Monomorium ant's trail pheromones: Glandular source,optimal concentration,longevity and specificity

Many ants use pheromone trails to organize collective foraging. Trail pheromones are produced from different glandular sources and they may be specific to a single species or shared by a number of species. I investigated the source of trail pheromones in three Monomorium ant species: Monomorium niloticum (Emery), M. najrane (Collingwood & Agosti) and M. mayri (Forel). I also examined the optimal concentration, longevity and specificity of the pheromones. M. niloticum and M. najrane secrete trail pheromone from their venom glands, whereas M. mayri secrete trail pheromone from its Dufour's gland. The optimum concentration was 1.0 and 0.1 gaster equivalent (GE)/30 cm trail in M. niloticum, 1.0 GE in M. najrane and 5.0 GE in M. mayri. Longevity of the optimal concentration was about one day for all species. There is no species specificity among the three species of Monomorium in their trail pheromone.     

An integumentary pheromone-secreting gland in Atta sp: Territorial marking with a colonyspecific pheromone in Atta cephalotes

Workers of Atta cephalotes mark the area around their nest with a pheromone that has at least two components, one of which is colony-specific. Another, which was isolated and tested for its activity, is genus- or species-specific in its action; it appears to be similar in A. sexdens and A. cephalotes, but differs in Acromyrmex octospinosus. The pheromone is produced in a newly described gland, located near the sting. A synthetic trail pheromone component in very low concentrations stimulates some behavioural effects similar to those of the territorial pheromone.     

Revisiting the trail pheromone components of the red imported fire ant,Solenopsis invicta Buren

Ants use species-specific trail pheromones to coordinate their sophisticated foraging behavior. During the past decades, many trail pheromone components with various structures have been identified in ants, including the red imported fire ant, Solenopsis invicta, a notorious invasive species worldwide. Four compounds, Z,E- (ZEF) and E,E-α-farnesene (EEF), Z,E- (ZEHF) and E,E-α-homofarnesene (EEHF), have been reported as components of S. invicta trail pheromone. However, another study reported an analog of α-farnesene, Z,Z,Z-allofarnesene, as a key trail pheromone component. These contrasting results caused some uncertainty about the trail pheromone composition in S. invicta. In this study, we synthesized ZEF and EEF, ZEHF and EEHF, and reanalyzed the chemicals in the Dufour gland extract and in the trail pheromone fraction of S. invicta worker body extract. The reported isomers of farnesene and homofarnesene were detected and showed trail-following activity, with ZEF as the major compound, while no allofarnesene was found, neither in the Dufour gland extract nor in the whole-body extract. Our results confirm ZEF and EEF, ZEHF and EEHF as trail pheromone components of S. invicta.     

Geographic variation of sex pheromone and mitochondrial DNA in Diatraea saccharalis (Fab., 1794) (Lepidoptera: Crambidae)

(9Z,11E)-hexadecadienal and (Z11)-hexadecenal, the main sex pheromone components of the sugarcane borer, Diatraea saccharalis, were identified and quantified from four Brazilian and one Colombian populations using GC-EAD, GC-MS and GC analyses. Three different ratios were observed, 9:1, 6:1, and 3:1. The pheromone concentration for the major component, (9Z,11E)-hexadecadienal, varied from 6.8 ng/gland to 21.9 ng/gland and from 1.7 ng/gland to 6.5 to the minor component, (Z11)-hexadecenal. The 25 D. saccharalis cytochrome oxidase II sequences that were analyzed showed low intra-specific variation and represented only 11 haplotypes, with the most frequent being the one represented by specimens from São Paulo, Paraná, and Pernambuco states. Specimens from Colombia showed the highest genetic divergence from the others haplotypes studied. Data on the genetic variability among specimens, more than their geographic proximity, were in agreement with data obtained from analyses of the pheromone extracts. Our data demonstrate a variation in pheromone composition and a covariation in haplotypes of the D. saccharalis populations studied.     

