Behavior and pheromone studies withAttagenus elongatulus Casey (Coleoptera: Dermestidae)

Males ofAttagenus elongatulus Casey responded to a source of female odor with a characteristic sequence of actions which included: extension of the antennae, elevation of the body by leg extension, rapid zig-zag running, and intermittent bobbing up and down. The courtship sequence also consisted of several activities and was usually followed by a typical copulatory act of less than 1-minute duration. Virgin females exhibited calling behavior which was associated with pheromone release. Female calling activity, female pheromone content, and male responsiveness followed a diurnal cycle with peak values occurring during the earlier hours of the 16L8D photoperiod. Quantitative bioassay indicated that a 50% male response level (RD₅₀) occurred at ca. 0.014 female equivalent (FE) exposure.     

A new component of the female sex pheromone ofBlattella germanica (L.) (Dictyoptera: Blattellidae) and interaction with other pheromone components

A fourth component, 3,11-dimethyi-2-heptacosanone, was identified as a cuticular contact sex pheromone of the female German cockroach,Blattella germanica. In behavioral assays, higher dosages of 3,11-dimethyl-2-heptacosanone were needed to elicit similar sexual responses in males to those elicited by the major pheromone component, 3,11-dimethyl-2-nonacosanone. A 1585 blend of the C₂₇ and C₂₉ methyl ketone homologs resulted in a dose-response curve intermediate between that of each of the components alone, indicating independence of activity of each component and lack of synergism. Moreover, the activity of 3,11-dimethyl-2-nonacosanone was not enhanced by female cuticular hydrocarbons. The relationship between sexual responses of males to females and to isolated female antennae, and the amount of cuticular pheromone on whole females was investigated. Cuticular sex pheromone found on females increased with the age of the female, as did the male response to whole females. However, a bimodal male response was elicited by isolated female antennae. Differences between behavioral and analytical assays of pheromone are discussed.     

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.     

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.     

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.     

Role of sex pheromone components in behavioral reproductive isolation betweenAutographa gamma (L.) and eitherTrichoplusia ni (Hübner) ORChrysodeixis chalcites (Esp.) (Lepidoptera: Noctuidae: Plusiinae)

The composition of theAutographa gamma sex pheromone was reexamined and only (Z)-7-dodecenyl acetate and (Z)-7-dodecenol were identified by capillary GC, GC-MS, and dimethyl disulfide derivatization and subsequent GC-MS analysis. The fatty acid content of the pheromone glands was also studied, and a series of saturated and unsaturated acids was identified. However, most of the related pheromonal compounds were not detected. The male response to the pheromone components was studied in a flight tunnel and compared with the response to calling females. The best synthetic baits evoked a response similar to that observed to the virgin females, but males spent significantly more time at calling females than at the synthetic baits. The preferred synthetic baits consisted of (Z)-7-dodecenyl acetate alone or of a blend with 5% (Z)-7-dodecenol. Increasing the relative amount of the alcohol caused a gradual reduction in male response, particularly in the last steps of the courtship sequence. The addition of the minor sex pheromone components of the sympatric Plusiinae species,Trichoplusia ni andChrysodeixis chalcites, to theA. gamma pheromone was also investigated in the flight tunnel. Some of these components exhibited a significantly antagonistic effect on theA. gamma male courtship behavior. The most potent antagonists were (Z)-5-dodecenyl acetate and (Z)-9-tetradecenyl acetate. The response ofA. gamma andT. ni males to conspecific and heterospecific females was also compared in the flight tunnel. WhereasA. gamma males were attracted only to their conspecific females, a small percentage ofT. ni males were also attracted toA. gamma females and 11% performed the whole courtship sequence.Contribution from the Agricultural Research Organization (ARO), No. 3459-E, 1992 series.     

