Ant Crematogaster Research Articles

Relative colony size of parabiotic species demonstrates inversion with growth

Ant-gardens are a mutualistic association involving epiphyte plants and one or several ant species. Ant-gardens inhabited by Camponotus femoratus (Fabricius, 1804) and Crematogaster levior (Longino, 2003), are the most commonly found in the Neotropical Region. These two ant species share the nest and their foraging trails but keep their brood separated (i.e., parabiosis). The larger Ca. femoratus defends the nest, while benefits from the foraging ability of C. levior. However, it is still not experimentally proven which of the two parabiotic species initiates nest building. Moreover, the growth dynamic of population for these two ant species is unknown. To address these topics, we analyzed the change in proportion of individuals from the two species depending on the nest volume. Our results show that (1) the proportion of Ca. femoratus workers increased with nest volume leading to a numerically domination of Ca. femoratus in the largest nests and (2) C. levior workers are likely to initiate the nest construction given that it represents the overwhelming majority of the small nests. These results reinforce the knowledge of the complex and understudied interaction between these two ant species. Ant-gardens arise as a mutualistic association between ants and epiphyte plants. Plants benefit from the dispersal of their seeds and defense by the patrolling ants, while provide nest structure to the ants. The ants Crematogaster levior and Camponotus femoratus live within common Ant-gardens. We studied the growth dynamic of the two species population with the volume of the Ant-garden nest. The proportion of Ca. femoratus increases with the nest volume resulting in a domination of the latter species on C. levior in the largest nets. Furthermore, our results, combined with field observations, suggest that C. levior can initiate the nest construction. These findings precise the complex relationship between the two ant species.

Application of CO2 carbon stable isotope analysis to ant trophic ecology

AbstractStable isotope analysis of animal tissues is commonly used to infer diet and trophic position. However, it requires destructive sampling. The analysis of carbon isotopes from exhaled CO2 is non‐invasive and can provide useful ecological information because isotopic CO2 signatures can reflect the diet and metabolism of an animal. However, this methodology has rarely been used on invertebrates and never on social insects. Here, we first tested whether this method reflects differences in δ13C‐CO2 between workers of the Mediterranean ant Crematogaster scutellaris (Olivier) (Hymenoptera: Formicidae, Crematogastrini) fed with sugar from beet (C3; Beta vulgaris L., Amaranthaceae) or cane (C4; Saccharum officinarum L., Poaceae). We found that a significant difference can be obtained after 24 h. Consequently, we used this technique on wild co‐occurring ant species with different feeding preferences to assess their reliance on C3 or C4 sources. For this purpose, we sampled workers of C. scutellaris, the invasive garden ant Lasius neglectus (van Loon et al.) (Lasiini), and the harvester ant Messor capitatus (Latreille) (Stenammini). No significant differences in their carbon isotopic signatures were recorded, suggesting that in our study site no niche partitioning occurs based on the carbon pathway, with all species sharing similar resources. However, further analysis revealed that M. capitatus, a seed‐eating ant, can be regarded as a C3 specialist, whereas L. neglectus and C. scutellaris are generalists that rely on both C3 and C4 pathways, though with a preference for the former. Our results show that this methodology can be applied even to small animals such as ants and can provide useful information on the diets of generalist omnivores.

Browsing impacts on Acacia drepanolobium Sjostedt and associated ant guilds in Ol Pejeta Conservancy, Kenya.

