Contact Sex Pheromone Research Articles

Contact Sex Pheromones Identified for Two Species of Longhorned Beetles (Coleoptera: Cerambycidae)Tetropium fuscumandT. cinnamopterumin the Subfamily Spondylidinae

Male Tetropium fuscum (F.) and T. cinnamopterum Kirby mated with live and dead (freeze-killed) conspecific females upon antennal contact, but did not respond to dead females after cuticular waxes were removed by hexane rinsing. Significantly fewer males of each species attempted to copulate with live or dead heterospecific females than with conspecifics, indicating that mate recognition was mediated by species-specific contact sex pheromones in the female's cuticular hydrocarbons. GC/MS analysis of T. fuscum elytra identified n-alkanes and mono-methyl branched alkanes of which 11-methylheptacosane and 3- and 5-methyltricosanes were dominant in females. Full male responses, including copulatory behavior, were restored with application of enantiomerically pure synthetic (S)-11-methyl-heptacosane at 40 μg/female (one female equivalent) but not with racemic or (R)-11-methyl-heptacosane. The cuticular hydrocarbons on T. cinnamopterum elytra included 11-methyl-heptacosane as well as n-alkanes, methyl-branched alkanes, mono-alkenes, and (Z, Z)-6, 9-alkadienes. (Z)-9-pentacosene, (Z)-9-heptacosene, and 11-methyl-heptacosane were female dominant, but only (Z)-9-pentacosene elicited precopulatory behaviors in conspecific males at levels similar to those behaviors elicited by unrinsed females, but elicited copulation in fewer than half of males. At female equivalent dosages (10 μg), neither (Z)-9-heptacosene nor (S)-11-methyl- heptacosane elicited responses in males that were significantly different from those responses to a rinsed female but when applied together, the proportion of males responding was significantly increased. 11-methyl-heptacosene is thus a contact pheromone component common to both species, which may explain the heterospecific mating attempts by some males.

Cuticular hydrocarbons as contact sex pheromone in the parasitoid Dibrachys cavus

Cuticular hydrocarbons (CHCs) cover the cuticle of virtually any insect and do not only protect them from desiccation, but also possess various communicative functions. Previous studies suggested a function as contact sex pheromones in the parasitic wasp family Pteromalidae, but further species need to be studied before more general conclusions are possible. Here, we demonstrate a contact sex pheromone in females of Dibrachys cavus (Walker) (Hymenoptera: Pteromalidae). Males of this parasitoid were arrested on cadavers of 1- to 2-day-old females, but neither on newly emerged females nor on males. Extracts from 1- to 2-day-old females and non-polar fractions were also behaviorally active suggesting a non-polar contact sex pheromone. Chemical analyses of bioactive and non-active CHC profiles by gas chromatography–mass spectrometry and subsequent principal component analysis (PCA) revealed that the bioactive profiles from 1- to 2-day-old females were clearly distinguishable from all other profiles. Among the chemicals showing the strongest impact in the PCA were the two 3-methylalkanes 3-methylnonacosane and 3-methylhentriacontane, which were absent or trace components in the inactive profiles and whose relative amounts increased in females when they became sexually attractive. The putative function of 3-methylalkanes as key components of the contact sex pheromones in Pteromalidae is discussed.

Simultaneously hermaphroditic shrimp use lipophilic cuticular hydrocarbons as contact sex pheromones.

Successful mating is essentially a consequence of making the right choices at the correct time. Animals use specific strategies to gain information about a potential mate, which is then applied to decision-making processes. Amongst the many informative signals, odor cues such as sex pheromones play important ecological roles in coordinating mating behavior, enabling mate and kin recognition, qualifying mate choice, and preventing gene exchange among individuals from different populations and species. Despite overwhelming behavioral evidence, the chemical identity of most cues used in aquatic organisms remains unknown and their impact and omnipresence have not been fully recognized. In many crustaceans, including lobsters and shrimps, reproduction happens through a cascade of events ranging from initial attraction to formation of a mating pair eventually leading to mating. We examined the hypothesis that contact pheromones on the female body surface of the hermaphroditic shrimp Lysmata boggessi are of lipophilic nature, and resemble insect cuticular hydrocarbon contact cues. Via chemical analyses and behavioural assays, we show that newly molted euhermaphrodite-phase shrimp contain a bouquet of odor compounds. Of these, (Z)-9-octadecenamide is the key odor with hexadecanamide and methyl linoleate enhancing the bioactivity of the pheromone blend. Our results show that in aquatic systems lipophilic, cuticular hydrocarbon contact sex pheromones exist; this raises questions on how hydrocarbon contact signals evolved and how widespread these are in the marine environment.

