Comparison of known and suspected pheromonal constituents in males of the African ticks,Amblyomma hebraeum Koch andAmblyomma variegatum (Fabricius)

Three low molecular weight compounds were found in hexane: diethyl ether extracts of fed males of the African ticks,Amblyomma variegatum (tropical bont tick) andA. hebraeum (bont tick), namely,o-nitrophenol, methyl salicylate and 2,6-dichlorophenol. These same compounds were also found in a rinse of fedA. variegatum males, but were absent or present in only trace amounts in a rinse of fedA. hebraeum males.o-Nitrophenol and methyl salicylate were present in much higher concentrations (i.e., amounts/tick) inA. variegatum than inA. hebraeum. 2,6-Dichlorophenol was also more abundant inA. variegatum than inA. hebraeum, but the differences were not as great as with the former two compounds. Extraction in hexane over a 3-week period revealed four additional compounds, benzaldehyde, benzyl alcohol, benzothiazole and nonanoic acid. The first three compounds were found in males of both species; nonanoic acid was found only inA. hebraeum males. Published reports consistently show strong attraction byo-nitrophenol and methyl salicylate for both sexes of the two bont tick species; 2,6-dichlorophenol and benzaldehyde have been reported to be attractive to both sexes ofA. hebraeum. The possible roles of these compounds, as well as others occasionally reported fromA. hebraeum andA. variegatum, as components of the aggregation/attachment pheromone or other pheromones is discussed.Supported by Cooperative Agreement No. AFR-0435A-00-9084-00 with the U.S. Agency for International Development to the Department of Infectious Diseases, College of Veterinary Medicine, University of Florida, Gainesville, FL.     

Efficacy of pheromone-acaricide-impregnated tail-tag decoys for controlling the bont tick,Amblyomma hebraeum (Acari: Ixodidae), on cattle in Zimbabwe

A large-scale field test using pheromone-acaricide-impregnated plastic tail-tag decoys demonstrated excellent efficacy of these devices for control of the bont tick,Amblyomma hebraeum, on cattle in Zimbabwe. The tail tags were impregnated with a mixture containingo-nitrophenol, methyl salicylate, 2,6-dichlorophenol and phenylacetaldehyde and one of three different acaricides (cyfluthrin, flumethrin or alphacypermethrin).o-Nitrophenol and methyl salicylate are components of theA. hebraeum attraction-aggregation-attachment pheromone, while 2,6-dichlorophenol and phenylacetaldehyde are proven attractants for this tick. Botho-nitrophenol and methyl salicylate were lost gradually from the tags over 12 and 14 week periods, respectively. In field trials, tick counts were compared between cattle that received tail tags either impregnated with pheromone mixture alone, cyfluthrin and pheromone mixture, flumethrin and pheromone mixture, alphacypermethrin and pheromone mixture or were left untreated. During the first 3 month trial period, control of adult bont ticks was 94.9% with cyfluthrin tail tags and 87.5% with flumethrin tail tags. In general, there was no significant difference in bont tick numbers on cattle without tags and those with tail tags containing pheromone only. When the trial was repeated for another 3 month period, control of bont ticks with tail tags containing cyfluthrin and flumethrin was 99.3 and 95.1%, respectively. However, control of bont ticks using alphacypermethrin was only 79.2%. Overall, retention of tail tags was excellent although some loss was encountered during the rainy season. In addition to controlling bont ticks, the tail tags provided moderate control of other tick species (Rhipicephalus evertsi evertsi, Rhipicephalus zambeziensis andHyalomma spp.) simultaneously infesting cattle in the trials.Deceased.     