The numbers of Acacia drepanolobium trees are declining over much of Africa and large mammals particularly more prone and vulnerable to loss of habitat owing to human settlement encroachment. In Ol pejeta conservancy a sanctuary for the protection of the endangered black rhino, there is significant browse and vegetation pressure on the habitat particularly on the Acacia drepanolobium tree population. This study aimed to investigate the Acacia drepanolobium and ants’ interaction under different browsing intensities, determine effect of prescribed burnings on Crematogaster ants and Acacia drepanolobium interaction, investigate the tenancy dynamics of ants under varying morphological characteristics of Acacia drepanolobium trees, and finally to determine if Crematogaster ants’ communities/ colonization on Acacia drepanolobium change over time. Twelve (12) randomly chosen plots (keyed in a waypoint on the GPS) with fifty or more Acacia drepanolobium trees were studied for the study as follows, two (2) in a Chimpanzee Sanctuary where elephant, giraffe and rhino are excluded (control), six (6) in the reserve and four (4) in the Ranch. Two (2) plots treated with prescribed burning (fire) were compared with two un-burnt plots. All data collected was fed and entered into Excel spreadsheet and Statistical Package for the Social Science version 20 for analysis. The data were then processed into quantitative tables to give a comparative analysis for response obtained. Size class distributions of the reserve, Ranch and control were compared by means of Analysis of Variance (ANOVA) and other relevant parametric statistics. The result shows that in Ol pejeta conservancy browsing levels has statistically significant effect on Crematogaster ants and Acacia drepanolobium interaction. There was a strong and notable distinction between the four acacia ant species in the overall extends and levels of tenancy while responding to varied browsing pressures; Crematogaster mimosae and Tetraponera penzigi were found to be the most abundant/frequently observed ant species occupying trees in the reserve where there is intensive browsing (Reserve) and the ranch with medium browsing intensity. From this research experimental evidence explains the ability of trees to re-induce greater spine and gall numbers and that ant tenancy in A. drepanolobium is influenced by the tree’s morphological characteristics. The findings and results also indicated that prescribed burning significantly affected the type of ant inhabiting the A. drepanolobium tree. Going by the results of this paper, it was concluded that this mutualism is a key component of Ol pejeta biodiversity and ecosystem function. The study recommends that the results in this research should be used in determining ecological factors that influence conservation sustainability and predict the consequences of heavy browsing pressure, morphological characteristics and prescribed burning on the health of Acacia drepanolobium.

Two additions to the Iberian myrmecofauna: Crematogaster inermis Mayr, 1862, a newly established, tree-nesting species, and Trichomyrmex mayri (Forel, 1902), an emerging exotic species temporarily nesting in Spain (Hymenoptera, Formicidae)

Exotic ants are a growing component of urban and disturbed habitats worldwide. Sampling in two Iberian Mediterranean localities revealed several exotic species. The tree-nesting, black acrobat ant Crematogaster inermis Mayr, 1862, has been detected nesting outdoors on a Robinia pseudoacacia tree in a public garden in Valencia (Spain) and represents a new addition to the continental European fauna. Collection details, a morphological description, biometry, and the remarkable presence of short spines in smaller specimens are also given for this species. A case of an ephemeral establishment of several exotic ant species in a palm grove is also discussed. This case includes C. inermis and Trichomyrmex mayri, also a novelty for the Iberian Peninsula.

Tools of the trade: MicroCT reveals native structure and functional morphology of organs that drive caterpillar\u2013ant interactions

Caterpillars of many lycaenid butterflies are tended by ants that offer protection from predators and parasitoids. Specialized structures such as glands, ciliary organs and chitinous ornamentation in caterpillars play key roles in the underlying tactile, acoustic, and chemical communication between caterpillars and ants. Although the ecological, evolutionary, and behavioural aspects of these interactions are well studied, the mechanisms (i.e., the functional morphology) that drive the specialized interactive organs are poorly characterized. We used advanced X-ray microtomography (MicroCT) to delineate internal, native morphology of specialized larval dew patches, nectar glands, and tactile ciliary organs that mediate interactions between Crematogaster ants and caterpillars of the obligate myrmecophilous Apharitis lilacinus butterfly. Our non-destructive MicroCT analysis provided novel 3-D insights into the native structure and positions of these specialized organs in unmatched detail. This analysis also suggested a functional relationship between organ structures and surrounding muscles and nervation that operate the glands and tactile organs, including a ‘lasso bag’ control mechanism for dew patches and muscle control for other organs. This provided a holistic understanding of the organs that drive very close caterpillar–ant interactions. Our MicroCT analysis opens a door for similar structural and functional analysis of adaptive insect morphology.

Resource-dependent mutual association with sap-feeders and a high predation rate in the ant Crematogaster scutellaris: help or harm in olive pest control?

