death, respectively, relative to the worker monocaste treatment. These results suggest that although Nasutitermes terpenoid secretions may have antifungal properties, the caste composition of groups and the social interactions of termites also play a role in determining susceptibility to fungal infection.     

Chemical ecology ofReticulitermes flavipes (Kollar) andR. virginicus (Banks) (Rhinotermitidae)

Reticulitermes flavipes andR. virginicus have been examined for the presence and possible defense functions of soldiers specific secretions. The cephalic extracts for soldiers of both species contained the identical two major sesquiterpenes which were absent from other castes. The sesquiterpenes have been identified as ₁-cadinene (I) and the corresponding aldehyde (II) by high-resolution nuclear magnetic resonance spectrometry using homonuclear proton decoupling and by high-resolution mass spectrometry. When groups of termite soldiers were exposed to foraging parties of the sympatric native fire ant,Solenopsis geminata, the termites utilized only mechanical defenses. No evidence was obtained to indicate that the ants had been sprayed or coated with either an irritant or toxicant, and there was no evidence that an alarm had been promulgated.     

Multichemical defense of plant bugHotea gambiae (westwood) (Heteroptera: Scutelleridae)

Chemical defense in larvae of the plant bugHotea gambiae has been investigated. Results of analyses (GC, GC-MS) on the secretions from the three dorsally situated larval abdominal defense (scent) glands are reported. The secretion from the first abdominal gland consists of a mixture of C₁₀ and C₁₅ isoprenoids: (C₁₀) -pinene, -pinene, limonene, -phellandrene; (C₁₅) -caryophyllene, caryophyllene oxide, -humulene, and (the major component) humulene epoxide II. The secretions from the second and third abdominal glands are similar mixtures consisting of (E)-2-decenal, (E)-4-oxohex-2-enal, andn-tridecane together with lesser amounts of (E)-2-hexenal,n-dodecane, and other materials. Isoprenoid defense is now known from four species of plant bugs (Heteroptera) associated with Malvaceae.     

Attraction of scolytids and associated beetles by different absolute amounts and proportions of α-pinene and ethanol

The attraction of bark and ambrosia beetles as well as associated beetles to -pinene and ethanol was studied in field experiments with flight barrier traps. -Pinene and ethanol were released individually and as combinations in approximately 11 or 110 ratios and at four different release rates. Ethanol attractedTomicus piniperda (L.),Hylurgops palliatus (Gyll.),Trypodendron lineatum (Oliv.),Hylastes cunicularius Er.,H. brunneus Er.,H. opacus Er., andAnisandrus dispar (F.) (Scolytidae);Glischrochilus quadripunctatus (L.) andEpuraea spp. (Nitidulidae);Thanasimus formicarius (L.) (Cleridae); andRhizophagus depressus (F.) (Rhizophagidae). -Pinene attracted all these species with the exception ofT. lineatum, H. cunicularius, andA. dispar. Combinations of a-pinene and ethanol resulted in synergistically increased attraction of all species with the exception ofH. opacus andA. dispar. A. dispar, the only hardwood-associated species in the study, was repelled by -pinene. Both the release rates and the ratio at which the two substances were released influenced the response of the beetles. The differences in response between the beetle species seem to reflect dissimilarities in the release of the two substances among the various types of breeding material to which the species are adapted.     

Allelopathic properties of α-terthienyl and phenylheptatriyne,naturally occurring compounds from species of asteraceae

Alpha-terthienyl (-T), a naturally occurring polyacetylene derivative from roots ofTagetes erecta L., and phenylheptatriyne (PHT), from leaves ofBidens pilosa L., were tested as possible allelopathic agents against four seedling species (Asclepias syriaca L.,Chenopodium album L.,Phleum pratense L.,Trifolium pratense L.).Asclepias was the most sensitive of the species. Allelopathic activity was enhanced in the presence of sunlight or sources of near-UV, with LC_50s forA. syriaca of 0.15 ppm and 0.66 ppm with -T and PHT, respectively; 0.27 and 0.85 forC. album; 0.79 and 1.43 forP. pratense, and 1.93 and 1.82 forT. pratense. Near-UV exposure was saturating but never more than found in summer sunlight at Ottawa, Canada. Growth inhibition was observed with seedlings treated with -T and PHT but without near-UV irradiation. Germination of seedlings was also sensitive to -T and PHT with or without near-UV treatment. -T was extracted from soil surrounding the roots ofTagetes. Concentrations calculated for the soil (0.4 ppm) indicate that seedling growth could be significantly hindered. The activity and specificity of -T was sufficiently high to warrant future field trials to assess its potential as a natural weed-control agent.     

