Trail Communication Research Articles

Trail Communication Regulated by Two Trail Pheromone Components in the Fungus-Growing Termite Odontotermes formosanus (Shiraki)

The eusocial termites are well accomplished in chemical communication, but how they achieve the communication using trace amount of no more than two pheromone components is mostly unknown. In this study, the foraging process and trail pheromones of the fungus-growing termite Odontotermes formosanus (Shiraki) were systematically studied and monitored in real-time using a combination of techniques, including video analysis, solid-phase microextraction, gas chromatography coupled with either mass spectrometry or an electroantennographic detector, and bioassays. The trail pheromone components in foraging workers were (3Z)-dodec-3-en-1-ol and (3Z,6Z)-dodeca-3,6-dien-1-ol secreted by their sternal glands. Interestingly, ratio of the two components changed according to the behaviors that the termites were displaying. This situation only occurs in termites whereas ratios of pheromone components are fixed and species-specific for other insect cuticular glands. Moreover, in bioassays, the active thresholds of the two components ranged from 1 fg/cm to 10 pg/cm according to the behavioral contexts or the pheromonal exposure of tested workers. The two components did not act in synergy. (3Z)-Dodec-3-en-1-ol induced orientation behavior of termites that explore their environment, whereas (3Z,6Z)-dodeca-3,6-dien-1-ol had both an orientation effect and a recruitment effect when food was discovered. The trail pheromone of O. formosanus was regulated both quantitatively by the increasing number of workers involved in the early phases of foraging process, and qualitatively by the change in ratio of the two pheromone components on sternal glandular cuticle in the food-collecting workers. In bioassays, the responses of workers to the pheromone were also affected by the variation in pheromone concentration and component ratio in the microenvironment. Thus, this termite could exchange more information with nestmates using the traces of the two trail pheromone components that can be easily regulated within a limited microenvironment formed by the tunnels or chambers.

Polyrhachis loweryi (Formicinae): A guest ant parasitizing Rhytidoponera sp. (Ponerinae) in Queensland, Australia

At the type locality near Miles in Queensland, Australia a queenright colony of Polyrhachis loweryi was found (1 dealate queen, 91 workers, males and brood) within a colony of Rhytidoponera sp. (near aciculata), whereas other colonies of this Rhytidoponera species contained only a few workers of P. loweryi. For experiments and behavioural observations P. loweryi and its hosts were kept in the laboratory for some time. The queenright P. loweryi colony constructed closed nests out of soil and plant fibres, within the host nest, and only containing Polyrhachis specimens. P. loweryi workers in part, remained amid the assembly of Rhytidoponera, from whom they obtained carbohydrate and protein food. In addition, Polyrhachis workers regularly left the host nest. They were able to collect liquid carbohydrate food and to distribute it among conspecific nest mates via trophallaxis. The care of the P. loweryi brood was fully done by P. loweryi itself. However, Rhytidoponera workers were observed carrying P. loweryi brood in addition to their own brood. In artificially induced nest relocations, P. loweryi was able to move to a new nest independently from its host ants, displaying the typical invitation behaviour, trail laying behaviour, and leader independent trail communication found in other members of the genus. Rhytidoponera sp., which in addition to inconspicuous trail marking, performs nest relocation via social carrying, rarely but regularly also carried P. loweryi to the new nest. Whereas Rhytidoponera sp. workers were carried in the typical ponerine posture, P. loweryi workers were carried by them in the formicine posture. We conclude that P. loweryi is best described as a guest ant of Rhytidoponera sp.. The species seems to be less well integrated into the societies of its Rhytidoponera sp. host than the closely related P. lama, a social parasite of Diacamma sp. in Java.

Recruitment behavior in the ant genus Polyrhachis (Hymenoptera, Formicidae)

We present a detailed behavioral analysis of the signals involved in recruitment of 11 syntopic Polyrhachis species from West Malaysia. We found a considerable variety of recruitment techniques, including “social carrying behavior,” “tandem running,” “group recruitment,” and a technique which we call “leader-independent trail communication.” The latter mode superficially resembles “chemical mass communication” (sensu Wilson, 1962). All these recruitment techniques involve mechanical invitation behavior inside the nest, comprising back-and-forth jerking or pulling movement often combined with a sideways waggling. However, not in all cases of leader-independent trail communication is a mechanical invitation behavior obligatory. The trail pheromone of all investigated Polyrhachis species originates from the hindgut. Only in the tandem running P. proxima do additional secretions from the poison gland appear to be involved in tandem calling.

Recruitment and trail communication in two species of Messor ants (Hymenoptera, Formicidae)

Behavioural patterns and chemical signals mediating recruitment communication of the harvesting ants M. minor and M. was‐manni were studied. Recruitment towards a food source was investigated in the laboratory. Bioassays showed that successful scouts induce nestmates to leave the nest by substances from Du‐four's gland. This gland was also found to be the source of the chemical trails by which foragers reach newly discovered feeding sites. Glandular secretions from the last abdominal tergites as well as from the poison gland induced typical alarm reactions, suggesting their involvement in alarm communication and recruitment towards a source of danger. Production of stridulations by scouts and recruited foragers was also recorded on the food items under both field and laboratory conditions. The possible role of such vibrational signals in foraging communication is discussed. Finally, a comparison of the communication systems employed by both species was made and some ecological implications are discussed.

