Behavioral and electrophysiological evidence for volatile sex pheromones in Parcoblatta wood cockroaches

Species within the cockroach genus Parcoblatta are sexually dimorphic for wing length; females have reduced wings and are flightless, while males have long wings that are used in flight. We predicted that Parcoblatta females would release a volatile sex pheromone to attract the more mobile males. Nymphs of the broad wood cockroach, P. lata, and the Caudell's wood cockroach, P. caudelli, were collected in forested areas in North Carolina, USA, and reared in the laboratory for observations of sexual behavior and for pheromone analysis. After several days of sexual maturation, virgin females of both species exhibited distinct calling behaviors. In females of P. lata, calling commenced 6 days after adult emergence. Under a light–dark photoperiod regime, calling behavior in both species was restricted to the scotophase. Calling consisted of a repeated pattern of raising and lowering the abdomen with occasional exposure of the genital vestibulum. To test whether calling behavior is associated with the release of pheromone, volatiles from calling and noncalling females were collected on Super-Q and tested by electroantennogram (EAG) and behavioral assays. Volatile collections from calling females elicited higher male-specific EAG responses than collections from noncalling females of the same physiological stage. In an olfactometer choice test (Y-tube), males preferred volatiles from calling females over those from noncalling females. To determine the anatomical source of the pheromone, solvent extracts of various body parts were analyzed by EAG. The first through seventh tergites were the only body parts that elicited male-specific EAG responses in both species. In P. lata, the activity of the extract increased from 1- to 7-day-old females, but was lower in mated than in virgin females of the same age. The putative pheromone gland appears to consist of numerous class-3 secretory units, each composed of a secretory cell connected to a cuticular pore via a tubular duct. We conclude that female P. lata and P. caudelli produce sex-specific volatile pheromones that are emitted during calling behavior.     

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

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

Sesamia calamistis calling behavior and its role in host finding of egg parasitoids Telenomus busseolae,telenomus isis,and Lathromeris ovicida

In the Republic of Benin, the African pink stem borer Sesamia calamistis Hampson is kept under control by the two scelionid egg parasitoids Telenomus busseolae (Gahan) and T. isis (Polaszek). A third species, the trichogrammatid Lathromeris ovicida Risbec, although commonly obtained from egg batches, is of low importance. High egg and egg batch parasitism by Telenomus spp. at low host densities suggests excellent host-finding capacity. Previously it was hypothesized that pheromones produced by calling S. calamistis virgins play an important role in attracting the parasitoids to the area where oviposition is likely to occur. Thus, after determining the effect of age (1–4 days) on the calling rhythm of S. calamistis, 1-day-old virgin females were chosen to investigate the response of the parasitoids to calling and noncalling females and two empty controls, in a four-arm olfactometer. The results showed that calling started earliest and lasted longest with 1-day-old females, but was similar for 2- to 4-days-old females. The percentage of females calling was higher in early than latter scotophases. The highest percentage of active females was obtained between 8 and 9 hr after the beginning of the first scotophase. All three parasitoid species responded to calling females, while there were no differences between noncalling females and the empty controls. The response pattern was similar for the two Telenomus spp. but considerably weaker for L. ovicida, reflecting differing host specificity of the three parasitoid species.     

Parthenogenesis,calling behavior,and insect-released volatiles of leafminer moth Phyllonorycter emberizaepenella

We proved that the leafminer moth Phyllonorycter emberizaepenella (Lepidoptera: Gracillariidae) reproduces by parthenogenesis of the thelytoky type. Despite a complete absence of males, parthenogenetically reproducing females diurnally demonstrated the calling posture normally used for releasing signaling compounds. Two compounds, which we collected from a calling female, were identified as potential sex pheromone components: (8E,10E)-8,10-tetradecadienyl acetate and (8E,10E)-8,10-tetradecadienol, the latter occurring only in trace amounts. In field experiments, no males were attracted to traps baited with either the potential sex pheromone or with virgin females. Both the pattern of behavior and the chemical characteristics of the pheromone of Ph. emberizaepenella species were similar to those known for Lepidoptera with the usual amphimictic mode of reproduction. Theoretical speculations that in thelytoky, where there is no need to find a sexual partner, the individuals would obtain certain advantages due to reduction in their sexual behavior, were, thus, not confirmed for Ph. emberizaepenella.     