Sexual communication in the termite Prorhinotermes simplex (Isoptera, Rhinotermitidae) mediated by a pheromone from female tergal glands

We studied the post-flight behavior and sex attraction in imagoes of the termite Prorhinotermes simplex (Rhinotermitidae, Prorhinotermitinae). Pairing is mediated by the secretion from tergal glands, exposed by females in a calling posture and highly attractive to males. Analysis of extracts of these glands by means of gas chromatography with electroantennographic detection indicated a chromatographic area corresponding to an intense physiological response of males. The retention characteristics of this area proved to be identical with those of (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol. Electroantennographic and behavioral assays revealed that units of picograms of the compound represent a stimulus qualitatively and quantitatively equivalent to one female tergal gland. Thus, we hypothesize that (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol is a major component of the female sex pheromone in P. simplex.     

Sex pheromone composition of the cotton caterpillar,Palpita indica (Lepidoptera: Pyralidae), in Korea

This study was conducted to investigate the sex pheromone composition of Palpita (=Diaphania) indica (Saunders) (Lepidoptera: Pyralidae) in Korea. Two sex pheromone components, E11-16:Al and E,E-10,12-16:Al, were identified by GC and GC-EAD analysis of sex pheromone gland extracts. The mean ratios of the two components, E11-16:Al and E,E-10,12-16:Al, were about 6.5:3.5 and 7.5:2.5 in gland extracts and in SPME collection, respectively. In field bioassays, maximum attraction occurred in traps baited with a 7:3 ratio of E11-16:Al and E,E-10,12-16:Al. The head extracts of P. indica stimulated the sex pheromone production of P. indica, as well as Hez-PBAN and PssPT, indicating that a PBAN-like substance exists in the head extracts of P. indica. Whole-mount immunocytochemistry showed that three groups of neurosecretory cells showed PBAN-like immunoreactivity in the SEG of P. indica. The PBAN-like immunoreactivity connected to the Corpora Cardiaca, a neurohemal organ. Also, PBAN-like immunoreactivity was found in the brain and in the thoracic and third/fourth abdominal ganglia. The addition of sex pheromone components of Peridroma saucia to the sex pheromone of P. indica greatly improved the attraction of P. indica males. The mixing of the sex pheromone components of S. exigua did not significantly increase the catches of P. indica, while the sex pheromone of H. armigera completely inhibited the attractiveness.     

Trail‐sharing among tropical ants: interspecific use of trail pheromones?

1. Trail‐sharing between different ant species is rare and restricted to a small number of species pairs. Its underlying mechanisms are largely unknown. For trail‐sharing to occur, two factors are required: (i) one or both species must recognise the other species or its pheromone trails and (ii) both species must tolerate each other to a certain extent to allow joint use of the trail. A species that follows another's trails can efficiently exploit the other's information on food sources contained in the pheromone trails. Hence, food competition and thus aggressive interactions between a species following another's trail and the species being followed, seem likely. 2. In the present study, we investigated interspecific trail following and interspecific aggression in trail sharing associations (i) among Polyrhachis ypsilon, Camponotus saundersi, and Dolichoderus cuspidatus, and (ii) among Camponotus rufifemur and Crematogaster modiglianii. We tested whether trail‐sharing species follow each other's pheromone trails, and whether the ants tolerated or attacked their trail‐sharing partners. In both associations, we confronted workers with pheromone trails of their associated species, and, for the former association, measured interspecific aggression among the trail‐sharing species. 3. In our assays, D. cuspidatus and C. rufifemur regularly followed heterospecific pheromone trails of P. ypsilon and C. modiglianii, respectively. However, only few workers of the remaining species followed heterospecific pheromone trails. Thus, shared trails of P. ypsilon and C. saundersi cannot be explained by interspecific trail‐following. 4. Interspecific aggression among P. ypsilon, C. saundersi, and D. cuspidatus was strongly asymmetric, C. saundersi being submissive to the other two. All three species differentiated between heterospecific workers from the same or another site, suggesting habituation to the respective trail‐sharing partners. We therefore hypothesise that differential tolerance by dominant ant species may be mediated by selective habituation towards submissive species and this way determines the assembly of trail‐sharing associations.     