Mating stimulant pheromone and cuticular lipid constituents ofFannia femoralis (Stein) (Diptera: Muscidae)

The cuticular lipids of male and femaleFannia femoralis were similar for recently emerged insects but soon began to develop chromatographic patterns characteristic of each sex. Mature females contained more C₃₁ and C₃₃ monoolefin in the cuticular lipid than males. Also, the double bonds in the monoolefins of the female lipid were situated predominantly at the eleventh and thirteenth carbons, while most of those from the males were centrally located in the molecule or at the ninth carbon.The female C₃₁ monoolefin stimulated copulation by the males, but more mating activity occurred when the saturated hydrocarbons present in the female cuticular lipids were added. The synthetic monoolefin most active as a mating stimulant pheromone was (Z)-11-hentriacontene, but the addition of female alkanes or of syntheticn-alkanes to (Z)-11-hentriacontene increased the activity of the synthetic pheromone.A portion of a dissertation intended for submission by the first author to the Graduate School of the University of Maryland in partial fulfillment of the requirements for the Ph.D. degree.Mention of a proprietary or commercial product in this paper does not constitute an endorsement of this product by the U.S. Department of Agriculture or the University of Maryland.     

Intrapopulational changes in sex pheromone composition during scotophase in oriental tobacco budworm,Helicoverpa assulta (Guenée) (Lepidoptera: Noctuidae)

Solvent extracts of individual pheromone glands were prepared from femaleHelicoverpa assulta (Guenée) at 2-hr intervals throughout the scotophase. The amounts of female sex pheromone components, (Z)-9-hexadecenal, (Z)-11-hexadecenal, (Z)-9-hexadecenyl acetate, and (Z)-11-hexadecenyl acetate, in the extracts were determined by gas chromatographic analysis. Although females called from early scotophase (2 hr) until late scotophase (6 hr) the quantity of extracted pheromone remained high at 8 hr, the end of the scotophase. More than 70% of the pheromone gland extracts contained sex pheromone components regardless of whether the donor females had been called or resting. Pheromone components were absent from gland extracts prepared at the onset of the scotophase. The quantity of (Z)-9-hexadecenal and (Z)-11-hexadecenal increased rapidly to reach a maximum of approximately 260 and 30 ng/female, respectively, that was maintained for up to 8 hr, the duration of the scotophase. The quantity of (Z)-9-hexadecenyl acetate and (Z)-11-hexadecenyl acetate increased continuously during the scotophase to peak at 600 and 30 ng/female, respectively, 8 hr into the scotophase. At the end of scotophase the quantity of all pheromone components decreased significantly.     

Laboratory and field evidence for maleproduced aggregation pheromone inRhynchophorus cruentatus (F.) (Coleoptera: Curculionidae)

Laboratory and field assays were conducted to determine if palmetto weevil,Rhynchophorus cruentatus (F.), adults produce an aggregation pheromone. Attraction of females in a Y-tube olfactometer to conspecific males was greater than to clean air. Male and female attraction to conspecific male volatiles combined with host-palm,Sabal palmetto (Walter), volatiles was greater than to host-palm volatiles alone. Similarly, more weevils were caught in the field in traps baited with conspecific males plus host-palm tissue than in similar traps baited with only males, or palm tissue, or females, or females plus palm tissue. These results suggest thatR. cruentatus males produce an aggregation pheromone(s) that is highly attractive to conspecific adults of both sexes when combined with host-palm volatiles. This study is an important step towards understanding the chemical ecology ofR. cruentatus.     

Sexual communication and associative learning in the parasitic waspItoplectis conquisitor (Say)

Extracts of newly emerged virgin females and newly emerged virgin males of the parasitic waspItoplectis conquisitor were highly active in eliciting sexual behavior in older males. Newly emerged males did not respond to the extracts. A reliable biological assay was devised in which the responses of males to extract could be evaluated under varying conditions. Optimum male responses to female extract were obtained at 27 °C and at 1.0 female equivalents (the amount of pheromone extractable from the body surface of a female). A decrease in sexual response was observed when males were repeatedly exposed to pheromone. Males also learned to associate bioassay conditions with the presence of pheromone.     

