G. G. S. King

Determination of chirality of alcohol or latent alcohol semiochemicals in individual insects

A method is described for determining the enantiomeric composition of chiral alcohols, lactones, and hydroxy acids in quantities ranging from 25 ng to 10 μg. Derivatization of the substance with chirally pure acetyl lactate, followed by splitless capillary gas chromatography, enables enantiomeric determinations to be made within 1–3% of the actual value. This technique was applied in the determination of semiochemical inIps pini (Say),Apis mellifera (L.), andCryptolestes ferrugineus (Stephens). The results indicate that considerable variability exists within populations of some insects in the composition of their chiral semiochemicals, whereas others produce substances of constant composition.

The influence of age and task specialization on the production and perception of honey bee pheromones

Abstract The production and perception of honey bee pheromones were studied in workers of different ages and task specializations. Electroantennogram responses increased to a maximum by days 6–12 and no differences were seen between bees performing different tasks. Levels of production of isopentyl acetate, octyl acetate, ( E )-2-octenyl acetate, butyl acetate, and hexyl acetate increased with age to maximal levels at days 30–40. Production of 2-nonanol, 2-nonyl acetate, benzyl acetate, and benzyl alcohol differed from the above compounds, with most workers producing very low levels and a few producing very high levels. When examined by task specialization, foragers produced higher levels of benzyl acetate, benzyl alcohol, and 2-nonanol than guards, fanners, or comb bees respectively.

Primary attraction of the fir engraver, Scolytus ventralis.

In laboratory bioassays, Porapak Q-captured and steam-distilled volatiles from the bark of host trees, Abies grandis, particularly from root-rot-infected trees, attracted 50–70% of male and female fir engravers, Scolytus ventralis. Gas chromatographic–electroantennographic detection (GC-EAD) analyses of Porapak Q-captured bark volatiles revealed 19 EAD-active compounds of which 13 (mostly monoterpenes) were identified by GC–mass spectrometry (GC-MS). In separate field experiments, multiple-funnel traps baited with two blends of these 13 synthetic volatiles released at 280 and 340 mg/ 24 hr attracted 66 and 93% of the total S. ventralis captured, respectively. The clerid predator, Thanasimus undulatus, also responded strongly to the kairomonal volatiles. Additional experiments produced no evidence for aggregation pheromones in S. ventralis. These included laboratory bioassays and GC and GC-EAD analyses of Porapak Q-captured volatiles from male- and female-infested logs or trees undergoing mass attack in the field, GC analyses and/or bioassays of extracts from female accessory glands, extracted volatiles from emerged, attacking and juvenile hormone-treated beetles of both sexes, and videotape analysis of the behavior of attacking beetles on the bark surface. We argue against the hypothesis of pheromone-mediated secondary attraction in S. ventralis and conclude that the attack dynamics of this species can be explained solely by its sensitive primary attraction response to host volatiles.

Chirality of macrolide pheromones of grain beetles in the generaOryzaephilusandCryptolestes and its implications for species specificity.

The chiralities of macrolide lactone aggregation pheromones of five species of economically important grain beetles have been determined by capillary gas chromatographic separation of the diastereomeric (S)-O-acetyllactate derivatives of the hydroxy methyl esters derived from boron trifluoride-catalyzed cleavage of the macrolides in methanol. Chirally pure (Z)-3-dodecen-11-olide (I) is produced in theS configuration byCryptolestes ferrugineus (Stephens) and in theR configuration byOryzaephilus mercator (Fauvel). (Z,Z)-3,6-Dodecadien-11-olide (II) is produced in theR configuration by bothO. mercator andO. surinamensis (L.). (Z,Z)-5,8-Tetradecadien-13-olide (IV) is produced in theR configuration byO. surinamensis and as a 85∶15 mixture ofR andS isomers byC. turcicus. (Z)-5-Tetradecen-13-olide (V) is produced in the S configuration byC. pusillus (Schönherr) and as a 33∶67 mixture of theR andS isomers byC. turcicus (Grouvelle). The results indicate that in these cucujids, species specificity in pheromone response is maintained at least in part by pheromone chirality.

Sex pheromone components of the oblique-banded leafroller,Choristoneura rosaceana in the Okanagan Valley of British Columbia

Abstract(Z)-11-Tetradecen-1-yl acetate, (E)-11-tetradecen-1-yl acetate, and (Z)-11-tetradecen-1-ol were previously reported as the sex pheromone in New York strains of the oblique-banded leafroller,Choristoneura rosaceana (Harris), and (E)-11-tetradecen-1-ol was tentatively identified in female tip extracts. For Okanagan Valley strains ofC. rosaceana, an additional component, (Z)-11-tetradecenal, was identified from female tip extracts by split-less capillary gas-liquid chromatography and mass spectroscopy and was strongly stimulatory in electroantennogram studies. In field tests, 3 mg of 96.5∶2∶1.5 (Z)-11-tetradecen-1-yl acetate, (E)-11-tetradecen-1-yl acetate, and (Z)-11-tetradecen-1-ol (containing approx. 1%E isomer) was not as attractive as female-baited traps, and significant numbers of European leafrollerArchips rosanus L. were attracted. The above blend with 1% (Z)-11-tetradecenal added was significantly more attractive than traps baited with femaleC. rosaceana, butA. rosanus males were still attracted. Increased percentages of (Z)-11-tetradecenal up to 4% caused increased catches ofC. rosaceana and decreased catches ofA. rosanus. Low amounts of (E)-11-tetradecen-1-ol and (E)-11-tetradecenal male also contribute to increased specificity of the synthetic pheromone blend toC. rosaceana.