Crematogaster scutellaris is a common tree-nesting ant in Mediterranean olive groves, where it acts as both predator and soft scale insect tender. We aimed to quantify the predatory action of this species and assess whether it influences the distribution of soft scale insects. Predation was investigated through experiments using live prey. The mutualistic relationship between ants and soft scales was assessed by supplementing sugar, amino acids or water to ant colonies, then monitoring for changes in scale tending activity. The probability of soft scale infestation on trees hosting or not hosting ant nests was also estimated. Predation rates on trees hosting a C. scutellaris nest were significantly higher than on trees without nests. Tending activity was affected by carbohydrate and, surprisingly, water availability. While the presence of C. scutellaris was significantly correlated to soft scale infestation, it also favoured predation towards other insects, suggesting a potential role in influencing different insect pests.

Palatability of glyphosate in ants: a field experiment reveals broad acceptance of highly polluted solutions in a Mediterranean ant.

Glyphosate is a systemic herbicide still used in many countries, though there are several known detrimental effects on animals. Previous studies concerning its effects on social insects are available, but they are primarily focused on honeybees; little is known about the interactions of this compound with ants. Here, we assessed whether different concentrations of glyphosate can be perceived by ant workers and to what extent. As a model species, we used the Mediterranean ant Crematogaster scutellaris, commonly found in agroecosystems. We performed 3000 individual tests of acceptance using ten different solutions of various concentrations of the herbicide. Half of the solutions contained added sucrose in order to test the possible masking effect of the sugar taste on glyphosate. We used comparable glyphosate concentrations to those previously used in other studies on social insects or suggested by the producer. We found that the acceptance of the solutions decreased as the concentration of the herbicide increased. However, a significant percentage of ants drank the solutions with concentrations up to dozens of times higher than those inducing toxic effects in bees. In light of these results, we urge further assessment of the effects of glyphosate on ants, particularly because the food ingested by workers is transferred to the brood and queens, posing a potential threat to the health of the entire colony. Surprisingly, we did not record any difference in acceptance between solutions with and without sugar; this point is discussed regarding drought stress.

A new subterranean Crematogaster with one ommatidium from Cambodia, based on morphology and DNA (Hymenoptera: Formicidae)

Abstract A subterranean myrmicine ant Crematogaster monocula sp. nov. is described based on two worker specimens from Cambodia. This species belongs to the C. biroi group of the subgenus Orthocrema Santschi, 1918, which is characterized by developed subpetiolar process, developed subpostpetiolar process and sculptured mesosoma. The new species is easily distinguished from other species of Crematogaster Lund, 1831 by having only one ommatidium. DNA sequences comprising a 761 bp fragment of the 3’ region of the mitochondrial COI gene were amplified and analyzed for C. monocula sp. nov. and other closely related species from the same group. The interspecific COI divergence is 17.8% for C. monocula sp. nov. and C. reticulata Hosoishi, 2009. This species is unique in having the smallest eye in the genus Crematogaster.

Mating frequency and colony genetic structure analyses reveal unexpected polygyny in the Mediterranean acrobat ant Crematogaster scutellaris

Among eusocial Hymenoptera, ants represent an unrivalled example of diversity in number of queens and mating systems. Ant colonies may have one (monogyny) or several queens (polygyny) which can mate once (monoandry) or several times (polyandry). In this study, we analysed the genetic structure and breeding system of the Mediterranean acrobat ant Crematogaster scutellaris. Despite its widespread distribution and pivotal role in regulating arthropod communities, many details of the biology of this species have yet to be fully investigated. According to previous studies based on few observations, C. scutellaris is monogynous and monandrous with a claustral foundation phase. We assessed the mating frequency and the number of queens in 40 colonies using highly polymorphic, species-specific nuclear DNA microsatellite loci. The number of queens in each colony was directly inferred from the relatedness of workers. Moreover, in order to determine the proportion of multiple matings by queens, we performed both parental reconstruction analysis using offspring data and direct analysis of the sperm stored in the queen’s spermathecae. We investigated relatedness between queens and their mated males. The results showed that, although the majority of the colonies were monogynous, polygyny occurred in 10% of the nests. Monoandry was the norm: we found evidence of multiple paternity in just two out of 40 colonies. Finally, no relatedness was found between queens and their mates, indicating that the latter were from different colonies. This work is the first description of the genetic structure of the colonies of C. scutellaris and provides new insight for further investigation on the social organization, behaviour and ecology of Mediterranean acrobat ants.

