Comparison of Age-dependent Quantitative Changes in the Male Labial Gland Secretion of <Emphasis Type="Italic">Bombus Terrestris</Emphasis> and <Emphasis Type="Italic">Bombus Lucorum</Emphasis>

Age-related changes of antennal-active components of male labial gland extracts were studied in two closely related bumblebee species, Bombus terrestris and B. lucorum. In B. terrestris, compounds eliciting electroantennogram (EAG) responses of virgin queens were ethyl dodecanoate, 2,3-dihydrofarnesal, 2,3-dihydrofarnesol, hexadecan-1-ol, octadeca-9,12,15-trien-1-ol, and geranylcitronellol. Compounds that elicited EAG responses from queens of B. lucorum were ethyl dodecanoate, ethyl tetradec-7-enoate, ethyl tetradec-9-enoate, ethyl hexadec-9-enoate, hexadecan-1-ol, hexadec-7-enal, octadeca-9,12-dien-1-ol, octadeca-9,12,15-trien-1-ol, and octadecan-1-ol. Quantities of these compounds in the labial glands changed significantly over the lifetime of the respective males of the two species. In both species, concentrations of the respective compounds reached their maximum within seven days after eclosion. Subsequently, a rapid decrease in the amount of EAG-active compounds occurred in B. terrestris, whereas in B. lucorum the amount of active compounds stayed approximately constant or decreased at a slow rate. Microscopy showed that in B. terrestris secretory cells of the labial glands undergo apoptosis from the fifth to the tenth day of life, whilst in B. lucorum labial gland cells remain unchanged throughout the life of the males.     

Age-Dependent Changes in the Chemistry of Exocrine Glands of Bombus terrestris Queens

Extracts of three different glands (mandibular, labial, and Dufour’s) of virgin Bombus terrestris queens at ten different ages (1–8, 12, and 18 days) were analyzed for chemical composition. One hundred and twenty-seven compounds were identified in the extracts. The mandibular and labial glands contained previously reported electroantennogram-active compounds (3-hydroxydecanoic acid, fatty acids of different chain lengths, their esters, and heptacosene). These compounds reached a maximum concentration in 3- to 7-d-old queens. Geranylcitronellol was found in both labial and Dufour’s glands. Its amount was inversely correlated to age of queens.     

Identity and Function of Scent Marks Deposited by Foraging Bumblebees

Foraging bumblebees can detect scents left on flowers by previous bumblebee visitors and hence avoid flowers that have been depleted of nectar. Tarsal secretions are probably responsible for this repellent effect. The chemical components of the tarsal glands were analyzed by combined gas chromatography–mass spectrometry for three species of bumblebee, Bombus terrestris, B. lapidarius, and B. pascuorum. The hydrocarbons identified were similar for each species, although there were interspecific differences in the relative amounts of each compound present. The tarsal extracts of all three species comprised complex mixtures of long-chain alkanes and alkenes with between 21 and 29 carbon atoms. When B. terrestris tarsal extracts were applied to flowers and offered to foraging bumblebees of the three species, each exhibited a similar response; concentrated solutions produced a repellent effect, which decreased as the concentration declined. We bioassayed synthetic tricosane (one of the compounds found in the tarsal extracts) at a range of doses to determine whether it gave a similar response. Doses 10^–12 ng/flower resulted in rejection by foraging B. lapidarius. Only when 10^–14 ng was applied did the repellent effect fade. We bioassayed four other synthetic compounds found in tarsal extracts and a mixture of all five compounds to determine which were important in inducing a repellent effect in B. lapidarius workers. All induced repellency but the strength of the response varied; heneicosane was most repellent while tricosene was least repellent. These findings are discussed in relation to previous studies that found that tarsal scent marks were attractive rather than repellent.     