Determination of chirality in 5-hydroxy-4-methyl-3-heptanone, the aggregation pheromone ofSitophilus oryzae (L.) andS. zeamais Motschulsky

The chirality of the pheromone of the rice weevil,Sitophilus oryzae (L.), and the maize weevil,S. zeamais (Motschulsky), 5-hydroxy-4-methyl-3-heptanone, was determined using an acetyl lactate derivatization procedure. Maize weevils were shown to produce >98% 4S,5R. Determination was more difficult with rice weevils due to a smaller quantity of insect extract, but they were shown to produce at least 92% 4S, 5R.The attractancy of the four synthetic stereoisomers of 5-hydroxy-4-methyl-3-heptanone was tested using rice and maize weevils. As expected, both species were most strongly attracted to the 4S, 5R enantiomer. Maize weevils also showed low but significant responses (P < 0.05) to both 4R, 5R and 4S,5S. Rice weevils showed a highly significant (P < 0.01) response to 4R, 5S, although it was only about one third the response to 4S, 5R. Thus, (4S,5R)-5-hydroxy-4-methyl-3-heptanone is clearly the major component of the pheromone of bothS. zeamais andS. oryzae.

Sex-specific production of ipsdienol and myrcenol byDendroctonus ponderosae (Coleoptera: Scolytidae) exposed to myrcene vapors.

Male mountain pine beetles,Dendroctonus ponderosae Hopkins, produced ipsdienol [97.0% ± 0.3S-(+)] and myrcenol (90.3% ± 4.0E) when exposed to myrcene vapors. Females which were exposed to myrcene vapors did not produce any ipsdienol, but did produce low levels of myrcenol (98.0% ± 0.7E). Neither sex produced detectable levels of ipsdienol or myrcenol when fed for 24 hr on lodgepole pine,Pinus contorta var.latifolia Engelmann. The sex-specific conversion of myrcene to ipsdienol and myrcenol suggests that these compounds may have behavioral significance within the species. In addition, the S-(+)-ipsdienol produced by maleD. ponderosae probably functions as a repellent allomone againstIps pini (Say).

Ipsenol: an aggregation pheromone for Ips latidens (LeConte) (Coleoptera: Scolytidae)

Ipsenol was identified from the frass of male, but not female,Ips latidens from British Columbia, feeding in phloem tissue of lodgepole pine,Pinus contorta var.latifolia. The responses ofJ. latidens to sources of ips-enol andcis-verbenol were determined with multiple-funnel traps in stands of lodgepole pine in British Columbia. Ipsenol attracted both male and femaleI. latidens, verifying that it is a pheromone for this species. MaleI. latidens showed a slight preference for (S)-(−)-ipsenol.cis-Verbenol was not produced by beetles of either sex and, in contrast to an earlier report, both enantiomers inhibited attraction to ipsenol-baited traps. The predators,Enoclerus sphegeus andThanasimus undatulus (Cleridae), were attracted to traps baited withcis-verbenol and ipsenol.

Copulation releaser pheromone in body scales of female whitemarked tussock moth,Orgyia leucostigma (Lepidoptera: Lymantriidae): Identification and behavioral role.

The copulatory behavior of the male whitemarked tussock moth,Orgyia leucostigma, was released by extracts of female body scales applied to rubber septum models baited with a female sex pheromone gland. The major compounds in the scale extracts were identified by GC-MS as a series ofn-alkanes from C-21 to C-29. Of these,n-tricosane,n-tetracosane,n-pentacosane, andn-heptacosane, applied at 10 ng/septum, caused significantly more males to attempt copulation than hexane-treated controls. Mixtures of then-alkanes, resembling the composition in the scale extracts, were no better than the two most active alkanes,n-tetracosane andn-pentacosane, alone. The releaser effect of then-alkanes was dose dependent. EAG responses to the identifiedn-alkanes were small suggesting, along with the behavioral observations, that their perception occurred at very close range. Other factors releasing male copulatory behavior are discussed.

Chirality of 5,11-dimethylheptadecane, the major sex pheromone component of the hemlock looper,Lambdina fiscellaria (Lepidoptera: Geometridae).

Of the four possible stereoisomers of 5,11-dimethylheptadecane, the major sex pheromone component of the eastern hemlock looper (EHL),Lambdina fiscellaria fiscellaria Guen., and the western hemlock looper (WHL),Lambdina fiscellaria lugubrosa Hulst, (5R,11S)-5,11-dimethylheptadecane was the only stereoisomer eliciting electrophysiological responses by male EHL and WHL antennae. In field bioassays with EHL and WHL populations, traps baited with (5R,11S)-5, 11-dimethylheptadecane caught as many males as did traps baited with all four stereoisomers combined or a synthetic mixture of 5,11-dimethylheptadecanes. Catches in traps baited with the other three stereoisomers did not significantly differ from those in the unbaited control traps. We conclude that male antennae lack chemoreceptors for the other three stereoisomers of 5,11-dimethylheptadecane and hypothesize that only (5R,115)-5,11-dimethylheptadecane is produced by female EHLs and WHLs.