Reactions by army ant workers to nestmates having had contact with sympatric ant species

It was recently shown that Pheidole megacephala colonies (an invasive species originating from Africa) counterattack when raided by the army ant, Eciton burchellii. The subsequent contact permits Pheidole cuticular compounds (that constitute the “colony odour”) to be transferred onto the raiding Eciton, which are then not recognised by their colony-mates and killed. Using a simple method for transferring cuticular compounds, we tested if this phenomenon occurs for Neotropical ants. Eciton workers rubbed with ants from four sympatric species were released among their colony-mates. Individuals rubbed with Solenopsis saevissima or Camponotus blandus workers were attacked, but not those rubbed with Atta sexdens, Pheidole fallax or with colony-mates (control lot). So, the chemicals of certain sympatric ant species, but not others, trigger intra-colonial aggressiveness in Eciton. We conclude that prey-ant chemicals might have played a role in the evolution of army ant predatory behaviour, likely influencing prey specialization in certain cases.     

Convergent evolution,superefficient teams and tempo in Old and New World army ants

Swarm raiding army ants, with hundreds of thousands or millions of workers per colony, have evolved convergently in the Old World and New World tropics. Here we demonstrate for the first time, to our knowledge, superefficient foraging teams in Old World army ants and we compare them quantitatively with such teams in New World army ants. Colonies of Dorylus wilverthi in the Old World and Eciton burchelli in the New World retrieve almost identical sizes of prey item and the overall size range of their workers is very similar. However, 98% of D. wilverthi workers are within the size range of the smallest 25% of E. burchelli workers. In E. burchelli larger workers specialize in prey retrieval, whereas in D. wilverthi workers form many more teams than in E. burchelli. Such teams compensate for the relative rarity of larger workers in Dorylus. The proportions of prey items retrieved by teams in Dorylus and Eciton are 39% and 5%, respectively. The percentages of all prey biomass retrieved by teams in Dorylus and Eciton are 64% and 13%, respectively. Working either as single porters or teams, Dorylus carry more per unit ant weight than do Eciton, but Eciton are swifter. However, these different ergonomic factors counterbalance one another, so that performance at the colony level is remarkably, although by no means completely, similar between the Old and New World species. The remaining differences are attributable to adaptations in worker and colony tempo associated with the recovery dynamics of their prey populations. Our comparative analysis provides a unique perspective on worker-level and colony-level adaptations and is a special test of the theory of worker caste distributions.     

Response of an open‐forest ant community to invasion by the introduced ant,Pheidole megacephala

The introduced tramp ant, Pheidole megacephala, is a well‐known pest of urban areas and coastal dune ecosystems in eastern Australia. Until recently, establishment and spread of P. megacephala colonies has been regarded as likely only in disturbed areas. Here we describe the extent of an established colony of P. megacephala in a long undisturbed open forest near Maryborough in southeast Queensland and compare ant community structure with those of nearby uninfested sites. Tuna baiting revealed three distinct zones: (i) a zone totally dominated by P. megacephala (at least 10 ha) where few other ant ant species were detected; (ii) a zone where P. megacephala was absent and many other ant species were found; and (iii) a zone where opportunists (species of Ochetellus and Paratrechina) competed with P. megacephala at baits. Pitfall trapping over a 9‐month period resulted in 12 species being recorded at the infested site, compared with a mean of 25 species recorded at adjoining uninfested forest. Over 94% of ants recorded in pitfalls at the infested site were P. megacephala. Most notably, P. megacephala had completely displaced dominant Dolichoderines (species of Iridomyrmex), subordinate Camponotini (species of Camponotus, Opisthopsis and Polyrhachis) and other species of Pheidole which are common at forest sites.     

