Giving-up time variation in response to differences in nectar volume and concentration in the giant tropical ant,Paraponera clavata (Hymenoptera: Formicidae)

Giving-up times in resource patches by workers of the giant tropical ant,Paraponera clavata, are associated with travel time and reward volume but not reward concentration. The discovery of an artificial nectar reward stimulates local search which is centered around the initial reward site. Longer giving-up times increase the likelihood that a worker will find a second reward, but the search appears to be more effective for renewed rewards at the same location than for nearby rewards. When workers are near the colony, larger rewards cause the workers to stop searching and to initiate recruitment behavior. At patches distant from the nest, the threshold in reward volume for recruitment is much higher. These results are consistent with expectations for search strategies when energy expenditure in search is minimal, resources are renewable, and recruitment can occur.     

Temporal learning in the giant tropical ant, Paraponera clavata

ABSTRACT. Our findings suggest that the capacity for temporal learning in ants may be associated with nectivory. We tested for the existence of time and location learning in the nectivorous tropical ant, Paraponera clavata (F.). Artificial nectar sources were provided at fixed times and locations to P. clavata workers for 5 days. Ants appeared at the feeding location at the appropriate time on the first day that no reward was provided. By the third day without reward there was no difference in visitation between the feeding site and a control site equidistant from the colony. Most ants arrived at the feeding sites within 30 min of the training time, indicating that the precision of ant time sense is similar to that previously documented for honeybees.     

The significance of visual landmarks for navigation of the giant tropical ant,Paraponera clavata (Formicidae,Ponerinae)

Summary Workers of the giant tropical ant,Paraponera clavata, use trail pheromones for orientation and recruitment of nestmates. However, chemical markings may not always be sufficient for successful navigation in complex three-dimensional terrain, and additional orientation cues may be required. Behavioral field experiments were performed to investigate the significance of visual landmarks for homing foragers. Animals which were prevented from seeing the canopy were unable to navigate back to the nest, even though trail pheromones were still present. In contrast, foragers found their way back to the nest after their trail pheromones had been abolished but their visual scenes remained unchanged. This emphasizes the important role of visual landmarks during spatial orientation in homingP. clavata foragers. Individually foraging scouts were discovered in the understory of the forest floor up to 30 m away from their nest. They were rewarded, and displaced between 0.8 m and 13.6 m. Fifteen out of 16 animals had no difficulties in finding the nest entrance despite the altered appearance of local and distant landmarks at the release site. Apparently the scouts were able to recognize the visual scenes at the release site, and used them for reference to locate the nest entrance. In contrast, ants displaced from their nest to sites around 4 m away had more difficulties to re-find the nest.     

Allometry in the giant tropical ant, Paraponera clavata

Summary: Workers of the ponerine ant, Paraponera clavata, grow allometrically, with the head disproportionately larger in larger workers. The anterior (clypeus)-posterior (occiput) dimension of the head capsule is allometric with the lateral (interocular) dimension, so that larger workers have elongate heads. The degree of head capsule allometry varies among colonies; this could result either from differences in colony maturity or from variation in developmental patterns among colonies. These data resolve a previously controversial issue concerning caste in Paraponera clavata.     

Distance effects on resource profitability and recruitment in the giant tropical ant,Paraponera clavata

Summary We examine how cost and benefit components of resource profitability affect recruitment in the giant tropical ant, Paraponera clavata. To vary resource profitability, we changed the quantity of artificial nectar baits presented to foragers and the distance of nectar baits from the nest. Both distance to and amount of resource affected quantitative aspects of recruitment. At increased distances foragers were less likely to recruit, and fewer workers were recruited to the resource area. The amount of nectar affected the tendency of foragers to recruit, but had no effect on the number of ants recruited. Variation in resource distance was also associated with qualitative changes in recruitment strategy. Foragers at distant sites recruited from the canopy rather than from the nest, and often transferred nectar to other workers for transport to the nest. Nectar transfer and extra-nidal recruitment significantly reduced the time required for resource collection. It may also have increased the ability of workers to specialize in specific foraging tasks. A portion of the colony's foraging force specialized spatially by remaining in distant foraging areas without returning to the nest. The flexible recruitment system of P. clavata increases colonial net energetic gain rates by concentrating foraging effort on resources yielding the highest net energetic rewards, and increases the competitive abilities of individual colonies at resource sites by decreasing collection times.     

