Firebrats,Thermobia domestica,aggregate in response to the microbes Enterobacter cloacae and Mycotypha microspora

The firebrat, Thermobia domestica (Packard) (Thysanura: Lepismatidae), aggregates in response to the faeces of conspecifics as well as shelters previously inhabited by conspecifics. Our objective was to determine the source of the aggregation signal. Filter paper previously exposed to firebrats induced strong arrestment of firebrats. Polar solvents (water, methanol, acetonitrile) and less polar solvents (hexane, dichloromethane, ethyl ether), alone or in combination, failed to extract the aggregation signal from firebrat‐exposed paper. Moreover, solvent‐extracted paper continued to induce firebrat arrestment. In contrast, the aggregation signal could be obtained by physical extraction (freeze/thawing or ultrasonication) of firebrat‐exposed paper submerged in water. Five fungal species and four bacterial species were isolated from ultrasonicant solutions on potato dextrose‐, nutrient‐, and GlcNAc‐agar. Of the nine isolated microbes tested, only the fungus Mycotypha microspora Fenner (Mucorales) and the bacterium Enterobacter cloacae (Jordan) Hormaeche & Edwards (Enterobacteriaceae) induced arrestment of firebrats in bioassays. Our data support the conclusion that firebrats do not form aggregations in response to pheromones; instead, they aggregate in the presence of specific microbes or their metabolites.     

Evidence for male- and juvenile-specific contact pheromones of the common bed bug Cimex lectularius

Males and females of the common bed bug, Cimex lectularius L. (Heteroptera: Cimicidae), have been shown to produce and respond to an aggregation pheromone. We tested whether juvenile C. lectularius also produce and respond to aggregation pheromone, and whether the pheromone is perceived by contact chemoreception. In dual‐choice laboratory experiments, juveniles, but not males or females, preferred juvenile‐exposed paper discs to control discs. Unlike juveniles, males and females preferred male‐exposed paper discs to control discs. Neither juveniles, males, nor females preferred female‐exposed discs to control discs. When test stimuli were inaccessible, C. lectularius failed to show any preference. Male‐ and juvenile‐specific contact pheromones may have contrasting functions of marking shelters as safe refugia for development and growth (juveniles) or mate encounter (adults), but result in the same phenomenon, the aggregation of conspecifics.     

Behavioural responses of the vine weevil, Otiorhynchus sulcatus, to semiochemicals from conspecifics, Otiorhynchus salicicola, and host plants

The vine weevil Otiorhynchus sulcatus is a parthenogenetic reproducing species which forages for suitable host plants at night, but is found congregated in dark places during the day. Frass of this weevil species is suspected to contain attractive compounds that are host‐plant related. Using a still‐air olfactometer, we tested adult vine weevils at night for their behavioural response to odours from conspecifics, feeding on a mixture of spindle tree (Euonymus fortunei) and yew (Taxus baccata), and to a sexually reproducing related species (Otiorhynchus salicicola), feeding on a mixture of ivy (Hedera helix) and cherry laurel (Prunus laurocerasus). Their attraction to conspecifics and O. salicicola appeared to be related to frass production. Freshly collected frass from O. sulcatus and from O. salicicola males and females was attractive. Prunus laurocerasus and H. helix have not been observed to be hosts of the vine weevil in the field. However, our tests showed that the vine weevil was attracted to mechanically damaged leaves of both plant species, whereas undamaged leaves were not attractive. Only undamaged young unfolding leaves of H. helix were also attractive. The attraction to odours from mechanically damaged host and non‐host plants suggested the involvement of compounds that are commonly found in many plant species. The involvement of plant compounds and/or aggregation pheromones in attraction to frass of the vine weevil and frass of the related weevil species O. salicicola is discussed.     

Pheromone-mediated communication disruption in Guatemalan potato moth, Tecia solanivora

Chemical analysis of pheromone gland extracts followed by behavioural studies in the wind tunnel and by field trapping tests show that the sex pheromone of the Guatemalan potato moth, Tecia (Scrobipalpopsis) solanivora Povolny (Lepidoptera: Gelechiidae), is a blend of (E)‐3‐dodecenyl acetate, (Z)‐3‐dodecenyl acetate, and dodecyl acetate. A 100 : 1 : 20 blend of these compounds, formulated at 1000 µg on rubber septa, captured more males than the main compound alone. This lure was species‐specific and did not capture the potato tubermoth, Phthorimaea operculella. A potato field was treated with a blend of these three compounds at a rate of 28 g ha^?1. Male T. solanivora attraction to synthetic pheromone traps was almost completely suppressed for 2 months, demonstrating the potential use of pheromones for control of this economically important insect pest of potato in Central and Southern America.     