Regulation of worker activity in a primitively eusocial wasp, Ropalidia marginata

Ropalidia marginala, a tropical, primitively eusocial, polistinewasp, is unusual in that the queen (the sole egg-layer) is neitherthe most behaviorally dominant nor the most active individualin the colony. The queen by herself rarely ever initiates interactionstoward her nest mates or unloads returning foragers. There arealways a few workers in the colony who are more dominant andactive than the queen. Absence of the queen from her colonydoes not affect colony maintenance activities such as foragingor brood care, but it always results in one individual becomingvery aggressive and dominant. The dominant worker becomes thenext queen if the original queen does not return. The queendoes not appear to play any significant role in colony activityregulation. Instead, colony activities appear to be regulatedby several mechanisms including dominance behavior toward foragers,feeding of larvae, and the unloading of returning foragers,all mediated by workers themselves. Regulation of colony maintenanceappears to be based on direct evaluation of the needs of thecolony by the workers themselves. The queen however has perfectreproductive control over all workers; workers never lay eggsin the presence of the queen. It appears therefore that themechanisms involved in regulation of worker activity and workerreproduction are separate in R marginata. These findings contrastwith other primitively eusocial species where the queen actsas a "central pacemaker" and controls both worker activity andworker reproduction.     

Introduced Pheidole of the world: taxonomy,biology and distribution

The objective of this study is to provide a detailed taxonomic resource for identifying and studying ants in the genus Pheidole that have established beyond their native ranges. There is an increasing need for systematists to study taxa of specific concern to 21^st century environmental, food security and public health challenges. Systematics has an important role to play in both the theoretical and applied disciplines of invasion biology. Few invaders impact terrestrial ecosystems more than ants. Among the world’s 100 worst invasive species is the cosmopolitan and highly destructive Pheidole megacephala (Fabricius). Accurate identification of Pheidole megacephala is imperative for the success of screening, management and eradication programs designed to protect native ecosystems from the impacts of this destructive species. However, accurate identification of Pheidole species is difficult because of their taxonomic diversity, dimorphic worker caste and lack of taxonomic resources. Illustrated keys are included, along with the taxonomic history, taxonomic diagnoses, biological notes and risk statements for the 14 most invasive members of the genus. Global distribution maps based on over 14,000 specimen and literature records are presented for each species. These results of this work will facilitate identification of pest species, determination of climatic and habitat requirements, discovery of pest origins, horizon scanning and assessment of invasion pathways. The following new synonym is proposed, with the senior synonym listed first and the junior synonyms in parentheses: Pheidole indica Mayr (= Pheidole teneriffana Forel, and its synonyms Pheidole taina Aguayo and Pheidole voeltzkowii Forel). Pheidole navigans Forel, stat. rev., stat. n. is removed from synonymy and elevated to species rank. It is proposed that records of Pheidole moerens Forel outside of the Mesoamerica and the Caribbean refer instead to Pheidole navigans or other heterospecific taxa in the Pheidole flavens species complex. We propose that the names Pheidole anastasii Emery and Pheidole floridana Emery have been widely misapplied to North American outdoor records of Pheidole bilimeki Mayr. It is suggested that the synonymy of Pheidole lauta Wheeler be transferred from Pheidole floridana Emery to Pheidole bilimeki Mayr.     

Contents of the poison apparatus of some species of Pheidole ants

Four Old World species of Pheidole ants contain different mixtures of farnesene-type hydrocarbons in their poison apparatus, and the mixture is different between the minor and major workers within a species. A bishomofarnesene (C₁₇H₂₈) provides approximately half of the secretion of the Dufour glands of minor workers of Pheidole pallidula. (Z,E)-α-Farnesene constituted 96% of the Dufour secretion of major workers of P. pallidula, but only 20% of that of minors. The Dufour glands of minor workers of Pheidole sinaitica contain a mixture of farnesene homologues with (Z,E)-α-farnesene and the bishomofarnesene also found in P. pallidula predominant. The mixture in major workers was similar but had, in addition, a small amount of (E)-β-farnesene. The Dufour glands of Pheidole teneriffana minors contain chiefly the same bishomofarnesene found in P. pallidula and P. sinaitica while major workers contain (Z,E)-α-farnesene. Pheidole megacephala minor workers contained small amounts of eight farnesenes, while major workers contained essentially no farnesenes. The poison glands of minor workers of P. pallidula contain 3-ethyl-2,5-dimethylpyrazine. No pyrazine compounds were found in the major workers of P. pallidula or the minor workers of P. sinaitica. The poison glands of the major workers of P. sinaitica contained larger amounts of tetra-substituted pyrazines. No pyrazines were found in the poison reservoirs of major or minor workers of P. teneriffana or P. megacephala.     

