Assisted dispersal and reproductive success in an ant species with matchmaking

Workers of the ant Cardiocondyla elegans drop female sexuals into the nest entrance of other colonies to promote outbreeding with unrelated, wingless males. Corroborating the results from previous years, we document that carrier and carried female sexuals are typically related and that the transfer initially occurs mostly from their joint natal colonies to unrelated colonies. Female sexuals mate multiply with up to seven genetically distinguishable males. Contrary to our expectation, the colony growth rate of multiple‐mated and outbred female sexuals was lower than that of inbred or single‐mated females, leading to the question of why female sexuals mate multiply at all. Despite the obvious costs, multiple mating might be a way for female sexuals to “pay rent” for hibernation in an alien nest. We argue that in addition to evade inbreeding depression from regular sibling mating over many generations, assisted dispersal might also be a strategy for minimizing the risk of losing all reproductive investment when nests are flooded in winter.     

Massacre of the innocents in Cardiocondyla thoracica: Manipulation by adult ant males incites workers to kill their immature rivals

Wingless males of the ant genus Cardiocondyla exhibit a remarkable range of intrasexual competition, from mutual tolerance among males in the colonies of some species to regular lethal fighting in the nests of others. Here, we describe male–male antagonism in Cardiocondyla thoracica (Smith, 1859) from Northern Australia. Males appear to widely ignore adult competitors, but grab defenseless, young rivals during or immediately after emergence and daub them with hindgut secretion. This fluid elicits fatal worker aggression against the besmeared individual. Besmearing and subsequent worker aggression is known from other species of Cardiocondyla but is usually directed towards adult contenders, whereas males kill freshly eclosing males by biting or dismembering. The behavior of C. thoracica males thus constitutes a novel nuance of rival elimination.     

Behavior of ergatoid males in the ant,Cardiocondyla nuda

Summary Ergatoid males of the ant,Cardiocondyla nuda, attack and frequently kill young males during or shortly after eclosion. Smaller colonies therefore contain typically only one adult male, which may inseminate all alate queens which are reared in the colony over a few weeks. In larger colonies, several males may be present, however, fighting among adult males was not observed. We discuss the significance of male fighting behavior in ants.     

Between fighting and tolerance: reproductive biology of wingless males in the ant Cardiocondyla venustula

Male reproductive tactics vary widely across the species of the ant genus Cardiocondyla, from obligatory lethal combat among co‐occurring males to complete mutual tolerance. The African species C. venustula Wheeler, 1908 has an intermediate phylogenetic position between taxa with fighting males and taxa with tolerant males and also shows an intermediate male behavior. Males from 2 native populations in South Africa and a population introduced to Puerto Rico attacked and killed freshly eclosing rivals but rarely engaged in deadly fights with adult competitors. Instead, several males per colony established small “territories” in their natal nests and defended them against other males. Males with a stable territory had more contact with female sexuals than nonterritorial males and more frequently engaged in mating attempts. In controlled choice experiments, female sexuals did not show any preference for particular males. We suggest that male territoriality in C. venustula is an adaptation to the seasonal production of large numbers of female sexuals by multiple mothers.     

Isozymes of two fire ant species and their hybrid

Electrophoretic banding patterns of eight enzyme systems in Solenopsis xyloni, S. germinata and their hybrid were studied. Repression of paternal alleles was found in aldehyde oxidase, isocitrate dehydrogenase, leucine amino peptidase and malic enzyme.     

β-eudesmol-induced aggression in the leaf-cutting ant Atta sexdens rubropilosa

Leaf‐cutting ants are highly polyphagous insects, but some plants escape their attack due to the presence of secondary metabolites that are toxic to the ant–fungus symbiosis. Previous studies have demonstrated that the terpenoid β‐eudesmol extracted from Eucalyptus species (Myrtaceae) is responsible for the deleterious behavior in colonies of leaf‐cutting ant species. The objective of this study was to evaluate the effect of β‐eudesmol on workers of the leaf‐cutting ant Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae). This chemical caused behavioral modification in the colonies, leading to mutilation and death of workers. It is suggested that β‐eudesmol interferes with colony nestmate recognition. As a consequence, colony cohesion may be disrupted by β‐eudesmol what could be used as an additional control tactic against this important pest ant.     

