Spatial organization of olfactory receptor neurons on the antenna of the cabbage looper moth

Electrophysiological responses to stimulation with behaviorally relevant compounds were recorded from receptor neurons within specialized classes of sensilla on the antennae of male cabbage looper moths. Receptor neurons were found that specifically respond to stimulation with Z-7,12:AC, Z-7,14:AC, Z-9,14:AC, and Z-7,12:OH. Specialized receptor neurons were not found for the three remaining pheromone blend components, 12:AC, Z-5,12:AC, or 11,12:AC. However, a new class of sensillum containing a pair of neurons insensitive to all of the cabbage looper pheromone components was encountered. In addition, spatial patterns of distribution along the flagellum for identified classes of sensilla are described. Sensilla containing Z-7,12:AC-sensitive neurons are preferentially located on the proximal half of the antennal flagellum. In addition to this distribution along the length of the antenna, a pattern across individual flagellar subsegments is described. Sensilla containing neurons sensitive to Z-9,14:AC were found exclusively on the lateral margins of individual flagellar subsegments. Accepted: 19 June 1998     

Measuring activity in olfactory receptor neurons in Drosophila: Focus on spike amplitude

Olfactory responses at the receptor level have been thoroughly described in Drosophila melanogaster by electrophysiological methods. Single sensilla recordings (SSRs) measure neuronal activity in intact individuals in response to odors. For sensilla that contain more than one olfactory receptor neuron (ORN), their different spontaneous spike amplitudes can distinguish each signal under resting conditions. However, activity is mainly described by spike frequency.Some reports on ORN response dynamics studied two components in the olfactory responses of ORNs: a fast component that is reflected by the spike frequency and a slow component that is observed in the LFP (local field potential, the single sensillum counterpart of the electroantennogram, EAG). However, no apparent correlation was found between the two elements.In this report, we show that odorant stimulation produces two different effects in the fast component, affecting spike frequency and spike amplitude. Spike amplitude clearly diminishes at the beginning of a response, but it recovers more slowly than spike frequency after stimulus cessation, suggesting that ORNs return to resting conditions long after they recover a normal spontaneous spike frequency. Moreover, spike amplitude recovery follows the same kinetics as the slow voltage component measured by the LFP, suggesting that both measures are connected.These results were obtained in ab2 and ab3 sensilla in response to two odors at different concentrations. Both spike amplitude and LFP kinetics depend on odorant, concentration and neuron, suggesting that like the EAG they may reflect olfactory information.     

Response of olfactory receptor neurons in honeybees to odorants and their binary mixtures

Recordings were made from single sensilla placodea of the worker honeybee (Apis mellifera). The sensilla were stimulated with one of two sets of four compounds and their binary mixtures, at two dosage levels. Aromatic compounds comprised one set, and saturated n-octane derivatives comprised the other set. Correlation, principal component, and cluster analyses indicate that responses to binary mixtures are not linear combinations of responses to the component compounds. The first principal component indicated that neuronal units had either more excitatory or more inhibitory responses to all odorants than would be expected from a model where inhibitory and excitatory responses are randomly distributed among the neuronal units. When compared to the responses to the component odorants, synergistic responses to binary odors occurred more often than would be expected by chance. Clear inhibitory responses to binary odors were less prevalent. This study agrees with an earlier study employing aromatic odorants in that most of the aromatic odorants each had groups of receptor neurons that were relatively selective for it, and each odorant had a distinctly different number of receptor neurons selective for it. Among the octane derivatives, receptor neurons were selective for the level of oxidation of the functional group or its site of attachment, rather than specific compounds.     

Parental Body Mass as a Determinant of Egg Size and Egg Output in an Arctiid Moth (Utetheisa ornatrix)

Females of the moth Utetheisa ornatrix (family Arctiidae) mate preferentially with larger males. As a consequence, females have larger sons and daughters, which have been shown to be more acceptable in courtship and more fecund, respectively. We demonstrate that mating with larger males results in accelerated oviposition by the female on the day after mating and that females are intrinsically prone to lay larger eggs in the first days after mating. Both these additional size-dependent effects have potential adaptive consequences.     