Differential response of Trichogramma wasps to extreme sex pheromone types of the noctuid moth Heliothis virescens

1. Chemical espionage in nature may occur when predators or parasitoids home in on animal or plant communication signals. Parasitoid wasps are known to use pheromones emitted by adults hosts to locate host eggs, larvae or pupae. The response of Trichogramma egg parasitoids to a synthetic sex pheromone blend of moths has been shown in a number of studies over the past 40 years. 2. Trichogramma pretiosum (Hymenoptera, Trichogrammatidae) is a tiny parasitic wasp, attacking the eggs of the noctuid moth Heliothis virescens (Lepidoptera, Noctuidae). This study investigated whether T. pretiosum homes in on the sex pheromone of H. virescens at close range. The arrestment response of the wasps to sex pheromone gland extracts of two types of female moths, so‐called high and low females, was also tested, referring to two selected extreme pheromone types of H. virescens. The study also investigated whether the wasps would mount females, possibly to hitchhike with them. 3. The wasps were arrested by the common, ‘low’ pheromone, but not by the rare, ‘high’ pheromone or by extracts from male hairpencils. The wasps did not show a preference for separate sex pheromone compounds, but when pre‐exposed to the major sex pheromone component of H. virescens before the tests together with H. virescens eggs, they did show a preference, indicating learning behaviour. In the mounting experiments, mated females were mounted significantly more than virgin females or males, suggesting that hitchhiking is a strategy used by these wasps to locate moth eggs. 4. This represents the first study to show a differential response of parasitoid wasps to two different sex pheromone types in a single host species. The results warrant further investigations into the potential role of parasitic wasps in the evolution of sexual communication in moths.     

Chemically-mediated pre-mating behavior in two tetranychid species

We used bioassays to evaluate the arrestment response of male twospotted spider mite, Tetranychus urticae Koch, and Banks grass mite, Oligonychus pratensis (Banks) to whole-body extract from conspecific quiescent deutonymphs. We examined the effect of previous behavior on mite response to extract from female quiescent deutonymphs. We also examined male arrestment and guarding behavior in response to 2 extract concentrations and to extract from male quiescent deutonymphs. Male T. urticae and O. pratensis exhibited similar changes in their behavior in response to the different extracts with which we presented them. Males that were guarding quiescent deutonymphs immediately prior to testing spent more time in an untreated 3.5-mm-diameter circle than did males that were previously engaged in other behaviors. However, when nonguarding males were presented with extract of conspecific female quiescent deutonymphs they remained in the stimulus circle as long as guarding males did in an untreated circle. Arrestment duration of nonguarding males increased at 2 higher extract concentrations. The arrestment response was not exclusive to extracts from female quiescent deutonymphs; nonguarding male mites were also arrested by extracts from male quiescent deutonymphs, although for a shorter time. Duration of arrestment was related roughly to size differences between male and female quiescent deutonymphs. Furthermore, males did not show an exclusive preference for guarding conspecific male or female quiescent deutonymphs. It seems unlikely that the arrestant is a specific sex pheromone. Rather, male mites probably use the arrestant as a necessary cue to focus their attention on an individual that may be a suitable mate. Other tactile, visual, and chemical stimuli may then help males to decide whether to remain and assume mate guarding behaviors.     

Effects of host-plant quality on male two-spotted spider mite (Acari: Tetranychidae) mate location and guarding behavior

Effects of host-plant quality on two-spotted spider mite,Tetranychus urticae Koch, mate location and guarding behaviors were described using a no-choice bioassay. Males and quiescent deutonymphs were collected from lima bean leaves of one of two host qualities. High-chlorophyll (HC) leaves had been infested with spider mites for 6–10 days, while low-chlorophyll (LC) leaves had been infested for>21 days. Three parameters of maleT. urticae guarding behavior were quantified: approach arrestment, and arrestment duration. HC males approached quiescent deutonymphs more often than did LC males, even though host quality of females had no effect on male approach frequency. HC males were arrested more frequently by HC quiescent deutonymphs than were LC males, while LC males were arrested more often by LC females than were HC males. However, a different pattern was observed for arrestment duration. HC males were arrested for twice as long by LC quiescent deutonymphs than by HC females, while the LC-male arrestment durations elicited by HC and LC females did not differ. These results show that host-plant quality affectsT. urticae intersexual communication, in terms of both the female signal and the male response. Whether the differing male responses observed in this study indicate alternativeT. urticae mating strategies or are incidental by-products of host-induced physiological changes remains to be determined.     