Identification and bioassay of kairomones forHelicoverpa zea

Hexane extracts of leaves of 307 accessions from 73 host plant species ofHelicoverpa zea were analyzed by gas chromatography (GC) and used forH. zea oviposition and neonate larvae orientation bioassays. The gas chromatographic (GC) retention times of compounds statistically associated with behavioral activity were identified by correlation of GC peak area with oviposition and larval orientation preferences. Although taxonomically diverse in their origin, compounds for study were purified from extracts of species of the genusLycopersicon, due to their relative abundance. The structures of eight long-chain alkanes associated with oviposition preference were assigned by mass spectrometry, and the structures of five similarly associated organic acids and a terpenoid alkene were identified by¹H and¹³C nuclear magnetic resonance spectroscopy. The structures of a number of other phytochemicals from the plant leaves were identified for comparative purposes, including a previously unknown terpene, 7-epizingiberene. Bioassays were performed on the isolated acids and on the alkane wax fractions of severalLycopersicon species, and significant differences were found in oviposition stimulation for both classes of compounds. Of the hundreds of compounds found in the extracts, none were observed to act as oviposition deterrents. The results of these bioassays may be useful in explaining the broad host range ofH. zea, as well as the process and evolution of host plant selection for oviposition.     

Chemistry of venom alkaloids in someSolenopsis (Diplorhoptrum) species from Puerto Rico

A number of 15-carbon alkaloids have been identified in venom extracts of four Puerto Rican species of ants in the genusSolenopsis (Diplorhoptrum). Workers of a species from El Verde produced thecis andtrans isomers of 2-methyl-6-nonylpiperidine with the latter isomer predominating. The same compounds were identified in queens of a species from Río Grande, but in this species no alkaloids were detected in worker extracts. Workers of aDiplorhoptrum species collected on Mona Island produced primarily atrans-2-methyl-6-(Z-4-nonenyl)piperidine,3, with smaller amounts of thecis isomer, whereas the major compound found in the queens of the same species on Mona Island was (5Z,9Z)-3-hexyl-5-methylindolizidine, identical with the alkaloid produced by queens of a species collected on Cabo Rojo. Surprisingly, workers of the Cabo Rojo species produced (5Z,9Z)- and (5E,9E)-3-butyl-5-propylindolizidine (4 and5, respectively) reported earlier as the 223AB indolizidines from skins of dendrobatid frogs. The possible significance of the qualitative and quantitative differences in the venom alkaloids synthesized by queens and workers is discussed as is the possibility that ants containing such alkaloids may serve as a dietary source for the skin alkaloids used by certain frogs in chemical defense.     

Oviposition stimulants inBarbarea vulgaris forPieris rapae andP. napi oleracea: isolation,identification and differential activity

The closely related butterflies,Pieris rapae andP. napi oleracea, readily laid eggs onBarbarea vulgaris in greenhouse cages. When offered a choice between cabbage andB. vulgaris, P. rapae showed no preference, butP. napi oleracea preferredB. vulgaris. Bioassays of extracts ofB. vulgaris foliage revealed the presence of oviposition deterrent(s) in l-butanol extracts as well as stimulants in the postbutanol water extracts. However, the deterrent effect was apparently outweighed by the strong stimulatory effect in the whole plants. The postbutanol water extract was preferred over an equivalent cabbage extract by both species, but more significantly in the case ofP. napi oleracea. The stimulants were isolated by open column chromatography and HPLC, and the activity was associated with three glucosinolates.P. napi oleracea was more sensitive thanP. rapae to the natural concentration of compounds1 and3, whereas both species were strongly stimulated to oviposit by natural concentrations of compound2. Compounds1 and2 were identified as (2R)-glucobarbarin and (2S)-glucobarbarin, respectively, and3 was identified as glucobrassicin, on the basis of their UV, mass, and NMR spectra. When the pure compounds were tested at the same concentrations applied to bean plants, the (2R)-glucobarbarin at 0.2 mg/plant was preferred over a standard cabbage extract by both butterfly species. However, at a dose of 0.02 mg/plant,P. rapae preferred the cabbage extract whereasP. napi oleracea still preferred the (2R)-glucobarbarin. No such difference in response of the two species to the same two concentrations of (2S)-glucobarbarin was obtained. The results indicate a distinct difference in sensitivity of these butterflies to the epimers of glucobarbarin, and the differences in behavioral responses of the two butterfly species depend to a large extent on the concentration of stimulant present.     

Species-specific composition of free amino acids on the leaf surface of fourSenecio species

The specificity of the chemical composition of the leaf surface of fourSenecio species was studied in order to understand the host selection ofTyria jacobaeae, a monophagous moth that hasSenecio jacobaea as its principal host plant. Pyrrolizidine alkaloids characteristic forSenecio species were not detected in water and sulfuric acid extracts of the leaf surface ofSenecio jacobaea. Water extracts of the leaf surfaces ofS. jacobaea, S. vulgaris, S. viscosus, andS. sylvaticus contained low concentrations of free amino acids. The proportions of these amino acids were very different from those inside the leaf tissues. In a discriminant analysis, the four species could be completely separated on the basis of the relative proportions of amino acids on the leaf surface.     