Characterization of olfactory receptor neurons for pheromone candidate and plant volatile compounds in the clover root weevil,Sitona lepidus

Antennal olfactory receptor neurons (ORNs) for pheromone and plant volatile compounds were identified and characterized in male and female clover root weevil, Sitona lepidus (Gyllenhal), using the single sensillum recording technique with five pheromone-related compounds, and 40 host and non-host plant volatile compounds. Overall, seven different types of olfactory sensilla containing specialized ORNs were identified in each sex of S. lepidus. Among them, three different types of sensilla in the males and two types in the females housed ORNs specialized for pheromone-related compounds. The ORNs in males were specialized for 4-methyl-3,5-heptanedione or one or more of four stereoisomers of 5-hydroxy-4-methyl-3-heptanone. In contrast, female sensilla did not contain ORNs sensitive to 4-methyl-3,5-heptanedione while they contained ORNs sensitive to and specialized for the stereoisomers of (4S,5S)-5-hydroxy-4-methyl-3-heptanone. In addition to the pheromone-related ORNs, four types of olfactory sensilla contained ORNs responsive to plant volatile compounds in male S. lepidus, and five types in females. Most of the ORNs identified in S. lepidus showed a high degree of specificity to specific volatile compounds although some of the active compounds showed overlapping response spectra in the ORNs across different types of sensilla. The most active plant volatile compounds were the four green leaf volatile compounds, (E)-2-hexenol, (Z)-2-hexenol, (Z)-3-hexenol and (E)-2-hexenal, and isomers of two monoterpenols, (±)-linalool and (±)-α-terpineol, all eliciting strong responses from relatively large numbers of ORNs in male and female S. lepidus. Our study indicates that S. lepidus has a set of highly sensitive and selective ORNs for pheromone and plant volatile compounds. Further work is needed to elucidate the behavioral implications of these findings.     

Peripubertal exposure to male odors influences female puberty and adult expression of male-directed odor preference in mice

Testosterone-dependent olfactory signals emitted by male are well known to accelerate female puberty in mice (Vandenbergh effect). However, it remains unclear whether these chemosignals also influence adult expression of male-directed odor preference. Therefore, we exposed female mice to intact or castrated male bedding (vs clean bedding as control) during the peripubertal period (postnatal day (PD) 21–38) and measured male-directed odor preference in adulthood. At PD45 or PD60, females exposed to intact male odors, and thus showing puberty acceleration, preferred to investigate odors from intact males over females or castrated males. Females exposed to castrated male odors did not show puberty acceleration but preferred male (intact or castrated) over female odors. Finally, control females did not show any odor preference when tested at PD45, although a preference for male odors emerged later (PD60). In a second experiment, females that were exposed to intact male odors after pubertal transition (PD36–53) also preferred intact male over castrated male odors. In conclusion, our results indicate that peripubertal exposure to male odors induced early expression of male-directed odor preference regardless of puberty-accelerating effect and that induction of male-directed odor preference is not specific to the peripubertal period.     

Octopamine modulates the sensitivity of silkmoth pheromone receptor neurons

Effects of octopamine and its antagonist epinastine on electrophysiological responses of receptor neurons of Antheraea polyphemus specialised to the pheromone components (E,Z)-6,11-hexadecadienyl acetate and (E,Z)-6,11-hexadecadienal were investigated. Injections of octopamine and epinastine into the moths had no effect on the transepithelial potential of the antennal-branch preparation nor on the spontaneous nerve impulse frequency in either type of receptor neuron. However, in the presence of continuous low-intensity pheromone stimulation, octopamine significantly increased the nerve impulse frequency in the acetate receptor neuron, but not in the aldehyde receptor neuron. Octopamine and epinastine had no significant effect on the receptor potential amplitudes elicited in both receptor neuron types by pheromone stimulation. However, the peak nerve impulse frequency in the response of both receptor neuron types to pheromone was significantly affected: decreased by epinastine and increased by octopamine over a broad range of pheromone concentrations. In control experiments, injection of physiological saline did not significantly alter the peak nerve impulse frequency. The effect of octopamine was established within 1 h after injection and persisted for about 4 h. The possibility of a direct action of octopamine on the nerve impulse generation by the receptor neurons is discussed. Accepted: 8 January 2000     

Temporal analysis of adaptation in moth (Trichoplusia ni) pheromone receptor neurons

