Showing papers by "Jocelyn G. Millar published in 2001"

Geographic variation in the pheromone system of the saturniid mothhemileuca eglanterina

Abstract: The common sheep moth,Hemileuca eglanterina (Boisduval), appears to have at least two distinct pheromone types. Male moths from the population in the San Gabriel Mountains of southern California are attracted optimally to a blend ofE10,Z12-hexadeca-10,12-dien-1-yl acetate (acetate);E10,Z12-hexadeca-10,12-dien-1-ol (alcohol); andE10,Z12-hexadeca-10,12-dienal (aldehyde), whereas males from the population at Robinson Summit, northwest of Ely, Nevada, are attracted to the two-component blend of alcohol and aldehyde. Populations along the eastern edge of the Sierra Nevada Mountains are composed of individuals of both pheromone types and a type intermediate between the two. Antennae from male moths from the different pheromone types give distinctly different electroantennographic responses when challenged with blends of the pheromone components, with San Gabriel Mountains males showing a large response to acetate and lesser responses to alcohol and aldehyde. In contrast, antennae from Robinson Summit males, which are attracted to lures containing only alcohol and aldehyde, exhibit a large response to alcohol, a smaller response to aldehyde, and minimal or no response to acetate. Male moths from the eastern Sierra Nevada Mountains give antennal responses similar to those of either San Gabriel Mountains or Robinson Summit males. However, eastern Sierra populations also contain an intermediate type that does not occur in areas where the major pheromone types do not occur together. This third type may be a hybrid between the two other pheromone types, and it is attracted in approximately equal numbers to synthetic pheromone lures with and without acetate. The antennae of male moths in all populations tested responded toE10,E12-16:Ac, a major pheromone component of the congenerH. nuttalli, which is sympatric with someH. eglanterina populations, and in mostH. eglanterina populations tested, the addition ofE10,E12-16:Ac antagonized responses to otherwise attractive lure blends. Overall, the existence of different pheromone types in the differentH. eglanterina populations may represent a case of reproductive character displacement.

Comparison of Substrate-Borne Vibrational Signals of Two Stink Bug Species, Acrosternum hilare and Nezara viridula (Heteroptera: Pentatomidae)

Abstract: Substrate-borne vibrational signals (songs) were recorded from the green stink bug, Acrosternum hilare (Say) and the southern green stink bug, Nezara viridula (L.). Female A. hilare emitted one song type in the calling phase of mating behavior, and the production of this song was stimulated by male presence or calling. The temporal characteristics of the pulses and pulse trains of this song were similar to the narrow-band type of pulse trains that constituted the N. viridula female calling song. Male A. hilare produced two different songs, each associated with a different phase of mating behavior. In the calling phase, males produced a song composed of regularly repeated, complex pulse trains whose temporal structure resembled that of the N. viridula male courtship song. In the courtship phase of behavior, males of A. hilare emitted a song that terminated female singing. The pulses of this song had similar temporal characteristics to those of the narrow-band type of the N. viridula male calling song. Immediately after initiating copulation, A. hilare pairs emitted another song, which had no counterpart in the repertoire of N. viridula or other pentatomid species that have been examined. In contrast, males of A. hilare did not appear to produce a song equivalent to the N. viridula male rival song, and neither sex of A. hilare produced songs equivalent to the broad-band pulses and pulse trains found within male and female N. viridula calling songs. Orientation of males toward females was mediated by the female calling song, which had similar spectral and temporal characteristics in both species. Male songs of the two species, although they shared some spectral characteristics, differed in temporal structure and in the contexts in which they were emitted.

Male-produced sex attractant pheromone of the green stink bug, Acrosternum hilare (Say).