Phloeophagous and predaceous insects responding to synthetic pheromones of bark beetles inhabiting white spruce stands in the Great Lakes region

Tree killing and saprophytic bark beetles exert important ecological and economic roles in North American spruce forests. Chemical signaling among bark beetles, and responses by associate insects such as predators and competitors, have significant effects on the population dynamics and ecology of this community. Synthetic pheromones of primary (tree killing) and secondary (saprophytic) bark beetle species and blank controls were tested using multiple funnel and lower stem flight traps in white spruce forests in Wisconsin, Michigan, and Minnesota. Six phloeophagous and four predaceous species were collected with significant attraction by the bark beetles Dryocoetes affaber, Dryocoetes autographus, and Polygraphus rufipennis, and the predatory checkered beetles (Coleoptera: Cleridae) Thanasimus dubius and Enoclerus nigrifrons. In general, trap catches to synthetic lures resembled the species composition obtained by felling trees and collecting emerging beetles in a companion study, although several species showed differing trends. Some cross attraction occurred among bark beetles and between bark beetles and predatory beetles. For example, P. rufipennis was abundant in traps baited with Dryocoetes spp. pheromones. Thanasimus dubius and E. nigrifrons were collected in significant numbers in traps baited with the pheromone of the spruce beetle (Dendroctonus rufipennis), frontalin plus -pinene. This is a new observation for E. nigrifrons. Attraction of T. dubius to the pheromones of at least three bark beetle species in the Great Lakes region, as well as to several southern and western species, reflects its role as a habitat specialist and feeding generalist. Several other important predators and competitors commonly obtained in pine forests in this region were not obtained in these spruce stands, either in response to synthetic pheromones of spruce colonizing beetles, or in host material colonized by these beetles. Potential differences in predator prey dynamics between spruce and pine ecosystems in the Great Lakes region are discussed.     

Tandem calling pheromone in the genusLeptothorax (Hymenoptera: Formicidae): Behavioral analysis of specificity

Ants of the genusLeptothorax recruit to new nest sites and newly discovered food sources by tandem running. This involves one ant directly leading a nestmate to the target area. Pheromones from the poison gland have proved the most important signal employed during this recruitment behavior. Comparative behavioral analysis with 11 species ofLeptothorax demonstrated a subgenus specificity of the tandem calling pheromone between the subgeneraLeptothorax andMychothorax.     

Influence of cnicin,a sesquiterpene lactone ofCentaurea maculosa (Asteraceae), on specialist and generalist insect herbivores

The sesquiterpene lactone cnicin was extracted fromCentaurea maculosa andCentaurea vallesiaca. We examined its effects on the ovipositional response and larval development of generalist and specialist insect herbivores associated withC. maculosa. For the oviposition trials, three plant species (C. maculosa, Achillea millefolium, andCichorium intybus), half of which were sprayed with 3% of cnicin, were exposed to the specialist mothsStenodes straminea, Agapeta zoegana, andPterolonche inspersa in field cages. All three species significantly preferredC. maculosa to other plants andP. inspersa significantly preferred cnicin-sprayed plants to untreated plants for oviposition. Tested over all species, cnicin significantly increased the number of eggs laid on a given plant. A larval diet test examined the toxicity of cnicin for larvae of the generalist noctuid mothSpodoptera littoralis. Cnicin concentrations of 3% and 6% were lethal and 1% and 0.5% seriously inhibited growth and development. The larvae of theC. maculosa specialistStenodes straminea survived at 6% cnicin, but none of the pupae hatched.Agapeta zoegana was able to survive at 1% and 3% cnicin. Both specialists had difficulties with the artificial diet, but weight increase and survival was not further reduced when cnicin was present compared with on the control diet. In conclusion, cnicin influenced host recognition by the specialist species, and larvae of the generalist did not survive on natural levels of cnicin. Growth and survival of the specialist were not influenced by cnicin but were considerably hampered on artificial diet.     

Trail-following pheromones of the rhinotermitidae: Approaches to their authentication and specificity

A method for determining the authenticity of subterranean termite trail pheromones is suggested and utilized to verify the presence of trail pheromones inReticulitermes virginicus, R. flavipes, andR. tibialis. In addition, a possible trail pheromone has been demonstrated forCoptotermes formosanus. A choice bioassay method shows that the above trail pheromones are species specific.     