Mating behavior and contact pheromones of Batocera horsfieldi (Hope) (Coleoptera: Cerambycidae)

AbstractThe mating behavior of Batocera horsfieldi (Hope) was observed in the laboratory. The results showed that copulation of this longhorned beetle consisted of three phases: (i) encountering and pair‐bonding; (ii) mating attempt and ejaculation; and (iii) post‐copulatory guarding. Frozen females, with cuticular hydrocarbons stripped by hexane extraction, showed no attraction for males. Reapplying the solvent extract of frozen females to both washed dead males and females caused mating attempts by males, confirming that cuticular hydrocarbons (contact sex pheromones) played an important role in recognition of females by male B. horsfieldi.

Mating Sequence and Evidence for the Existence of a Female Contact Sex Pheromone in Brontispa longissima (Coleoptera: Chrysomelidae)

To clarify the presence of a pheromone in Brontispa longissima (Coleoptera: Chrysomelidae), we observed its mating behavior and conducted a series of bioassays. When male and female B. longissima came in contact, the male was observed to hold and mount the female, extend its penis toward her abdominal tip, and copulate. The male was observed to hold the female only after he had touched her with his antennae and/or forelegs. Males showed similar mating attempts toward females killed by freezing. On the other hand, no males showed mating attempts toward females washed with hexane, but they did toward females washed with hexane and re-treated with hexane extract of the female body or female elytra. Furthermore, males showed similar mating attempts toward a glass dummy treated with a solvent extract of female elytra. These results indicate the presence of a female sex pheromone that is perceptible by direct contact and plays an important role in mating in B. longissima. When the crude extract of female elytra was subjected to silica gel chromatography, only the fraction eluted with hexane elicited mating behavior in males. Furthermore, when the active fraction was chromatographed on AgNO3-impregnated silica gel, only the fraction eluted with hexane elicited mating behavior in males. The contact sex pheromone of B. longissima is therefore believed to consist of one or more less-polar compounds, probably saturated hydrocarbons.

Contact Sex Pheromone Components of the Seed Beetle, Callosobruchus analis (F.)

Callosobruchus analis (Coleoptera: Chrysomelidae: Bruchinae), found throughout tropical Asia and Africa, is a pest of stored legumes. Previous work has shown that females of this species produce a contact sex pheromone that elicits copulatory behavior in males. Comparisons of copulatory activity between any two of four congeneric species suggest that the contact sex pheromones are species specific. In laboratory bioassays, male C. analis exhibited copulatory behavior to a female dummy to which a crude extract of virgin females was applied. The extract had been collected by a filter paper method and was purified by acid-base partition and chromatographic techniques. Gas chromatography-mass spectrometry (GC-MS) analyses of active fractions revealed that the active compounds were 2,6-dimethyloctane-1,8-dioic acid (1) and callosobruchusic acid, (E)-3,7-dimethyl-2-octene-1,8-dioic acid (2), previously identified as contact sex pheromones of Callosobruchus maculatus (F.) and C. chinensis (L.), respectively. The stereoisomeric and chemical compositions were determined by the 2D-HPLC-Ohrui-Akasaka method as (2S,6R)-1:(S)-2=1.8:1, which meant that both compounds in C. analis were stereochemically pure, unlike the case of C. maculatus and C. chinensis. An examination of the influence of synthetic pheromone compounds on male copulatory activity revealed that (2S,6R)-1 is the main component, and that (S)-2 has an additive effect. In the examination of the stereochemistry-activity relationship, no copulatory behavior was elicited by (2R,6S)-1, and, furthermore, the enantiomer significantly masked the pheromonal activity of (2S,6R)-1. Glass rod dummy assays also suggested the presence of synergists. These results could elucidate the specificity of mate recognition in C. analis.