Acrobat Ant, Crematogaster ashmeadi Emery (Insecta: Hymenoptera: Formicidae: Myrmicinae)

The ant Crematogaster ashmeadi (Emery) is commonly known as an acrobat ant. There are perhaps 10 species of Crematogaster in Florida, and C. ashmeadi is commonly found throughout the state (Deyrup, personal communication). Members of this genus are referred to as acrobat ants because of the flexible way that a worker holds its abdomen (gaster) up over the rest of its body. This document is EENY-333 , one of a series of Featured Creatures from the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: August 2004. 
 EENY333/IN610: Acrobat Ant, Crematogaster ashmeadi Emery (Insecta: Hymenoptera: Formicidae: Myrmicinae) (ufl.edu)

Acacia Ants Respond to Plant-Borne Vibrations Caused by Mammalian Browsers

Living in the African savanna is dangerous, especially for plants. Many plants therefore engage in mutualism with ants, in which plants provide food and shelter in exchange for protection against herbivores. Ants become alarmed when the plant takes on some sort of damage. They immediately emerge from their plant shelter and aggressively defend the plant. Mammalian herbivores can have devastating effects on trees by browsing, breaking tree branches, stripping bark, and pushing over entire trees. However, mutualistic ants substantially reduce the amount of damage. To efficiently protect the tree, ants need to rapidly react together when the tree is under attack. Here, we show that the acacia ant Crematogaster mimosae defends its host tree by exploiting plant-borne vibrations caused by browsers feeding on the tree. Experiments with controlled vibrations show that ants discriminate browser-induced vibrations from those induced by wind, become alarmed, and patrol on the branches. Browser-induced vibrations serve as a long-distance alarm cue. The vibrations propagate through the whole acacia tree and trigger ants' defensive behavior, even on the other side of the tree. Furthermore, the ants make use of tropotactic directional vibration sensing to orient to the attacked part of the tree and fight back the attacker.

Making the right choice: how Crematogaster scutellaris queens choose to co-found in relation to nest availability

One of the main tasks a freshly mated ant queen has to face is to find a safe and suitable nest site to start a new colony. Colony foundation by associated queens, also known as pleometrosis, has been described for several ant species and, under specific selective pressures, represents an alternative to independent colony foundation. Despite most newly mated queens of the common Mediterranean acrobat ant Crematogaster scutellaris generally adopting independent colony foundation inside tree trunks, both field and laboratory studies have demonstrated that the formation of pleometrotic groups may occur, particularly inside lignified aphid galls on poplar or oak trees. These associations typically end with the survival of only one queen after the foundation phase, and the benefits they may provide remain unclear. In this study, we investigated how queen density and different nest availability may promote the formation of pleometrotic associations in C. scutellaris. We found that occupied nests are not actively sought after by queens, as hypothesised in previous studies, but might be accepted when they are the only safe refugia available. Moreover, the tendency to form groups increases as queen density increases, and nest availability is a limiting factor. Finally, we found no evidence that the size of the queen affects whether to join an already occupied nest.

Host‐plant dissections reveal contrasting distributions of Crematogaster ants and their symbionts in two myrmecophytic Macaranga species