Temporal and spatial patterns of foraging in two syntopic ant species,Manica yessensis and Formica lemani,on Mount Fuji,Japan

Spatiotemporal characteristics of terrestrial foraging were studied in two ant species, Manica yessensis and Formica lemani, in a volcanic desert on the southeast slope of Mount Fuji, Gotenba, Japan. Both ants are common in this habitat, and they construct underground nests in this dry area with sparse vegetation. Nests of M. yessensis have multiple nest-openings on the surface, whereas nests of F. lemani have very few openings, but their nesting and foraging areas overlap completely. A “mark-and-observe” method applied to M. yessensis demonstrated that worker ants of this species move between openings more than 3 m away. A study plot (6 m × 12 m quadrat) was set up, in which all nest-openings of both species were mapped. Day-long observations on numbers of foragers in this plot revealed that foraging M. yessensis are active in morning and evening, while F. lemani continues foraging all day, but both species cease activity at night. Associations between locations of foragers and nest-openings differed significantly between the two species, that is, surface foraging of M. yessensis workers was largely confined to the vicinity of their nest-openings, whereas foragers of F. lemani travelled far from their nest-openings. The function of multiple nest-openings in M. yessensis is discussed.     

A new record ant species of the genus Cardiocondyla Emery from China(Hymenoptera: Formicidae)

An ant species, Cardiocondyla gibbosa Kuznetzov-Ugamsky, 1927, is newly recorded from China. The specimens were collected from Shule County of Kashgar, Xinjiang(39°14′N, 76° 22′E; elev. 1 248 m). All the specimens are kept in Institute of Zoology, Shaanxi Normal University. A key based on worker caste to known species of Cardiocondyla from China is provided.     

Effect of park age,size, shape and isolation on ant assemblages in two cities of Southern Spain

In the context of conservation biology, we have searched for the most influential characteristics of urban parks on ecological diversity. In this study, therefore, we studied the ant community of 24 parks in two cities of Southern Spain (Cordoba and Seville). In total, 46 species were found. Abundant and widely distributed species were synanthropic ones, such as Lasius grandis, Pheidole pallidula or Tapinoma nigerrimum, and exotic species such as Cardiocondyla mauritanica. However some parks also harbored natural habitat‐preferring species. Park size, shape and distance to city outskirts were the most important predictors of species richness and diversity. Likewise, park age influenced the composition of the ant fauna.     

Biodiversity in tropical agroforests and the ecological role of ants and ant diversity in predatory function

Abstract.  1. Intensive agricultural practices drive biodiversity loss with potentially drastic consequences for ecosystem services. To advance conservation and production goals, agricultural practices should be compatible with biodiversity. Traditional or less intensive systems (i.e. with fewer agrochemicals, less mechanisation, more crop species) such as shaded coffee and cacao agroforests are highlighted for their ability to provide a refuge for biodiversity and may also enhance certain ecosystem functions (i.e. predation).
2. Ants are an important predator group in tropical agroforestry systems. Generally, ant biodiversity declines with coffee and cacao intensification yet the literature lacks a summary of the known mechanisms for ant declines and how this diversity loss may affect the role of ants as predators.
3. Here, how shaded coffee and cacao agroforestry systems protect biodiversity and may preserve related ecosystem functions is discussed in the context of ants as predators. Specifically, the relationships between biodiversity and predation, links between agriculture and conservation, patterns and mechanisms for ant diversity loss with agricultural intensification, importance of ants as control agents of pests and fungal diseases, and whether ant diversity may influence the functional role of ants as predators are addressed. Furthermore, because of the importance of homopteran-tending by ants in the ecological and agricultural literature, as well as to the success of ants as predators, the costs and benefits of promoting ants in agroforests are discussed.
4. Especially where the diversity of ants and other predators is high, as in traditional agroforestry systems, both agroecosystem function and conservation goals will be advanced by biodiversity protection.     

Analysis of brood development in the ant Amblyopone silvestrii, with special reference to colony bionomics

There are five larval instars in the temperate, subterranean ponerine ant, Amblyopone silvestrii (Wheeler). An examination of the seasonal developmental patterns of immatures collected from more than 100 colonies collected in the field revealed that most or all of the newly hatched individuals overwintered as second to fifth instar larvae and emerged as adults in the next summer. The fifth instar larvae were most abundant in the colony's larval population all year round. The number of eggs present in the nest diminished temporarily in midsummer, although queens collected during this period maintained fully developed ovaries with mature oocytes. When the larvae matured, they were usually moved to temporary nests away from the nest area of the colony and finished pupation and eclosion there, while accompanied by a small number of workers. Pupation of sexuals occurred in the more distant cocoon chambers compared with pupation of workers.     