Communication in the primitive cryptobiotic ant Prionopelta amabilis (Hymenoptera: Formicidae)

Summary The Neotropical ant Prionopelta amabilis, a cryptobiotic species in the phylogenetically primitive tribe Amblyoponini, lives in subterranean habitats, where it preys preferentially on campodeid diplurans and other small arthropods. Here we report that the species employs chemical recruitment and orientation trails during foraging and nest emigrations. The trail pheromone originates in a hitherto unknown basitarsal gland located in the basitarsus of the hindlegs. Trails are laid by a special foot dragging behavior. During the recruitment process the chemical trail signal is complemented by body shaking on the part of the recruiting ant. Foragers frequently wipe the basitarsal gland opening in the hindlegs with the grooming apparatus of the front legs. This latter structure is equipped with unusual glands evidently specialized for this purpose.     

Foraging decisions of individual workers vary with colony size in the greenhead ant Rhytidoponera metallica (Formicidae, Ectatomminae)

Summary. The ability of worker ants to adapt their behaviour depending on the social environment of the colony is imperative for colony growth and survival. In this study we use the greenhead ant Rhytidoponera metallica to test for a relationship between colony size and foraging behaviour. We controlled for possible confounding ontogenetic and age effects by splitting large colonies into small and large colony fragments. Large and small colonies differed in worker number but not worker relatedness or worker/brood ratios. Differences in foraging activity were tested in the context of single foraging cycles with and without the opportunity to retrieve food. We found that workers from large colonies foraged for longer distances and spent more time outside the nest than foragers from small colonies. However, foragers from large and small colonies retrieved the first prey item they contacted, irrespective of prey size. Our results show that in R. metallica, foraging decisions made outside the nest by individual workers are related to the size of their colony.Received 23 March 2004; revised 3 June 2004; accepted 4 June 2004.     

Analysis of the local ant fauna (Hymenoptera, Formicidae) in Southern Vietnam

The ant fauna of Nam Cat Tien in the southern part of the Cat Tien Biosphere Reserve (Dong Nai Prov., Southern Vietnam) was studied in 2007–2008. The zonal type of vegetation under study is closed deciduous tropical forests dominated by Lagerstroemia spp. in association with Dipterocarpaceae and Fabaceae. The local ant fauna comprises 272 species from 68 genera and 12 subfamilies. The maximum number of species was found in the genera Polyrhachis (31), Camponotus (21), Pheidole (21), Leptogenys (17), and Crematogaster (13). Seven ant genera (Echinopla F. Sm., Indomyrma Brown, Liomyrmex Mayr, Paratopula Wheeler, Proatta For., Protanilla Taylor, and Rotastruma Bolton) are reported from Vietnam for the first time. The ecological pattern of the ant fauna in the main forest biotopes of the study area is considered. In the dipterocarp forests in the central part of the reserve, the complex of stratobiont species was the most diverse. In the bamboo forests, the stratobiont complex is less diverse but the fraction of dendrobionts is greater. The forests with similar layer structure occurring on sand and loamy soils were shown to differ in the species composition of ant assemblages. Repeated population inventories of ants were carried out in 8 model plots of 100 m2 each during the dry and rainy season. The specificity of revealing species of different biomorphs is discussed in the seasonal aspect. The structure of the ant fauna of Nam Cat Tien is compared to that in other territories of the Oriental Region. The zoogeographic unity of the study area and some localities of the Indo-Malayan Subregion (Borneo, Java) is demonstrated.     

Effects of experience on food-searching behavior in the antFormica schaufussi (Hymenoptera: Formicidae)

Foragers of the ant Formica schaufussitend to return to and search at a site of a previous food find. The search tactic employed by a forager on its return trip is related to the type of food previously encountered: search is more persistent in response to carbohydrate than to protein food. Using different reinforcement schedules with carbohydrate and protein food rewards, we show that, on a short-term as well as on a long-term basis, the basic pattern of search observed in naive foragers is only slightly modified through foraging experience. Foragers do not increase their search effort or adjust their search pattern when either type of food is systematically renewed on a fixed reward schedule and thus do not seem to be able to learn to assess the food predictability. Collective responses that could compensate for this lack of individual flexibility and increase foraging efficiency at the colony level are discussed.     