Tradeoffs in the Evolution of Caste and Body Size in the Hyperdiverse Ant Genus Pheidole

The efficient investment of resources is often the route to ecological success, and the adaptability of resource investment may play a critical role in promoting biodiversity. The ants of the “hyperdiverse” genus Pheidole produce two discrete sterile castes, soldiers and minor workers. Within Pheidole, there is tremendous interspecific variation in proportion of soldiers. The causes and correlates of caste ratio variation among species of Pheidole remain enigmatic. Here we test whether a body size threshold model accounts for interspecific variation in caste ratio in Pheidole, such that species with larger body sizes produce relatively fewer soldiers within their colonies. We evaluated the caste ratio of 26 species of Pheidole and found that the body size of workers accounts for interspecific variation in the production of soldiers as we predicted. Twelve species sampled from one forest in Costa Rica yielded the same relationship as found in previously published data from many localities. We conclude that production of soldiers in the most species-rich group of ants is regulated by a body size threshold mechanism, and that the great variation in body size and caste ratio in Pheidole plays a role in niche divergence in this rapidly evolving taxon.     

Unadapted behaviour of native,dominant ant species during the colonization of an aggressive,invasive ant

Among the factors driving the invasive success of non-indigenous species, the “escape opportunity” or “enemy release” hypothesis argues that an invader’s success may result partly from less resistance from the new competitors found in its introduced range. In this study, we examined competitive interactions between the little fire ant Wasmannia auropunctata (Roger) and ant species of the genus Pheidole in places where both are native (French Guiana) and in places where only species of Pheidole are native (New Caledonia). The experimental introduction of W. auropunctata at food resources monopolized by the Pheidole species induced the recruitment of major workers only for the Guianian Pheidole species, which were very effective at killing Wasmannia competitors. In contrast, an overall decrease in the number of Pheidole workers and no recruitment of major workers were observed for the New Caledonian species, although the latter were the only ones able to kill the Wasmannia workers. These results emphasize the inappropriate response of native dominant New Caledonian species to W. auropunctata and, thus, the importance of enemy recognition and specification in the organization of ant communities. This factor could explain how invasive animal species, particularly ants, may be able to successfully invade species-rich communities.     

Worker policing limits the number of reproductives in a ponerine ant

Reproductive division of labour is an essential feature of insect sociality, but the regulation of sterility among colony members remains incompletely understood. Ant workers and queens are morphologically divergent and workers are only capable of producing males in a colony, although they usually do not do so. Worker policing is one mechanism proposed for their infertility and it can be expressed as either aggressive inhibition of ovarian activity among workers or destruction of worker-laid eggs. A few studies have shown that workers with developed ovaries are preferentially attacked by nest-mates, but adequate demonstration of worker policing also requires evidence that these attacks result in the suppression of ovarian activity or death. We investigated worker policing in the ponerine ant Harpegnathos saltator in which workers are able to mate and replace the founding queen. Five colonies were each divided into two groups, one of which consisted exclusively of infertile workers. Some individuals in the orphaned groups began laying eggs during the three-week separation and upon reunification these were vigorously attacked by infertile workers of the other groups. The ovarian activity of these new egg layers became inhibited, as revealed by subsequent dissection of marked individuals. Worker policing in H. saltator appears to function primarily in preventing an excess of reproductive workers.     

Information needs at the beginning of foraging: grass-cutting ants trade off load size for a faster return to the nest

Background

Acquisition of information about food sources is essential for animals that forage collectively like social insects. Foragers deliver two commodities to the nest, food and information, and they may favor the delivery of one at the expenses of the other. We predict that information needs should be particularly high at the beginning of foraging: the decision to return faster to the nest will motivate a grass-cutting ant worker to reduce its loading time, and so to leave the source with a partial load.

Principal Findings

Field results showed that at the initial foraging phase, most grass-cutting ant foragers (Acromyrmex heyeri) returned unladen to the nest, and experienced head-on encounters with outgoing workers. Ant encounters were not simply collisions in a probabilistic sense: outgoing workers contacted in average 70% of the returning foragers at the initial foraging phase, and only 20% at the established phase. At the initial foraging phase, workers cut fragments that were shorter, narrower, lighter and tenderer than those harvested at the established one. Foragers walked at the initial phase significantly faster than expected for the observed temperatures, yet not at the established phase. Moreover, when controlling for differences in the fragment-size carried, workers still walked faster at the initial phase. Despite the higher speed, their individual transport rate of vegetable tissue was lower than that of similarly-sized workers foraging later at the same patch.