Host-Plant Chemicals and Distribution of Neuquenaphis on Nothofagus

Extractable metabolites from leaves (EM) and volatiles released from six Nothofagus species were analyzed by TLC and GC-MS, respectively. Aphids of the genus Neuquenaphis, closely associated to Nothofagus, were sampled on each Nathofagus species. Cluster analyses of Nothofagus species were performed based on the presence or absence of EM and volatiles. Dissimilarity distances, from the cluster analyses of EM and volatiles, were used to evaluate their association with the aphid distribution. A major component identified from EM and volatiles of three species of Nothofagus, -agarofuran, was attractive to alates of the oligophagous Neuquenaphis sensoriata, which use them as hosts. These results suggest that chemicals play a significant role in the host-plant associations between Neuquenaphis and Nothofagus.     

New sesquiterpenes fromMaytenus species (Celastraceae). Taxonomic and chemotaxonomic considerations concerning chileanMaytenus

Three new dihydro--agarofuran sesquiterpenes from two species ofMaytenus were isolated and their structures were elucidated by means of¹H and¹³C NMR studies. The differences and similarities noted in the chemical content of the dihydro--agarofuran sesquiterpenes from the fourMaytenus species from Chile are in line with the taxonomic characterization of these species; their geographical distribution is also given.     

Chemical defense secretions of the termite soldiers ofAcorhinotermes andRhinotermes (Isoptera,Rhinotermitinae)

The defense secretions of advanced nasutoid rhinotermitine soldiers from the New World contain enolic -ketoaldehydes as the major components. The secretions of minor soldiers ofRhinotermes hispidus (Emerson) andR. marginalis (Emerson) consist primarily of 3-keto-13-tetradecenal and 3-ketotetradecanal, but possess in addition C₁₃, C₁₄, C₁₅, and C₁₇ saturated and unsaturated ketones. Major soldiers lacked these compounds and in fact had virtually no frontal gland secretion. The defense secretion of the monomorphic soldiers ofAcorhinotermes subfusciceps (Emerson) contains mostly 3-keto-(Z)-9-hexadecenal and (Z)-8-pentadecen-2-one. Biosynthetic origins and interrelationships are postulated for these compounds, and the concomitant evolution of chemical weaponry and the modified labral brush is discussed.Fellow of the Alfred P. Sloan Foundation (1981–1983).     

Chemical composition of the frontal gland secretion ofSyntermes soldiers (Isoptera,Termitidae)

The defensive secretions from the frontal glands of soldier termites of the genusSyntermes contain similar mixtures of mono- and sesquiterpene hydrocarbons. The major components inS. dirus, S. molestus, S. brevimalatus, S. peruanus, and a new species (Syntermes sp. n), iscis--ocimene. A substantial amount of aristolochene is found inSyntermes sp. n. and is present at lower levels in all the other species;S. brevimalatus contains onlycis--ocimene and aristolochene. The four other species also contain minor amounts of epi--selinene and germacrene A. The latter compound has been identified on the basis of its rearrangement product -elemene. The termiteS. grandis differed markedly from the otherSyntermes species in that no terpenoid components were found in the soldier extract. With the obvious exception ofS. grandis, the same soldier-specific mono- and sesquiterpenes occurred in all species. The total amount of secretion per unit weight of soldiers varies with the species and is inversely proportional to the development of the mandibular apparatus. InS. molestus smaller gland size is compensated for by a greater number of soldiers foraging trails.     