1. Ant–plant mutualisms are among the most widespread and ecologically important insect–plant interactions in the tropics. The multitrophic mutualism involving Macaranga plants (Euphorbiaceae) and Crematogaster ants (Formicidae) is the most diverse in Southeast Asia. This interaction also includes trophobiotic scale insects (Coccidae) and nematodes inhabiting ant refuse piles.2. Here two myrmecophytic systems were compared, Macaranga trachyphylla with Crematogaster captiosa (Mt + Cc) and Macaranga beccariana with Crematogaster decamera (Mb + Cd), using a fine‐scale dissection of the stems. For the two plant species, for each internode, both contents (ants, coccids, refuse piles) and structure (internode height, numbers of open and occluded ant holes) were recorded.3. There were significant patterns in the vertical distribution of ant colonies and their symbionts in the plant stems. Most coccids were kept in the highest sections of both systems, although Mb + Cd hosted a broader range of coccid species than Mt + Cc. Three nematode species were recorded, but with a rather low specificity to plant or ant species. Furthermore, the fine‐scale distribution showed aggregation of closed holes with ant brood and separation of nematode‐infested refuse piles from eggs.4. The results of this study indicate that ants manipulate spatial colony structure via distribution of brood, holes and the symbionts. It is suggested that ants optimise the location of refuse piles and occluded holes via spatial heterogeneity in their distribution among internodes. This paper discusses the protective role of occluded holes and demonstrates some general interactions with other symbiotic fauna.

Phylogenetic analysis and systematic position of two new species of the ant genus Crematogaster (Hymenoptera, Formicidae) from Southeast Asia

Two distinct new species of the ant genus Crematogaster, C. khmerensis sp. nov. and C. pfeifferi sp. nov., are described from Cambodia and Malaysia, respectively. The two species are unique among Asian Crematogaster in that they have vertically directed propodeal spines, but their systematic positions have not been determined based on morphological characters alone. Molecular phylogenetic analysis of 89 Crematogaster taxon matrices previously published plus C. khmerensis sp. nov., using nuclear genes, reveals that C. khmerensis sp. nov. is nested within the Australo-Asian Crematogaster clade. Morphological assignment of the developed pronotal shoulders implies a close relationship between C. khmerensis sp. nov. and the C. tetracantha-group. Based on molecular and morphological evidence, we erect a new species group, C. khmerensis-group, to contain C. khmerensis sp. nov. and C. pfeifferi sp. nov. Divergence time estimates using MCMCTree shows that the root node of the C. khmerensis sp. nov. terminal is estimated to be of middle Miocene age at 15 million years old. The position of the C. khmerensis-group well supports the Oriental- to Australian-region dispersal history that has been proposed for the Australo-Asian Crematogaster clade.

Ant-mediated ecosystem services and disservices on marketable yield in cocoa agroforestry systems

Abstract The impact of complex direct and indirect interactions between multiple functional groups on plants is poorly documented. In tropical agroecosystems, ants interact with crop mutualists and antagonists, however, little is known about effects of dominants ant community properties on the consequence of such cascading interactions which can be measured through final ecosystem service, crop yield. Here, we present a replicated ant fauna manipulation experiment in cocoa agroecosystems, where we used ant exclusion treatments to test the economic importance of the presence of ants, and two additional treatments where we experimentally introduced one of two common dominant ant species which allowed comparing their effects with those of the naturally occurring ant fauna. The proximate aim was to assess the impact of ants Crematogaster sp., Camponotus brutus Auguste-Henri Forel and Oecophylla longinoda Latreille on cacao yield, which is known to depend on several, cascading intermediate ecosystem services (e.g. control of specific pests). Ants provided ecosystem services in term of reduced pest damage caused by Salhbergella singularis Hagh (Hemiptera: Miridae) and Characoma stictigrapta Hmps (Lepidoptera: Noctuidae) but also disservices such as increased pathogen disease caused by Phyphthora megakarya Brasier and Griffin dissemination and indirectly enhanced damage of other pest species. Yields were highest in non-manipulated and species-rich ant communities, whereas ant exclusion and communities dominated by a single species decreased yield by more than 30%. Associated ant communities between dominant and non-dominant species resulted in the same yields as in non-manipulated controls. Dominant ant communities maximized the control of a particular pest species, but not cacao yield. We show a positive relationship between ant species rich communities and financial performance and we postulate that complex agroecosystems can offer competitive business opportunities for small-scale farmers, while contributing to biodiversity conservation. However, more interdisciplinary studies are needed to quantify financial and biodiversity performance opportunities to allow up-scaling of these findings.