Maintenance of foraging trails by the giant tropical antParaponera clavata (Insecta: Formicidae: Ponerinae)

Summary Establishment and maintenance of foraging trails to an artificial nectar source by ten colonies ofParaponera davata (Fabr.) in Panama is reported. The first forager to locate the artificial nectar source was responsible for recruiting additional foragers and for marking trails to orient these foragers. More than half of the trail marking was performed by the first two ants to mark the path back to the colony, although up to 11 ants per colony per hour marked trails. The number of trail marks and the number of marking ants decreased through time, presumably as foragers learned the location of the artificial nectar source. Four categories of recruits were noted: markers, foragers, patrollers, and visitors.     

Regulated food recruitment through individual behavior of scouts in the ant,Myrmica sabuleti (Hymenoptera: Formicidae)

By presenting different kinds of food sources to colonies ofM. sabuleti, we have demonstrated that this species regulates its foraging activity by altering the proportion of scouts that return to the nest to recruit nestmates after discovering a food source and by varying the number of nestmates recruited by a scout. These two parameters are related to the kind of food discovered. Our behavioral experiments showed that the probability that a scout returned to the nest decreased with a decreasing quantity of sucrose solution. In contrast, the number of returned scouts that elicited recruitment from the nest and the mean number of nestmates recruited by one of these scouts were independent of the quantity of the sucrose solution. Recruitment even occurred toward a 1- or 0.25-µl droplet of sucrose solution. When a scout discovered a large dead prey, a large drop of prey juice, a cluster of 30 dead fruit flies, or 1 isolated fruit fly, it always went back to the nest, but it elicited recruitment only when the food source was a large dead prey or a large drop of prey juice. No recruitment occurred when the food source was a single fruit fly and recruitment occurred only once in 30 trials when a cluster of 30 fruit flies was discovered.     

Samsum ant,Brachyponera sennaarensis (Formicidae: Ponerinae): Distribution and abundance in Saudi Arabia

Invasive species are capable of causing considerable damage to natural ecosystems, agriculture and economies throughout the World. Samsum ant, Brachyponera (Pachycondyla) sennaarensis has been a reason for medical implication and social nuisance through its poisonous and severely painful sting causing anaphylactic shock in many cases. We surveyed for the presence of the samsum ant in various provinces of Saudi Arabia. B. sennaarensis was the abundant Ponerinae species in human settlements. In the Eastern provinces, however, few samples were collected, and none were found in the Northern and Western provinces. Infestations of B. sennaarensis were particularly severe in the spring and summer seasons, when the ants make nests in moist areas and in cracks in cemented structures, whereas the extent of infestation reduced in winter seasons.     

Foraging Behavior in Two Species of Ectatomma (Formicidae: Ponerinae): Individual Learning of Orientation and Timing

The foraging behavior of marked individuals of Ectatomma ruidum and E. tuberculatum (Formicidae: Ponerinae) was observed on Barro Colorado Island, Panama, in order to determine whether learning of orientation and timing is involved when foraging on patchy resources on the forest floor. Foraging experiments under seminatural conditions were designed to control for the spatiotemporal distribution of resources at one or two preying sites. Using both single- and multi–event past experience, individual foragers of E. ruidum and (although less significantly) E. tuberculatum made directional and temporal adjustments to their behavior in response to previous differential foraging success. In spite of considerable individual variation in foraging efficiency, it is hypothesized that the observed differences in cognitive abilities can be invoked to explain ecological differences among both species.     