Behavioural responses of diverse insect groups to electric stimuli

Anecdotal evidence suggests that cockroaches respond to electrical appliances or outlets. Our objectives were to determine the effect of field‐inducing sources and field attributes on attraction of German cockroaches, Blattella germanica (L.) (Blattodea: Blattellidae), and to test those parameters found effective for attraction of B. germanica for attraction of other groups of insects. In two‐choice, large‐arena experiments, significantly more female, but not nymphal, B. germanica settled in or near electrified coils with static or fluctuating electromagnetic fields produced by low‐level direct current (DC) or alternating current (AC) sources than in control coils without current. Electromagnetic fields with the magnetic, but not the electric, component of the field nulled still attracted B. germanica, suggesting that the electric component of the field may contribute to the attraction or arrestment response of B. germanica. DC‐powered coils with static electromagnetic fields also attracted/arrested brown‐banded cockroaches, Supella longipalpa (Fabricius) (Blattodea: Blattellidae), common silverfish, Lepisma saccharina (L.), firebrats, Thermobia domestica (Packard) (both Thysanura: Lepismatidae), and European earwigs, Forficula auricularia (L.) (Dermaptera: Forficulidae), but they repelled American cockroaches, Periplaneta americana (L.) (Blattodea: Blattidae). If proven in field experiments, electrified coils as trap baits may offer non‐toxic alternatives to pesticides for selective insect control in urban environments.     

Concentration-dependent parsimonious releaser roles of gregarious male pheromone of the desert locust, Schistocerca gregaria

The responses of (i) groups of crowd-reared mature males of desert locust, Schistocerca gregaria to a choice of two columns of air, one permeated with different concentrations of phenylacetonitrile (PAN), the major component of gregarious-phase male-produced pheromone, and the other untreated, and (ii) individual crowd-reared mature males of the insect to varying concentration gradients of PAN, were studied in two different types of arena. In the choice assay, locusts preferred to be within PAN-permeated air column at low relative doses of the pheromone, but away from PAN at high relative doses. In the second assay, individual locusts were arrested close to PAN source at low PAN concentration gradients, but away from the source at high concentration gradients. The results are consistent with two reported releaser functions of the adult male-released pheromone that are dependent on different sensory thresholds: arrestment and cohesion at lower relative concentrations and male-male homosexual avoidance at higher relative concentrations.     

Ingestion and excretion of nitrogen by larvae of a cabbage armyworm: the effects of fertilizer application

• 1 Insect frass has significant impacts on decomposition and soil nitrogen dynamics. Although the frass contains various forms of nitrogen that may differently influence nitrogen dynamics in the decomposition process, how the nitrogen form in the insect frass is influenced by host plant quality remains poorly understood.
• 2 The present study examined the effects of application of fertilizer on leaf quality of Brassica rapa L. var. perviridis Bailey (Brassicaceae), and on the consumption, frass excretion and frass quality of its insect pest Mamestra brassicae (L.) (Lepidoptera: Noctuidae), with a particular focus on the dynamics of inorganic nitrogen.
• 3 Brassica rapa increased total nitrogen concentration, and accumulated inorganic nitrogen [i.e. leaf nitrate‐nitrogen (NO₃^?‐N) and ammonium‐nitrogen (NH₄⁺‐N)] in the leaves in response to the application of fertilizer.
• 4 Although leaf consumption and frass excreted by M. brassicae was not affected by fertilizer treatment, frass quality was influenced by host plant quality as altered by fertilizer applications. Frass contained high concentrations of total nitrogen, NO₃^?‐N, and NH₄⁺‐N under high fertilizer treatment. In particular, the larvae excreted much more NH₄⁺‐N than ingested. The relationship between host plant quality and insect frass quality, as well as the potential implications for decomposition and nutrient dynamics, are discussed.