Chemical Communication in Schizocosa malitiosa: Evidence of a Female Contact Sex Pheromone and Persistence in the Field

Mate finding in many spider species is mediated, at least in part, by chemical cues. Although few have been characterized, most spider sex pheromones seem to be associated with the silk threads of adult females, attracting and/or triggering sexual behaviors in males. Schizocosa malitiosa (Araneae: Lycosidae) is a wolf spider common in dry environments in Southern Uruguay. Here, we report evidence for the occurrence of a female sex pheromone in the silk of virgin S. malitiosa females. The pheromone elicits typical courtship displays by conspecific males (palpal drumming and leg shaking), when it is applied to an artificial substrate. We also showed that this pheromone is quickly inactivated under field conditions, possibly due to the effect of dew, and that it is readily extracted from the silk by water, which renders the silk threads inactive. Preliminary chemical analyses by mass spectrometry suggest that the pheromone is a low molecular weight, highly oxygenated polar compound, present in a high concentration only in older virgin females. Quick inactivation in the field of the pheromone would allow males to discriminate between recent and old cues, thus facilitating mate searching and sexual meeting, by preventing males from following old cues for wandering females that could be distant in space and/or time.

Variation in mate recognition specificities among fourCallosobruchusseed beetles

AbstractDifferentiation of mate recognition systems is one of the important steps for speciation in animals. For some insects, a contact sex pheromone present on the cuticular surface is indispensable in discriminating reproductive partners. InCallosobruchusspecies (Coleoptera: Chrysomelidae: Bruchinae), contact sex pheromones have been found in two species,Callosobruchus chinensis(L.) andCallosobruchus maculatus(Fabricius). It was suggested, however, that these two species lacked the ability to discriminate their conspecific and/or heterosexual partners. To elucidate this inconsistency, we verified the existence of contact sex pheromones from two other species,Callosobruchus rhodesianus(Pic) andCallosobruchus analis(Fabricius). As a result, unlikeC. chinensisandC. maculatus, the males ofC. rhodesianusandC. analiswere able to discriminate their heterosexual partners. Comparing cross‐copulation behavior, i.e., copulation behavior between two species, against these four species indicated that the mate recognition specificities were quite different. Males ofC. rhodesianusandC. analishad highly species‐specific mating behavior, whereas males ofC. chinensisandC. maculatuswere much less specific. These results indicate that variation in mate recognition can arise even among congeneric species living in a sympatric environment, and this variation might have arisen during species differentiation. Based on our results in combination with previous reports on interspecific competition, we suggest that the observed asymmetric cross‐copulation behavior might be, at least partially, an adaptation for surviving interspecific competition.

Mate Recognition and Sex Differences in Cuticular Hydrocarbons of the Diurnal Firefly Ellychnia corrusca (Coleoptera: Lampyridae)

Abstract There are several genera of diurnally active fireflies (Coleoptera: Lampyridae), and these adults generally do not produce bioluminescent signals. We investigated whether contact sex pheromones play a role in mate recognition in the diurnal firefly Ellychnia corrusca (L.). In laboratory behavioral assays, after antennal contact >70% of males attempted copulation with freeze-killed females, whereas no copulation attempts occurred when freeze-killed females had been washed with hexane. This shows that E. corrusca mate recognition relies on contact chemoreception and suggests that male mating responses are mediated by contact sex pheromones on the female cuticle. Using direct contact solid phase microextraction (SPME) and solvent extraction, we sampled cuticular hydrocarbons (CHCs) from both sexes of E. corrusca adults. Gas chromatography-mass spectrometry showed that SPME was more effective than solvent extraction in detecting CHCs (a two-fold increase in the number of compounds detected). Although E. corrusca males and females showed similar CHCs profiles, we documented several quantitative and qualitative differences between the sexes that may play a role in mate recognition. This report provides the first behavioral evidence for the existence of contact sex pheromones in any diurnal firefly.

Monoalkenes as Contact Sex Pheromone Components of the Woodwasp Sirex noctilio

A pheromone on the cuticle of females of the woodwasp Sirex noctilio, a recently introduced pest of pines in North America, induces conspecific males to attempt copulation. Dead females washed with hexane did not elicit copulation attempts from males, whereas reapplication of a female hexane body wash onto the cuticle of dead females elicited copulation attempts by 65% of males tested. Analysis of the hexane extract revealed saturated and unsaturated hydrocarbons as major components of the female cuticle. Behavior-guided fractionation of the female body wash led to the identification of three components, (Z)-7-heptacosene, (Z)-7-nonacosene, and (Z)-9-nonacosene, of the sex pheromone of S. noctilio that elicited copulatory responses from males.