Pheromone attraction in the soybean cyst nematodeHeterodera glycines race 3

MaleHeterodera glycines responded to female nematodes during in vitro bioassay. The male's response was dosage-dependent and significant with a pheromone source of more than five females. Male responsiveness was influenced by the pheromone diffusion and response times. Males were most responsive at three days after emergence from the host plant, while females were also most attractive at the same age. Light intensities that ranged from dark to bright had no effect on female location by the male, although bioassay in a nitrogen atmosphere eliminated sexual communication. Mate location was not significant below 25 °C and declined slightly at 30 or 33 °C. Bioassay at pHs from 5 to 8.5 showed a bimodal effect, with maximal attraction around pH 6.     

(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.     

Sexual behavior ofMatsucoccus josephi (Homoptera: Margarodidae)

The daily emergence patterns ofMatsucoccus josephi adults and third-instar male larvae raised on artificially infested saplings ofPinus halepensis were determined. A single peak of emergence was found for adult males between 0300 and 0500 hr. Adult females emerged throughout the day, with maximum emergence between 0500 and 0700 hr. Two daily emergence periods were observed in third-instar male larvae, one between 0300 and 0900 hr and the other between 1700 and 2100 hr. Airborne pheromone emitted by adult virgin females was collected using a flow system. No significant differences were recorded in the attraction of the male to crude pheromone collected at different times of day. A single female, virgin or half an hour after mating, was sufficient to attract the males in an olfactometer system. From minor differences in pheromone release throughout the day, and from the lesser degree of attraction by females half an hour after mating, it is assumed that there is no mechanism controlling the daily release of the female sex pheromone. Reduction of pheromone emission after mating is suggested.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 2743-E, 1989 series.     

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.     

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.     

Sex pheromone components of three species ofSemiothisa (Geometridae), (Z,Z,Z)-3,6,9-heptadecatriene and two monoepoxydiene analogs

Adult males ofSemiothisa signaria dispuncta (Walker) were attracted to field traps baited with (Z,Z,Z)-3,6,9-octadecatriene and (Z,Z)-6,9-cis-3,4-epoxy-octadecadiene. However, analyses of sex pheromone gland extracts of females of this species by GC-MS and by GC in combination with an electroantennograph detector (GC-EAD) showed the pheromone to be comprised of a mixture of the next lower homologs: (Z,Z,Z)-3,6,9-heptadecatriene and (Z,Z)-6,9-cis-3,4-epoxy-heptadecadiene. Blends of these two C₁₇ compounds were subsequently found to be more attractive to males in the field than the corresponding C₁₈ mixtures. Sex pheromones of two otherSemiothisa species were also found to contain C₁₇ components. (Z,Z,Z)-3,6,9-Heptadecatriene, detected by GC-EAD analysis of a female abdominal tip extract ofS. bicolorata (Fabricius), attracted conspecific males, and this attraction was significantly reduced by additions of (Z,Z)-6,9-cis-3,4-epoxyheptadecadiene, the major pheromone component ofS. signaria dispuncta, to the lure. (Z,Z)-3,9-cis-6,7-Epoxy-heptadecadiene was detected by GC-EAD analysis as the primary male antennal stimulatory component present in abdominal tip extracts ofS. ulsterata (Pearsall), and males of this species were attracted to traps baited with this epoxide. Each of these three C₁₇ compounds constitute previously unknown lepidopteran sex pheromone components. Blends of (Z,Z, Z)-3,6,9-heptadecatriene and (Z,Z)-3,9-cis-6,7-epoxyheptadecadiene attracted males of a fourth species,S. delectata Hulst, but no females of this species were obtained to permit analysis of its sex pheromone. The occurrence of (Z,Z,Z)-3,6,9-heptadecatriene inS. neptaria (Guenee) females was indicated by GC-MS analysis of an abdominal tip extract; however, no males were attracted to any of the fielded mixtures containing this hydrocarbon.     