Trail Pheromone of the Argentine Ant,Linepithema humile (Mayr) (Hymenoptera: Formicidae)

The Argentine ant (Linepithema humile) is recognized as one of the world''s most damaging invasive species. One reason for the ecological dominance of introduced Argentine ant populations is their ability to dominate food and habitat resources through the rapid mobilization and recruitment of thousands of workers. More than 30 years ago, studies showed that (Z)-9-hexadecenal strongly attracted Argentine ant workers in a multi-choice olfactometer, suggesting that (Z)-9-hexadecenal might be the trail pheromone, or a component of a trail pheromone mixture. Since then, numerous studies have considered (Z)-9-hexadecenal as the key component of the Argentine ant trails. Here, we report the first chemical analyses of the trails laid by living Argentine ants and find that (Z)-9-hexadecenal is not present in a detectible quantity. Instead, two iridoids, dolichodial and iridomyrmecin, appear to be the primary chemical constituents of the trails. Laboratory choice tests confirmed that Argentine ants were attracted to artificial trails comprised of these two chemicals significantly more often than control trails. Although (Z)-9-hexadecenal was not detected in natural trails, supplementation of artificial dolichodial+iridomyrmecin trails with an extremely low concentraion of (Z)-9-hexadecenal did increase the efficacy of the trail-following behavior. In stark contrast with previous dogma, our study suggests that dolichodial and iridomyrmecin are major components of the Argentine ant trail pheromone. (Z)-9-hexadecenal may act in an additive manner with these iridoids, but it does not occur in detectable quantities in Argentine ant recruitment trails.     

Sensory Aspects of Trail-Following Behaviors in the Asian Longhorned Beetle, <Emphasis Type="Italic">Anoplophora glabripennis</Emphasis>

Anoplophora glabripennis has a complex suite of mate-finding behaviors, the functions of which are not entirely understood. These behaviors are elicited by a number of factors, including visual and chemical cues. Chemical cues include a male-produced volatile semiochemical acting as a long-range sex pheromone, a female-produced cuticular hydrocarbon blend serving as a sex-identification contact pheromone, and a recently identified female-produced trail sex pheromone that is followed by mate-seeking males. However, the sensory appendages and sensilla on these appendages used to detect the trail sex pheromone are unknown. We evaluated the ability of virgin male A. glabripennis to follow a sex pheromone trail after removal of the terminal four antennal segments and/or the maxillary and labial palps using a two-choice behavioral bioassay. We also tested the ability of males to follow the trail sex pheromone using volatile pheromone cues only, without physical contact with the pheromone. Results indicate that the palps are primarily responsible for sensing the pheromone, with males lacking palps unable to respond behaviorally to the trail sex pheromone. Under the conditions of this study, males could not follow the sex pheromone trail without direct contact, suggesting that olfaction may not be involved in detection of this pheromone. However, we did not determine to what degree the trail pheromone chemicals can volatilize under our experimental conditions. This work is important in elucidating the behaviors and sensory structures involved in mate-finding by this species on host trees, and these studies may help determine whether the trail sex pheromone has applications for monitoring and management.     

Fire ant trail pheromones: Analysis of species specificity after gas chromatographic fractionation

The specificity of the trail pheromones of four Solenopsis species was determined using natural trails. Dufour's gland extracts, and purified fractions from Dufour's gland extracts collected after gas-chromatographic separation. S. richteri and S. invicta possess species-specific major trail pheromones, while S. geminata and S. xyloni appear to have a common trail pheromone. Preliminary chemical characterization of the main trail pheromone of S. richteri indicates a M.W. of 218 and empirical formula of C₁₆H₂₆. The trail pheromone system of S. richteri consists of a blend of compounds and this phenomenon may also occur in the other species. The lowest concentration of their trail pheromone that workers of S. richteri could detect was about 10 fg per cm. The significance of blends of pheromones being utilized to generate chemical trails is discussed.     