Surface glycoproteins are not the contact pheromones in the Lysmata shrimp

Behavioral evidence suggests that some male caridean shrimp, such as those of Lysmata species, identify conspecific females via contact pheromones that coat the cuticle surface of the females. In this study, we attempted to determine whether the contact pheromones in three Lysmata species, Lysmata ankeri, Lysmata boggessi, and Lysmata wurdemanni, are glycoproteins as hypothesized previously in a diverse group of aquatic invertebrates. Twenty lectins were screened and lectin-binding experiments indicated that lectin treatment did not affect mate recognition in the shrimps. The behavior of the male-phase (MP) shrimp in the three treatments (non-lectin-treated MP and lectin-treated euhermaphrodite-phase (EP) shrimp, lectin-treated MP and lectin-treated EP shrimp, and lectin-treated MP and non-lectin-treated EP shrimp) and in the control was not different in responding to lectin-treated and control EP shrimp. All the MP shrimp copulated with lectin-treated and control EP shrimp successfully. All the MP shrimp copulated with ethylenediamine tetraacetate-treated EP shrimp (with glycoproteins removed from their cuticle surface) immediately after they detected the EP shrimp. The results suggest that glycoproteins are not likely to be the contact sex pheromones in the three Lysmata shrimp species.

Jail baits: how and why nymphs mimic adult females of the German cockroach, Blattella germanica

The male German cockroach performs a characteristic courtship behaviour upon contacting a sexually receptive female: he turns away from the female and raises his wings, thereby exposing tergal glands whose reservoirs contain phagostimulatory substances. The female then mounts the male and feeds upon these nuptial secretions; this behaviour places her in the appropriate precopulatory position. The contact sex pheromone on the cuticular surface of the female, responsible for eliciting courtship behaviour in males, consists of a blend of six components that share a common biosynthetic pathway. An excised female antenna can elicit the full courtship display in males. We found that antennae taken from either male or female nymphs of various ages also could elicit the full courtship response in adult males. We extracted lipids from the cuticular surface of nymphs and, guided by behavioural assays, we fractionated the extracts using various chromatography procedures, including flash (column) chromatography, high-performance liquid chromatography and gas chromatography. Mass spectrometry analysis of behaviourally active fractions revealed two classes of courtship-eliciting compounds: all nymphs possessed a novel, still unidentified compound that elicited courtship in adult males. In addition, in last-instar females, we isolated four of the six adult female-specific contact sex pheromone components, consistent with differentiation of the sexes at this stage, and the onset of sexual maturation of the pheromone biosynthetic machinery. Our results support the interpretation that nymphs engage in sexual mimicry to gain access to male-produced nuptial tergal secretions that are exposed and can be secured only during courtship.

Identification of an Important Component of the Contact Sex Pheromone ofCallidiellum rufipenne(Coleoptera: Cerambycidae)

Adult male and female Callidiellum rufipenne (Motschulsky) (Coleoptera: Cerambycidae) aggregate on severely stressed or fallen trees and cut logs of cypress species (Cupressaceae) that are the hosts of their larvae. Our studies showed that male C. rufipenne actively search for females on these trees and only respond to females after contacting them with their antennae. Removing cuticular hydrocarbons from fresh carcasses of females with solvent rendered the carcasses unattractive to males, but activity was restored when the solvent extract was reapplied. These findings suggest that contact pheromones mediate mate recognition in this species. Bioassays of fractions of the extracts determined that the branched chain hydrocarbon fraction was primarily responsible for activity. 5,17-Dimethylnonacosane was a key sex-specific component in extracts of females, and synthetic 5,17-dimethylnonacosane elicited a strong mating response from males. We conclude that this compound is an important component of the contact sex pheromone of C. rufipenne if not the sole component. Solvent extracts of both sexes also contained 9-pentacosyne and 9-heptacosyne. To our knowledge, this is only the second report of alkynes in the cuticular lipids of insects.

Studies on contact sex pheromones of the caridean shrimp Palaemonetes pugio: I. Cuticular hydrocarbons associated with mate recognition