Responses of the tropical bont tick, Amblyomma variegatum (Fabricius), to its aggregation-attachment pheromone presented in an air stream on a servosphere

Male Amblyomma variegatum ticks feeding on a host release a mixture of o -nitrophenol and methyl salicylate which serves to attract conspecifics. The behavioural responses of A. variegatum on a servosphere to these volatiles presented in an air stream are detailed here. In still air, ticks walked on all eight legs, but with long halts. In contrast, the air stream caused continuous walking and induced a reaching response where the forelegs actively sampled the air. Such reaching increased the angular velocity and reduced walking speed, effects that were amplified in the presence of vapours from o -nitrophenol and methyl salicylate in the air flowing over the ticks. Vapour from a 1:1 mixture of o -nitrophenol and methyl salicylate was attractive over a 10⁴-fold concentration range providing an increase in upwind displacement of 20–40%, significantly higher than the natural ratio where o -nitrophenol vapour predominates. Although the responses to o -nitrophenol vapour were variable when presented alone, this chemical was consistently attractive when delivered with steer hair odour – unattractive on its own. Moreover, the upwind walk to this combination did not cause a change in speed or angular velocity. This supports the hypothesis that the response to the pheromone is enhanced by host odour. Accepted: 16 October 1999     

Field tests of the response of femaleAmblyomma variegatum (Acari:Ixodidae) to the synthetic aggregation-attachment pheromone and its components

Fifty percent of anAmblyomma variegatum female population were able to find upwind-positioned targets containing the synthetic aggregation-attachment pheromone of this species or the pheromone componento-nitrophenol alone. The ticks were not attracted to the other components of the pheromone: methyl-salicylate and pelargonic acid. The mean time required for the ticks to reach a target at 1 m from the starting point was 3 min and 20 s.     

Responses of the ticksAmblyomma hebraeum andA. variegatum to known or potential components of the aggregation-attachment pheromone. IV. Attachment stimulation of nymphs

Ten known or potential components of the aggregation-attachment pheromone (AAP) of the ticksAmblyomma hebraeum andA. variegatum, as well as a mixture of these components and extracts of prefed males of the two species, were tested as attachment stimulants for nymphs. Unfed nymphs were confined in linen bags on the ears of rabbits that had been treated with the test compounds, mixture or extracts; the numbers attached were recorded after 24 h. InA. hebraeum, attachment was induced by four compounds (2-methyl propanoic acid, methyl salicylate,o-nitrophenol and salicylaldehyde), the mixture and extracts from both species. InA. variegatum, attachment was induced by three compounds (methyl salicylate,o-nitrophenol and salicylaldehyde), the mixture and extracts from both species. Methyl salicylate ando-nitrophenol are primary components of the AAP of bothA. hebraeum andA. variegatum. 2-methyl propanoic acid is a species-specific attachment stimulant forA. hebraeum. Salicylaldehyde, a phenolic compound, is not a naturally occurring AAP component. Nymphs of both species respond to fewer attachment stimulants than the adults and, as shown by their respective host ranges, are less dependent on the AAP in the regulation of attachment than the adults.     

Responses of the ticksAmblyomma hebraeum andA. variegatum to known or potential components of the aggregation-attachment pheromone. III. Aggregation

Ten known or potential components of the aggregation-attachment pheromone (AAP) of the ticksAmblyomma hebraeum andA. variegatum, as well as mixtures of these components, extracts of prefed males and live prefed males, were tested as aggregation stimulants. In field assays, laboratory-reared unfed male and female ticks were released 20 cm downwind of CO₂/pheromone release sites; the numbers of ticks that aggregated at the release sites were recorded after 30 min. InA. variegatum, aggregation was induced by methyl salicylate,o-nitrophenol, 2,6-dichlorophenol, phenylacetaldehyde and some mixtures containing these compounds; a strong aggregation response was induced by an extract of five prefed malesA. variegatum and a weak response was induced by an extract of 50 prefed males ofA. hebraeum. InA. hebraeum, aggregation was induced by phenylacetaldehyde, mixtures of compounds that included phenylacetaldehyde, extracts of 50 prefed males ofA. hebraeum orA. variegatum and 50 live prefed males ofA. hebraeum. InA. variegatum, aggregation was inhibited if compounds that do not occur naturally in the AAP of the species were included in mixtures. InA. hebraeum, phenylacetaldehyde appeared to act as an arrestant for ticks that had been attracted to release sites by other compounds.     