Allelopathic potential ofErica vagans,calluna vulgaris,andDaboecia cantabrica

In laboratory tests the allelopathic potential ofErica vagans, Calluna vulgaris, andDaboecia cantabrica was determined. Aqueous extracts of flowers ofD. cantabrica and leaves ofC. vulgaris inhibit root and hypocotyl growth of red clover, the former causing 51% inhibition of germination. Intact aerial parts of the Ericaceae here studied drastically reduced the growth of red clover and 100% inhibition of germination was caused by flowers ofD. cantabrica. Inhibition of aqueous extracts remains after Chromatographic separation, and two well-defined inhibition zones may be observed. Hydrosoluble organic compounds (phenol-like compounds) could probably be responsible for the inhibitions detected.     

Identification of Queen Sex Pheromone Components of the Bumblebee Bombus terrestris

We investigated the origin and chemical composition of the queen sex pheromone of the primitively eusocial bumblebee, Bombus terrestris (Apidae). Physiologically and behaviorally active compounds were identified by coupled gas chromatography electroantennography (GC-EAD), gas chromatography-mass spectrometry (GC-MS), and laboratory behavioral tests. In the behavioral assays, virgin queens frozen previously at −20°C were highly attractive to males. Dummies impregnated with surface and cephalic extracts obtained from virgin queens that had been frozen at −50°C were more attractive to males than odorless dummies. Male mating behavior was stimulated by components of cephalic secretions that are smeared onto the cuticle surface by the queen. Overall, 21 compounds present in surface and cephalic extracts evoked electroantennographic responses in male antennae. These included saturated and unsaturated fatty acids, ethyl- and methyl esters of the fatty acids, heptacosene, 2-nonanone, and geranyl geraniol. A blend of synthetic versions of these compounds elicited typical male mating behavior. Since solvent-impregnated dummies were approached by the males, but did not release copulatory behavior, visual cues may be important in the initial step of stimulating male mating behavior. Close-range olfactory signals are more important for releasing male mating behavior as well as for species recognition. In further behavioral assays, the attractiveness of a frozen virgin queen decreased as the storage time at −20°C increased from 2 hr to 1 d. Therefore, the chemical composition of the sex pheromone may change during freezing as behaviorally active compounds may decompose.     

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.     

Behavioral and electrophysiological responses of Aphids to host and nonhost plant volatiles

Alate and apterous virginoparae ofAphis fabae Scop, and alate virginoparae ofBrevicoryne brassicae (L.), walking in a linear track olfactometer, were attracted by odor from leaves of their host plants.A. fabae responded to odor from undamaged but not damaged bean leaves. Gynoparae (autumn migrants) ofA. fabae, however, did not respond to their host plant (spindle,Euonymus europaeus) odor. Odors of certain nonhost plants masked the attractiveness of the host plant leaves, but tansy (Tanacetum vulgare) and summer savory (Satureja hortensis) volatiles repelledB. brassicae andA. fabae, respectively. 3-Butenyl isothiocyanate attractedB. brassicae andLipaphis erysimi (Kalt.), the latter species being more sensitive in both behavioral and electrophysiological studies. Isothiocyanate receptors were found on the antennae ofA. fabae, which was repelled by these compounds, 4-pentenyl isothiocyanate being the most active.     

Role of volatile inforchemicals emitted by feces of larvae in host-searching behavior of parasitoidCotesia rubecula (Hymenoptera: Braconidae): A behavioral and chemical study