Chemical and behavioural studies of the trail-following pheromone in the leaf-cutting ant Atta opaciceps,Borgmeier (Hymenoptera: Formicidae)

To understand the significance of the trail pheromone used in chemical communication of the leaf-cutting ants Atta opaciceps we investigated, under laboratory conditions, the trail-following behaviour of different castes. We observed a clear behavioural discrimination of conspecific venom gland extract of foraging ants from those of other species. Additionally, we determined the pheromone composition of A. opaciceps venom gland secretion using a two-dimensional gas chromatography coupled with mass spectrometry. Chemical analyses revealed the presence of three nitrogen-containing compounds, identified as 2,5-dimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine and methyl 4-methylpyrrole-2-carboxylate (M4MPC). Four different bioassays performed with workers from different castes of A. opaciceps suggested that the trail pheromone elicits the trail-following behaviour in conspecifics of all castes, but the foragers respond more strongly to their own pheromone than to that of other castes (gardeners, generalists and soldiers). In addition, A. opaciceps foragers follow the trails made with the venom gland extracts of the unrelated Acromyrmex subterraneus subterraneus foragers as well as they follow the trails made with their own venom gland extract. M4MPC was identified to be the most abundant and the most behaviourally active component of the venom gland extract of A. opaciceps foragers.     

Methyl 4-methylpyrrole-2-carboxylate: a volatile trail pheromone from the leaf-cutting ant, tatta cephalotes

Methyl 4-methylpyrrole-2-carboxylate, a volatile trail pheromone previously identified from Atta texana, has been isolated and identified from the ant species, Atta cephalotes. The natural and the synthetic compound produce strong trail-following activity in a laboratory colony of A. cephalotes.     

Chemical analysis of the female sex pheromone in Palpita nigropunctalis (Lepidoptera: Crambidae)

The lilac pyralid, Palpita nigropunctalis Bremer (Lepidoptera: Crambidae), is a common pest of Oleaceae plants. A crude extract of the female sex pheromone glands was examined by gas chromatography-electroantennogram detection (GC-EAD) and GC coupled to a mass spectrometer (GC/MS). The GC-EAD analysis revealed three EAG-active components (I–III) in a ratio of 1:0.2:0.01 (I: II: III). GC/MS analysis successfully recorded the mass spectra of I and II. For I, ions at m/z 238 (M⁺) and 220 ([M-18]⁺) indicated the structure of a monoenyl aldehyde with a 16-carbon chain. For II, M⁺ was not detected, but ions at m/z 222 ([M-60]⁺) and 61 ([AcOH+1]⁺) suggested that II was a monoenyl acetate with a 16-carbon chain. Further GC/MS analysis of the extract treated with dimethyl disulfide revealed that the double bonds in both I and II are located at the same position of 11th-carbon. In addition, the pheromone extract was examined by GC/Fourier transform-infrared spectrophotometer (GC/FT-IR). An IR spectrum of I showed characteristic absorption at 1716 and 966?cm^?1, indicating a formyl group and E configuration of the double bond, respectively. In the case of II, absorption at 1745 and 968?cm^?1 indicated an ester carbonyl and E configuration, respectively. Taken together and by comparison with authentic standards, I and II were confirmed as (E)-11-hexadecenal and (E)-11-hexadecenyl acetate, respectively; while III was speculated as (E)-11-hexadecen-1-ol. The synthetic I, II and III all coincided well with those of the natural components in chemical data, and elicited strong electroantennographic activity in male P. nigropunctalis.     