Fire disturbance disrupts an acacia ant–plant mutualism in favor of a subordinate ant species

Although disturbance theory has been recognized as a useful framework in examining the stability of ant-plant mutualisms, very few studies have examined the effects of fire disturbance on these mutualisms. In myrmecophyte-dominated savannas, fire and herbivory are key drivers that could influence ant-plant mutualisms by causing complete colony mortality and/or decreasing colony size, which potentially could alter dominance hierarchies if subordinate species are more fire resilient. We used a large-scale, replicated fire experiment to examine long-term effects of fire on acacia-ant community composition. To determine if fire shifted ant occupancy from a competitive dominant to a subordinate ant species, we surveyed the acacia-ant community in 6-7 yr old burn sites and examined how the spatial scale of these burns influenced ant community responses. We then used two short-term fire experiments to explore possible mechanisms for the shifts in community patterns observed. Because survival of ant colonies is largely dependent on their ability to detect and escape an approaching fire, we first tested the evacuation response of all four ant species when exposed to smoke (fire signal). Then to better understand how fire and its interaction with large mammal herbivory affect the density of ants per tree, we quantified ant worker density in small prescribed burns within herbivore exclusion plots. We found clear evidence suggesting that fire disturbance favored the subordinate ant Crematogaster nigriceps more than the dominant and strong mutualist ant C.mimosae, whereby C.nigriceps (1) was the only species to occupy a greater proportion of trees in 6-7yr old burn sites compared to unburned sites, (2) had higher burn/unburn tree ratios with increasing burn size, and (3) evacuated significantly faster than C.mimosae in the presence of smoke. Fire and herbivory had opposite effects on ant density per meter of branch for both C.nigriceps and C.mimosae, with fire decreasing ant densities per meter of branch and the presence of large herbivores increasing ant density. Taken together, these experiments suggest that major ecosystem disturbances like fire can disrupt mutualistic associations and maintain diversity in partner quality and identity despite a clear dominance hierarchy.

Impacts of worker density in colony‐level aggression, expansion, and survival of the acacia‐ant Crematogaster mimosae

AbstractExperimental studies assessing the impact of demographic changes on aggression and inter‐group competitive outcomes in communities of social species are rare. This gap in our knowledge is important, not only because social species are foundational elements of many terrestrial ecosystems, but because interference competition among social groups often involves decision‐like processes influenced by demographic and environmental contexts. In East Africa, the symbiotic ant Crematogaster mimosae is a co‐dominant competitor that engages in high‐mortality, intra‐ and interspecific battles for sole possession of host trees. We manipulated worker density on C. mimosae Acacia host trees, and the colony's opportunity to expand onto neighboring trees to identify how these factors influenced colony‐level aggression, expansion success, and longer‐term survivorship. Worker density on focal trees was increased through translocation of domatia‐bearing branches, and was decreased using partial tree fumigations. We examined impacts of density manipulations on aggression and immediate expansion success under two different risk scenarios. We tied focal trees to either an experimentally emptied‐tree (low‐risk treatment), or to a C. nigriceps‐occupied tree (high‐risk treatment). Expansion success onto emptied neighbor trees was 100% for controls and increased‐density colonies, but only 50% for decreased‐density colonies, despite the fact that host trees are a limiting resource in this system. Success expanding onto trees occupied by a heterospecific competitor reached 36%, 40%, and 79% in decreased, control, and increased‐density trees, respectively. Our results show that changes in worker density due to disturbances or inter‐group battles have the potential to disrupt competitive hierarchies. Worker density manipulations also affected longer‐term colony persistence. Behavioral and genetic data revealed that 12 months after expansions 100% of the decreased‐density colonies, and 25% of control and increased‐density colonies, had been supplanted by neighboring opportunistic conspecifics. Intraspecific aggression may have lower costs in C. mimosae because aggressive colonies can incorporate workers or queens from defeated competitors. The unexpectedly high frequency of conflicts between conspecific C. mimosae, in combination with behaviors decreasing the cost of intraspecific competition relative to interspecific conflict, may create opportunities for the survival of subordinate competitors in this ant–plant system.