Dietary influences on terpenoids sequestered by the biological control agent Oxyops vitiosa: effect of plant volatiles from different Melaleuca quinquenervia chemotypes and laboratory host species

The weevil Oxyops vitiosa is an Australian species imported to Florida, USA, for the biological control of the invasive species Melaleuca quinquenervia. The larvae of this species feed on the leaves of their host and produce a shiny orange secretion that covers their integument. Previous results indicated that a major component of this secretion, viridiflorol, is sequestered from the host plant and repels a generalist predator, the red imported fire ant, Solenopsis invicta. When the larvae fed on a different chemotype of M. quinquenervia, which lacked viridiflorol but was rich in a different sesquiterpene, (E)-nerolidol, similar protection occurred. Solvent washes of these larvae indicated that (E)-nerolidol was sequestered from M. quinquenervia leaves and repelled S. invicta workers when applied to dog food baits at physiological concentrations (17.5, 35.0, and 52.5 g/mg). Additionally, -caryophyllene also repelled S. invicta workers when applied to dog food baits at concentrations that approximated those in the O. vitiosa larval secretions (3.5 and 35 g/mg). When the O. vitiosa larvae were fed leaves from laboratory hosts (nonfield hosts), similar repellent activity was found. This activity was traced to several of the same compounds (e.g., 1,8-cineole, viridiflorol) found to be active in their field host M. quinquenervia. These weevil larvae are opportunistic, sequestering the primary terpenoids in their host leaves that confer antipredator activity.     

Effects of biotic and abiotic stress on induced accumulation of terpenes and phenolics in red pines inoculated with bark beetle-vectored fungus

This study characterized the chemical response of healthy red pine to artificial inoculation with the bark beetle-vectored fungusLeptographium terebrantis. In addition, we sought to determine whether stress altered this induced response and to understand the implications of these interactions to the study of decline diseases. Twenty-five-year-old trees responded to mechanical wounding or inoculation withL. terebrantis by producing resinous reaction lesions in the phloem. Aseptically wounded and wound-inoculated phloem contained higher concentrations of phenolics than did constitutive tissue. Trees inoculated withL. terebrantis also contained higher concentrations of six monoterpenes,-pinene,-pinene, 3-carene, limonene, camphene, and myrcene, and higher total monoterpenes than did trees that were mechanically wounded or left unwounded. Concentrations of these monoterpenes increased with time after inoculation. Total phenolic concentrations in unwounded stem tissue did not differ between healthy and root-diseased trees. Likewise, constitutive monoterpene concentrations in stem phloem were similar between healthy and root-diseased trees. However, when stem phloem tissue was challenged with fungal inoculations, reaction tissue from root-diseased trees contained lower concentrations of-pinene, the predominant monoterpene in red pine, than did reaction tissue from healthy trees. Seedlings stressed by exposure to low light levels exhibited less extensive induced chemical changes when challenge inoculated withL. terebrantis than did seedlings growing under higher light. Stem phloem tissue in these seedlings contained lower concentrations of-pinene than did nonstressed seedlings also challenge inoculated withL. terebrantis. It is hypothesized that monoterpenes and phenolics play a role in the defensive response of red pine against insect-fungal attack, that stress may predispose red pine to attack by insect-fungal complexes, and that such interactions are involved in red pine decline disease. Implications to plant defense theory and interactions among multiple stress agents in forest decline are discussed.To whom correspondence should be addressed at USDA Forest Service, 2500 Shreveport Hwy., Pineville, Louisiana 71360.     

Defensive secretion of chrysomelid larvaeGastrophysa atrocyanea Motschulsky andPhaedon brassicae Baly

The active substance of the larval defensive secretion of the Japanese chrysomelid beetles,Gastrophysa atrocyanea Motschulsky andPhaedon brassicae Baly was identified as chrysomelidial.This is report No. 2 of the Defensive Secretion of Chrysomelid Beetles, Report No. 1 is Sugawara et al. (1978).     

