Diel periodicity and influence of age and mating on sex pheromone titer in gypsy moth,Lymantria dispar (L.)

The diel periodicity of sex pheromone titer from pheromone glands of femaleLymantria dispar is described. On the day of emergence (day 0), pheromone titer was generally low; means ranged from 1 to 4 ngcis- 7,8-epoxy-2-methyloctadecane during photophase and gradually increased to 8.4 ng over the course of scotophase. For day-1, -2, and -3 females, the diel fluctuations of titer were more pronounced. Lowest titers (5–9 ng) occurred 0–4 hr after lights-on, and peak titers (19–32 ng) were found 0–4 hr before lights-off. Comparison of the average daily titer among the different age groups (data pooled over six time points at 4-hr intervals) indicated that significantly less pheromone was extracted from glands of day-0 (4.5 ng) than day-1 (12.4 ng), day-2 (15.4 ng), or day-3 females (13.5 ng). No significant differences were found among the three older ages. Femalesin copula exhibited a rapid reduction in titer within the first 0.5 hr of mating initiation (7.6 ng vs. 19.5 ng from virgin females of similar age). After the second 0.5 hr, the reduction in titer was not nearly as marked, falling only to 4.5 ng. Twenty-four hours after mating, titer fell below the limits of detection (0.5 ng). All extracts from pheromone glands of virgin or mated females contained < 1.0 ng of the putative pheromone precursor, 2-methyl-cis-7-octadecene.     

Chemical basis for asymmetric mating isolation between strains of screwworm fly,Cochliomyia hominivorax

Laboratory mating tests and bioassays for a contact, mating-stimulant pheromone were conducted within and between two strains of the screwworm fly,Cochliomyia hominivorax. No strain or sex difference in pheromone activity occurred at emergence. However, the pheromone activity of females increased with age in one strain but declined in the other. Activity also declined in males of both strains but more steeply than in the females. Thus, sexual dimorphism in pheromone activity developed with age in both strains but to differing degrees. The decline in female pheromone activity was partly compensated for within that strain by a higher male responsiveness to pheromone. Female pheromone activity and mating success were positively correlated. Virgin females and those inseminated 24–48 hr previously were equally stimulatory. It appears that the strain differences arose from selection for reduced pheromone activity during laboratory colonization.     

Mating Disruption of Guatemalan Potato Moth Tecia Solanivora by Attractive and Non-Attractive Pheromone Blends

The behavioral mechanisms of mating disruption in Guatemalan potato moth Tecia solanivora were studied using the sex pheromone components, (E)-3-dodecenyl acetate, (Z)-3-dodecenyl acetate, and dodecyl acetate, formulated in a 100:1:20-ratio mimicking the female-produced blend, and in a 100:56:100 off-blend ratio. The mode of action of these two blends was tested in mating disruption experiments in the field and in a greenhouse, as well as in a laboratory wind tunnel. Field treatments with both blends at 80 g pheromone per ha reduced male attraction to trap lures baited with 100 μg of female sex pheromone. In mesh-house treatments, these two blends were equally effective at reducing male attraction to traps baited with live females and mating of caged females. Subsequent flight tunnel tests corroborated that both blends reduced attraction of naive males to calling females, and pre-exposure of males with either dispenser blend for 24 hr resulted in a strongly reduced response to calling females. The pre-exposure effect was reversible, with males again responsive after 24 hr in clean air. The two dispenser formulations produced a similar effect on male behavior, despite the differences in blend composition. One mating disruption dispenser formulated with either the female-blend or off-blend elicited the same rate of male upwind attraction in a wind-tunnel bioassay. Sensory overload and camouflage, therefore, are contributing mechanisms to mating disruption using either blend. The off-blend, which is more economical to synthesize, is a valuable tool for further development of mating disruption against this major pest of potatoes in Latin America.     

