Recruitment pheromone in the harvester ant genus Pogonomyrmex

Workers of the harvester ant genus Pogonomyrmex employ recruitment trail pheromones discharged from the poison gland. In P. barbatus, P. maricopa, P. occidentalis and P. rugosus we identified three pyrazines [2,5-dimethylpyrazine, trimethylpyrazine and 3-ethyl-2,5-dimethylpyrazine (EDMP)] as major compounds of the volatile part of the poison-gland secretions. Laboratory and field tests revealed EDMP to be the main recruitment pheromone.     

Isolation of the trail pheromone of the ant Myrmica rubra

The trail pheromone of Myrmica rubra is a volatile substance, or substances of low polarity and moderately low molecular weight, in the poison gland contents. The pheromone can be separated and concentrated by the use of thin layer chromatography. The non-polar contents of the poison gland associated with the pheromone vary with caste, age of workers, and species.     

The trail of the african urticating antTetramorium aculeatum: Source,potency, and workers' behavior (Hymenoptera: Formicidae)

This paper studies the production of and the response to the trail in the African urticating ant,Tetramorium aculeatum under a variety of laboratory conditions. The trail was found to contain a complex mix of substances. Two of these components are secreted by the poison gland: The most volatile one is an attractant and increases the ants' linear speed; the other is the trail pheromone, which may act for days on a dry substrate. A third component is present on the last abdominal sternite. It acts as an attractant and a locostimulant and is synergistic of the trail pheromone. The activity of these substances increases with the age of the workers. While following a trail, foragers, even unrewarded, reinforce it with both the poison gland contents and the synergistic compound. The ants follow trails better in darkness than in light. A wetted trail rapidly loses its activity. The article suggests an explanation for the functioning ofT. aculeatum's natural trails, including the role of its different components.     

The trail pheromone of the termite, Trinervitermes trinervoides

By using a T-junction choice assay workers of Trinervitermes trinervoides have been shown to lay and follow pheromone trails. The trials are not polarized and there is a quantitative relation between the number of termites laying the trail and the fraction of test termites which follw correctly. Workers reinforce trails whenever they follow them, and the degree of this reinforcement seems to be independent of trail strength. The trail pheromone is volatile and need not be perceived by contact chemoreception. Activity loss from filter paper is approximately exponential with a half-life of about 2 hr. Extracts of papers over which workers had laid trails were used to show a linear relationship, on a log-probit scale, between dose and response. Soldier termites also follow trails about as well as do workers, but workers lay trails that are about six to seven times as strong as soldier trails. No preference of either caste for their own trails could be demonstrated. Thin-layer chromatography indicated that the trail pheromone(s) is a fairly polar substance.     

Coordination of Raiding and Emigration in the Ponerine Army Ant Leptogenys distinguenda (Hymenoptera: Formicidae: Ponerinae): A Signal Analysis

Several glandular sources of trail pheromones have been discovered in army ants in general. Nevertheless, at present the understanding of the highly coordinated behavior of these ants is far from complete. The importance of trail pheromone communication for the coordination of raids and emigrations in the ponerine army ant Leptogenys distinguenda was examined, and its ecological function is discussed. The secretions of at least two glands organize the swarming activities of L. distinguenda. The pygidial gland is the source of an orientation pheromone holding the group of raiding workers together. The same pheromone guides emigrations to new nest sites. In addition, the poison sac contains two further components: one with a weak orientation effect and another which produces strong, but short-term attraction and excitement. The latter component is important in prey recruitment and characterizes raid trails. This highly volatile recruitment pheromone allows the extreme swarm dynamic characteristic of this species. Emigration trails lack the poison gland secretion. Due to their different chemical compositions, the ants are thus able to distinguish between raid and emigration trails. Nest emigration is not induced chemically, but mechanically, by the jerking movements of stimulating workers.     

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.     