Response on the ground of bark beetle and weevil species colonizing conifer stumps and roots to terpenes and ethanol

Responses of threeHylastes species,Dryocoetes autographus, and twoHylobius species to terpenes and ethanol were studied in field experiments on clear-cut forest sites in Sweden using baited ground traps.-Pinene alone did not attract any of the six species. A terpene blend (spruce turpentine consisting mainly of-pinene,-pinene, and 3-carene) attractedHylastes cunicularius, H. brunneus, andHylobius abietis in some experiments, but not in others. The attractiveness of ethanol also varied; the only species consistently attracted wasH. abietis. Baits containing both terpenes and ethanol, particularly the combination of spruce turpentine and ethanol, were attractive to all species exceptHylobius pinastri. InH. abietis, the terpene plus ethanol/ ethanol catch ratios increased during early summer. Seasonal differences in catch levels were observed inH. cunicularius andH. abietis. The addition of-pinene reduced the attractiveness of the combination of spruce turpentine and ethanol toH. cunicularius, H. opacus, andD. autographus. The differences in response to the volatiles between species are probably related to differences in reproductive behavior and host preferences.     

Chemical Characters of Two Related Species of Giant Honeybees (Apis dorsata and A. laboriosa): Possible Ecological Significance

The Himalyan honeybee, Apis laboriosa, is sometimes considered to be a form of the rock honeybee, A. dorsata, rather than a separate species. Analyses of potential exocrine compounds produced by both forms revealed that the cephalic and abdominal natural products of these two honeybees shared no common denominators. The sting shaft of workers of A. dorsata is the source of a large series of esters dominated by 1-acetoxy-2-decene. Other major constituents include isopentyl acetate, accompanied by isopentyl propionate, farnesyl acetate, and several other esters. On the other hand, nothing but presumed structural lipids (e.g., ethyl palmitoleate) were identified from sting shafts of workers of A. laboriosa. By contrast, cephalic (including mandibular glands) extracts from workers of A. laboriosa contained -octanoic lactone, whereas comparable extracts of A. dorsata workers contained only structural lipids. The major qualitative differences in the chemical characters between A. laboriosa and A. dorsata are consistent with the designation of these two forms as distinct species.     

Sticky secretion from two pairs of defensive glands of rove beetleDeleaster dichrous (Grav.) (Coleoptera: Staphylinidae)

The phylogenetically primitive rove beetleDeleaster dichrous (Grav.) (Oxytelinae) has been shown for the first time to possess two pairs of neighboring abdominal glands which are depleted simultaneously on molestation. The morphology of these glands is described. The defensive constituents of theDeleaster glands were elucidated directly from the mixtures by gas chromatographic-mass spectroscopic methods and microchemical reactions. The paired whitish glands secrete iridodial, which polymerizes on exposure to air to form an adhesive that probably deters small predatory arthropods. The red gland system ofD. dichrous contains the toxicp-toluquinone and a variety of isopropyl andsec-butyl esters. Artificial quinoid ester mixtures simulating the secretion ofD. dichrous showed only weak effects on mortality ofLucilia larvae in comparison with more effective secretions of phyiogenetically derived Oxytelinae. The secretion of the primitive genusDeleaster is characterized chemotaxonomically by , -unsaturated C₁₂ acids and esters, which are postulated as precursors for the characteristic defensive compounds of the derived species, thus indicating a clear evolutionary trend at the micromolecular level.     

High-pressure liquid chromatographic techniques for the separation and quantification of norsesquiterpenes from gyrinids

A rapid, sensitive, stable, and quantitative high-pressure liquid chromatographic technique was developed for the analysis of the norsesquiterpenes, gyrinidal, isogyrinidal, gyrinidone, and gyrinidione. Methods were developed for both normal-phase (Porasil) and reverse-phase (Bondapak) columns. The applicability of this technique was demonstrated when the norsesquiterpenes of the defensive secretions of the water beetleGyrinus frosti Fall were isolated and identified as gyrinidal and isogyrinidal. This method was then used for the quantification of the norsesquiterpene titer ofG. frosti andDineutus assimilis (Kirby).