     

An enemy of your enemy is your friend: Impact of predators on aggregation behavior of gammarids

Predation pressure may affect many aspects of prey behavior, including forming groups and changes in social interactions. We studied the aggregation behavior of competing gammarids Dikerogammarus villosus and Pontogammarus robustoides (Amphipoda, Crustacea) to check whether they modify their preferences for conspecifics or heterospecifics in response to predator (the racer goby Babka gymnotrachelus) kairomones in the presence or absence of stone shelters (alternative protection source). Both species exhibited preferences toward shelters occupied by conspecifics over empty shelters and conspecifics apart from shelters, suggesting that their aggregation depends not only on habitat heterogeneity, but also on their social interactions. Moreover, gammarids in the presence of shelters (safer conditions) preferred conspecifics over heterospecifics, but predator kairomones made them form aggregations irrespective of species. In the predator presence, P. robustoides increased its aggregation level only in the sheltered conditions, whereas D. villosus exhibited this response only in the absence of shelters, suggesting that this behavior can protect it against predators. Therefore, we tested the antipredator effectiveness of D. villosus aggregations by exposing them to fish predation. Gobies foraged most effectively on immobile single gammarids compared to moving and aggregated individuals. Fish also avoided aggregated prey, confirming the protective character of aggregations. We have demonstrated that the predator presence increases aggregation level of prey gammarids and affects their social behavior by reducing antagonistic interactions and avoidance between competing species. This is likely to affect their distribution and functioning in the wild, where predator pressure is a standard situation.     

Forage collection,substrate preparation,and diet composition in fungus‐growing ants

1. Variation and control of nutritional input is an important selective force in the evolution of mutualistic interactions and may significantly affect coevolutionary modifications in partner species. 2. The attine fungus‐growing ants are a tribe of more than 230 described species (12 genera) that use a variety of different substrates to manure the symbiotic fungus they cultivate inside the nest. Common ‘wisdom’ is that the conspicuous leaf‐cutting ants primarily use freshly cut plant material, whereas most of the other attine species use dry and partly degraded plant material such as leaf litter and caterpillar frass, but systematic comparative studies of actual resource acquisition across the attine ants have not been done. 3. Here we review 179 literature records of diet composition across the extant genera of fungus‐growing ants. The records confirm the dependence of leaf‐cutting ants on fresh vegetation but find that flowers, dry plant debris, seeds (husks), and insect frass are used by all genera, whereas other substrates such as nectar and insect carcasses are only used by some. 4. Diet composition was significantly correlated with ant substrate preparation behaviours before adding forage to the fungus garden, indicating that diet composition and farming practices have co‐evolved. Neither diet nor preparation behaviours changed when a clade within the paleoattine genus Apterostigma shifted from rearing leucocoprinous fungi to cultivating pterulaceous fungi, but the evolutionary derived transition to yeast growing in the Cyphomyrmex rimosus group, which relies almost exclusively on nectar and insect frass, was associated with specific changes in diet composition. 5. The co‐evolutionary transitions in diet composition across the genera of attine ants indicate that fungus‐farming insect societies have the possibility to obtain more optimal fungal crops via artificial selection, analogous to documented practice in human subsistence farming.     

Odour quality discrimination for behavioural antagonist compounds in three tortricid species

The antennal and behavioural response of three tortricid species (Lepidoptera: Tortricidae) to their corresponding sex pheromones and known or putative behavioural antagonists was tested by electroantennography and in field trials. The species and their pheromones and known or proposed behavioural antagonist were lightbrown apple moth, Epiphyas postvittana (Walker) [pheromone: 95% (E)‐11‐tetradecenyl acetate (E11‐14Ac) and 5% (E,E)‐9,11‐tetradecadienyl acetate (E9E11‐14Ac); antagonist: (Z)‐11‐tetradecenyl acetate (Z11‐14Ac)], codling moth, Cydia pomonella (L.) [pheromone: (E,E)‐8,10‐dodecadien‐1‐ol (codlemone); antagonist: (E,E)‐8,10‐dodecadienyl acetate (codlemone acetate)], and gorse pod moth, Cydia ulicetana (Haworth) [pheromone: (E,E)‐8,10‐dodecadienyl acetate (codlemone acetate); putative antagonist: (E,E)‐8,10‐dodecadien‐1‐ol (codlemone)]. In all three species, the antennal response to the antagonists was not significantly different from the antennal response to con‐specific sex pheromone compounds. In the field trapping experiments, significantly fewer males of all three species were attracted to the respective pheromone when blended with the behavioural antagonist compound. However, this response varied between the species, with lightbrown apple moth and codling moth showing stronger responses to the antagonist compounds than gorse pod moth. Both lightbrown apple moth and codling moth males were able to discriminate between pure pheromone and pheromone blended with the antagonist when placed in traps side‐by‐side separated by ca. 10 cm. The presence of the behavioural antagonist not only affected the catch of males of both species within their own traps but also affected the catch in the neighbouring trap that contained con‐specific sex pheromone; the catch of gorse pod moth was not reduced by the presence of codlemone in the neighbouring trap. These results suggest that strong behavioural antagonists such as codlemone acetate for codling moth and Z11‐14Ac for lightbrown apple moth induce their inhibition effect at a substantial distance downwind from the odour source; however, most of those males that were able to overcome this inhibition effect at the early stage of orientation to odour source, were able to discriminate between the pheromone source and the pheromone source admixed with behavioural antagonist. Moderate behavioural antagonists such as codlemone for gorse pod moth did not elicit a discrimination effect.     