Factors affecting internest variation in the aggressiveness of a polygynous ant, Camponotus yamaokai

The facultatively polygynous ant Camponotus yamaokai shows various degrees of internest hostility. We examined the relationship between aggressiveness and possible factors that affect the level of hostility, such as internest distance, numbers of queens and workers, and brood size. We found that the aggression level did not significantly correlate with these factors. Our study suggests that information on the colony genetic structure is important in understanding variation in the aggressiveness of polygynous colonies.     

Genetic structure and reproductive strategy of the ant Cardiocondyla elegans: strictly monogynous nests invaded by unrelated sexuals

Cardiocondyla elegans is a Mediterranean ant that nests on river banks. It rears only wingless (ergatoid) males that live peacefully in the same nest as opposed to other species of the same genus, which have both peaceful, winged and mutually aggressive 'ergatoid' males. Using microsatellite analysis, we investigated the genetic structure of 21 colonies from three different locations as well as the parentage of sexuals of two colonies of C. elegans. We show that C. elegans is strictly monogynous, and that its nests can contain foreign sexuals. The presence of alien sexuals inside ant nests is described for the first time and probably counteracts inbreeding resulting from matings between siblings. In the laboratory, aggression tests showed that workers only allow alien males to enter their nests, while all winged female sexuals attempting to enter were attacked. Nevertheless, the presence of alien female sexuals in nests in the field seems to result from active carrying behaviour by workers during the reproductive period.     

Influence of the wood ant, Formica polyctena, on soil nutrient and the spruce tree growth

The effect of Formica polyctena ant nests on the distribution of soil nutrients, soil pH and the growth of Norway spruce trees was studied in the southern part of the Czech Republic. Soil nutrient content (exchangeable P, N, K and pH) and growth of mature spruce trees were measured at four distances from the nearest ant hill (0–1, 3–5, 10–50 and >200 m). Trees at all distances were visited by ants, except for those >200 m from the nearest nest. Soil pH and of P, K and NO₃ concentrations were higher near ant nests (<1 m), and pH and K at distances of 3–5 m, when compared with distances of 10–50 and >200 m from the nests, where no significant differences in these variables were detected. In contrast, tree ring analyses (1974–2004) showed that trees >200 m from the ant nests grew significantly faster than trees at other distances, followed by trees within 1 m of the nests. No growth differences were found between the growth of trees at 3–5 and 10–50 m from ant nests. We postulate that nutrient and carbohydrate removal of honeydew collected by ant‐tended aphids are slowing growth of tree. However, trees may partly compensate for this depletion by having access to a larger supply of soil nutrients near ant nests.     

Evidence for mating plugs in the fire ant <Emphasis Type="Italic">Solenopsis invicta</Emphasis>

Summary Male inhibition of female re-mating is com-mon in many insects. Mating plugs, used by males to con-trol female re-mating, have been postulated in several ant species. Recent studies of bumblebees have described re-mating inhibition by male accessory gland secretions. Fire ants Solenopsis invicta possess accessory glands containing the same four fatty acids as do the bumblebees. Furthermore it appears that some of these acids are transferred to the female at mating. Thus, it is possible that single mating of fire ant females may be enforced by male mating plugs.     

Diel and seasonal patterns of foraging activity in the arboreal ant Crematogaster matsumurai Forel

The foraging habits of the arboreal ant Crematogaster matsumurai Forel were studied in natural and captive colonies in southern Kyushu, Japan. The nests of C. matsumurai are made mainly in the trunks of living trees. In the natural environment, the species mainly lives in decayed parts of relatively tall trees, such as Acer palmatum, Prunus jamasakura and Prunus yedoensis. Observation over a 24 h period showed that C. matsumurai foraged actively at night as well as during the day. The foraging of the workers out of the nest was seen from early spring to late autumn, both on the tree and on the ground. As protein sources, aphids were mainly collected by foragers from the tree, while small parts of dead insects or other arthropods were mainly collected from the ground surface. The foraging activity of workers is assumed to be influenced by the quantity and quality of food rather than seasonality.     