Evidence for a sex pheromone in the hide beetle,Dermestes maculatus (De Geer) (Coleoptera: Dermestidae)

Adults of the hide beetle,Dermestes maculatus (De Geer), were shown to have a female-produced sex pheromone which excited males. Male response was positively correlated with increasing age, but females produced a higher level of pheromone at 6–8 days of age than at younger or older ages. Extractable female pheromone and male response varied over the photophase with peak values that occurred during the latter hours. Quantitative bioassay indicated that the 50% male response level (RD₅₀) would be elicited by a pheromone exposure of 0.01 female equivalents (FE). Females extracted 24 hr after mating had a lower level of extractable pheromone than did virgin females of the same age.Mention of a proprietary product does not constitute an endorsement by the Minnesota Agricultural Experiment Station.     

Interspecific attractivity of female sex pheromone components ofPeriplaneta americana

Female sex pheromones ofPeriplaneta americana, P. australasiae, andBlatta orientalis elicit locomotion and upwind orientation in conspecific males. Interspecific attraction between these species was observed in a wind tunnel assay for most species combinations, with the exception ofP. australasiae males not being attracted toP americana females. The role of twoP. americana sex pheromone components, periplanone-A (PA) and periplanone-B (PB) in male attraction was analyzed. PA induced locomotion in males of all three species, with highest threshold concentration inP. americana. PB was effective inP. americana andB. orientalis, but not inP. australasiae. Experiments with mixtures of both components confirmed an inhibitory influence of PB onP. australasiae males when it was added to PA in a ratio of 31 or higher. SinceP. americana andP. australasiae have been found to be syntopous, and their daily mating periods overlap, the female sex pheromone ofP. americana is discussed as an isolating factor between both species.     

Effects of Age and Mating on Female Sex Attractant Pheromone Levels in the Sorghum Plant Bug, <Emphasis Type="Italic">Stenotus rubrovittatus</Emphasis> (Matsumura)

Previous work has shown that male sorghum plant bugs, Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae), are more attracted to young virgin females than to old virgin females and are not attracted to mated females. Therefore, we examined the effects of age and mating status on female sex pheromone levels. The pheromone components, hexyl butyrate, (E)-hex-2-en-1-yl butyrate, and (E)-4-oxohex-2-enal, were collected from females in two different ways. First, the compounds were extracted from whole bodies of each female and quantified by gas chromatography-mass spectrometry (GC-MS). Pheromone levels extracted from virgin female bodies decreased with age. In females that had just mated, pheromone levels did not differ from those of virgin females, and pheromone levels in mated females remained relatively constant up to 15 d after mating. This absence of change in pheromone levels extracted from whole bodies of mated females is not congruent with previous reports of lack of male attraction to these females. In a second method for pheromone recovery (adsorption on a PDMS-coated stir bar), GC-MS analysis showed that mated females released lower amounts of pheromone components compared to those emitted by virgin females of the same age (4 d). As was the case with whole body extracts, young virgin females (3 d) released higher amounts of pheromone components than did old virgin females (8 d). The results suggest that male response in S. rubrovittatus is dictated more by the quantities of pheromone components released into the volatile headspace by females than by the quantities present in the body.     

Field responses of redheaded pine sawfly males to a synthetic pheromone and virgin females in Florida

Field tests using the sawfly pheromone [3,7-dimethylpentadecan-2-ol acetate with (–)-erythro configuration (2S,3S)] were conducted near Gainesville, Florida, during 1978–1981 to determine the attraction ofNeodiprion lecontei males to baited traps with respect to time of year and time of day. Greatest numbers of males were caught during May, July, and September in traps placed within a pine stand from July 1978 to July 1979. Males were only caught between 1400 and 2000 hr on 10 dates in June and 10 dates in September–October 1980, and 10 dates in June 1981, with greatest catches from 1600–1800 hr. Catches in a synthetic-baited trap and in virgin female-baited traps were similar with respect to time of day.University of Florida Agriculture Experiment Stations Journal Series 2920.Hymenoptera: Diprionidae.     