The role of volatile infochemicals emitted by feces of larvae in the host-searching behavior of the parasitoidCotesia rubecula was evaluated during single- and dual-choice tests inside a wind tunnel. The following treatments were tested: feces produced by second and fourth instars ofPieris rapae (preferred host), second instars ofP. brassicae (inferior host), second instars ofP. napi (nonhost), and wet feces of second instars ofP. rapae. During a single-choice situation females ofC. rubecula oriented to all types of feces tested. When a preference was to be made,C. rubecula preferred feces of second instars ofP. rapae over that of fourth, feces ofP. rapae over that ofP. brassicae, feces ofP. napi over that ofP. brassicae, and wet over normal host feces. No preference was exhibited between feces of second instars ofP. napi and that of second instars ofP. rapae. The relative importance of infochemicals from host feces versus plant damage caused by host larvae to the searching behavior ofC. rubecula was also evaluated. Plant damage was more important to the searching females than host feces when feces were present in specific concentrations in relation to damage. The volatiles released by normal and wet feces of second instars ofP. rapae, wet feces of fourth instars ofP. rapae, and normal and wet feces ofP. brassicae were collected and identified. Overall, 85 chemical compounds were recorded belonging to the following chemical groups: alcohols, ketones, aldehydes, esters, isothiocyanates, sulfides, nitriles, furanoids, terpenoids and pyridines. The blend of chemicals emitted by feces of different instars ofP. rapae and different species ofPieris exhibited an instar and species specificity in both quantity and quality. Wetting of normal feces increased the amount of volatile chemicals released, and it was also responsible for the appearance of new compounds. The role of feces of larvae in the host-seeking behavior ofC. rubecula is discussed.     

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.     

Olfactory receptor cell responses ofIps grandicollis (eichhoff) (Coleoptera: Scolytidae) to intra- and interspecific behavioral chemicals

Electrophysiological recordings from antennal olfactory receptor cells were obtained fromIps grandicollis. Recordings were made from olfactory receptor cells from nine regions of the antennae in response to stimulation with the semiochemicals-pinene, frontalin,endo-brevicomin, verbenone,trans-verbenol,cis-verbenol, ipsdienol, and ipsenol. In many cases, up to two cells were recorded concurrently from the same location. When compared to males, females had a greater percentage of cells responsive to the primary pheromones ofDendroctonus frontalis, frontalin andtrans-verbenol, and ofIps spp., ipsdienol and ipsenol. Among females, more cells responded totrans-verbenol and theIps-produced volatiles than to host or otherD. frontalis-produced compounds. Olfactory cells of males responded mostly tocis-verbenol, followed by-pinene, verbenone,trans-verbenol, andendo-brevicomin. Of those cells responsive primarily to one compound, the greatest percentage were responsive totrans-verbenol in females and to verbenone in males. The response of the antennal olfactory receptor cells to semiochemicals used by male and femaleI. grandicollis is consistent with the presence of these compounds during the host colonization period for each sex. Our results, which show a lack of specificity in most pheromone and host odor receptor cells, is in contrast with previously published accounts of olfactory receptor cell specificity in otherIps species.     

Influence of opposite sex on attraction produced by pioneer sex of four bark beetle species cohabiting pine in the Southern United States

Catches ofDendroctonus frontalis andIps avulsus on traps surrounding bolts infested with both sexes of each species in the gallery were not significantly different from catches at bolts infested only with the sex which normally pioneers the host colonization process. In contrast, the presence of the second sex in the gallery significantly reduced catches ofI. grandicollis andI. calligraphus and, additionally, the presence of females in the male galleries ofI. calligraphus significantly reduced the catch ofI. avulsus females as compared with their response to bolts infested with the maleI. calligraphus only.     

Allelochemical regulation of reproduction and seed germination of two BrazilianBaccharis species by phytotoxic trichothecenes

The potent phytotoxic trichothecene roridins and baccharinoids occur naturally in the Brazilian plants,Baccharis coridifolia andB. megapotamica. Biosynthesis of roridins inB. coridifolia appears to be linked to pollination, and the phytotoxins then accumulate in the seed. The roles of the phytotoxins in pollination, seed maturation, and germination of theBaccharis species were investigated. The high production of roridins occurred only in seeds resulting from intraspecific pollination, and the concentration of the toxins in the seeds generally increased with seed maturity. Removal of seed coats from trichothecene-producing BrazilianBaccharis species (B. coridifolia andB. megapotamica) and non-trichothecene-producing AmericanBaccharis species (B. halimifolia andB. glutinosa) resulted in improved seed germination ofB. halimifolia andB. glutinosa but complete inhibition of seed germination ofB. coridifolia andB. megapotamica. Addition of seed coat extracts of the BrazilianBaccharis species of dilute solutions (10^–6g/ml) of roridins or baccharinoids to the decoated seeds ofB. coridifolia andB. megapotamica resulted in germination, while seeds ofB. halimifolia andB. glutinosa were killed by the phytotoxins. Roridins interacted with gibberellic acid, a germination promoter, but not with abscisic acid, a germination inhibitor. The results from this study suggest that macrocyclic trichothecenes have a regulatory role(s) on reproduction and germination of BrazilianBaccharis species in their natural habitat.     