Use of carbon dioxide and natural or synthetic aggregation-attachment pheromone of the bont tick,Amblyomma hebraeum,to attract and trap unfed adults in the field

It was determined previously that unfed adults ofAmblyomma hebraeum become active in response to carbon dioxide but are not attracted by it. We have now shown in field experiments that males and females which are activated by carbon dioxide are attracted to the aggregation-attachment pheromone produced by males after a period of feeding on the host. Unfed adults were attracted too-nitrophenol, a component of the aggregation-attachment pheromone ofAmblyomma variegatum, pre-fed males ofA. hebraeum, and extracts of such males. Live males were more attractive than the extracts which, in turn, were more attractive thano-nitrophenol. The ticks were attracted to sources ofo-nitrophenol from as far away as 11 m in 90 min. Simple traps, baited with carbon dioxide and aggregation-attachment pheromone (from pre-fed males or extracts of pre-fed males), were used to capture unfed adults that had been released in the field. The response of unfed adults to carbon dioxide and the aggregation-attachment pheromone presents an obvious host-location mechanism and a means for the ticks to discriminate between suitable hosts (those with males already attached) and potentially unsuitable hosts (those with no males attached).     

Attraction of Amblyomma variegatum (ticks) to the attraction-aggregation-attachment-pheromone with or without carbon dioxide

The responses of adult Amblyomma variegatum ticks released from various distances to different doses of the synthetic attraction-aggregation-attachment pheromone (AAAP) (made up of ortho-nitrophenol, methyl salicylate and nonanoic acid in paraffin oil), dispensed from the center of circular field plots, were studied in the presence or absence of elevated levels of CO₂. Up to 90% of the ticks released were attracted to the pheromone source in the presence of CO₂ within 3h. CO₂ alone was unattractive, similar to previous findings in Zimbabwe, but unlike results from a Caribbean A. variegatum population, which was significantly attracted to this signal. In the absence of CO₂, smaller but significant proportions of the released ticks were attracted to the pheromone, albeit more slowly, suggesting another variation in the responses of this bont tick to inter- and intra-specific signals. Our results are interpreted in the light of a study undertaken elsewhere demonstrating relatively high heterozygosity among tick populations. Possible directions of further research to explore the use of the pheromone in off-host control of the tick are also highlighted.     

Olfactory attraction to aggregation pheromone is mediated by disti-flagellum of antennal segments in Riptortus pedestris

Riptortus pedestris (Hemiptera: Alydidae) is a serious pest of soybean and sweet persimmon and uses male produced aggregation pheromone, (E)-2-hexenyl (Z)-3-hexenoate, (E)-2-hexenyl (E)-2-hexenoate, and tetradecyl isobutyrate to facilitate food location and recognition by conspecifics. Using electroantennogram (EAG) and greenhouse bioassay, we determined which antennal segment is involved in the detection of their aggregation pheromone. In the first EAG test using individual antennal segments, significant EAG responses to 1:1:1 mixture of the aggregation pheromone were observed only from the disti-flagellum segments of both male and female antennae at both pheromone doses tested (1 µg and 100 µg). In the following EAG tests using gradually removed antennal segment(s), EAG response was still maintained when the distal half of a disti-flagellum was surgically removed, while EAG response was lost when whole segment of disti-flagellum or other whole segments were gradually removed from intact antenna of both sexes. In greenhouse experiment, removing one or both segment(s) of disti-flagellum from male or female antennae resulted in significant reduction in their attraction to the aggregation pheromone. Together, these findings support that the disti-flagellum of R. pedestris houses olfactory neurons associated with attraction to their aggregation pheromone.     