Temporal variation in foraging activity and efficiency and the role of hitchhiking behaviour in the leaf-cutting ant, Atta cephalotes

Two phenomena are integral to the foraging behaviour of leaf‐cutting ants in the genus Atta: hitchhiking (where small ants ride on leaf fragments carried by larger workers) and rhythmic foraging (where foraging activity shows marked fluctuations over time). While parasitism by phorid flies has been implicated in eliciting both behaviours, recent research suggests fungal contaminants and the need to procure sap also play a key role in eliciting hitchhiking. For wild colonies of Atta cephalotes L. (Hymenoptera: Formicidae), we investigated the extent to which hitchhiking frequency varied in space and time and the foraging performance of day‐time and night‐time workers. Day‐time foragers were considerably smaller than nocturnal foragers, a trend previously described as a response to diurnal phorids. Despite their smaller size, day‐time foragers had higher foraging performance, perhaps as a consequence of decreased trail congestion. Larger leaf‐carriers were more likely to carry hitchhikers and hitchhiking frequency was higher at night, an observation that conflicts with the parasitoid defence hypothesis, but not with the leaf sap and fungal defence hypotheses. Hitchhikers constitute a major proportion (typically 12%) of the loads carried by workers, and have three times the effect of leaf fragment mass on forager velocity. However, they reduced energetic efficiency by only 2.6% and provisioning rate by 5.9%. Our results provide partial support for the parasitoid defence hypothesis, but suggest that both the risks of parasitism and the opportunity‐cost to foraging associated with carrying hitchhikers may be low.     

蚜虫触角感受器结构及功能研究进展

本文综述了蚜虫触角上感受器在形态和生理功能方面的研究进展;介绍了常用的触角感受器研究方法;文中对分布于蚜虫触角上的感受器种类进行了阐述,描述了各类感受器的外部形态特征,及其内部超微结构.此外,探讨了不同类型的感受器的生理功能,及其在分子水平上的化学感受接收的机制.     

Structure of ground‐dwelling ant communities in burned and unburned areas in Brazilian subtropical grasslands

Fire is frequently used in the management of pastures in southern Brazil, but its effects on ground‐dwelling ant communities in Brazilian subtropical grasslands is still poorly understood. Here, we compared ant species richness and composition between periodically burned and unburned areas in native grasslands of the Atlantic Forest biome. In total, we found 35 epigeic ant species in burned and unburned areas. There was slightly higher species richness in burned than in unburned areas, independent of the sampling period (season). There was a significant difference in richness over the sampling period (season effect). Species composition varied significantly between the areas, in which nine species (26%) occurred only in burned areas, eight (23%) occurred only in unburned areas, and 18 (51%) occurred in both. Four species showed a significant preference for burned sites (Camponotus crassus, Linepithema humile and two undetermined species of Pheidole and Solenopsis). Although this study did not separate fire effects on ground‐dwelling ant communities (due to sampling design), it provides new information regarding subtropical native grasslands that can be used as a baseline for future studies.     

Refuse dumps of leaf‐cutting ants as a deterrent for ant herbivory: does refuse age matter?

Leaf‐cutting ants often avoid contact with their waste because it harbors microorganisms that are dangerous to the ants and their symbiotic fungus. Therefore, the use of ant waste (i.e., refuse dumps) has been proposed as a deterrent method against leafcutter attack. We tested experimentally whether the age of the refuse dump (fresh vs. old) affects the herbivory‐deterrent effect against the leaf‐cutting ant Acromyrmex lobicornis Emery (Hymenoptera: Formicidae). Refuse placed around seedlings significantly delayed the initiation attacks of leaf‐cutting ants, and this deterrent effect decreased gradually over a period of 30 days. The initial strength of this decrease was the same for newly‐discarded ( ‘new’) refuse and refuse from the bottom of the ants’ waste pile (‘old’ refuse). However, the loss of deterrent effect over time was more rapid for new than old refuse. A further experimental manipulation, replacement of refuse every 3 days, had no effect on the deterrent effect for old refuse, but increased this effect for new refuse, although the amount of this increase gradually weakened over the course of the 30‐day experiment. We speculate on the possible causes of these effects, their consequences for the hygienic behavior of leaf‐cutting ants, and on the use of ant debris as short‐term control method against leaf‐cutting ants.