Abstract: Sexually mature virgin adult males of the green stink bug, Acrosternum hilare attracted sexually mature virgin adult females in laboratory bioassays using a vertical Y-tube. There was no indication that males attracted other males, or that females attracted either sex. These results suggested that A. hilare males produce a sex pheromone. Extracts of odors collected from sexually mature males contained compounds that were not present in extracts from females or sexually immature males. (4S)-Cis-(Z)-bisabolene epoxide ((4S)-cis-Z-BAE) was the major sex-specific component of the extract. The crude extract was attractive to female A. hilare, but when separated into four fractions, only the portion containing (4S)-cis-Z-BAE and the minor component (4S)-trans-Z-BAE was attractive to females. This fraction was as attractive as the crude extract, suggesting that the former contained all the pheromone components. Neither synthetic (4S)-cis-Z-BAE nor (4S)-trans-Z-BAE alone was attractive to females, but a 95:5 cis:trans blend, mimicing the ratio naturally produced by males, was attractive to females in Y-tube bioassays. Bioassays in a field cage showed that significantly more A. hilare females were attracted to cotton string lures treated with 1 mg of a 95:5 blend of (4S)-cis-Z-BAE and (4S)-trans-Z-BAE placed inside a bouquet of alfalfa than to an alfalfa bouquet containing a pentane-treated control. In field cage studies, attraction of females was greatest during the late afternoon and evening hours, and female A. hilare approached the synthetic pheromone source almost exclusively by walking.

Identification and synthesis of a male-produced sex pheromone from the stink bug Chlorochroa sayi.

Abstract: The reproductive behavior of the stink bug Chlorochroa sayiwas studied in the laboratory. There was a sexual maturation period of about 10 days before bugs began mating. Sexually mature adult bugs engaged in courtship consisting of antennation and head-butting of the female by the male, before the female adopted a receptive posture and copulation occurred. Both sexes mated multiple times during their life-spans, with the mean duration of copulations of virgin bugs (42.3 ± 19.6 min) and experienced bugs (37.3 ± 28.4 min) being similar. Most matings were initiated in the late afternoon or evening, when pheromone production by males was greatest. Males transferred sperm and nutrients constituting about 17% of their body weight to females during mating. Three male-specific components, methyl geranate, methyl citronellate, and methyl (E)-6-2,3-dihydrofarnesoate in a ratio of 100 : 0.45 : 1.6, were first detected in volatiles collected from male bugs on green beans about 9–12 days after the final molt to the adult stage. In vertical Y-tube bioassays, females were attracted to odors from mature male bugs, and to a blend of the three male-produced components. Low numbers of females also were attracted in field trials with the three-component blend. The relatively weak attraction may be a result of other, as yet unknown cues being required in addition to the pheromone, such as visual or substrate-borne vibrational cues.

Identification and synthesis of male-produced sex pheromone components of the stink bugs Chlorochroa ligata and Chlorochroa uhleri.

Abstract: The reproductive behaviors of the stink bugs Chlorochroa ligata and C. uhleri were studied in the laboratory. Adults of both species became sexually mature about 12–14 days after the final molt, and both sexes mated multiple times during their lifetimes. The mean duration of copulation was 54 ± 24 min for virgin bugs and 46 ± 33 min for experienced bugs for C. ligata and 78 ± 55 min for field-collected C. uhleri of unknown mating status. Male C. ligata were found to transfer a significant fraction of their body mass (19%) to females during mating. Sexually mature C. uhleri males produced three sex-specific compounds, methyl (R)-3-(E)-6-2,3-dihydrofarnesoate, methyl (2E,6E)-farnesoate, and methyl (E)-5-2,6,10-trimethyl-5,9-undecadienoate, in a ratio of 100:0.9:0.6. These three compounds were also produced by sexually mature male C. ligata in a ratio of 100:0.5:0.4. Identifications of the compounds were confirmed by synthesis. Production of the male-specific compounds peaked in late afternoon to early evening, coincident with the peak period of reproductive activity. Laboratory and field bioassays demonstrated that female bugs were attracted to odors from live males and to reconstructed blends of the male-specific compounds.

Identification and Synthesis of the Sex Pheromone of the Vine Mealybug, Planococcus ficus.

Abstract: Sexually mature females of an important agricultural pest, the vine mealybug Planococcus ficus, produce the monoterpene (S)-lavandulol and the corresponding ester, (S)-(+)-lavandulyl senecioate. The racemic ester was highly attractive to mature male mealybugs, whereas lavandulol was not. The naturally produced 2:5 blend of lavandulol and the ester also was no more attractive than the ester alone.

