Sexual role reversal in mate-finding strategies of the cabbage looper moth.

The mate-finding behavior of the cabbage looper moth Trichoplusia ni (Lepidoptera: Noctuidae) includes both female- and male-produced sex pheromones used in distinct mate-finding strategies. Both sexes release multicomponent pheromones attractive to the opposite sex. Male pheromone is comprised of d-linalool, m-cresol, and p-cresol released from abdominal hair pencils. Males exposed to host plant odor or to the female sex pheromone (Z)-7-dodecen-1-ol acetate are more attractive to females, suggesting stimulation of male pheromone release.

Intrasexual mounting in the beetle Diaprepes abbreviatus (L.).

The weevil Diaprepes abbreviatus shows three kinds of same-sex mountings: males mount other unpaired males, males mount males already engaged in copulation and females mount other females. Four hypotheses were evaluated in order to explain same-sex matings by males: (i) female mimicry by inferior males, (ii) dominance of larger males which affects the behaviour of small males, (iii) sperm transfer in which smaller males gain some reproductive success by 'hitchhiking' their sperm with the sperm of larger males, and (iv) poor sex recognition. Data from mate choice and sperm competition experiments rejected the female mimicry, dominance and sperm transfer hypotheses and supported the poor sex recognition hypothesis. We tested three hypotheses in order to explain female mounting behaviour: (i) females mimic male behaviour in order to reduce sexual harassment by males, (ii) females mount other females in order to appear larger and thereby attract more and larger males for mating, and (iii) female mimicry of males. The results of our mate choice experiments suggested that the female mimicry of males hypothesis best explains the observed female mounting behaviour. This result is also consistent with the poor sex recognition hypothesis which is the most likely explanation for male and female intrasexual mating behaviour in many insect species.

New chemical attractants for trapping Lacanobia subjuncta, Mamestra configurata, and Xestia c-nigrum (Lepidoptera: Noctuidae).

Significant numbers of 3 pest species of noctuid moths were captured in traps baited with acetic acid, 3-methyl-1-butanol, and 3-methyl-1-pentanol. These were Lacanobia subjuncta (Grote & Robinson); Mamestra configurata Walker, bertha armyworm; and Xestia c-nigrum (L.), spotted cutworm. The combination of acetic acid and 3-methyl-1-butanol was superior to the individual chemicals in attracting all 3 species, whereas the combination of acetic acid and 3-methyl-1-pentanol was superior to the individual chemicals in attracting X. c-nigrum. For the 3 species of moths, numbers captured were similar in traps baited with the combination of acetic acid and 3-methyl-1-butanol or acetic acid and 3-methyl-1-pentanol. Traps baited with these attractants captured both males and females at a ratio near 1:1.

Trapping social wasps (Hymenoptera: Vespidae) with acetic acid and saturated short chain alcohols.

Nineteen compounds were evaluated in combination with a solution of acetic acid as baits for trapping the German yellowjacket, Vespula germanica (F.), the western yellowjacket Vespula pensylvanica (Sausssure), and the golden paper wasp Polistes aurifer Saussure. Compounds with three to six carbon chains or branched chains and with a hydroxy functional group were selected for testing based on their similarity to isobutanol. They were compared with isobutanol with acetic acid, which is a known wasp attractant. None of the compounds tested were superior to isobutanol when presented with acetic acid as a lure for these species of wasps. However, traps baited with either the S-(-)- or the racemic mixture of 2-methyl-1-butanol in combination with acetic acid captured similar numbers of both species of yellowjackets, compared with isobutanol with acetic acid. Polistes aurifer responded strongly to the S-(-)-enantiomer and to the racemic mixture of 2-methyl-1-butanol with acetic acid and not to the R-(+)-enantiomer with acetic acid.

Spatial and temporal dynamics of potato tuberworm (Lepidoptera: Gelechiidae) in the Columbia Basin of the Pacific Northwest.

A landscape-scale study from 2004 to 2006 investigated the spatial and temporal dynamics of a new pest to the Columbia Basin of the Pacific Northwest, the potato tuberworm, Phthorimaea operculella (Zeller). Male P. operculella were monitored in spring, summer, and fall each year with a pheromone-baited trapping network in Oregon and Washington. The objectives of the study were to (1) describe the temporal and spatial dynamics of the recent outbreak of P. operculella in the region and (2) examine the relationship of the spatial and temporal distribution of the outbreak and weather (air temperature, precipitation, and dew point) and geographic variables (elevation and latitude). Weather data during the P. operculella outbreak were compared with a reference period (1993-1999) that occurred before the outbreak. The outbreak in 2004, which caused the first widespread tuber damage in the region, was positively associated with warmer temperatures in the preceding fall and in the spring, summer, and fall of the growing season. October and November 2003 and March 2004 were also drier than the reference period. However, the winter of 2003/2004 was colder than the reference period and thus mild winter conditions did not explain the outbreak. The importance of environmental variables on the seasonal spatial distribution of the pest each year was examined using nonparametric multiplicative regression. Locations with higher spring, summer, or fall temperatures were associated with increased trapping rates in most seasons. Elevation and latitude seemed to play a constraining role, because low trapping rates of P. operculella were associated with higher elevations and latitudes.