Arboreal search in ants: Search on branches (Hymenoptera: Formicidae)

Ants (Formicidae) perform two distinct search behaviors for resources: on the ground they use irregular, almost random alternating looping, and on branches and leaves they resort to outline-tracing (arboreal systematic search), whereby the individual systematically turns to one side at bifurcations and to the opposite side when turning about at end points. Experiments with searching Formica pallidefulva and Crematogaster cerasion artificial stick mazes under seminatural conditions demonstrated that bifurcations and end points only trigger turn decisions, whereas an intrinsic mechanism specifies the handedness of such turns. Arboreal homing differs from arboreal searching by a much stronger tendency to rectify paths by counterturning. The theory is advanced that searching on branches by outline-tracing is evolutionarily derived from ranging search by superposing a sustained intrinsic turn bias and by suppressing random turns.     

Patterns in foraging and nesting ecology in the neotropical ant, <Emphasis Type="Italic">Gnamptogenys moelleri</Emphasis> (Formicidae,Ponerinae)

Summary This study provides quantitative field data on the natural history and foraging behaviour of the Neotropical bromeliad-nesting ant Gnamptogenys moelleri (Ponerinae) in a sandy plain forest in Southeast Brazil. The ant nested on different bromeliad species and the nests were more frequently found in bigger bromeliads. The species used a wide array of invertebrates in its diet, hunting for live prey and scavenging the majority of the items from dead animals. The food items varied greatly in size (1 to 26 mm). Hunting was always performed by solitary workers. Retrieving was performed by solitary workers (small items), or by a group of 3 to 12 workers recruited to the food source (large items). Almost all G. moelleri foraging activity was restricted to the nest bromeliad. In the warm period more ants left the nest to forage, and foraging trips achieved greater distances compared to the cool season. Trap data revealed that overall availability of arthropod prey is higher in the summer than in the winter. The opportunism in nest site use and in foraging behaviour, the small foraging area, as well as the seasonal differences in foraging activity are discussed and compared with other tropical ants.Received 30 May 2003; revised 22 September 2003; accepted 3 October 2003.     

Description of a new species of the genus Anochetus Mayr (Hymenoptera: Formicidae) from Orchid Island,Taiwan

A trap-jaw ant Anochetus lanyuensis sp. nov., belonging to the graeffei species group Brown, 1978, is described on the basis of worker and gyne castes from Orchid Island (Lanyu), Taiwan. A. lanyuensis sp. nov. is easily distinguishable from the other species in the graeffei species group by the large size of its eye, longitudinal striae on the pronotal disc, and concave dorsal margin of the petiolar node in the frontal view.     

Spatial specialization of the foragers and foraging strategy inLasius fuliginosus (Latreille) (Hymenoptera,Formicidae)

Summary The spatial specialization inLasius fuliginosus was investigated in the field by a mass-marking of foragers with colors. In the spring, summer and autumn, foragers exhibit a high degree of persistence, with coefficients of fidelity between 83 and 96%, in using a particular foraging trail, in visiting a particular tree or shrub housing aphid colonies, and even micro-sites like a particular branch. A high degree of fidelity to particular temporary hunting ground areas has also been shown. Trail and aphid site fidelity persist for at least 1 to 3 months and are preserved through the hibernation period (about 5 months). However, in early spring, a period during which food sources are scarce, trail fidelity is lower (coefficient of fidelity: 57%).Spatial specialization develops quickly in foragers recruited to a new permanent food source. Once acquired, the specialization is not rigid since specialized honeydew collectors can shift from a no more rewarding aphid site to other aphid sites of the same trail on which they develop a secondary specialization.The ecological and behavioral aspects of the spatial specialization inL. fuliginosus are discussed with reference to the resource structure of the habitat.     

Observation of group recruitment to prey in a primitive ponerine ant,Amblyopone sp. (reclinata group) (Hymenoptera: Formicidae)

Summary Group recruitment during foraging was observed in a primitive ponerine ant,Amblyopone sp. (reclinata group) under laboratory condition. Workers searched for prey singly; however, if a item of prey was stung by a worker, other ants joined the attack. After the prey became immobile, one of the workers laid a trail directly toward the nest. This scout worker recruited additional workers (between 3 and 33). They formed a single file procession to the point of prey capture, and cooperatively transported the prey. A scout worker could stimulate nest workers to leave the nest without direct contact, and the recruited workers could trace the trail without guidance by the scout worker. This is the first report of recruitment behavior during foraging in the primitive antAmblyopone.