Male olive fruit fly attraction to synthetic sex pheromone components in laboratory and field tests

Male olive fruit fly attraction to the four synthetic components of the female sex attractant pheromone was studied under laboratory and field conditions. In laboratory tests males responded to all four components tested separately. Component I, (1,7-dioxaspiro[5.5]undecane) was more attractive than any of the remaining three components alone, but a combination of all four was more attractive than component I alone. In field tests with polyethylene vials as pheromone dispensers, the complete mixture, although not statistically significant, was constantly more attractive to males than component I alone. A tendency of enhancement of attraction of component I by combining it with component II (-pinene) or III (n-nonanal) was also observed. In field tests with rubber septa as pheromone dispensers only component I was attractive. Mixtures containing component I were also attractive but not more attractive than component I alone. Evaporation rate and ratio of components as they come out of the dispenser appear to be critical for male response.     

A study on the feasibility of quantifying the population density of stored product insects in air-tight grain storage using CO2 concentration measurements

This study was aimed at estimating the number of insects per 1 kg of paddy (IPK) in an air-tight mock-up silo by CO₂ concentration monitoring. The first experiment was to determine the respiration rates of adult Sitophilus zeamais, Rhyzopertha dominica, and Tribolium castaneum. CO₂ concentrations were recorded from groups of 50, 100 and 200 insects with and without 125 g of brown rice. The respiration rate was calculated from the slope of the CO₂ concentration curve. A sample size of at least 100 insects was recommended. In 100-insect group, with the presence of food the respiration rates of S. zeamais, R. dominica, and T. castaneum were 9.57–14.13, 1.96–3.93 and 4.59–11.76 μl_CO2/insect−h, respectively. In the second experiment, S. zeamais populations at actual IPK = 2, 0.5, 0.25, 0.125 and 0.0625 in a 1.618 m³ silo filled with paddy were quantitatively determined. Similarly, R. dominica and T. castaneum populations at actual IPK = 0.5, 0.25, 0.125 and 0.0625 in 0.064 m³ silos were estimated in the third experiment. In each trial, small containers filled with a known number of adult insects along with brown rice were buried in the silo. Additionally, a control silo containing only disinfested paddy was set up in parallel. The insect population density was calculated from the difference in the slopes of the CO₂ curves between the infested and control silos divided by the respiration rate of one insect. On average, for each species and each infestation level the estimated population density was not greater than twice of the actual ones. Although several assumptions (e.g., silos being completely sealed, only one species and one life stage of infesting insects) had to be made, monitoring CO₂ concentrations could potentially be an effective tool for determining insect population density during grain storage.     

植物性杀虫剂防治储粮害虫的研究进展

储粮害虫的危害能够引起粮食减产和品质下降,目前使用化学农药的负面影响的出现,使得亟待发现新的环境友好型农药进行储粮害虫的防治.植物成为寻找新的环境友好型绿色农药的重要来源,很多学者在植物性杀虫剂的应用研究方面做了大量的工作.针对植物性杀虫剂在储粮害虫防治研究中所取得的成果,系统介绍了植物性杀虫剂的作用方式、作用机理、活性成分等方面的研究进展,以期为从事植物性杀虫剂研究的工作提供参考.     

Geometrical and optical isomerism of pheromones in two sympatricDryocoetes species (Coleoptera: Scolytidae), mediates species specificity and response level

In a field-trapping experiment, western balsam bark beetles,Dryocoetes confusus Swaine, were highly attracted to a 51 mixture of (±)-exo-and (±)-endo-brevicomin. Beetles in the sympatric speciesD. affaber (Mann.), were best attracted to a 11 blend of these semiochemicals [either (±)(±) or (±)(±)], suggesting that both geometrical isomers are pheromone components in these species. In laboratory bioassays and further field experiments, attraction ofD. confusus was greatest when the (+) enantiomers of both geometrical isomers of brevicomin were presented in a 91 ratio. Responses by maleD. confusus to attractive mixtures were reduced in the presence of (–)-exo-brevicomin. Exploitation of the complete range of variability in pheromone structure (both geometrical and optical isomerism) would allow for optimization and regulation of response levels within a species and also could maintain reproductive isolation among sympatric congeneric species primarily through production and response to species-specific blends.During the course of the research, A.D. Camacho was on educational leave from the Escuela Nacional de Ciencias Biológicas. I.P.N. Depto. de Zoología. Prol. Carpio y Plan de Ayala, Mexico 11340D.F. México.     