The rove beetle Drusilla sparsa (Coleoptera: Staphylinidae) is a myrmecophilous species associated with a myrmicine ant, Crematogaster osakensis (Hymenoptera: Formicidae)

AbstractThe rove beetle genus Drusilla includes some myrmecophilous species. The Japanese species Drusilla sparsa (Sharp, 1874) has been regarded as a non‐myrmecophilous beetle. In Kagawa Prefecture, Shikoku Island, western Japan, however, we often observed that D. sparsa adults were walking in the vicinity of foraging workers of the myrmicine ant Crematogaster osakensis Forel, 1990. The body color of the beetle is similar to C. osakensis as in other myrmecophilous beetles found near the trails of the host ants. To examine whether D. sparsa is myrmecophilous, we investigated the distribution of D. sparsa and C. osakensis in the field, as well as their behavior including prey preference of the beetle in the laboratory. Drusilla sparsa beetles were collected only in sites where C. osakensis ants occurred. When the beetles encountered the ant workers, they bent the abdominal tip toward the ants. The ants licked the abdominal tip, and then the beetles usually walked away. Such behavioral reaction of the ants was not observed when the beetles encountered workers of the formicine ant Nylanderia flavipes (Smith, 1874) that continuously attacked the beetles. Drusilla sparsa preferred to feed on dead workers of C. osakensis even when other ants were available as food, indicating that D. sparsa is a myrmecophilous species associated with C. osakensis. Crematogaster osakensis was frequently found in the stomach in the ant predator, the Japanese treefrog Hyla japonica Günther, 1859. Thus, the significance of body color similarity between the host ants and beetles is not a case of Batesian mimicry.

Nuclear DNA based species delineations ofCoccusscale insects in symbiosis with plants and ants, and the role of plant epicuticular wax in structuring associations

We undertook phylogenetic analysis of nuclear DNA to elucidate species boundaries in the symbiotic Coccus scale insects associated with mutualistic Crematogaster ants and Macaranga plants occurring in the ever-wet forests of Southeast Asia. The coccid specimens clustered into ten lineages, each corresponding to a morphospecies assignment. The lineage identified as C. secretus was separated from the Main Clade by an outgroup. We also examined all pairwise associations among the three symbiont guilds to understand how patterns of association were structured. The analyses revealed that each ant, plant or coccid operational (taxonomic) unit often associated with multiple O(T)Us of each of the other two guilds. However, where testing was feasible, a ‘preference’ for one or sometimes two partner O(T)Us of each guild was often detected. Mutual ‘preferences’ or ‘avoidances’ were relatively common among the symbionts, and no conflicts of interest were apparent. The network of preferred partners among all three guilds showed compartmentalization structured by the presence/absence of plant epicuticular wax, suggesting that this feature plays a fundamental role in how the symbionts select partners that best serve their needs. To a lesser degree, the network was also structured by whether the host plant stems were ant-excavated or hollowed naturally.

Social structure of the polygynous ant, Crematogaster osakensis

The colony structures of social insects vary greatly among species. In ant societies, the number of queens within a colony is variable during colony maturation. We investigated the social structure of a polygynous ant Crematogaster osakensis in a series of field and laboratory experiments. First, the initial colonies headed by multiple queens were found in the field. In laboratory experiments, queens that were artificially cohabited after their nuptial flight harmoniously co-existed even in the presence of newly emerged workers, suggesting that mated queens of this species can establish their colony cooperatively as primary polygynous colonies. In addition, the mating frequency of a queen was typically more than one, estimated from the sperm number stored in field-collected males and queens, and from genetic relatedness among daughters of lab-reared monogynous colonies. Second, our assessment of genetic relatedness in a mature field colony of this species revealed that dealated queens, as well as workers and alates, were relatives. The number of developed oocytes identified reproductive skew in two of five field-collected nests. Moreover, under laboratory conditions, the most fertile egg layer altered over 3 months of observation. Based on these lines of evidence, we propose that in C. osakensis, polygynous foundresses might either be unrelated and subsequently be replaced by daughter queens of particular foundresses, or be related in the first place.