Identification of the Aggregation Pheromone of the Melon Thrips,Thrips palmi

The objective of this study was to identify the aggregation pheromone of the melon thrips Thrips palmi, a major pest of vegetable and ornamental plants around the world. The species causes damage both through feeding activities and as a vector of tospoviruses, and is a threat to world trade and European horticulture. Improved methods of detecting and controlling this species are needed and the identification of an aggregation pheromone will contribute to this requirement. Bioassays with a Y-tube olfactometer showed that virgin female T. palmi were attracted to the odour of live males, but not to that of live females, and that mixed-age adults of both sexes were attracted to the odour of live males, indicating the presence of a male-produced aggregation pheromone. Examination of the headspace volatiles of adult male T. palmi revealed only one compound that was not found in adult females. It was identified by comparison of its mass spectrum and chromatographic details with those of similar compounds. This compound had a structure like that of the previously identified male-produced aggregation pheromone of the western flower thrips Frankliniella occidentalis. The compound was synthesised and tested in eggplant crops infested with T. palmi in Japan. Significantly greater numbers of both males and females were attracted to traps baited with the putative aggregation pheromone compared to unbaited traps. The aggregation pheromone of T. palmi is thus identified as (R)-lavandulyl 3-methyl-3-butenoate by spectroscopic, chromatographic and behavioural analysis.     

Reduction in responsiveness of males of Epiphyas postvittana (Lepidoptera) to sex pheromone following previous brief pheromonal exposure

The responsiveness to sex pheromone of males of Epiphyas postvittana was reduced by previous brief exposure to pheromone. Males were exposed to a standard quantity of pheromone for various durations and at various intervals before the time at which bioassay was performed.The reduction in responsiveness was related both to the duration of the previous exposure and to the time at which the previous exposure was given in relation to the bioassay. It was not related to the occurrence or intensity of any behavioural response elicited at the time of previous exposure to the pheromone.     

The effects of different blend ratios and temperature on the active space of the Oriental fruit moth sex pheromone

Abstract The wing-fanning activation response of male Oriental fruit moths (OFM), Grapholita molesta (Busck), in the field to the three-component pheromone containing the female-produced ratio of components (Z8-12:OAc + 6% E8-12:OAc + 3% Z8-12:OH) was compared with the response to blends containing 2,10 and 20% E with 3% OH, and the 6% E blend containing 30 and 100% OH. Comparisons were made over three temperature ranges: 15–17, 20–21 and 26–28^oC. Both the maximum response distance and male response specificity were significantly altered by changes in odour quality as well as temperature. For blends containing different Z/E ratios the maximum response distance increased significantly with temperature. Response specificity was most pronounced at the 20–21^oC range, with males displaying a lower threshold for the natural 6% E ratio, evidenced by the fact that fewer males responded and at closer distances to the source with off-ratios. At 26–28^oC response specificity for the Z/E ratios was much reduced, primarily due to more males activating to off-ratios. With blends containing different proportions of Z8-12:OH in the 6% E blend, increasing temperature increased the maximum response distance for all treatments, but in addition increasing the proportion of OH alone from 3% to 30% significantly increased the maximum response distance over the three temperature ranges tested. This increase occurred without affecting the proportion of responders or the distribution of response distances around the mean value. However, with 100% OH added to the blend, whereas male response was high at 20–21^oC, the distribution of response distances was significantly more variable than with 3% or 30%, and male response was eliminated or very low at 15–17^oC and 26–28^oC. Our results support previous studies showing that peak response levels in this species are dependent on male perception of the natural blend of components, and that males have a high degree of specificity for the qualitative properties of the pheromone. However, the present results also extend those of previous flight tunnel tests in which response specificity was most pronounced in the upwind flight phase of the sequence, by showing that male OFM also display a     

The seabird tick, <Emphasis Type="Italic">Ixodes</Emphasis><Emphasis Type="Italic">uriae</Emphasis>, uses uric acid in penguin guano as a kairomone and guanine in tick feces as an assembly pheromone on the Antarctic Peninsula