Evidence for mediation of two releaser pheromones in the aggregation behavior of the gregarious desert locust,Schistocerca gregaria (forskal) (Orthoptera: Acrididae)

The response of nymphal and adult gregarious phase desert locust,Schistocerca gregaria, to a choice of two columns of air, one permeated with airborne volatiles emanating from nymphs or adults and the other untreated, was investigated in a single-chamber bioassay arena. The nymphs, whether released individually or in groups, preferred to be within the precinct of the air column treated with airborne volatiles of the nymphs but were indifferent to volatiles of the adults. Conversely, older adults responded only to their own volatiles but not to those of the nymphs or young adults. The young adults were responsive only to volatiles of the older adults. Charcoal-trapped volatiles from the nymphs and the adults reproduced the effect of living locusts. These results indicate that there are two different aggregation pheromones inS. gregaria: a juvenile pheromone produced by nymphs and an adult pheromone specific to adults.     

Species discrimination in five species of winter-flying geometrids (Lepidoptera) based on chirality of semiochemicals and flight season

Enantiomer separation of (6Z,9Z)-cis-3,4-epoxynonadecadiene and (3Z,9Z)-cis-6,7-epoxynonadecadiene could be achieved using chiral high-resolution gas chromatography and a cyclodextrin-bond column. (3Z,9Z)-(6R,7S)-Epoxynonadecadiene was identified from ovipositor extracts ofColotois pen-Naria, while inErannis defoliaria the 6S,7R-enantiomer was found. In field trapping tests pure synthetic enantiomers caught only conspecific males of these species. (3Z,6Z,9Z)-Nonadecatriene was found in both species, while the presence of (3Z,6Z,9Z)-heneicosatriene was indicated inC. Pennaria only. A 10103 blend of (3Z,9Z)-(6R,7S)-epoxynonadecadiene, (3Z,6Z,9Z)-heneicosatriene, and (3Z,6Z,9Z)-nonadecatriene was found to be optimal for catchingC. Pennaria, whileE. Defoliaria males were optimally caught by a 11 mixture of (3Z,9Z)-(6S,7R)-epoxynonadecadiene and (3Z,6Z,9Z)-nona-decatriene. (6Z,9Z)-(3S,4R)-Epoxynonadecadiene was identified from ovipositor extracts ofAgriopis (Erannis) aurantiaria. In field tests the pure enantiomer proved to be a highly specific sex attractant for both the late autumn/early winter flyingA. Aurantiaria and the late winter/early spring flyingA. Leucophearia. Males ofAgriopis marginaria, which fly in late winter/early spring, were attracted to (3Z,9Z)-(6S,7R)-epoxynonadecadiene. The addition of (3Z,6Z,9Z)-nonadecatriene to theS,R-enantiomer increased captures. Optimal catches were recorded with a 103 epoxide-hydrocarbon blend. Enantiomer specificity in all species was confirmed in EAG measurements.     

Response ofDendroctonus brevicomis andIps paraconfusus (Coleoptera: Scolytidae) to combinations of synthetic pheromone attractants and inhibitors verbenone and ipsdienol

DendroctonusBrevicomis andIps paraconfusus are sympatric bark beetle species colonizingPinus ponderosa in western North America. Interspecific and intraspecific competition for resources is, in part, mediated through semiochemicals. The response ofD. brevicomis to its attractant pheromone was significantly reduced by simultaneous release of either verbenone or racemic ipsdienol. Trap catch was significantly further reduced by including both inhibitors with the attractant pheromones. However, although the response ofIps paraconfusus was significantly inhibited with the addition of either verbenone or racemic ipsdienol, both compounds together did not result in a significant further reduction in trap catch. There was a trend for greater reduction in response ofD. brevicomis to attractant pheromones with increased release rates of either 69% (+)-/31% (–)-verbenone or 84% (–)-/16% (+)-verbenone. Response of associates to attractants and inhibitor combinations was also determined.     