Factors Accounting for the Variability in the Behavioral Response of the Onion Fly (Delia antiqua) to n-Dipropyl Disulfide

The onion fly Delia antiqua is a specialist herbivore attacking only onions and closely related Allium species. n-Dipropyl disulfide (Pr₂S₂) has long been known to be attractive to onion flies in the laboratory and in the field. However, the insect's response is highly variable. Using behavioral bioassays we found that Pr₂S₂ was highly attractive to gravid, mated female onion flies, but did not stimulate oviposition. The response of female onion flies was concentration dependent. The physiological state of the flies (i.e., age, mating status, egg load/oviposition experience) also affected their responsiveness. The response of both sexes of onion flies varied with age, but females were always more strongly attracted than males. Responsiveness of females increased during the first 10 days after emergence. It stayed at a high level until 21 days after which the experiment was terminated. The responsiveness of males reached a maximum at 6–7 days after which it declined. Mated, gravid females responded more strongly to Pr₂S₂ than unmated, gravid females. Females deprived of the opportunity to oviposit were more attracted compared to females that had oviposited on cut onions prior to the experiment. Electroantennograms (EAG) of females revealed a higher response to stimulation compared to males. The EAG-response of females was not affected by mating status.     

Influence of diel rhythm and brain hormone on pheromone production in two lepidopteran species

Heliothis armigera andSpodoptera littoralis females produced sex pheromone during their scotophase. Maximum levels of pheromone in Heliothisarmigera were extracted from 2- to 3-day-old females during their 4.5-hr scotophase. On ligation between the head and the thorax of both species, normal pheromone production was inhibited. Homogenates of brains (consisting of brains, subesophageal ganglia, corpora cardiaca, and corpora allata) from both species induced a normal level of pheromone production by ligated females. Moreover, inS. littoralis, female brain hormone induced the production of the two components (Z)-9- and (Z, E)-9,11-tetradecenyl acetate tested by gas chromatography. Partial separation of brain homogenates, using low pressure C18-silica reversed-phase columns, produced a stable and active hormone source that gave a dose-dependent response. This hormone was found in brain extracts of both male and femaleH. armigera andS. littoralis females. In addition,S. littoralis induced pheromone production byH. armigera ligated females.     

Flight-mediated attraction ofBiprorulus bibax breddin (Hemiptera: Pentatomidae) to natural and synthetic aggregation pheromone

The attraction of female spined citrus bugs,Biprorulus bibax, to natural and synthetic aggregation pheromone was studied using an olfactometer and a large flight cage. No locomotory response by postdiapause, prereproductive females to heptane extracts of male dorsal abdominal glands (DAGs) (site of pheromone production) was recorded in the olfactometer study. However, postdiapause, prereproductive females showed significant attraction to sites baited with DAG extracts in the flight cage (1.9–3.0 times that of unbaited sites). Prereproductive and reproductive females showed greatest attraction to sites baited with a synthetic blend of pheromone [(3R,4S,1E-3,4-bis(1-butenyl)tetrahydro-2-furanol, linalool, farnesol, nerolidol] (2.3–4.7 times the attraction of unbaited sites). Females also responded significantly to sites baited with the hemiacetal major component alone (1.7–2.2×). Diapausing females collected from fall populations did not respond to natural or synthetic pheromone baits. Potential applications of the synthetic aggregation pheromone are discussed with respect toB. bibax management.     

Close-range attraction in Lygocoris pabulinus (L.)

Males of the green capsid bug, Lygocoris pabulinus, exhibit a specific courtship behavior, i.e., a vibration of the abdomen. When both live and dead females were offered to males, this vibration behavior was elicited in most of the males tested. When females were dissected into separate body parts, heads, wings, and legs elicited equal responses, while thorax plus abdomen elicited a much lower response. When separate body parts were extracted, the leg extracts elicited significantly stronger responses than any other extract. This suggests that female L. pabulinuslegs are either the source of a close-range sex pheromone or that pheromone is accumulated on the legs due to grooming behavior. The leg extracts contained several hydrocarbons such as n-alkenes, n-alkanes, and some methylalkanes. Female extracts contained more (Z)-9-pentacosene and male extracts contained more (Z)-9-heptacosene. Substrates on which females had walked elicited similar responses as female legs, indicating that the pheromone is deposited on the substrate. This enlarges the functional range of low-volatility compounds, which are thought to function only when sexes are in close vicinity or in contact.