In the vicinity of Palmer Station, Antarctica, the seabird tick, Ixodes uriae, forms large aggregations under rocks at the periphery of Adelie penguin rookeries. When the adult penguins return to the rookeries at the beginning of the nesting season the ticks leave their off-host aggregation site, attach to the penguins for a period of feeding, and then subsequently return to the aggregation site. In this study, we searched for chemical cues that may be used by the ticks to locate their aggregation sites as well as cues involved in finding penguins. Tick excreta and soil extracts from beneath tick aggregations contained a pheromone that elicited assembly behavior in unfed larvae, non-fed nymphs and non-fed adults. Guanine, the major excretory product of ticks, elicited assembly behavior, thus, guanine is likely an active component involved in assembly. Non-fed stages also responded positively to penguin guano and uric acid, the primary excretory product of penguins, suggesting that uric acid and other components of penguin guano function as a kairomone used by the non-fed ticks to locate their host. After feeding, the immature ticks’ response to both the assembly and kairomones is switched off for several days, and the ticks regain responsiveness only after they have molted. Fed adult females lay eggs and die without ever regaining responsiveness. Thus, I. uriae relies on two closely related chemicals to regulate two critical aspects of its life: assembly and host-finding. Guanine and other components of tick excreta function as an assembly pheromone in promoting the formation of off-host aggregations, while uric acid and other components of penguin guano function as a kairomone used by the tick to locate its host.     

Pheromonal effects on sexual maturation,yellowing, and the vibration reaction in immature male desert locusts (Schistocerca gregaria)

Both yellow (crowded) and non-yellow (isolated) mature males of Schistocerca gregaria are equally capable of accelerating the sexual maturation and inducing integumental yellowing in immature adult males. The bioassay of a mature male extract shows conclusively the presence of the maturation-accelerating pheromone in this species. The pheromone does not appear to be effective in inducing yellowing, or in initiating the vibration reaction, in immature males.     

Assortative Mating in Two Pheromone Strains of the Cabbage Looper Moth, Trichoplusia ni

The evolution of animal communication systems is an integral part of speciation. In moths, species specificity of the communication channel is largely a result of unique sex pheromone blends produced by females and corresponding specificity of male behavioral response. Insights into the process of speciation may result from studies of pheromone strains within a species in which reproductive isolation is not complete. Toward this end we investigated assortative mating based on female pheromone phenotypes and male response specificity between mutant and normal colonies of the cabbage looper moth, Trichoplusia ni. There was no evidence of assortative mating in small cages in which the density of moths was high. In larger cages with lower densities of moths, assortative mating was evident. In these larger cages, matings between normal males and normal females and mutant males and mutant females were more frequent than interstrain matings. Wind tunnel tests indicated that normal males responded preferentially to pheromone released by normal females, whereas mutant males did not discriminate between normal and mutant pheromone blends. In large field cages, pheromone traps baited with normal females caught equal numbers of mutant and normal males, while pheromone traps baited with mutant females caught primarily mutant males. The overall pattern of assortative mating could be explained primarily based on the normal males' preference for the pheromone blend released by normal females.     

Location,morphology and histology of sex pheromone glands of the female gypsy moth, Lymantria dispar (L.)

Scanning electron microscopy, histology and a male wing fanning bioassay were used in this study to locate the sex pheromone-producing glands of the female gypsy moth, Lymantria dispar. When exposed to female sex pheromone, adult males exhibit a strong wing fanning behaviour prior to take off. We found that adult males showed positive response to calling females and to tissue extract from both dorsal and ventral portions of the intersegmental membrane between 8th and 9th-abdominal segments. A typical male response usually starts with elevation of antennae, movement of head in different directions, walking, wing fanning and onset of search flight. Histological and scanning electron microscopic studies suggested that the sex pheromone glands are located on the dorsal and ventral aspects of the intersegmental membrane. The glands appear as two highly convoluted integumentary areas with hypertrophied glandular epidermal cells.     

Pheromonal composition of two species of african Amblyomma ticks: similarities,differences and possible species specific components

Two species of bont ticks, Amblyomma hebraeum and Amblyomma variegatum, common to Africa were studied to compare types and quantities of compounds known or believed to serve as components of the attraction-aggregation-attachment pheromone (AAAP). A complex of attraction, aggregation and attachment stimulating pheromone components are used by these to detect hosts, mates and, perhaps, minimize interspecific breeding. Solvent extraction of pheromone emitting ticks followed by gas chromatography and mass spectrometry revealed little qualitative difference in the composition of the AAAP in these two species. However, subtle differences in the relative proportions of the pheromonal blend are noted suggesting that such differences in concentration may facilitate species-specific discrimination during aggregation and attachment. Differences in the relative abundance of benzaldchyde and methyl salicylate in the males of the two species were especially noteworthy. Possible means by which such differences in phenolic compound composition may affect the behavior of these ticks are discussed.     