(3Z,6Z,8E)-3,6,8-Dodecatrien-1-ol: Sex pheromone in a higher fungus-growing termite,Pseudacanthotermes spiniger (Isoptera,macrotermitinae)

The female sex pheromone of the fungus-growing termitePseudacanthotermes spiniger (Termitidae, Macrotermitinae) was isolated from sternal glands of alates. The compound inducing attraction and excitation in males was identified as the (3Z,6Z,8E)-3,6,8-dodecatrien-1-ol by GC-MS, microhydrogenation, GC-FTIR, and NMR. This unsaturated alcohol is present in both sexes but in much higher quantities in females than in males (about 10 times). The hypothesis is suggested that this alcohol, which is detected at extremely low concentrations by the workers ofP. spiniger, may be used either as a trail-following pheromone or a sex pheromone according to concentrations and to target castes. The presence of this alcohol in Macrotermitinae reinforces the idea of a phylogenetic proximity between this subfamily of higher termites and the lower termites Rhinotermitidae, where the unsaturated alcohol was previously found. The sternal glands of alates ofP. spiniger also contain a geometric isomer of (3Z,6Z,8E)-3,6,8-dodecatrien-1-ol.     

Sex pheromone evidence for two distinct taxa withinGraphania mutans (Walker)

The sex pheromones of two populations ofGraphania mutans (Walker) were analyzed. Females from an Auckland population produced (Z)-9-tetradecenol (Z9-14OH), (Z)-9-tetradecenyl acetate (Z9-14OAc), (Z)-7-tetradecenol (Z7-14OH) and (Z)-7-tetradecenyl acetate (Z7-14OAc), while females from a Lincoln population produced these four compounds and a large amount of (Z)-9-tetradecenal (Z9-14Ald). Significant differences, paralleling the difference between females, were observed when the responses of males of both populations to the above and other related compounds were tested by electroantennogram, field-trapping, and wind-tunnel bioassays. The most distinct difference was observed in the wind tunnel. Males from both taxa flew upwind and touched pheromone sources containing sex pheromone extract of females of their own taxon, but either did not initiate upwind flight or arrested upwind flight shortly after taking flight in response to extract from females of the other taxon. The difference between the pheromone systems of the two populations is probably due to the presence and importance of Z9-14Ald in the pheromone blend of the Lincoln population. Thus the addition of a relatively large amount of Z9-14Aid to a four-component pheromone blend (i.e., Z9-14OH, Z9-14OAc, Z7-14OH, andZ7-14OAc) attractive to Auckland males completely suppressed trap catches of male G.Mutans in Auckland but large numbers of males were caught at both Lincoln and Nelson in traps baited with this five-component blend. In wind-tunnel studies, the addition of even small (1% of amount of Z9-14OH) amounts ofZ9-14Ald to the four-component blend resulted in a significantly greater proportion of Auckland males arresting upwind flight than to the four-com ponent blend. It is suggested that these two populations of G. nations represent distinct sibling species within the described concept.LepidopteraNoctuidaeHadeninae.     

Defense by Volatiles in Leaf-Mining Insect Larvae

The defense strategy of an insect toward natural enemies can include a trait that appears at first sight to contradict its defensive function. We explored phylogeny, chemistry, and defense efficiency of a peculiar group of hymenopteran sawfly larvae where this contradiction is obvious. Pseudodineurini larvae live in leaf mines that protect them from some enemies. Disturbed larvae also emit a clearly perceptible lemon-like odor produced by ventral glands, although the mine hampers the evaporation of the secretion. The mine could also lead to autointoxication of a larva by its own emitted volatiles. Citral was the major component in all Pseudodineurini species, and it efficiently repels ants. We conclude that full-grown larvae that leave their mine to pupate in the soil benefit from citral by avoiding attacks from ground-dwelling arthropods such as ants. In some species, we also detected biosynthetically related compounds, two 8-oxocitral diastereomers (i.e., (2E,6E)- and (2E,6Z)-2,6-dimethylocta-2,6-dienedial). Synthetic 8-oxocitral proved to be a potent fungicide, but not an ant repellent. The discrete distribution of 8-oxocitral was unrelated to species grouping in the phylogenetic tree. In contrast, we discovered that its presence was associated with species from humid and cold zones but absent in species favoring warm and dry environments. The former should be protected by 8-oxocitral when faced with a fungal infestation while crawling into the soil. Our work shows the importance of integrating knowledge about behavior, morphology, and life history stages for understanding the complex evolution of insects and especially their defense strategies.