Conclusions/Significance

At the initial foraging phase, workers compromised their individual transport rates of material in order to return faster to the colony. We suggest that the observed flexible cutting rules and the selection of partial loads at the beginning of foraging are driven by the need of information transfer, crucial for the establishment and maintenance of a foraging process to monopolize a discovered resource.     

Buying time for colony mates: the anti-predatory function of soldiers in the eusocial aphid Ceratovacuna japonica (Homoptera, Hormaphidinae)

Eusocial aphids produce sterile individuals (soldiers) that specialize in colony protection. Killing predators is often considered the main function of soldiers. In this study, we tested the effect of harassment by soldiers of a eusocial aphid, Ceratovacuna japonica (Homoptera, Hormaphidinae), on predation by this species’ natural enemy, the larvae of Atkinsonia ignipicta (Lepidoptera, Stathmopodidae). We experimentally introduced some aphids and a predator to petri dishes and compared the survivorship of first-instar reproductives in the presence and absence of soldiers. We showed that soldiers can reduce the rate of predation on their colony mates without killing the predators. When predators encountered soldiers, they did not attempt to prey on them. Instead, they evaded them and often started to make a nest by spinning silken threads. The soldiers, in contrast, waved their forelegs and attacked the predator, and they sometimes succeeded in grasping the predator’s body. Because the predator used its mandibles to remove any soldier that succeeded in grasping its body, the soldier did not kill the predator. The reduction of predation was apparently caused by the delay of predation resulting from the harassment behavior of the soldiers. In eusocial aphids, a defensive strategy that delays predation may buy the soldiers’ colony mates time to reproduce or to escape from the predator.     

Honeybee (Apis cerana) guards do not discriminate between robbers and reproductive parasites

A hopelessly queenless honeybee colony has only one reproductive option: some workers must produce sons before the colony dies. This requires the workers to curtail egg policing (removal of worker-produced eggs), rendering the colony vulnerable to non-natal reproductive parasitism. In the Western honeybee, Apis mellifera, guarding (prevention of foreign workers from entering a colony) increases in queenless colonies, providing a defence against non-natal parasitism. However, in the closely related Eastern honeybee A. cerana, queenless colonies appear to be more tolerant of bees from other colonies. We presented guards of four A. cerana colonies with three types of workers: nestmate returning foragers, non-nestmate returning foragers and non-nestmates from a laying-worker colony. The latter are likely to have active ovaries, allowing us to test whether guard bees can detect which potential invaders are more likely to be reproductive parasites. After assessing guards’ reactions, we recaptured test bees and dissected them to determine levels of ovary activation. We found that nestmates were accepted significantly more frequently than the other two types of workers. However, there was no difference in the overall acceptance rates of non-nestmate returning foragers and bees from within laying-worker colonies. In addition, ovary-activated workers were no less likely to be accepted than those with inactive ovaries. Interestingly, colonies were more accepting of all three types of test bee after being made queenless. We conclude that, as has been previously suggested, guarding has no specific role in the prevention of non-natal parasitism in A. cerana.     

Resource competition assays between the African big‐headed ant,Pheidole megacephala (Fabricius) and the invasive Argentine ant,Linepithema humile (Mayr): mechanisms of inter‐specific displacement

1. The spread of Argentine ants, Linepithema humile (Mayr), in introduced areas is mainly through the displacement of native ant species owing to high inter‐specific competition. In South Africa, L. humile has not established in the climatically suitable eastern and northern escarpments dominated by the African big headed ant, Pheidole megacephala (Fabricius), probably owing to local biotic resistance. 2. Inter‐specific aggression, at the individual and colony level, and competition for a shared resource were evaluated in the laboratory. 3. Aggression between the two ant species was very high in all of the assays. Both species suffered similar mortality rates during one‐on‐one aggression assays, however, during symmetrical group confrontations, L. humile workers showed significantly higher mortality rates than P. megacephala workers. During asymmetrical group confrontations both species killed more of the other ant species when they had numeric advantage. Both ant species located the shared resource at the same time; however, once P. megacephala discovered the bait, they displaced L. humile from the bait through high inter‐specific aggression, thereafter dominating the bait for the remainder of the trial. 4. The results demonstrate the potential of P. megacephala to prevent the establishment and survival of incipient L. humile colonies through enhanced resource competition and high inter‐specific aggression. This is the first study to indicate potential biotic resistance to the spread of L. humile in South Africa.     