Inhibition of sexual response in males of the moth Argyrotaenia velutinana by brief exposures to synthetic pheromone or its geometrical isomer

When cis-11-tetradecenyl acetate (RiBLuRe) and its geometrical isomer, trans-11-tetradecenyl acetate were simultaneously presented to male red-banded leaf roller moths their response was significantly lower than that to an equal quantity of RiBLuRe alone. When the males were exposed to RiBLuRe for a duration of 10 min at times up to 60 min before bioassay there was a complete absence of response to RiBLuRe at the time of bioassay. Similar exposure to an equal quantity of the trans-isomer before bioassay resulted in significant reduction of the response to RiBLuRe at the subsequent bioassay but without complete inhibition.     

The inhibition of the uridine diphosphate-transglucuronylase activity of mouse-liver homogenates by thiol reagents

1. A study of the catalysis of the formation of the glucuronides of o-aminophenol and p-nitrophenol by the uridine diphosphate transglucuronylase of homogenates of female mouse liver has been made, with reference to the effect of reagents reacting with thiol groups. 2. The synthesis of both glucuronides was completely inhibited by organic mercurials and N-ethylmaleimide. The inhibition was only partial with arsenite and the arsenoxides, iodoacetamide and o-iodosobenzoate. 3. The o-aminophenol system was much more sensitive than that for p-nitrophenol to all the thiol reagents, except N-ethylmaleimide, which was equally active in both systems. 4. At very low concentrations of the organic mercurials, the o-aminophenol system was activated. 5. With o-aminophenyl glucuronide formation, complete protection was given by glutathione and cysteine against the organic mercurials, N-ethylmaleimide and iodoacetamide, and partial protection against the arsenicals. Reversal was complete against the mercurials, and very limited against the arsenicals and iodoacetamide. The effects of N-ethylmaleimide and o-iodosobenzoate were irreversible. Results with p-nitrophenol were very similar. 6. Uridine diphosphate transglucuronylase was partially protected against p-chloromercuribenzoate and lewisite oxide by uridine diphosphate glucuronate, but not by o-aminophenol. 7. Glutathione did not prevent the decline in the rate of conjugation of o-aminophenol when homogenates were aged by incubation at 30°. Cysteine was unable to prevent or reverse inactivation by ultrasonic radiation.     

Some differences in the conjugation of o-aminophenol and p-nitrophenol by the uridine diphosphate transglucuronylase of mouse-liver homogenates

1. A study of the catalysis of the formation of the glucuronides of o-aminophenol and p-nitrophenol by the uridine diphosphate transglucuronylase of homogenates of female mouse liver has been made, with reference to the effect of reagents reacting with thiol groups. 2. The synthesis of both glucuronides was completely inhibited by organic mercurials and N-ethylmaleimide. The inhibition was only partial with arsenite and the arsenoxides, iodoacetamide and o-iodosobenzoate. 3. The o-aminophenol system was much more sensitive than that for p-nitrophenol to all the thiol reagents, except N-ethylmaleimide, which was equally active in both systems. 4. At very low concentrations of the organic mercurials, the o-aminophenol system was activated. 5. With o-aminophenyl glucuronide formation, complete protection was given by glutathione and cysteine against the organic mercurials, N-ethylmaleimide and iodoacetamide, and partial protection against the arsenicals. Reversal was complete against the mercurials, and very limited against the arsenicals and iodoacetamide. The effects of N-ethylmaleimide and o-iodosobenzoate were irreversible. Results with p-nitrophenol were very similar. 6. Uridine diphosphate transglucuronylase was partially protected against p-chloromercuribenzoate and lewisite oxide by uridine diphosphate glucuronate, but not by o-aminophenol. 7. Glutathione did not prevent the decline in the rate of conjugation of o-aminophenol when homogenates were aged by incubation at 30°. Cysteine was unable to prevent or reverse inactivation by ultrasonic radiation.