Chemical trail systems,orientation, and territorial interactions in the antLasius neoniger

Foraging and territoriality in the ant Lasius neonigerinvolves a series of trails which channel foragers away from adjacent colonies. Experimental studies suggest that the trails are composed of colony-specific, persistent orientation components of hindgut material that accumulate on trails during foraging. A less durable component of the hindgut trail pheromone regulates recruitment. Foraging directionality and the use of a trail could be modified by experimentally arranging confrontations with conspecifics. The orientation of foragers is mediated by visual as well as chemical cues. Components of the foraging and territorial system of L. neonigerappear to include (1) a network of subnests which change in position seasonally within each polydomous nest; (2) a series of trails emanating from each subnest that adjusts search toward resource patches and away from aggressive, neighboring conspecifics; and (3) trail communication involving an ephemeral component of the hindgut trail pheromone that regulates the organization of cooperative prey retrieval and a more persistent component that serves as an orientation guide.     

Sex pheromone composition of the variegated cutworm,Peridroma saucia (Lepidoptera: Noctuidae), in Korea

This study was conducted to investigate the sex pheromone composition of the variegated cutworm (Peridroma saucia Hübner) in Korea. The sex pheromone components of P. saucia were identified as (Z)-9-tetradecenyl acetate (Z9-14:Ac) and (Z)-11-hexadecenyl acetate (Z11-16:Ac) through GC-EAD and GC–MS analysis. EAG tests of the male antennae revealed that the Z9-14:AC exerted significantly larger responses than other compounds. The female moths primarily called and copulated between 6 h and 7 h after the lights off, and the ratio of two pheromone components, Z9-14:Ac and Z11-16:Ac, in the sex pheromone gland during this period was 1:2.1 to 1:2.4. In the field trapping studies, a large number of male moths were caught in the traps baited with the mixtures of Z9-14:Ac and Z11-16:Ac at the ratios ranging from 2.3:1 to 1:4, with the highest trap catches at 1:1 to 1:2.3 ratios of the two components. The seasonal flight activities of P. saucia monitored by using pheromone lures revealed complicated patterns in Korea. Specifically, the first flight period was spread over a long period and irregular, while the second flight period differed among the localities examined.     

Stingless bees (<Emphasis Type="Italic">Scaptotrigona pectoralis</Emphasis>) learn foreign trail pheromones and use them to find food

Foragers of several species of stingless bees (Hymenoptera, Apidae and Meliponini) deposit pheromone marks in the vegetation to guide nestmates to new food sources. These pheromones are produced in the labial glands and are nest and species specific. Thus, an important question is how recruited foragers recognize their nestmates’ pheromone in the field. We tested whether naïve workers learn a specific trail pheromone composition while being recruited by nestmates inside the hive in the species Scaptotrigona pectoralis. We installed artificial scent trails branching off from trails deposited by recruiting foragers and registered whether newly recruited bees follow these trails. The artificial trails were baited with trail pheromones of workers collected from foreign S. pectoralis colonies. When the same foreign trail pheromone was presented inside the experimental hives while recruitment took place a significant higher number of bees followed the artificial trails than in experiments without intranidal presentation. Our results demonstrate that recruits of S. pectoralis can learn the composition of specific trail pheromone bouquets inside the nest and subsequently follow this pheromone in the field. We, therefore, suggest that trail pheromone recognition in S. pectoralis is based on a flexible learning process rather than being a genetically fixed behaviour.     

Site of production of an oviposition-deterring pheromone component in Rhagoletis pomonella flies

Using behavioural and electrophysiological assay techniques, we identified the posterior half of the midgut as being a principal site of production of a major component of the oviposition-deterring, fruit-marking pheromone of female Rhagoletis pomonella flies. Following secretion into, and accumulation in, the gut lumen, this component is released, together with other gut contents, in the marking trail deposited during dragging of the ovipositor on the fruit surface after egg-laying, as well as in the faeces. Other components of the pheromone may be produced elsewhere.     