Chemical trail communication in the amblyoponine species Mystrium rogeri Forel (Hymenoptera, Formicidae, Ponerinae)

Workers of the amblyoponine species Mystrium rogeri employ trail communication during recruitment to food sources and new nest sites. The trail pheromone originates from a hitherto unknown sternal gland located in the 7th abdominal sternite. The recruiting ant deposits the gland secretions by a special gaster-dragging behavior. The recruitment behavior can be complemented by a rapid vertical body shaking performed by some recruiting ants inside the nest. M. rogeri workers possess a large pygidial gland, the secretion of which elicits a repellent response in other ant species.

Communication in the migratory termite-hunting ant Pachycondyla (= Termitopone) marginata (Formicidae, Ponerinae)

The Neotropical species Pachycondyla marginata conducts well-organized predatory raids on the termite species Neocapritermes opacus and frequently emigrates to new nest sites. During both activities the ants employ chemical trail communication. The trail pheromone orginates from the pygidial gland. Among the substances identified in the pygidial gland secretions, only citronellal was effective as a trail pheromone. Isopulegol elicited an increase in locomotory activity in the ants and may function as a synergist recruitment signal. The chemical signal is enhanced by a shaking display performed by the recruiting ant.

Trail-laying and recruitment to sugary foods by foraging red wood-ants Formica aquilonia Yarrow (Hymenoptera: Formicidae)

The use of trail communication by red wood-ants, Formica aquilonia Yarrow, foraging to sugar baits, was investigated by providing a laboratory colony with aqueous sucrose at two novel feeding sites, with a third site, providing no food, as a control. During trials, the sites were connected to the nest by paper bridges which were replaced between treals. One of the sites providing food was reached by a two-way bridge, as was the control. The second baited site was reached by a one-way bridge: this site had a one-way exit from which returning foragers dropped to the nest. Hence, if returning foragers laid a trail from a bait, they would do so on the two-way bridge, but not on the one-way bridge by which foragers did not return, nor on the bridge to the unbaited site. This would lead to a greater increase in foraging traffic on the two-way bridge, relative to that on the other two bridges, during a given trial. Each trial was preceded by a 30-min counting session with no baits present, to establish the mean number of ants arriving per minute on each bridge through random exploration. After provision of food, ants arriving on each bridge per minute were counted in four separate 30-min sessions: each count was then converted to a proportion of the original mean traffic on that bridge, and the change in traffic with time was compared between bridges using analysis of variance. The increase in traffic was significantly greater on the two-way bridge than on the control and one-way bridges, indicating that replete ants returning from the bait left a trail on the homeward route, which other ants subsequently followed.

Adaptative properties of the chemical trail system of the African weaver antOecophylla longinoda Latreille (Hymenoptera, Formicidae, Formicinae)

Trail communication of the weaver antOecophylla longinoda is highly adapted to the African rain forests, insofar natural selection in the tropics might favour chemical trails which are durable in nature. A dry chemical trail can last over nine weeks, and over ten months when reinforced with fecal marking. The trail pheromones are resistant to rain, whether they are fresh or three months old, and whether they are reinforced or not with anal deposits.

Chemical communication in the dacetine antDaceton armigerum (Hymenoptera: Formicidae)

Contrary to previous assumptions,Daceton armigerum, the largest ant in the myrmicine tribe Dacetini, employs trail communication. We identified two anatomical sources of trail pheromones: Trails drawn with poison gland contents can last for more than seven days. Trails drawn with the newly discovered sternal glands (in the VIth and VIIth abdominal sternites) are effective but relatively short-lived. In addition, our bioassays revealed that the contents of the mandibular glands elicit alarm behavior, and secretions from the pygidial gland release attraction. When tested with artificial poison gland trails from seven other myrmicine species,Daceton did not exhibit trail following behavior. We confirmed, however, previous findings thatAtta respond toDaceton poison gland trails andSolenopsis followDaceton Dufour's gland trails.

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.

Communication of leaf suitability by gregarious eastern tent caterpillars (Malacosoma americanum)

ABSTRACT. 1. Previous work has shown that leaf age affects recruitment trail marking by eastern tent caterpillars (Malacosoma americanum Fabr.). Young leaves of host plants elicit trail marking to a greater degree than mature leaves.2. Experiments were conducted to establish the relationship between the differential behavioural responses of larvae to young and mature leaves and the suitability of foliage for larval growth and survival. Foliage of black cherry (Prunus serotina Ehrh.), a typical rosaceous host plant, was used for this comparison.3. Larvae preferred young leaves to mature leaves in choice tests, and marked more to young leaves than to mature leaves in no‐choice tests.4. Mature leaves supported adequate growth through two larval instars of rearing, but thereafter were unsuitable for growth. Larvae fed mature leaves had lower pupal weight, poorer survival, and grew less efficiently than larvae fed young leaves.5. The results support the hypothesis that the trail communication system of eastern tent caterpillars is an adaptation to efficiently locate leaves which are favourable for larval growth and survival.