Sexual Behavior and Diel Activity of Citrus Fruit Borer Ecdytolopha aurantiana

Males and virgin females of the citrus fruit borer Ecdytolopha aurantiana Lima, displayed two flight peaks during a 24-hr period, one at dawn and the other at dusk in an orange grove near Gavião Peixoto, São Paulo, Brazil. During the day, when temperatures were highest and relative humidity lowest, most individuals rested on leaves in the lower and middle crown. Moths rapidly moved higher in the crown after sunset, and many were observed flying above the tree canopy. This behavior was mainly associated with mating. Males and virgin females marked with fluorescent powder of different colors were observed in the dark with the aid of a black light. Mating was observed only in the upper crown of citrus trees from 6:00 to 9:00 PM, with a peak (64%) between 7:00 and 8:00 PM. Males of E. aurantiana were captured in traps baited either with virgin females or female extracts, suggesting the use of a long-range sex pheromone. At close distance (1–2 cm), males and females displayed a short-range communication behavior, with males exposing hairpencils and vibrating their wings. Females were frequently stimulated to contact the body of a male before copulation. The mean duration of copulation was 1 hr 40 min.     

Female-produced sexual pheromone ofSceliodes cordalis (Lepidoptera: Pyralidae)

(E)-11-Hexadecen-1-yl acetate and (E)-11-hexadecen-1-ol were identified in extracts from the abdominal pheromone gland of femaleSceliodes cordalis and in a 1∶1 ratio acted as a potent field attractant for males. Sustained upwind flight by males to this mixture in a wind tunnel confirmed the identity of these compounds as major components of the natural sex pheromone of this species. The synthetic pheromone was used to define the annual limits of male flight activity. In the presence of 1–10 μg of pheromone per liter of air, the mating rate of laboratory populations was halved. TheZ isomers of both pheromone components decreased the numbers of males captured in traps baited with virgin females in the field and inhibited upwind flight in the wind tunnel. The attraction of males ofMnesictena flavidalis to virgin females ofS. cordalis and synthetic mixtures was demonstrated to be due to the acetate component alone. MaleEudonia sp. nrlinealis were captured by (Z)-11-hexadecen-1-yl acetate.     

cis-Vaccenyl acetate as an aggregation pheromone inDrosophila melanogaster

Pentane extracts of matureDrosophila melanogaster males substantially increased the attractiveness of food odors to both males and females in a wind-tunnel olfactometer. Extracts of females caused no such increase. An active component of the extract was isolated and identified as (Z)-11-octadecenyl acetate (cis-vaccenyl acetate, cVA), and synthetic cVA was active in bioassay. Hydrolysis of the ester linkage or movement of the double bond to the 9 position destroyed the activity. Mature virgin males released cVA into their feeding vials, and amounts of synthetic CVA equal to that released per male caused significant bioassay responses. Females, which were known to receive cVA from males during copulation, were found to emit relatively large amounts of the ester into their feeding vials within 6 hr after mating. cVA had been demonstrated previously to be a close-range pheromone inD. melanogaster, discouraging males from courting other males or recently mated females; it now appears to have a longer-range function as well.     

Field evaluation ofAnomala schonfeldti ohaus (Coleoptera: Scarabaeidae) synthetic sex pheromone

Synthetic 2-(E)-nonenol, previously identified as the sex pheromone ofAnomala schonfeldti (Coleoptera: Scarabaeidae), is demonstrated to be very attractive to males in the field. Nevertheless, no significant differences were found between treatments with 1, 5, 10, and 20 mg dosages. Males ofA. schonfeldti were more significantly attracted to traps at 30 cm high than at 90 cm. Although the observed behavior seemed to indicate a trend of more attraction to buried traps than those placed at 30 cm, there was no statistical difference between the two treatments. Pheromone-baited traps caught significantly more beetles than traps containing three virgin females. Over 70% of released beetles were recaptured in six traps surrounding the point of release and separated from each other by 50 m, suggesting a possible use of the pheromone (in combination with floral compounds) in mass trapping.     