In the grass shrimp Palaemonetes pugio, evidence suggests that males respond to an insoluble substance (i.e., contact sex pheromone) in or on the exoskeleton of the postmolt parturial female. Cuticular hydrocarbons, glycoproteins, or other compounds present on the surface of the female might serve as recognition signals. Cuticular hydrocarbons are known to function as contact sex pheromones in many insect species. The purpose of this study was to test the hypothesis that the exoskeleton of postmolt parturial females contains cuticular compounds that might function as contact sex pheromones. Gas chromatography-mass spectrometry (GC-MS) analyses of chloroform—methanol extracts of the cuticle of postmolt parturial (sexually receptive) females (PPFs), postmolt nonparturial females (NPFs), postmolt males (PMMs), and intermolt females (IMFs) showed at least 55 compounds, 3 of which were unique to postmolt parturial females. Extracts of PPFs, NPFs, PMMs, and IMFs were characterized by 49, 50, 34, and 19 compounds, respectively, of which 22 could be identified. Twelve cuticular hydrocarbons and five fatty acids were found in the cuticular extractions of P. pugio. Multivariate analysis of GC-MS profiles demonstrated that the cuticular composition of postmolt parturial females differed significantly from that of nonparturial females, males, and intermolt females. A bioassay to test male response to cuticular extracts gave inconclusive results. Although GC-MS enabled identification and partial quantification of some cuticular compounds, it is still undetermined which, if any, compounds function in mate recognition in P. pugio.

Studies on contact sex pheromones of the caridean shrimp Palaemonetes pugio: II. The role of glucosamine in mate recognition

The role of surface glycoproteins in mate recognition of the shrimp Palaemonetes pugio was studied using mating bioassays and fluorescence microscopy. Our data indicate that a glycoprotein associated with female shrimp functions in mate recognition in P. pugio. This glycoprotein is likely to be a glucosamine or an N-acetylglucosamine-containing glycoprotein complemented by a lectinlike receptor on males. Significantly fewer copulations occurred in seawater augmented with glucosamine as compared to seawater augmented with glucose. Thus, it is likely that glucosamine competitively inhibits mate recognition by binding male receptors and significantly reducing recognition of parturial females. The antennal lagellum of decapod crustaceans has long been considered to be chemotactile with bimodal, touch/taste receptors. The fluorescent dye, Lucifer Yellow, is incorporated into antennal setae from the surrounding seawater. Furthermore, the fluorescent dye, DiI, stained neural tissues at the base of the antennal setae. Taken together, these results are consistent with a bimodal, sensory function. When fluo-treated male antennal setae were exposed to the carapace of postmolt, parturial females, an immediate and significant increase in fluorescence intensity was observed, suggesting that Ca2+ likely acts as a second messenger for the receptor system. Fluo-labeled antennal setae of both males and females showed larger increases in intracellular Ca2+ levels when exposed to glucosamine as compared to glucose. The effects produced by glucosamine were sexually dimorphic, with male setae displaying a significantly greater mean overall change in fluorescence intensity than female setae. The dimorphic response observed suggests that glucosamine or a related compound serves as a female signal (i.e., contact sex pheromone) in mate recognition.

Chemical communication in mate location and recognition in the white-spotted longicorn beetle, Anoplophora malasiaca (Coleoptera: Cerambycidae)

The mating sequence has been studied in the white-spotted longicorn beetle, Anoplophora malasiaca (Thomson) (Coleoptera: Cerambycidae). Both females and males are attracted to wounded host plant Citrus unshiu, and adults of both sexes, and both female and male elytra contained the sesquiterpenes that were identical with those in C. unshiu. Moreover, at close range orientation by males, some visual cues derived from females acted synergistically with olfactory factors. And, female contact sex pheromone was isolated from female elytra and revealed to consist of eight hydrocarbons, four ketones, and three lactones. The mating sequence of A. malasiaca was roughly considered to occur as follows. Emerged adults from trunks of the host plants must search for their mates over large areas. Highly mobile males may be attracted from long distances by the signal of sesquiterpenes released from wounded host plants which indicate the presence of other individuals and serve for intraspecific communication in A. malasiaca. At close range orientation, the sesquiterpenes also act as attractant for both females and males, and then visual cue guided them to their mates or rivals. After a male orients to another individual, he identifies it as a mate or a rival. Once a male recognizes a female, mating occurs.

7‐methylheptacosane is a major component of the contact sex pheromone of the cerambycid beetle Neoclytus acuminatus acuminatus

