Perilaku Pemilihan Makanan dan Pengenalan Anggota Koloni pada Semut Rangrang Oecophylla smaragdina

Weaver ants Oecophylla smaragdina are social insects that recognize nestmates using pheromone. This study analyzes the feeding behavior and nestmate recognition of weaver ants in the urban area of three different islands (Sumatra: Baturaja; Java: Banyuwangi; Papua: Sorong). The free ants were placed in the arena composed of chicken meat, sugar, bananas as the baits. Ten trapped ants were also located in the arena to explore the nestmate recognition between the free and the trapped ants. Five types of behaviors, i.e., approach, stalking, communication, competition, and agonistic, were recorded in 6 days. Food preferences were indicated by the number of conduct towards the feeding sites, and nestmate recognition was indicated by approaching the trapped nestmate. The results showed that the percentage of the approach behavior of free ants was the highest in the three islands but had no significant difference between Sumatra and Java and between Java and Sorong (p-value >0.05). However, the study showed significant differences for the other four behaviors observed. As predicted, the percentage of chicken meat foraged by the ants was the highest due to the carnivorous behavior. The free ants showed the nestmate recognition to the trapped ants in all behavior, except competition.

Olfactory System Morphology Suggests Colony Size Drives Trait Evolution in Odorous Ants (Formicidae: Dolichoderinae)

In social insects colony fitness is determined in part by individual worker phenotypes. Across ant species, colony size varies greatly and is thought to affect worker trait variation in both proximate and ultimate ways. Little is known about the relationship between colony size and worker trait evolution, but hypotheses addressing the role of social structure in brain evolution suggest workers of small-colony species may have larger brains or larger brain regions necessary for complex behaviors. In previous work on odorous ants (Formicidae: Dolichoderinae) we found no correlation between colony size and these brain properties, but found that relative antennal lobe size scaled negatively with colony size. Therefore, we now test whether sensory systems scale with colony size, with particular attention to olfactory components thought to be involved in nestmate recognition. Across three species of odorous ants, Forelius mccooki, Dorymyrmex insanus, and D. bicolor, which overlap in habitat and foraging ecology but vary in colony size, we compare olfactory sensory structures, comparing those thought to be involved in nestmate recognition. We use the visual system, a sensory modality not as important in social communication in ants, as a control comparison. We find that body size scaling largely explains differences in eye size, antennal length, antennal sensilla density, and total number of olfactory glomeruli across these species. However, sensilla basiconica and olfactory glomeruli in the T6 cluster of the antennal lobe, structures known to be involved in nestmate recognition, do not follow body size scaling observed for other structures. Instead, we find evidence from the closely related Dorymyrmex species that the larger colony species, D. bicolor, invests more in structures implicated in nestmate recognition. To test for functional consequences, we compare nestmate and non-nestmate interactions between these two species and find D. bicolor pairs of either type engage in more interactions than D. insaus pairs. Thus, we do not find evidence supporting a universal pattern of sensory system scaling associated with changes in colony size, but hypothesize that observed differences in the olfactory components in two closely related Dorymyrmex species are evidence of a link between colony size and sensory trait evolution.

Formic acid modulates latency and accuracy of nestmate recognition in carpenter ants

Decision-making processes face the dilemma of being accurate or faster, a phenomenon that has been described as speed-accuracy trade-off in numerous studies on animal behaviour. In social insects, discriminating between colony members and aliens is subjected to this trade-off as rapid and accurate rejection of enemies is of primary importance for the maintenance and ecological success of insect societies. Recognition cues distinguishing aliens from nestmates are embedded in the cuticular hydrocarbon (CHC) layer and vary among colonies. In walking carpenter ants, exposure to formic acid (FA), an alarm pheromone, improves accuracy of nestmate recognition by decreasing both alien acceptance and nestmate rejection. Here we studied the effect of FA exposure on the spontaneous aggressive mandible opening response of harnessed Camponotus aethiops ants presented with either nestmate or alien CHCs. FA modulated both MOR accuracy and the latency to respond to odours of conspecifics. In particular, FA decreased MOR towards nestmates but increased it towards aliens. Furthermore, FA decreased MOR latency towards aliens but not towards nestmates. As response latency can be used as a proxy of response speed, we conclude that contrary to the prediction of the speed-accuracy trade-off theory, ants did not trade off speed against accuracy in the process of nestmate recognition.