Summary The temporal pattern of response in chemoreceptor neurons reflects both the temporal distribution of stimuli and the timing of signal transduction, action potential generation and propagation. Here we analyze the temporal characteristics of the responses elicited in pheromone receptor neurons by computer-controlled rectangular pulses of odorant. Extracellular recordings from the HS sensilla trichodea on the antenna of male Trichoplusia ni reveal the activity of two neurons: the A neuron, which responds to the major component of the female pheromone blend, (Z)7-dodecenyl acetate and the B neuron, which responds to (Z)7-dodecenol. B neurons were divided into two classes (HR, LR), based on the magnitude and temporal pattern of their response to (Z)7-dodecenol. Most A and HR B neurons responded to rectangular pulses of various durations (0.1–40 s) with an initial phasic burst (100 ms), followed by a slowly declining tonic component. At moderate and elevated pheromone doses, prolonged stimulation resulted in significant reductions in the tonic response levels (adaptation); stimuli of increasing duration effected greater adaptation. Most LR B neurons lacked a phasic response component and showed virtually no adaptation with prolonged stimulation. Pheromone receptor neurons may differ in both their spectral and temporal response properties which may provide the animal with additional sensory information for blend discrimination and spatial orientation in complex natural pheromone plumes. The potential functional value of adaptation in the moth pheromone communication system is discussed.Abbreviations Z7,12:AC (Z)7-dodecenyl acetate - Z7,12:OH (Z)7-dodecenol - HR High response - LR Low response - HS High sensitivity     

Physiology and glomerular projections of olfactory receptor neurons on the antenna of female Heliothis virescens (Lepidoptera: Noctuidae) responsive to behaviorally relevant odors

The neurophysiology and antennal lobe projections of olfactory receptor neurons housed within short trichoid sensilla of female Heliothis virescens F. (Noctuidae: Lepidoptera) were investigated using a combination of cut-sensillum recording and cobalt-lysine staining techniques. Behaviorally relevant odorants, including intra- and inter-sexual pheromonal compounds, plant and floral volatiles were selected for testing sensillar responses. A total of 184 sensilla were categorized into 25 possible sensillar types based on odor responses and sensitivity. Sensilla exhibited both narrow (responding to few odors) and broad (responding to many odors) response spectra. Sixty-six percent of the sensilla identified were stimulated by conspecific odors; in particular, major components of the male H. virescens hairpencil pheromone (hexadecanyl acetate and octadecanyl acetate) and a minor component of the female sex pheromone, (Z)-9-tetradecenal. Following characterization of the responses, olfactory receptor neurons within individual sensilla were stained with cobalt lysine (N=39) and traced to individual glomeruli in the antennal lobe. Olfactory receptor neurons with specific responses to (Z)-9-tetradecenal, a female H. virescens sex pheromone component, projected to the female-specific central large female glomerulus (cLFG) and other glomeruli. Terminal arborizations from sensillar types containing olfactory receptor neurons sensitive to male hairpencil components and plant volatiles were also localized to distinct glomerular locations. This information provides insight into the representation of behaviorally relevant odorants in the female moth olfactory system. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Smoke,pheromone and kairomone olfactory receptor neurons in males and females of the pine sawyer Monochamus galloprovincialis (Olivier) (Coleoptera: Cerambycidae)

The response of antennal olfactory receptor neurons (ORNs) of Monochamus galloprovincialis to several odourants was tested using single sensillum electrophysiology. Behaviourally active pheromone, and kairomone (host and sympatric bark beetle pheromone) odours were tested alongside smoke compounds released by burnt wood that are potentially attractive to the insect. The antennae bore several types of sensilla. Two plate areas in the proximal and distal ends of each antennal segment were covered with basiconic sensilla that responded to the odour stimuli. Sensilla basiconica contained one or two cells of different spike amplitude. The 32 male and 38 female ORNs tested responded with excitations or inhibitions to the different plant odours. In general the response of male and female receptors was very similar so they were pooled to perform a cluster analysis on ORN responses. Six ORNs were clearly specialised for pheromone reception. Responses to kairomone and smoke odours were less specific than those of pheromone, but a group of 9 cells was clearly excited by smoke compounds (mainly eugenol and 4-methyl 2-methoxyphenol), a group of 8 cells was very responsive to α-pinene, β-pinene and cis-verbenol, and a group of 14 cells responded to a wider range of compounds. The rest of the cells (47%) were either non-responsive or slightly inhibited by smoke compounds. Dose–response curves were obtained for several compounds. Different compounds induced significantly different latencies and these appeared to be unrelated to their boiling point.     