Attraction of Female and Male Bactrocera papayae to Conspecific Males Fed with Methyl Eugenol and Attraction of Females to Male Sex Pheromone Components

The attraction of female and male Bactrocera papayae to conspecific males fed with methyl eugenol (ME) and female attraction to male synthetic sex pheromone, trans-coniferyl alcohol (CF), were evaluated in a wind tunnel. Earlier and greater attraction were exhibited by both females and males to ME-fed than to non-ME-fed males as dusk approaches. Males increased their precopulatory behavior (i.e., wing fanning and mounting) during the period of higher attractancy. These data confirm that the consumption of ME enhances the mating competitiveness of males and suggest that ME also functions as a precursor to the male sex and aggregation pheromones. Three phenylpropanoid compounds biosynthesized from ME, coniferyl alcohol, 2-allyl-4,5-dimethoxyphenol, and 3,4-dimethoxycinnamyl alcohol, were detected in male rectal gland along with an endogenous rectal compound, N-(3-methylbutyl) acetamide. When offered singly to the females, coniferyl alcohol was found to be most attractive.     

Effect of Female Age on Daily Cycle of Sexual Pheromone Emission in Gregarious Egg Parasitoid Anaphes listronoti

The temporal pattern of pheromone emission by Anaphes listronoti females was established in a four-arm olfactometer by observing, at 2-hr intervals, the response of <2-hr-old males to odor produced by individual virgin females of <1, 1, and 2 days of age. This is the first evidence of a sexual pheromone in a Mymaridae. Under a 16L:8D photoperiod and 24°C constant temperature, the responsiveness of males to females of different ages varied significantly during the photophase. When <1-day-old females were used, males made significantly more final choices in the pheromone field than odorless fields at 4 and 6 hr after the onset of the photophase, and their walking speed was significantly higher from 4 to 12 hr, suggesting that females began to release a long-range pheromone during this period. Final choices and high walking speed were observed earlier with 1- and 2-day-old females than with <1-day-old females, and there was a significant decrease in male responses at 6 hr after the onset of the photophase, suggesting a bimodal temporal pattern of sexual pheromone emission.     

(Z)-11-octadecenyl acetate,an aggregation pheromone inDrosophila simulans

Existence of a male-produced pheromone, which attracts both males and females in a wind-tunnel olfactometer, has been demonstrated inDrosophila simulans (Sturtevant). A pheromone component was identified as (Z)-11-octadecenyl acetate (Z11-18: Ac), also known ascis-vaccenyl acetate. The pheromone is synergized by food volatiles. In bioassay ca. 1/1000 of a mature male equivalent of Z11-18: Ac is attractive and activity increases with increased amounts of Z11-18: Ac. Flies do not begin responding to Z11-18: Ac until after they have been away from food for at least 2 hr. Z11-18: Ac is transferred from the male to the female during mating, and the female emits the majority of the transferred Z11-18: Ac within 6 hr after mating.     

Sex pheromone specificity inHeliothis

Electric grid traps baited withHeliothis subflexa (Guenée),H. virescens (F.), orH. zea (Boddie) females captured conspecific males with few exceptions.Heliothis subflexa females reduced the attraction ofH. virescens andH. zea males when used as bait simultaneously with females of either of these two species. Backcrosses were made withH. virescens males and female hybrids from a cross betweenH. subflexa females andH. virescens males. The backcross (BC) females andH. virescens females attracted approximately equal numbers ofH. virescens males in field traps. BC males released in field cages were attracted toH. virescens females and to the synthetic pheromone ofH. virescens. When laboratory-reared maleH. virescens, BC males,H. subflexa males, and F₁ hybrid males were exposed to the synthetic pheromone ofH. virescens in Plexiglas wind tunnels,H. virescens males and BC males responded to the pheromone, butH. subflexa and F₁ hybrid males did not. The peak activity of bothH. subflexa andH. zea males occurred approx. 4 hr after sunset. MaleH. zea were active throughout most of the night; maleH. virescens were most active approx. 6 hr after sunset.This paper reports the results of research only. Mention of a pesticide or of a commercial or proprietary product in this paper does not constitute a recommendation for use by the U.S. Department of Agriculture nor does it imply registration under FIFRA as amended.Lepidoptera: Noctuidae.     