Abstract Male Neoclytus acuminatus acuminatus (F.) (Coleoptera: Cerambycidae) attempt to mate with females only after touching them with their antennae, suggesting that mate recognition is mediated by contact pheromones in the cuticular wax layer of females. Consistent with that hypothesis, males exhibit similar responses to dead females in laboratory bioassays, but not to solvent‐washed dead females with their cuticular hydrocarbons removed. The mating response of males is restored when solvent extracts are reapplied to carcasses of solvent‐washed females, indicating that the contact pheromone is present in solvent extracts. Solvent extracts of the female cuticle contain six methylalkanes that are not present in extracts of males, three of which (7Me‐C25, 7Me‐C27 and 9Me‐C27) constitute almost 40% of the total hydrocarbons. The bioactivity of these three compounds is tested by applying synthetic standards to solvent‐washed carcasses of females and presenting them to males. Standards are tested singly, pairwise and as the complete blend; freeze‐killed females serve as controls. Males attempt to couple with solvent‐washed female carcasses treated with 7Me‐C27 alone and in combination with 9Me‐C27 but only the complete blend elicits the same number of mounting and coupling attempts as does the control. These findings suggest that 7Me‐C27 (7‐methylheptacosane) is the major component of the contact sex pheromone of N. a. acuminatus and that 7Me‐C25 and 9Me‐C27 act as synergists.

Synthesis of all the six components of the female-produced contact sex pheromone of the German cockroach, Blattella germanica (L.)

All of the following six components of the female sex pheromone of the German cockroach, Blattella germanica (L.) were synthesized: (3 S,11 S)-3,11-dimethyl-2-nonacosanone ( 1), its 29-hydroxy derivative 2, its 29-oxo derivative 3, (3 S,11 S)-3,11-dimethyl-2-heptacosanone ( 4), its 27-hydroxy derivative 5, and its 27-oxo derivative 6. Both the enantiomers of citronellal were employed as the chiral sources and Wacker oxidation was employed for the introduction of the carbonyl group at C-2.

New Contact Sex Pheromone Components of the German Cockroach, Blattella germanica, Predicted from the Proposed Biosynthetic Pathway

Upon contacting the cuticle of a sexually mature female, a male German cockroach exhibits a characteristic courtship behavior: he turns away from the female and raises his wings, thereby exposing tergal glands. The glandular secretion stimulates the female to mount the male and feed, thus positioning her appropriately for copulation. A multi-component contact sex pheromone produced by females is responsible for eliciting courtship behavior. The most abundant pheromone components are 3,11-dimethylnonacosan-2-one and 3,11-dimethylheptacosan-2-one, oxidation products of the abundant hydrocarbon analogs 3,11-dimethylnonacosane and 3,11-dimethylheptacosane, respectively. The C(29)-dimethyl ketone is thought to be further metabolized to two less abundant pheromone components, 29-hydroxy-3,11-dimethylnonacosan-2-one and 29-oxo-3,11-dimethylnonacosan-2-one. Based on this proposed biosynthetic pathway of pheromone production, we hypothesized that 3,11-dimethylheptacosan-2-one also would be oxidized to give two candidate pheromone components, 27-hydroxy-3,11-dimethylheptacosan-2-one, and 27-oxo-3,11-dimethylheptacosan-2-one. By using bioassay-guided fractionation and chemical analyses of cuticular extracts of virgin females and synthesis of the (3S,11S)-isomer of each of the two predicted pheromone components, we showed that the epicuticle of the German cockroach does indeed contain these two compounds. The contact sex pheromone of the female German cockroach, thus may consist of at least six biosynthetically related components.

Identification of cuticular lipids eliciting interspecific courtship in the German cockroach, Blattella germanica

The cuticular surface of sexually mature females of the German cockroach contains a sex pheromone that, upon contact with the male's antennae, elicits a characteristic species-specific courtship behavior. This female-specific pheromone is a blend of several long-chain methyl ketones, alcohols and aldehydes, all derived from prominent cuticular hydrocarbons found in all life stages of this cockroach. We found that contact with the antennae of 5 out of 20 assayed cockroach species elicited courtship behavior in German cockroach males. The heterospecific courtship-eliciting compounds were isolated by behaviorally guided fractionation of the active crude extracts and compared to the native sex pheromone components. We identified two active compounds from the cuticular extract of the Oriental cockroach, Blatta orientalis -- 11-methylheptacosan-2-one and 27-oxo-11-methylheptacosan-2-one; the former compound was confirmed by synthesis and proved to independently stimulate courtship in German cockroach males. These compounds share common features with, but are distinct from, any of the known contact sex pheromone components. This suggests that sex pheromone reception in the male German cockroach is unusually promiscuous, accepting a wide range of compounds that share certain features with its native pheromone, thus resulting in a broad spectrum of behavioral response to other species. We propose that several characteristics of their mating system -- chiefly, absence of closely related species in the anthropogenic environment, resulting in relaxation of selection on sexual communication, and a highly male-biased operational sex ratio -- have driven males to respond with extremely low thresholds to a wide spectrum of related compounds.