Body size variation and caste ratios in geographically distinct populations of the invasive big‐headed ant,Pheidole megacephala (Hymenoptera: Formicidae)

Body size is an important life history trait that can evolve rapidly as a result of how species interact with each other and their environment. Invasive species often encounter vastly different ecological conditions throughout their introduced range that can influence relative investment in growth, reproduction and defence among populations. In this study, we quantified variation in worker size, morphology and proportion of majors among five populations of a worldwide invasive species, the big‐headed ant, Pheidole megacephala (Fabricius). The sampled populations differed in ant community composition, allowing us to examine if P. megacephala invests differently in the size and number of majors based on the local ant fauna. We also used genetic data to determine if these populations of P. megacephala represented cryptic species or if morphological differences could be attributed to change following introduction. We found significant variation in worker mass among the populations. Both major and minor workers were largest in Australia, where the ant fauna was most diverse, and minor workers were smallest in Hawaii and Mauritius, where P. megacephala interacted with few to no other ants. We also found differences in major and minor worker morphology among populations. Majors from Mauritius had significantly larger heads (width and length) relative to whole body size than those from Hawaii and Florida. Minors had longer heads and hind tibias in South Africa compared with populations from Australia, Hawaii and Florida. The proportion of majors did not differ among populations, suggesting that these populations may not be subject to trade‐offs in investment in major size versus number. Our molecular data place all samples within the same clade, supporting that these morphologically different populations represent the same species. These results suggest that the variation in shape and morphology of major and minor workers may therefore be the result of rapid adaptation or plastic responses to local conditions. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 423–438.     

Invasive African big-headed ants, Pheidole megacephala, on coral cays of the southern Great Barrier Reef: distribution and impacts on other ants

Infestation of islands by exotic ants is widespread and increasing due to human activities throughout the world. Exotic ants, particularly the invasive African big-headed ant, Pheidole megacephala (Fabricius), are of great conservation concern for coral cays at the southern end of the Great Barrier Reef, Australia. Little is known, however, about the distribution and ecological impacts of invasive ants in this insular system. We surveyed the ants of 14 vegetated coral cays recording a total of 24 ant species, including at least nine exotics. Pheidole megacephala was by far the most abundant and widespread species, occurring on 11 of 14 islands, often in very large numbers. The inter-island distribution of P. megacephala was best explained by human activities, with frequently visited, and to a lesser degree disturbed islands, more likely to be infested. On large islands (≥?10?ha) P. megacephala exhibited distinct habitat preferences, occurring in significantly lower abundances within heavily-shaded Pisonia grandis forest in the centre of islands, compared to more open, fringing woodland or shrubland. On smaller islands (<10?ha) with less extensive Pisonia stands, P. megacephala penetrated throughout the forest where its abundance was similar to that in open woodland. Despite considerable differences in biotic (floristic composition) and abiotic factors (e.g. island size) as well as the spatial configuration among islands, the severity of infestation by P. megacephala best explained variation in species richness, abundance and assemblage composition of other ants. We suggest a number of strategies to manage P. megacephala infestations on these islands.     

Secondary seed dispersal by ants in Neotropical cerrado savanna: species‐specific effects on seeds and seedlings of Siparuna guianensis (Siparunaceae)

1. Most woody plant species in tropical habitats are primarily vertebrate‐dispersed, but interactions between ants and fallen seeds and fruits are frequent. This study assesses the species‐specific services provided by ants to fallen arillate seeds of Siparuna guianensis, a primarily bird‐dispersed tree in cerrado savanna. The questions of which species interact with fallen seeds, their relative contribution (versus vertebrates) to seed removal, and the potential effects on seedling establishment are investigated. 2. Seeds are removed in similar quantities in caged and control treatments, suggesting that ants are the main dispersers on the ground. Five ant species attended seeds. Pheidole megacephala (≈0.4 cm) cooperatively transported seeds, whereas the smaller Pheidole sp. removed the seed aril on spot. Large (> 1.0 cm) Odontomachus chelifer, Pachycondyla striata, and Ectatomma edentatum individually carried seeds up to 4 m. Bits of aril are fed to larvae and intact seeds are discarded near the nest entrance. 3. Overall, greater numbers of seedlings were recorded near ant nests than in control plots without nests. This effect, however, was only detected near P. megacephala and P. striata nests, where soil penetrability was greater compared with controls. Soil nutrients did not differ between paired plots. 4. This study confirms the prevalence of ant–seed interactions in cerrado and shows that ant‐derived benefits are species‐specific. Ant services range from seed cleaning on the spot to seed displacement promoting non‐random spatial seedling recruitment. Although seed dispersal distances by ants are likely to be shorter than those by birds, our study of S. guianensis shows that fine‐scale ant‐induced seed movements may ultimately enhance plant regeneration in cerrado.     