Does larval aggregation pheromone of codling moth, Cydia pomonella, induce attraction or arrestment of receivers?

Cocoon-spinning larvae of the codling moth, Cydia pomonella, emit a pheromone that mediates aggregation by pupation site-seeking fifth-instar larvae. It was unknown and, thus, we tested whether the aggregation pheromone induces arrestment or attraction responses. In paired straight-tube experiment 1, fifth-instars moved faster and farther upwind toward cospecific cocoons compared to blank controls. In still-air cage experiment 2, fifth-instars selected more often as first and final choices of pupation sites those with cocooning conspecifics than those without. Finally, in Y-tube olfactometer experiment 3, fifth-instars anemotactically responded to, and preferred, side arms with cocooning conspecifics to those without. Our data provide evidence that codling moth larvae are attracted to, rather than merely arrested by, larval aggregation pheromone. These results help explain reported aggregations or clumped distributions of larvae on tree trunks, which would likely not occur if they were based merely on chance encounter of cocoon-spinning larvae by foraging larvae.     

Non-additive effects of leaf litter and insect frass mixture on decomposition processes

Although there is a growing body of evidence that herbivorous insects have a significant impact on decomposition and soil nutrient dynamics through frass excretion, how mixtures of leaf litter and insect frass influence such ecosystem processes remains poorly understood. We examined the effects of mixing of leaf litter and insect frass on decomposition and soil nutrient availability, using a study system consisting of a willow, Salix gilgiana Seemen, and a herbivorous insect, Parasa consocia Walker. The chemical characteristics of insect frass differed from those of leaf litter. In particular, frass had a 42-fold higher level of ammonium–nitrogen (NH₄ ⁺–N) than litter. Incubation experiments showed that the frass was decomposed and immobilized with respect to N more rapidly than the litter. Furthermore, litter and frass mixtures showed non-additive enhancement of decomposition and reduction of NH₄ ⁺–N, depending on the litter–frass mixing ratio. These indicate that, while insect frass generally accelerated decomposition, the effect of frass on soil nutrient availability was dependent largely on the relative amounts of litter and frass.     

Developing pheromone traps and lures for Maruca vitrata in Benin, West Africa

In previous work successful trapping of the legume podborer, Maruca vitrata Fabricius (Lepidoptera: Pyralidae), was accomplished using a synthetic pheromone blend consisting of (E,E)‐10,12‐hexadecadienal, (E,E)‐10,12‐hexadecadienol, and (E)‐10‐hexadecenal in a 100 : 5 : 5 ratio. In the present work, experiments were conducted in cowpea fields in Benin to compare different trap designs, and other aspects of the lures. A water‐trap made from a plastic jerry‐can was found to be superior to commercial funnel‐ and sticky‐trap designs, and 120 cm was the optimum height for captures. Generally, lures consisted of polyethylene vials containing 0.1 mg of pheromone. Results showed that shielding the lures from the adverse effects of sunlight with aluminium foil did not increase trap catches of M. vitrata. The degree of isomeric purity of the (E,E)‐10,12‐hexadecadienal and (E,E)‐10,12‐hexadecadienol blend components, in the range 73–99%, had no significant effect on captures, while lures of 80% isomeric purity showed no loss of effectiveness for up to 4 weeks. Similar results were observed with lures from a commercial source containing 0.46 mg of pheromone in the blend ratio 100 : 11 : 6 and 95% isomeric purity. Residue analysis showed that vial lures exposed for 2 weeks in the field still contained 73% of the initial amount of (E,E)‐10,12‐hexadecadienal, compared to rubber septa dispensers, which only retained 22%. Females comprised 11–50% of total catches, confirming earlier, unexpected results for synthetic lures. The observations that effective traps can be made from locally available plastic containers, and that pheromone blend composition and purity are not critical, should reduce costs and improve the feasibility of traps as practical monitoring tools for M. vitrata.     