Lipid components in anal scent sacs of three mongoose species (Helogale parvula,Crossarchus obscurus,Suricata suricatta)

Anal sac secretions of three social mongoose species (Helogale parvula, Crossarchus obscurus, andSuricata suricatta) were chemically analyzed by means of gas chromatography-mass spectrometry. Compounds with high molecular weights (greater than 250) were found to distinguish the three species. Differences in composition suggest a possible species-specific role in scent marking. MaleH. parvula had vitamin E present in the anal sac, whereas it was absent in the females. This suggests a possible sex-specific function of vitamin E inH. parvula. No differences in chemical composition were found between male and femaleS. suricatta. Ten compounds were found in femaleC. obscurus that were not present in the male.     

A Male Sex Pheromone in a Scorpionfly

It has been postulated that males of a number of scorpionfly species produce sex pheromones. This is based on the observation that females often respond only to conspecific males when they evert their genital pouch, the proposed site of pheromone release. In this study, we prove that in Panorpa germanica (Mecoptera, Panorpidae), the eversion of a male’s genital pouch is associated with the release of a volatile sex pheromone. In dual choice situations, females showed a high preference for ‘calling’ (males with everted genital pouch) over noncalling individuals. Volatiles emitted by males and females were collected and identified by coupled gas chromatography–mass spectrometry. Two aldehydes [(2E,6Z)-nona-2,6-dienal and (E)-non-2-enal] were characteristic of calling males but not of noncalling or immature males or females. Bioassays with synthetic compounds confirmed that the identified substances are attractive to females. To the best of our knowledge, this is the first identification of a sex pheromone in scorpionflies.     

Influence of opposite sex on attraction produced by pioneer sex of four bark beetle species cohabiting pine in the Southern United States

Catches ofDendroctonus frontalis andIps avulsus on traps surrounding bolts infested with both sexes of each species in the gallery were not significantly different from catches at bolts infested only with the sex which normally pioneers the host colonization process. In contrast, the presence of the second sex in the gallery significantly reduced catches ofI. grandicollis andI. calligraphus and, additionally, the presence of females in the male galleries ofI. calligraphus significantly reduced the catch ofI. avulsus females as compared with their response to bolts infested with the maleI. calligraphus only.     

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

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

Fungal endophyte-infected grasses: Alkaloid accumulation and aphid response

The occurrence of the alkaloidsN-formyl andN-acetyl loline, peramine, lolitrem B, and ergovaline and the response of aphids to plants containing these compounds were determined in species and cultivars ofFestuca,Lolium, and other grass genera infected with fungal endophytes (Acremonium spp., andEpichloe typhina). Twenty-nine of 34 host-fungus associations produced one or more of the alkaloids, most frequently peramine or ergovaline. Three alkaloids (lolines, peramine, and ergovaline) were found in tall fescue and in perennial ryegrass infected withA. coenophialum, while peramine, lolitrem B, and ergovaline were present in perennial ryegrass and in tall fescue infected withA. lolii and inF. longifolia infected withE. typhina. WhileA. coenophialum andA. lolii produced similar patterns of alkaloids regardless of the species or cultivar of grass they infected, isolates ofE. typhina produced either no alkaloids or only one or two different alkaloids in the grasses tested. Aphid bioassays indicated thatRhopalosiphum padi andSchizaphis graminum did not survive on grasses containing loline alkaloids and thatS. graminum did not survive on peramine-containing grasses. Ergovaline-containing grasses did not affect either aphid.     

Sequestration of pyrrolizidine alkaloids in several arctiid moths (Lepidoptera: Arctiidae)

Sequestration of dietary pyrrolizidine alkaloids (PA) by larvae and adults of six European arctiid moth species (Spilosoma lubricipeda, Arctia caja, Phragmatobia fuliginosa, Callimorpha dominula, Diacrisia sannio, andTyria jacobaeae) was investigated for comparison with the well-studied Asian arctiidCreatonotos transiens. Larvae of all species metabolized free PA bases into the respectiveN-oxides. Only adults ofA. caja, P. fuliginosa, andS. lubricipeda, but not their larvae, converted dietary 7(S)-heliotrine to 7(R)-heliotrine, a direct precursor of a male pheromone in some arctiids, 7(R)-hydroxydanaidal. The larval integument figures as the main storage site for resorbed alkaloids; only minor amounts were found in other tissues. In addition, a significant amount of alkaloid is deposited in the cocoon ofArctia caja; only traces of alkaloids could be found in the meconium and the exuviae of this species. A substantial part of the alkaloids fed was degraded to unknown, nonalkaloidal products.     