Multiple glandular origins of queen pheromones in the fire ant Solenopsis invicta

The poison sac of the fire ant Solenopsis invicta is the only identified glandular source of pheromones produced by a functional ant queen. This structure, which contains the poison gland, has previously been shown to be the source of a releaser pheromone that mediates queen recognition and tending by workers. The poison sac has also been demonstrated to be the source of a primer pheromone that inhibits winged, virgin queens from shedding their wings (dealating) and developing their ovaries. To determine if the poison sac was the only source of these pheromones, we excised the poison sac from queens and observed whether operated queens retained their pheromonal effects. In a first experiment, the poison sac was removed from functional (egg-laying) queens which were then paired with unoperated nestmate queens in small colonies. Counts of the workers surrounding each queen two weeks after the operation showed that queens without poison sac were as effective as their unoperated nestmates in attracting worker retinues. In a second experiment, we removed the poison sacs of virgin queens which had not yet begun laying eggs and thus had not begun producing queen pheromone. After allowing them to develop their ovaries, these individuals produced amounts of queen recognition pheromone comparable to those secreted by unoperated or sham operated virgin queens as determined by bioassay. Testing the head, thorax and abdomens of functional queens separately revealed that the head was the most attractive region in relation to its relative surface area. Bioassays of extracts of two cephalic glands-the mandibular gland and postpharyngeal gland-showed that the postpharyngeal gland is a second source of the queen recognition pheromone. Finally, we found that virgin queens whose poison sacs were removed before they began producing queen pheromone initiated production of a primer pheromone that inhibits winged virgin queens from dealating, indicating that this pheromonal effect also has an additional but as yet undetermined source. These results parallel those on the honey bee in which several of the pheromonal effects of functional queens appear to have multiple glandular sources.     

Perceptual differences in trail-following leaf-cutting ants relate to body size

Leaf-cutting ants of the genus Atta have highly size-polymorphic workers, and size is related to division of labor. We studied trail-following behavior of different-sized workers in a laboratory colony of Atta vollenweideri. For small and large workers, we measured responsiveness and preference to artificial conspecific and heterospecific pheromone trails made from poison gland extracts of A. vollenweideri and A. sexdens. Responsiveness was measured as the probability of trail-following, and preference was measured by testing the discrimination between one conspecific and one heterospecific trail. Minute amounts of the releaser component methyl-4-methylpyrrole-2-carboxylate (0.4pg/1m), present in both, conspecific and heterospecific trails, suffice to elicit trail-following behavior. Workers followed heterospecific trails, and these trails (after normalizing their concentration) were as effective as conspecific trails. Small workers were less likely to follow a trail of a given concentration than large workers. In the discrimination test, small workers preferred the conspecific trail over the heterospecific trail, whereas large workers showed no significant preference. It is suggested that large workers primarily respond to the releaser component present in both trails, whereas small workers focus more on the conspecific traits provided by the blend of components contained in the trail pheromone.     

An agent-based model to investigate the roles of attractive and repellent pheromones in ant decision making during foraging

Pharaoh's ants organise their foraging system using three types of trail pheromone. All previous foraging models based on specific ant foraging systems have assumed that only a single attractive pheromone is used. Here we present an agent-based model based on trail choice at a trail bifurcation within the foraging trail network of a Pharaoh's ant colony which includes both attractive (positive) and repellent (negative) trail pheromones. Experiments have previously shown that Pharaoh's ants use both types of pheromone. We investigate how the repellent pheromone affects trail choice and foraging success in our simulated foraging system. We find that both the repellent and attractive pheromones have a role in trail choice, and that the repellent pheromone prevents random fluctuations which could otherwise lead to a positive feedback loop causing the colony to concentrate its foraging on the unrewarding trail. An emergent feature of the model is a high level of variability in the level of repellent pheromone on the unrewarding branch. This is caused by the repellent pheromone exerting negative feedback on its own deposition. We also investigate the dynamic situation where the location of the food is changed after foraging trails are established. We find that the repellent pheromone has a key role in enabling the colony to refocus the foraging effort to the new location. Our results show that having a repellent pheromone is adaptive, as it increases the robustness and flexibility of the colony's overall foraging response.