The evidence of temporary social parasitism by Polyrhachis lamellidens (Hymenoptera, Formicidae) in a Camponotus obscuripes colony (Hymenoptera, Formicidae)

Polyrhachis lamellidens is a temporary socially parasitic ant whose new queen utilizes other ant species in the early stages of colony foundation. Field observations and rearing experiments suggest that Camponotus japonicus is a host species of P. lamellidens. It is presumed that Camponotus obscuripes is also a host of P. lamellidens by rearing experiments and field observations; however, there are no records of P. lamellidens workers or brood coexisting in C. obscuripes colonies in field observations, and there is no clear evidence that C. obscuripes is a natural host of P. lamellidens. We conducted detailed field observations, behavioral tests, and rearing experiments to show that C. obscuripes is a host of temporary social parasites. We found colonies with P. lamellidens queens, workers, and larvae intermixed with C. obscuripes workers in the field. Behavioral tests showed that workers of both species in mixed colonies did not attack each other and maintained nestmate recognition ability, which suggests a collaborative nestmate relationship. Furthermore, a rearing experiment confirmed social parasitism by P. lamellidens among C. obscuripes by producing a mixed brood-producing colony. These are the first field and laboratory records of temporary social parasitism involving P. lamellidens and C. obscuripes.

Formic acid modulates latency and accuracy of nestmate recognition in carpenter ants

Decision-making processes face the dilemma of being accurate or faster, a phenomenon that has been described as speed-accuracy trade-off (SAT) in numerous studies on animal behaviour. In social insects, discriminating between colony members and aliens is subjected to this trade-off as rapid and accurate rejection of enemies is of primary importance for the maintenance and ecological success of insect societies. Recognition cues distinguishing aliens from nestmates are embedded in the cuticular hydrocarbon (CHC) layer and vary among colonies. In walking carpenter ants, exposure to formic acid (FA), an alarm pheromone, improves accuracy of nestmate recognition by decreasing both alien acceptance and nestmate rejection. Here we studied the effect of FA exposure on the spontaneous aggressive mandible opening response of harnessed Camponotus aethiops ants presented with either nestmate or alien CHCs. FA modulated both MOR accuracy and the latency to respond to odours of conspecifics. In particular, FA decreased MOR towards nestmates but increased it towards aliens. Furthermore, FA decreased MOR latency towards aliens but not towards nestmates. As response latency can be used as a proxy of response speed, we conclude that contrary to the prediction of the SAT theory, ants did not trade off speed against accuracy in the process of nestmate recognition.Summary statementExposure to an alarm pheromone increases both latency and accuracy of the response to recognition cues in ants

Magnetosensibility and Magnetic Properties of Ectatomma brunneun Smith, F. 1858 Ants

The aim of the present paper is to study magnetosensibility and to seek for magnetic nanoparticles in ants. The social insects, by living in colonies, developed very efficient methods of nestmate recognition, being less tolerant towards individuals from other colonies. Therefore, any kind of strange behavior between nestmates and/or conspecifics, besides those present in their own behavioral repertoire, is not expected. The behavior study in the present paper analyze whether changes in the intensity of applied magnetic fields on Ectatomma brunneun (Smith) ants can cause changes in the normal pattern of interaction between conspecifics. A pair of coils generating a magnetic field was used to change the whole local geomagnetic field. Magnetometry studies were done on abdomens and head + antennae using a SQUID magnetometer. The results show that changes in the geomagnetic field affect the usual pattern of interactions between workers from different colonies. The magnetometry results show that abdomens present superparamagnetic nanoparticles and heads present magnetic single domain nanoparticles. Behavior experiments show for the first time that Ectatomma brunneun ants are magnetosensible. The change in nestmate recognition of Ectatomma ants observed while a magnetic field is applied can be associated to some kind of disturbance in a magnetosensor presented in the body based on magnetic nanoparticles.

Nestmate recognition of early brood in ants

Brood is critically important in social insect colonies. It carries the colony fitness through delivering future reproductive adults as well as workers that will increase the colony's workforce. Adoption of non-nestmate brood can be a mean to increase colony's workforce but entails the risk of rearing unrelated sexuals or social parasites. For early brood (eggs and L1 larvae), this balance is less positive as young brood need a substantial amount of resource before becoming workers. Thus, it appears beneficial for ant workers to discriminate between nestmate and alien brood using the chemical cues displayed at the brood's surface. However, the chemical signature of ant early brood stages and its use by workers remains understudied. To fill this gap, we investigated the chemical basis of early brood nestmate and cross-species recognition in six Formicoid ants. We also tested the discrimination behaviour of workers in brood retrieval trials. We observed clear species-level cues and discrimination against heterospecific brood. We also found that eggs and most young larvae display a colony signature but that only some species discriminate against non-nestmate eggs and L1 larvae. Interestingly, these species appear to also be those belonging to genera subject to brood parasitism.

The gut microbiome defines social group membership in honey bee colonies

In the honey bee, genetically related colony members innately develop colony-specific cuticular hydrocarbon profiles, which serve as pheromonal nestmate recognition cues. Yet, despite high intracolony relatedness, the innate development of colony-specific chemical signatures by individual colony members is largely determined by the colony environment, rather than solely relying on genetic variants shared by nestmates. Therefore, it is puzzling how a nongenic factor could drive the innate development of a quantitative trait that is shared by members of the same colony. Here, we provide one solution to this conundrum by showing that nestmate recognition cues in honey bees are defined, at least in part, by shared characteristics of the gut microbiome across individual colony members. These results illustrate the importance of host-microbiome interactions as a source of variation in animal behavioral traits.