Positive interaction of a feeding attractant and a host kairomone for trapping the codling moth, Cydia pomonella (L.).

Codling moths are attracted to acetic acid and to ethyl-(E,Z)-2,4-decadienoate, the pear ester, when presented individually. The attraction to acetic acid is thought to be a food finding behavior, whereas the pear odorant, ethyl-(E,Z)-2,4-decadienoate, may be a host kairomone. We found, in a flight tunnel study, that more male and female codling moths were captured in traps when the compounds were presented together compared to tested separately. The combination of odorants provides a stronger lure for female codling moths than exists with pear ester alone and increases the potential for using lures in managing this pest of pome fruits and walnuts.

Role of female-produced sex pheromone in behavioral reproductive isolation betweenTrichoplusia ni (Hübner) andPseudoplusia includens (Walker) (Lepidoptera: Noctuidae, plusiinae).

In laboratory flight tunnel bioassays, response rates of male cabbage looper,Trichoplusia ni (Hübner), to female soybean looper,Pseudoplusia includens (Walker), were similar to response rates of maleT. ni to conspecific females for plume tracking and source contact. Male soybean loopers, however, exhibited a greatly reduced response to female cabbage loopers compared to conspecific females. Similar differences were observed in male responses to extracts of female abdominal tips. Studies of flight tunnel responses of male soybean loopers to the different chemicals known to be components of the female cabbage looper sex pheromone indicated that the reduction in response was due to inhibitory effects of (Z)-5-dodecen-1-ol acetate and (Z)-9-tetradecen-1-ol acetate, when added singly to (Z)-7-dodecen-1-ol acetate (major component of both species) at release rates and at ratios close to those observed in female cabbage loopers.

Sex attraction in paper wasp,Polistes exclamans viereck (Hymenoptera: Vespidae), in a wind tunnel.

A wind-tunnel bioassay was developed to test for the presence of sex attractants in the paper wasp,Polistes exclamans Viereck (Hymenoptera: Vespidae). Males exhibited significant upwind flight and attraction (chemoanemotaxis) in response to airflow passed over unmated females, and to hexane extracts of whole bodies and thoraces of unmated females. Unmated females were attracted to hexane extracts of males and to hexane extracts of each body tagma of males, suggesting distribution of the pheromone over the cuticle by grooming. The ectal mandibular and seventh sternal glands are the likely sources of the male-produced sex attractant(s) since extracts of each elicited female attraction in the flight tunnel. These glands are associated with gastral and mandibular rubbing of perch sites by territorial males ofPolistes species.

Host plant influences on sex pheromone behavior of phytophagous insects.

The sexual behavior of phytophagous insects is often integrated in a variety of ways with their host plants. This integration may be manifested as effects or influences of host plants on insect physiology and behavior, including sex pheromone communication, that reflect strategies by insects to optimize mating and reproduction. Certain insects sequester or otherwise acquire host plant compounds and use them as sex pheromones or sex pheromone precursors. Other insects produce or release sex pheromones in response to particular host plant cues. Chemicals from host plants often synergize or otherwise enhance insect responses to sex pheromones. By these means, host plants may be used by insects to regulate or mediate sexual communication. For many species of insects, host plant influences on insect sex pheromone communication may be important aspects of the formation of feeding and mating aggregations, of insect strategies to locate both hosts and mates, of behavioral reproductive isolation among sibling species, and of the regulation of reproduction to coincide with the availability of food and oviposition sites. Knowledge of these relationships is critical to understanding many different areas of the behavioral ecology of plant-feeding insects.

Identification of a male-produced pheromone ofAnticarsia gemmatalis (Hübner) (Lepidoptera; Noctuidae) attractive to conspecific males.

Observations in the laboratory and in the field indicated that maleAnticarsia gemmatalis (Hübner), the velvetbean caterpillar (VBC), are attracted to conspecific courting males. Male VBC subsequently were found to be attracted to extracts of male abdominal tips including the extrudable hairpencils. The active chemical in these extracts was identified as (Z,Z,Z)-3,6,9-heneicosatriene, which is also one of the major components of the female VBC sex pheromone. Male VBC in a wind tunnel and in the field exhibited a bimodal response distribution to a range of ratios of the (Z,Z,Z)-3,6,9-heneicosatriene and (Z,Z,Z)-3,6,9-eicosatriene, with one maximum at the pure heneicosatriene alone and the other at the 60∶40 female blend. This demonstrates that the male response to the male hairpencil component is distinct from that to the female sex pheromone.