Relationship between sex pheromone elicited behaviour and response of single olfactory receptor neurones in a wind tunnel

Responses from pheromone‐specific receptor neurones in male Agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae) were recorded in a laboratory wind tunnel. Stimuli were: (1) rubber septum dispensers loaded with single components or a four‐component pheromone blend, (2) excised glands from female A. segetum, (3) constrained A. segetum females with extruded glands. Dose–response curves for three neurone‐types with different specificity were established. The neurones were specifically tuned to respond to either one of the two pheromone components (Z)‐5‐decenyl acetate and (Z)‐7‐dodecenyl acetate, or to the behavioural antagonist (Z)‐5‐decenol. In parallel, a behavioural dose–response curve with males flying upwind to a four‐component pheromone blend was established. There was a clear correlation between behavioural arrestment of upwind flight and maximum spiking activity in Z5–10:OAc‐specific neurones. The pheromone release rates of individual females and synthetic dispensers were compared. A load of 50–200 ng of Z5–10:OAc on a rubber septum elicited approximately the same neural response as one female gland.     

Mating disruption of pea moth (Cydia nigricana) in organic peas (Pisum sativum)

We appraised mating disruption (MD) to control pea moth, Cydia nigricana (Fabricius) (Lepidoptera: Tortricidae), by assessing male attraction to monitor traps, larval pod infestation, and larval age structure in pheromone‐treated and untreated grain pea fields [Pisum sativum L. (Fabaceae)], over a 5‐year period. Cellulose pheromone dispensers were manually attached to the top shoots of pea plants and released 540 mg ha^?1 day^?1 synthetic pheromone E8,E10‐dodecadien‐1‐yl acetate in a first test series (2000–2001) and ca. 4 200 mg pheromone ha^?1 day^?1 in a second series (2004–2006). The dispensers had a half‐life of about 30 days. Although male attraction to pheromone monitoring traps was largely suppressed at the edges and within MD fields in both test series, MD treatments did not reduce pod infestation in the open field in 2000 and 2001. In the 2004–2006 series, larval damage reduction was achieved in the majority of the trials but overall MD efficacy in the open field was only 61% and not significant. In contrast, in field cages placed within the experimental sites and supplied with unmated pea moths, MD control was consistently high and significant. There were no obvious differences in the larval age distribution in all MD and control treatments, suggesting that infestations started and developed further similarly. As a univoltine species, C. nigricana larvae stay in the soil of pea fields for hibernation and pupate. The following year, emerging adults disperse and fly to the closest pea crop. Combined emergence site and pea crop treatments were conducted over 2 years to include this early migration phase of C. nigricana adults. However, the emergence site treatments did not enhance MD‐control efficacy. We conclude that mating activity was only prevented in cage tests, whereas substantial mating occurred during the transit phase outside the pheromone‐treated fields either within non‐crop vegetation and/or at the edges of pheromone‐treated pea fields orientated upwind. Thus, resulting gravid female entry can be regarded as the major constraint to reliable MD control.     

Adaptation of male moth antennal neurons in a pheromone plume is associated with cessation of pheromone-mediated flight

Recordings of the firing rates of single antennal neurons whenAgrotis segetum antennac were placed 70 cm downwind of a pheromonesource revealed that cells sensitive to the most volatile componentadapted rapidly in a plume from a high–concentration sourceknown from previous studies to cause in-flight arrestment ofprogress towards the source. No adaptation was found in responseto lower-concentration plumes known to promote high levels ofsustained flight to the source with little premature arrestment.Adaptation was not observed in antennal neurons of a secondspecies, Heliothis virescens, when they were placed in plumesof this species' sex pheromone blend, regardless of the concentration.In flight-tunnel tests these same pheromone sources evoked highlevels of source location with little arrestment. These resultsindicate that adaptation or attenuation of antennal neuronalburst frequencies in response to rapidly arriving pheromonefilaments in a plume may be important peripheral determinantsof whether or not prolonged upwind flight and successful pheromonesource location occurs.