Responses to sex pheromone and plant odours by olfactory receptor neurons housed in sensilla auricillica of the codling moth, Cydia pomonella (Lepidoptera: Tortricidae)

Antennal olfactory receptor neurons located in a limited number of two types of sensilla auricillica, the rabbit-eared shoehorn and the regular shoehorn, located on the 5-30 flagellomere of the codling moth, Cydia pomonella, antenna were screened for selectivity to 11 plant compounds, the major sex pheromone component, three minor pheromone components and one behavioural antagonist. Both types of sensilla housed at least three neurons characterised by different action potential amplitudes. Neurons in both males and females responded to the plant compounds, ethyl (E,Z)-2,4-decadienoate, (+/-)-linalool, (E)-ss-farnesene, hexanol, (Z)-3-hexenyl acetate, 4,8-dimethyl-1,3,(E)7-nonatriene, nonanol, the major pheromone component codlemone [(E,E)-8,10-dodecadienol] and the minor pheromone component tetradecanol. Additionally, (E,E)-alpha-farnesene and (Z)-3-hexenol elicited responses specifically in female neurons, whereas (E,E)-farnesol elicited a specific response in a male neuron. Neurons responded to 1-3 odorants, with sometimes overlapping response spectra. A scanning electron microscopic study of the antennae of both sexes supported an earlier study, apart from that long s. trichodea were present in a wreath at the proximal margin of the flagellomere and in addition evenly distributed over the remaining surface, and a previously non-described sensillum type with external basiconic features was revealed, distributed on the proximal and medial region of the flagellomeres.     

Responses of olfactory receptor neurons in the spiny lobster to binary mixtures are predictable using a noncompetitive model that incorporates excitatory and inhibitory transduction pathways

Coding of binary mixtures by a population of olfactory receptor neurons in the spiny lobster (Panulirus argus) was examined. Extracellular single-unit responses of 50 neurons to seven compounds and their binary mixtures were recorded. The ability of a noncompetitive model with correction for binding inhibition to predict responses to mixtures based on responses to their components was compared with the predictive abilities of other models. This model assumes that different compounds activate different transduction processes in the same neuron leading to excitation or inhibition, and it includes a term quantifying the degree to which binding of an odorant to its receptor sites is inhibited by other compounds. The model accurately predicted the absolute response magnitude of the population of neurons for 13 of 15 mixtures assessed, which is superior to the predictive power of any of the other models. The model also accurately predicted the across neuron patterns generated by the binary mixtures, as evaluated by multidimensional scaling analysis. The results suggest that there is no emergence of unique qualities for binary mixtures relative to components of these mixtures.Abbreviations AMP or A adenosine-5-monophosphate - ANP across neuron pattern - ARM absolute response magnitude - ASW artificial sea water - Bet or B betaine - Cys or C L-cysteine - Glu or G L-glutamate - MDS multidimensional scaling - MID mixture interaction distance - NC model noncompetitive model - NCBI model noncompetitive model with correction for binding inhibition - C model competitive model - CBI model competitive model with correction for binding inhibition - MEC more effective component - NH ₄ or N ammonium chloride - ORN olfactory receptor neuron - Suc or S DL-succinate - Tau or T taurine     

Transient and persistent tetrodotoxin-sensitive sodium currents in squid olfactory receptor neurons

Squid olfactory receptor neurons are primary bipolar sensory neurons capable of transducing water-born odorant signals into electrical impulses that are transmitted to the brain. In this study, we have identified and characterized the macroscopic properties of voltage-gated Na⁺ channels in olfactory receptor neurons from the squid Lolliguncula brevis. Using whole-cell voltage-clamp techniques, we found that the voltage-gated Na⁺ channels were tetrodotoxin sensitive and had current densities ranging from 5 to 169 pA pF⁻¹. Analyses of the voltage dependence and kinetics revealed interesting differences from voltage-gated Na⁺ channels in olfactory receptor neurons from other species; the voltage of half-inactivation was shifted to the right and the voltage of half-activation was shifted to the left such that a “window-current” occurred, where 10–18% of the Na⁺ channels activated and did not inactivate at potentials near action potential threshold. Our findings suggest that in squid olfactory neurons, a subset of voltage-gated Na⁺ channels may play a role in generating a pacemaker-type current for setting the tonic levels of electrical activity required for transmission of hyperpolarizing odor responses to the brain. Accepted: 1 October 1998     

Inhibitory receptor binding events among the components of complex mixtures contribute to mixture suppression in responses of olfactory receptor neurons of spiny lobsters