Isolation, identification, and synthesis of male-produced sex pheromone of papaya fruit fly,Toxotrypana curvicauda Gerstaecker (Diptera: Tephritidae).

A male-produced sex pheromone of the papaya fruit fly,Toxotrypana curvicauda Gerstaecker, was isolated from volatiles collected from air passed over calling males and was identified as 2-methyl-6-vinylpyrazine by comparative gas-liquid chromatographic and spectroscopic evidence. Synthetic 2-methyl-6-vinylpyrazine elicited typical pheromonal responses from unmated mature female flies such as walking, running, and flying in an arena bioassay; flying upwind with a zigzag flight pattern; and hovering in the pheromone plume in a wind-tunnel bioassay. These responses were similar quantitatively and qualitatively to responses to naturally occurring pheromone from calling male papaya fruit flies.

Identification of male cabbage looper sex pheromone attractive to females.

A multicomponent pheromone produced by male cabbage looper moths that is attractive to female moths in a flight tunnel bioassay was isolated and identified. Based on analyses of hairpencil extracts of male cabbage loopers and volatiles emitted by males, the pheromone has been identified as a blend consisting of (S)-(+)-linalool,p-cresol, andm-cresol. The chirality of the major component, (S)-(+)-linalool, is important for behavioral response of females. These pheromonal compounds were also identified as volatiles released by males when males were exposed to the principal pheromone component of female cabbage loopers, (Z)-7-dodecen-1-ol acetate. The amount of male pheromone released was increased significantly when males were exposed to a combination of (Z)-7-dodecen-1-ol acetate and the odor from cabbage. Neither linalool nor the cresols were detected in volatiles from cabbage or from males exposed to cabbage odor.

A bioassay system for collecting volatiles while simultaneously attracting tephritid fruit flies.

A bioassay system was developed that permits the testing of various substrates for biological activity in a flight tunnel, while simultaneously collecting a portion of the volatiles from the attractive source for subsequent chemical identification and quantification. Bioassays of the response of virgin female Caribbean fruit flies,Anastrepha suspensa (Loew) (Diptera: Tephritidae), to volatiles released by calling males were conducted in a greenhouse under natural light cycles and fluctuating environmental conditions, similar to those in the field. Using this system, the periodicity of response of the female flies between 1300 and 1845 hr (EST) was tested. Fifty to 75% response occurred between 1700 and 1845 hr. Male pheromone release was greatest between 1500 and 1800 hr. Videotaped records of insects, taken between 1700 and 1800 hr as flies approached and entered the traps, were analyzed to interpret the communicative role of the volatiles released. Significantly more flies landed on and entered the pheromone-emitting trap than the control trap. There was no difference in the amount of time spent on the trap face, an indication that volatiles were attractants. The system described should be of general utility in determination of the attraction of pest fruit flies to suspected attractants.

Effects of host plant,Gossypium hirsutum L., on sexual attraction of cabbage looper moths,Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae).

Unmated female or male cabbage looper moths,Trichoplusia ni (Hübner), were attracted more often in a flight tunnel to a cage with moths of the opposite sex and a bouquet of cotton foliage. Increased sexual attractiveness of females with plants may be a result of stimulation of pheromone release in response to plant odor, since more males were attracted when odor of cotton foliage was passed over females than when odor of females was passed over cotton foliage before venting into the flight tunnel. Increased sexual attractiveness of males with plants is due in part to host odor enhancement of female attraction to male pheromone, since more females were attracted to synthetic male pheromone (a blend of enantiomers of linalool and isomers of cresol) and a cotton leaf extract than were attracted to male pheromone alone. A short synthesis procedure was developed for (S)-(+)-linalool, the major component of the male sex pheromone, isolated from hair pencils, used in these tests.

Analysis, synthesis, formulation, and field testing of three major components of male mediterranean fruit fly pheromone.

Three major components, ethyi-(E)-3-octenoate, geranyl acetate, and (E,E)-α-farnesene, emitted as volatiles by laboratory-reared and wild male medflies were collected and analyzed qualitatively and quantitatively. Peak emission of these compounds occurred during the third to fifth hours of the photophase and differences were observed in the ratios of the three components emitted by male laboratory-reared and wild flies. These three compounds were synthesized, and a method was developed to formulate a synthetic blend that released the compounds in a ratio similar to that emitted by wild male medflies. Attractiveness of the blend to female medflies was demonstrated under field conditions by comparing trap catches. Black spherical traps, baited with the synthetic blend to release 1.6 male equivalents, caught significantly more females than blank traps and traps from which the blend released was 0.3, 3.2 or 6.4 male equivalents.