Inhibition of seedling growth of crop species by recirculating root exudates ofBidens pilosa L.

The allelopathic effects of root exudates ofBidens pilosa L. on seedling growth ofLactuca sativa L.,Phaseolus vulgaris L.,Zea mays L., andSorghum bicolor (L.) Moench were studied using a root exudate recirculating system that allows continuous exposure of crop plants to allelopathic chemicals. This system maintains an undisturbed rhizosphere and eliminates competition and physical contact between the donor and acceptor plants. Comparison of responses to hydrophobic and hydrophilic root exudates is made possible by removal of hydrophobic compounds using XAD-4. Treatments consisted ofB. pilosa, B. pilosa with an Amberlite XAD-4 resin column attached to the donor pot to remove hydrophobic allelochemicals, and a donor pot without weeds.B. pilosa significantly inhibited seedling growth of all crop species tested. The crop species varied in response to the root exudates, withL. sativa being most sensitive. Larger and olderB. pilosa plants caused greater inhibition of seedling growth ofL. sativa andP. vulgaris than did smaller (younger)B. pilosa plants.B. pilosa with XAD-4 caused significantly less inhibition to all crop species, exceptZ. mays, thanB. pilosa without XAD-4, indicating that the hydrophobic exudates played an important role in the allelopathic growth inhibition. Variability in species response toB. pilosa with and without XAD-4 was probably due to differences in sensitivity to hydophobic and hydrophilic allelochemicals.Supported by a grant under USDA Agreement No. 83-CRSR-2-2293. Journal Series No. 2887 of the Hawaii Institute of Tropical Agriculture and Human Resources.     

Cross-attraction between two species ofMatsucoccus

In laboratory bioassays, males ofMatsucoccus resinosae fromPinus resinosa in New York andMatsucoccus n. sp. fromPinus thunbergiana in Korea were strongly attracted to crude hexane extracts ofM. resinosae females, andM. resinosae males responded strongly to extracts ofMatsucoccus n. sp. females. Males of the two species responded similarly to gas chromatographic fractions and subfractions of a pentane extract ofM. resinosae females. Sex pheromones of these two species appear to be the same or very similar.Homoptera: Coccoidea: Margarodidae.     

Chemical investigation of aggregation behavior ofTriatoma bugs (Hemiptera: Reduviidae)

Nymphs ofTriatoma infestans andTriatoma mazzottii are weakly attracted to their feces and to extracts of feces in polar solvents, but not to nonpolar solvent extracts. The major volatile compounds identified in feces by solvent extraction and thermal desorption wereo-aminoacetophenone, 4-methylquinazoline, and 2,4-dimethylquinazoline, but these showed no attractant activity at a range of concentrations. Choice tests with a moving current of air gave no positive reaction to feces, extracts, or pure compounds.     

Antioxidant activities of selected oriental herb extracts

Antioxidant activities of methanol extracts of 180 Oriental herbs were studied by determining the peroxide values of linoleic acid during storage at 50°C. Among the herb extracts tested, 44 species showed strong antioxidant activities on the oxidation of linoleic acid. The antioxidative effects of these 44 selected herb extracts were studied further in a methyl linoleate system during storage for 35 d. Among the 44 species tested, 11 species had particularly high antioxidative effects. The effects of type of extraction solvent (methanol, petroleum ether and ethyl acetate) on the antioxidant activities of the 11 species were studied. Antioxidant activities of most herb extracts were greatly dependent on the extraction solvent used; however, some of the extracts showed strong antioxidant activities regardless of the solvents used for the extraction. Among the 11 herbs selected, based on the antioxidant activity of their methanol extracts, two (i.e.,Psoralea corylifolia L. andSorphora angustifolia Sieb. & Zucc.) were selected for further study in lard held at 75°C for 7 d. The methanol extracts ofP. corylifolia L. andS. angustifolia Sieb. & Zucc. greatly decreased the peroxide formation of lard during storage. Treatment with 0.20% methanolic extract ofP. corylifolia L. exhibited significantly stronger antioxidant effect on the oxidation of lard than treatment with 0.02% butylated hydroxyanisole (P<0.05).