Sex pheromone analysis and effective attraction of males of the cabbage webworm,Hellula undalis,inhabiting the Mekong Delta of Vietnam

Hellula undalis is a harmful insect pest of green mustard in the Mekong Delta of Vietnam. In order to establish a tool for a sustainable pest control program, the sex pheromone of H. undalis inhabiting the Mekong Delta was examined. GC-EAD and GC–MS analyses of pheromone gland extracts from the virgin females elucidated three new components, (Z)-11-tetradecenyl acetate (Z11-14:OAc), (Z)-11-hexadecenal (Z11-16:Ald), and (11E,13E)-11,13-hexadecadien-1-ol, in addition to the known pheromone component (11E,13E)-11,13-hexadecadienal (E11,E13-16:Ald). Double bond positions of the two monoenyl components were determined by GC–MS analysis of the pheromone extract treated with dimethyl disulfide. On the other hand, GC–MS analysis of the female body extract detected the unsaturated hydrocarbon (3Z,6Z,9Z)-3,6,9-tricosatriene (Z3,Z6,Z9-23:H). Field examinations of their synthetic compounds indicated the significant role of E11,E13-16:Ald as a major component and a clear synergistic effect of the two monoenyl compounds as a minor component. Although the 3:3:7 mixture of Z11-14:OAc, E11-16:Ald, and E11,E13-16:Ald captured the largest number of males among the tested mixtures, the activity was still quite a bit lower than that of virgin females. However, the 3:3:7:1 mixture, which was prepared by adding a small amount of Z3,Z6,Z9-23:H to the 3:3:7 ternary lure, succeeded in attracting males more powerfully than the females did. This strong synergistic effect was not observed when the triene was added to unmixed E11,E13-16:Ald, indicating important roles of not only the triene but also the two monoenyl compounds as natural pheromone components.     

A remarkable autosomal heteromorphism in Pseudoryzomys simplex 2n = 56; FN = 54–55 (Rodentia,Sigmodontinae)

Pseudoryzomys simplex, the false rice rat, is a monotypic genus of the Oryzomyini tribe (Sigmodontinae) distributed in part of Bolivia, Paraguay, Argentina and Brazil. Its diploid number has been described as 56 acrocentric chromosomes decreasing in size and no karyotype figure has been depicted. Herein, we present karyotypic data on P. simplex, including chromosome banding and molecular fluorescent in situ hybridization using telomeric sequences and the whole X-chromosome of its sister clade Holochilus brasiliensis (HBR) as probes. A case of remarkable autosomal heteromorphism due to the presence of a whole heterochromatic arm leading to the variability of FN is reported, as well as the occurrence of regions of homology between the X and Y chromosomes (pseudoautosomal regions) after chromosome painting with the HBR X probe on P. simplex metaphases.     

A male-specific odorant receptor conserved through the evolution of sex pheromones in Ostrinia moth species

In many moths, mate-finding communication is mediated by the female sex pheromones. Since differentiation of sex pheromones is often associated with speciation, it is intriguing to know how the changes in female sex pheromone have been tracked by the pheromone recognition system of the males. A male-specific odorant receptor was found to have been conserved through the evolution of sex pheromone communication systems in the genus Ostrinia (Lepidoptera: Crambidae). In an effort to characterize pheromone receptors of O. scapulalis, which uses a mixture of (E)-11- and (Z)-11-tetradecenyl acetates as a sex pheromone, we cloned a gene (OscaOR1) encoding a male-specific odorant receptor. In addition, we cloned a gene of the Or83b family (OscaOR2). Functional assays using Xenopus oocytes co-expressing OscaOR1 and OscaOR2 have shown that OscaOR1 is, unexpectedly, a receptor of (E)-11-tetradecenol (E11-14:OH), a single pheromone component of a congener O. latipennis. Subsequent studies on O. latipennis showed that this species indeed has a gene orthologous to OscaOR1 (OlatOR1), a functional assay of which confirmed it to be a gene encoding the receptor of E11-14:OH. Furthermore, investigations of six other Ostrinia species have revealed that all of them have a gene orthologous to OscaOR1, although none of these species, except O. ovalipennis, a species most closely related to O. latipennis, uses E11-14:OH as the pheromone component. The present findings suggest that the male-specific receptor of E11-14:OH was acquired before the divergence of the genus Ostrinia, and functionally retained through the evolution of this genus.