Influence of host log age and refuge from natural enemies on colonization and survival of Phoracantha semipunctata

Abstract: The eucalyptus longhorned borer Phoracantha semipuncata (F.) is native to Australia and has become established in most of the regions of the world where its Eucalyptus L'Heritier host trees have been introduced. To study the population dynamics of the insect in its native range, we investigated the influence of host log age (fresh or aged), protection from ant predation, and protection from parasitism by specialist larval parasitoids on numbers of initial larval feeding galleries, larval mortality, larval survivorship, and parasitization. There were greater numbers of initial larval galleries when ants were excluded, and greater numbers on fresh logs than on aged logs. However, mortality of larvae was greater in fresh logs, as well as when larvae were exposed to parasitism. Survivorship was greater when ants and parasitoids were excluded. Larvae achieved a larger size in fresh logs and in logs protected from parasitism. Fresh host material may provide a fitness advantage because it is a higher quality resource, brat greater infestation of that material also increases the probability of mortality from competition among larvae. The results suggest that there are potential ecological interactions among food quality, host resistance, natural enemies, and competition that must be considered in evaluating the population dynamics of this species in native and novel environments.

Sex pheromone components of the buck moth Hemileuca maia.

Abstract: The sex attractant pheromone blend of Hemileuca maia (Lepidoptera: Saturniidae) from the vicinity of Baton Rouge, Louisiana, has been identified. The major component of the blend is (E10,Z12)-hexadeca-10,12-dienal (E10,Z12–16:Ald), in combination with the minor components (E10,Z12)-hexadeca-10,12-dien-1-ol (E10,Z12–16:OH), and (E10,Z12)-hexadeca-10,12-dien-1-yl acetate (E10,Z12–16:Ac). Ratios of the compounds in extracts of female pheromone glands varied around a mean of 100:7.4:6.3. None of the three components were attractive to male moths when tested as single components. Several other compounds were tentatively identified from female pheromone gland extracts, including E10,E12–16:Ald, E10,E12–16:OH, and E10,E12–16:Ac, but addition of these components, either alone or in combination, at biologically relevant rates, did not significantly increase the attractiveness of lures. The saturated analogs, hexadecanal, hexadecanol, and hexadecyl acetate, also were identified in gland extracts, but had no apparent effect as pheromone components.

Attraction of female digger wasps, Astata occidentalis cresson (Hymenoptera: Sphecidae) to the sex pheromone of the stink bug Thyanta pallidovirens (Hemiptera: Pentatomidae)

Abstract: In field trials with male-produced sex pheromones of the stink bug Thyanta pallidovirens, the sphecid wasp Astata occidentalis, which preys on stink bugs, was also trapped. Only female wasps were trapped, suggesting that the bug pheromone is used by female A. occidentalis as a kairomone to locate prey for nest provisioning. The wasps were attracted by the main component of the stink bug pheromone, methyl (2E,4Z,6Z)-decatrienoate, and to blends of that compound with the minor components, the sesquiterpenes zingiberene, sesquiphellandrene, and α-curcumene.

(E4,Z9)-TETRADECADIENAL, A SEX PHEROMONE FOR THREE NORTH AMERICAN MOTH SPECIES IN THE GENUS Saturnia

Abstract: The lepidopteran genus Saturnia has three representatives in North America, S. walterorum, S. mendocino, and S. albofasciata. (E4,Z9)-Tetradecadienal (E4,Z9–14 : Ald) was identified as a sex pheromone component for all three species by combinations of coupled gas chromatography–electroantennogram detection (GC-EAD), GC–mass spectrometry (MS), and field trials. In field trials, all three species were strongly attracted to (E4,Z9–14 : Ald) as a single component. Small amounts of (Z)-9-tetradecenal (Z9–14 : Ald) also were found in extracts of all three species, but blends of this compound with E4,Z9–14 : Ald were no more attractive to male moths than E4,Z9–14 : Ald alone. Extracts of pheromone glands of female S. walterorum occasionally contained a third, trace compound eliciting responses from male antennae in GC-EAD experiments, but this compound was not identified. It is suggested that the three species can use the same, single component as a sex attractant because the flight period of S. albofasciata (fall) is different than that of the other two species (spring), whereas the geographic distributions of S. mendocino and S. walterorum overlap over only small portions of their ranges. Furthermore, the latter two species readily hybridize, so there may be minimal fitness cost to cross-attraction.