Ant repellent effect of the sternal gland secretion ofPolistes dominulus (Christ) andP. sulcifer (Zimmermann). (Hymenoptera: Vespidae)

The long-chain carboxylic acids identified in the sternal gland secretion ofPolistes dominulus andP. sulcifer females were tested individually on three species of ants,Crematogaster scutellaris, Formica cunicularia, andLasius sp., in order to verify if they have a repellent effect. The unsaturated acids (palmitoleic, linoleic, and oleic) act as repellents of all three ant species, while the saturated acids (lauric, myristic, palmitic, and stearic) have no effect. The mixture reproducing the secretion of the sternal glands ofP. dominulus maintained its repellency for at least four days.     

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

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

Cross-attraction between two species ofMatsucoccus

In laboratory bioassays, males ofMatsucoccus resinosae fromPinus resinosa in New York andMatsucoccus n. sp. fromPinus thunbergiana in Korea were strongly attracted to crude hexane extracts ofM. resinosae females, andM. resinosae males responded strongly to extracts ofMatsucoccus n. sp. females. Males of the two species responded similarly to gas chromatographic fractions and subfractions of a pentane extract ofM. resinosae females. Sex pheromones of these two species appear to be the same or very similar.Homoptera: Coccoidea: Margarodidae.     

Ancestral semiochemical attraction persists for adjoining populations of siblingIps bark beetles (Coleoptera: Scolytidae)

Three species ofIps pine bark beetles in Hopping's group IX (S.L. Wood'sgrandicollis group),Ips confusus, I. lecontei, andI. paraconfusus, are parapatrically distributed in the American Southwest. They share post-Pleistocene altitudinal ecotones with their host pines. Adjacent to these areas of host overlap, we tested the hypothesis that aggregation pheromones produced by male beetles and/or host volatiles are sufficient to elicit the speciesspecific colonization behaviors typical of these threeIps species in nature. A more distantly related species,I. pini (Hopping's group IV, S.L. Wood'spini group) was used for outgroup comparison. Under the influence of pheromone, males ofI. confusus andI. paraconfusus do not discern among unin-fested log bolts of host and nonhost pine prior to bark contact. Males responding to pheromones emanating from infested bolts are similarly undiscriminating. Females ofI. confusus andI. lecontei olfactorily discern the combination of conspecific males in host pine from other possible beetlepine combinations; females ofI. paraconfusus do not. FemaleI. pini discerned conspecific pheromone from that ofI. lecontei. The bark beetle predator,Enoclerus lecontei, is attracted by, but does not discriminate among, the male-produced volatiles of these Group IXIps species. These results support a hypothesis that divergence in pheromonal responses by these group IXIps species has evolved following their speciation, having been manifested first in the female sex. Evolutionarily, the derived pheromonal messages have preceded their behavioral discrimination by these beetles. Additional speciesspecific cues may operate between the sexes in the field that may preclude heterospecific pairings.     

Laboratory and field tests with the synthetic sex pheromone of threeMatsucoccus 1 pine bast scales

Matsunone, (2E,4E)-4.6,10,12-tetramethyl-2,4-tridecadien-7-one, is the primary sex pheromone ofMatsucoccus resinosae, M. thunbergianae, andM. matsumurae. The synthetic compound was tested in the laboratory and in field tests with all three species, and significantly more males responded to synthetic matsuone than to controls. The attraction of synthetic matsuone to males in field tests was not significantly different from that of virgin females at the same matsuone release rate. An analog of matsuone previously shown to be biologically active was also tested in the laboratory withM. resinosae andM. thunbergianae, and field tested withM. resinosae. The active analog required a dose approximately 100 times greater than matsuone to yield maximum laboratory bioassay response, and in field tests, attraction was not significantly different from controls at doses at which matsuone was significantly attractive.Homoptera: Coccoidea: Margarodidae.Deceased.     

Role of olfaction in host finding by aphid parasitoidAphidius nigripes (Hymenoptera: Aphidiidae)

The olfactory responses of the parasitoidAphidius nigripes Ashmead were investigated with a four-field airflow olfactometer. Female and male parasitoids did not respond to potato plants, the food plant of their host. However, females were strongly attracted by odors from a preferred host,Macrosiphum euphorbiae (Thomas), and also from less preferred hosts such asMyzus persicae (Sulzer) andAphis nasturtii Kalt. Moreover,A. nigripes females responded positively to odors from a nonhost aphid,Rhopalosiphum maidis Fitch. The honeydew produced by these four aphid species was also very attractive to females. Males did not respond to aphids or honeydew but were highly attracted by odors from conspecific female parasitoids.Contribution No. 394 from the Département de biologie, Université Laval.