Airborne Chemical Communication in the Wolf Spider Pardosa milvina

Most studies involving chemical communication in spiders focus on contact pheromones attached to spider silk. Here we tested if males of the wolf spider Pardosa milvina use airborne pheromones to identify, locate, and follow females. Using a two-choice olfactometer, we tested the response of adult male P. milvina to a number of potential chemical cues while controlling for concomitant visual and vibratory stimuli. An airborne chemical cue from adult virgin female P. milvina elicited a positive taxis response from the male. We also tested adult male responses to penultimate instar female P. milvina, one adult male P. milvina, and two adult males together. In each case, test males showed no attraction to the stimuli. Additional experiments were run with pitfall traps baited with adult virgin female P. milvina as attractants. Again, we controlled for visual and vibratory cues from females. Pitfall traps containing virgin females captured significantly more males than control traps. Collectively, these experiments demonstrate evidence of an airborne sex pheromone in P. milvina.     

Does pheromone-based aggregation of codling moth larvae help procure future mates?

In field and laboratory bioassay experiments, we show that larvae of the codling moth, Cydia pomonella, cocoon in aggregations. This aggregation behavior of fifth-instar larvae prior to pupation and arrestment of eclosed adult males by mature female pupae seems to allow mating as soon as an adult female ecloses. This synchronous timing is realized because foraging fifth-instar are attracted by cocoon-spinning larvae and prepupae, but not by pupae, and because male pupae develop faster than female pupae. Eclosed males are arrested by sex pheromone that disseminates from female pupae even before adult females eclose. Communication in C. pomonella within and among developmental stages (larva–larva and pupa–adult, respectively) may be a strategy to procure mates. If so, our data add to current knowledge that attraction of mates in insects relies on communication among adults, or pupae and adults.     

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.     

Cuticular hydrocarbons regulate mate recognition,male aggression,and female choice of the rove beetle,Aleochara curtula

Immature, starved, or multiply mated males of the staphylinid beetle,Aleochara curtula, mimic their females chemically. The titer of the female sex pheromone components (Z)-7-heneicosene and (Z)-7-tricosene was quantified for various physiological types and both sexes by gas chromatography and correlated with the sexual response of males towards the cuticular hydrocarbon fractions. Modulation of intermale aggression by production of the female pheromone was shown by (1) reduction of the alkene titer of females kept at elevated temperatures, (2) treating live males with the synthetic female pheromone mixture, and (3) gradual amputation of male antennal segments.A. curtula males do not fight against members of otherAleochara species with a different hydrocarbon pattern. Contamination ofA. peschkei males with the hydrocarbon fraction ofA. curtula males, however, provoked the release of aggression. Choosy females reject mating attempts of males bearing the female sex pheromone.     

Sex pheromone communication in the nematode,Rhabditis pellio

Both males and females ofRhabditis pellio release pheromones that attract the opposite sex prior to copulation. A quantitative bioassay for the female-produced pheromone was designed, based on male movement toward a pheromone source placed at one end of a 10-mm strip of bacterial material maintained on nutrient agar in a petri plate. Females produced pheromone from the age at which they attained the adult stage (3 days following hatching from the egg) and maintained a relatively constant production level until at least the ninth day of life. Similarly, males became responsive to the female pheromone by the third day and remained responsive through the ninth day, although the time required for the males to migrate toward a female pheromone source increased with increasing age. No daily rhythm of pheromone responsiveness by males or pheromone production by females was observed when the nematodes were conditioned to a 1212 h light-dark cycle.