Responses of olfactory receptor neurons of spiny lobsters Panulirus argus to two-component mixtures can be shaped by inhibitory events such as odor-activated hyperpolarizations and inhibition of odor-receptor binding (Daniel et al. 1996). In the current study, we extend this analysis to complex mixtures by examining responses of spiny lobster olfactory receptor neurons to mixtures containing up to seven odorants, consisting of adenosine-5′-monophosphate, ammonium, betaine, l-cysteine, l-glutamate, dl-succinate, and taurine. The response to a mixture was often less than the response to its most excitatory component. The effect of adding an excitatory odorant to a mixture depended on olfactory receptor neuron type, composition of the mixture, and which compound was added. In some cases the added excitatory compound had no effect or even decreased the mixture's response intensity, thus demonstrating nonlinear contributions of the components. Response intensities predicted by a noncompetitive model, which is most representative of these olfactory receptor neurons, were improved when the model included a term for empirical measurements of inhibitory binding interactions, suggesting that inhibitory binding interactions are one mechanism contributing to mixture suppression. This model's predictions were accurate for binary mixtures but not for larger mixtures, suggesting that additional inhibitory mechanisms are needed to account for mixture interactions in complex mixtures. Accepted: 24 July 1998     

Renewing olfactory receptor neurons in goldfish do not require contact with the olfactory bulb to develop normal chemical responsiveness

This study investigated whether contact with the olfactory bulb was necessary for developing and renewing olfactory receptor neurons (ORNs) to attain normal odorant responsiveness, and whether the anatomical and functional recoveries of the olfactory epithelium were similar in both bulbectomized (BE) and bilaterally axotomized (AX) preparations. In vivo electrophysiological recordings were obtained in response to amino acids, a bile acid [taurolithocholic acid sulfate(TLCS)] and a pheromonal odorant [17α, 20β,-dihydroxy-4-pregnen-3-one (17,20P)] from sexually immature goldfish. Both transmission and scanning electron microscopy indicated that the olfactory epithelium degenerated in BE and AX goldfish. Within 1–2 weeks subsequent to the respective surgeries, responses to high concentrations (>0.1 mmol · l⁻¹) of the more stimulatory amino acids remained, whereas responses were no longer obtainable to TLCS and 17,20P. At 4 weeks, responses to amino acid stimuli recovered to control levels, while responses to TLCS and 17,20P were minimal. By 7 weeks post bilateral axotomy, the olfactory epithelium recovered to a condition similar to control sensory epithelium; however, the rate of degeneration and proliferation of receptor neurons in BE preparations appeared to remain in balance, thus blocking further recovery of the olfactory epithelium. At 7 weeks post surgery, odorant responses of AX and BE goldfish to TLCS and 17,20P were still recovering. Accepted: 14 June 1997     

The cercal receptor system of the praying mantid,Archimantis brunneriana Sauss.

Summary The cerci of the praying mantid, Archimantis brunneriana Sauss., are paired segmented sensory organs located at the tip of the abdomen. Basally the cercal segments are slightly flattened dorso-ventrally and are fused to such a degree that it is difficult to distinguish them. Distally the segments become progressively more flattened laterally and their boundaries become more obvious.Two types of sensilla are present on the cerci, trichoid sensilla and filiform sensilla. Trichoid hairs are longest on the medial side of the cerci and toward the cercal base. On the proximal cercal segments they are grouped toward the middle of each segment while they are more uniformly distributed on the distal segments. Filiform sensilla are found at the distal end of each segment except the last and are most abundant on the middle segments of the cercus. Both the number of cercal segments and the number of sensilla are variable. Trichoid hairs are highly variable in appearance from short and stout to long and thin. They arise from a raised base, have a fluted shaft, and some have a pore at the tip. They are innervated by from one to five dendrites, one of which is always considerably larger than the others. Some of the dendrites continue out into the shaft of the hair.Filiform hairs have fluted shafts and are mounted in a flexible membrane within a cuticular ring in a depression. They are innervated by a single large sensory neuron, the dendrite of which passes across a flattened area on the inner wall of the lumen of the hair. The dendritic sheath forms the lining of the ecdysial canal and is therefore firmly attached to the hair. The dendrite is attached to the sheath by desmosomes distally and is penetrated by projections of the sheath more proximally. A fibrous cap surrounds the dendrite and may hold it in place relative to the hair.The cercal receptor system of Archimantis is compared to those of cockroaches and crickets.     

Responses of the antennal bimodal hygroreceptor neurons to innocuous and noxious high temperatures in the carabid beetle,Pterostichus oblongopunctatus

Electrophysiological responses of thermo- and hygroreceptor neurons from antennal dome-shaped sensilla of the carabid beetle Pterostichus oblongopunctatus to different levels of steady temperature ranging from 20 to 35 °C and rapid step-changes in it were measured and analysed at both constant relative and absolute ambient air humidity conditions. It appeared that both hygroreceptor neurons respond to temperature which means that they are bimodal. For the first time in arthropods, the ability of antennal dry and moist neurons to produce high temperature induced spike bursts is documented. Burstiness of the spike trains is temperature dependent and increases with temperature increase. Threshold temperatures at which the two neurons switch from regular spiking to spike bursting are lower compared to that of the cold neuron, differ and approximately coincide with the upper limit of preferred temperatures of the species. We emphasise that, in contrast to various sensory systems studied, the hygroreceptor neurons of P. oblongopunctatus have stable and continuous burst trains, no temporal information is encoded in the timing of the bursts. We hypothesise that temperature dependent spike bursts produced by the antennal thermo- and hygroreceptor neurons may be responsible for detection of noxious high temperatures important in behavioural thermoregulation of carabid beetles.     

The physiology of an olfactory sensillum of the termite Schedorhinotermes lamanianus: carbon dioxide as a modulator of olfactory sensitivity

There are three morphological types of wall-pore single-walled sensilla on the antennae of Schedorhinotermes lamanianus workers. Among these, the sensilla of the type SW1 always bear two neurons that are distinguishable by their impulse amplitudes in electrophysiological recordings. Both neurons are odour-sensitive and respond with excitation to an equally narrow and strikingly congruent spectrum of odours. 1-Pentanol, 1-hexanol and 2-hexanol cause maximum excitation in both cells. In addition one cell responds to CO₂. Short pulses of CO₂ up to 3 s duration inhibit this cell totally. The duration of total inhibition increases with the logarithm of the CO₂-concentration between 0.06% and 100%. Pulses of CO₂ with concentrations above 0.15% cause an inhibition that lasts longer than the period of stimulation. Prolonged CO₂ -stimuli (> 300 s) with a concentration between 0.5% and 5% CO₂ initially cause total inhibition. However, after 1 to 5 min, activity reappears and reaches a new constant but dose-dependent frequency. None of the stimulatory odours leads to a response in the cell when applied together with CO₂. The sensitivity to odours of this one cell type is switched off by CO₂, whilst CO₂ does not influence the other neuron in the same sensillum. The CO₂-concentration, (high in the centres of termite nests, low outside the nests) may give important information about the context in which an individual receives a signal. The described modulation of odoursensitivity by CO₂ allows the presentation of two hypothetical mechanisms of context-dependent signal interpretation.     

Structure and function of antennal lobe neurons in the male turnip moth,Agrotis segetum (Lepidoptera: Noctuidae)

Interneurons with dendritic branches in the antennal lobe of the male turnip moth, Agrotis segetum (Schiff., Lepidoptera: Noctuidae), were investigated with intracellular recording and staining methods. Seventeen projection neurons that transmit information from the antennal lobe to higher centers in the brain displayed dendritic arbors in the male specific macroglomerular complex (MGC) and responded to chemical components of the female sex pheromone used in species-specific sexual communication. Most of the projection neurons responded to several of the pheromone components tested, and a precise correlation between the location of the dendritic arborization and the physiological response could not be demonstrated. One MGC-projection neuron fit the definition of blend specialist. It did not respond to the individual components of the behaviorally active pheromone blend, but showed a strong response to the components when combined in the species-specific blend. Some of the projection neurons also showed clear responses to phenylacetaldehyde, a flower-produced compound and/or to (E)-2-hexenal, a common green-leaf volatile. In eight neurons, the axonal projection could be followed to the calyces of the mushroom body, and subsequently to the inferior lateral protocerebrum.Four local interneurons were characterized both morphologically and physiologically. Each neuron arborized extensively throughout the antennal lobe, and each responded to one or several of the pheromone compounds, and/or to one or both of the plant-produced compounds. One of the local interneurons responded exclusively to the pheromone blend, but not to the individual components.Abbreviations AL antennal lobe - AN antennal nerve - CB cell body - E2H (E)-2-hexenal - IACT inner antennocerebral tract - ILPR inferior lateral protocerebrum - LH lateral horn of the protocerebrum - LN local interneuron - MB mushroom body - MGC macroglomerular complex - OACT outer antennocerebral tract - PAA phenylacetaldehyde - PN projection interneuron - RN receptor neuron - Z5-10:OAc (Z)-5-decenyl acetate - Z5-10:OH (Z)-5-decenol - Z5-12:OAc (Z)-5-dodecenyl acetate - Z7-12:OAc (Z)-7-dodecenyl acetate - Z9-14:OAc (Z)-9-tetradecenyl acetate