Inter- and intraspecific alarm response in the termiteMacrotermes subhyalinus (Rambur)

Summary In laboratory studies we analysed the reaction of aMacrotermes subhyalinus (Rambur) colony in contact with a small group of test termites placed at the head of a gallery system. As test termites we usedMacrotermes subhyalinus of the same nest,Macrotermes subhyalinus of a foreign nest and the related sympatric speciesMacrotermes bellicosus (Smeathman).Contact with an introduced group of foragers evokes a significant recruitment of workers and minor soldiers. The intensity of the response depends on the test groups we introduced. The highest recruitment results withM. bellicosus andM. subhyalinus from a foreign nest. During the recruitment the increase in the number of minor soldiers is greater than the increase in the number of workers, and as a result, the relative proportion of the soldiers in the population leaving the nest is significantly higher than before.Direct observations at the place of contact show thatM. bellicosus individuals are immediately attacked and killed. In the case ofM. subhyalinus from a foreign nest, not all individuals are killed; some are only intensively examined with the antennae or seized with the mandibles.M. subhyalinus from the same nest are rarely attacked. Mostly they are antennally inspected or enter the gallery system unhindered.The recruitment of termites from the nest is released by major workers which, after contact with the test termites, run back into the nest and provoke an alarm by tactile stimuli. On their way back into the nest the major workers, in all probability, lay a pheromone trail which leads the outgoing alarmed termites towards the place of contact.     

Intra- and Inter-colonial Agonistic Behavior in the Termite, Microcerotermes fuscotibialis Sjostedt (Isoptera: Termitidae: Termitinae)

Pairing termite workers from cultures obtained from same colony of Microcerotermes fuscotibialis Sjostedt did not result in agonistic behavior or mortality of the paired individuals. Termite pairings from different colonies located at different distances resulted in serious encounters and aggressive behavior leading to significant mortality of the individuals. Subtle agonistic behavior was observed when colony mates were reunited after months of separation, but this did not result in any significant mortality. These results confirmed observations of non-overlap of foraging trails of these termites in the field which averts possible encounters and conflict. Therefore these termites are able to recognize their colony mates irrespective of period of separation, a factor for colony affiliation, kinship and recognition.     

Host queen killing by a slave-maker ant queen: when is a host queen worth attacking?

A new colony of the slave-making ant Polyergus breviceps is initiated when a newly mated gyne invades a host nest and kills the resident queen. This process seems to result in chemical camouflage of the invading gyne and allows her to usurp the position of colony reproductive. Young, recently mated Formica gynes, however, are not attacked. To determine whether worker and/or immature presence is the basis for aggression, we placed eggs, larvae, pupae and workers from mature F. gnava queens with newly mated F. gnava queens and observed the responses of introducedP. breviceps queens. Because no newly mated gyne was attacked, we tested newly mated F. gnava queens (1) once they had produced eggs, (2) when the offspring reached the larval, pupal and callow stages of development, and (3) every 2 weeks until aggression ensued. Eventually all F. gnava queens were attacked but only 29 weeks after having mated. Thus, although offspring are the ultimate benefit from attacking an established F. gnava queen,P. breviceps queens detect mature queens using another time-dependent feature that is reliably indicative of reproductive status. The similarity of host queen hydrocarbon profiles, often correlated with reproductive status in other ant species, suggests that other compounds reflect queen fecundity and produce a kairomonal effect, or that another cue signals host queen and colony suitability. Our findings indicate P. breviceps gynes have evolved to respond aggressively to a host gyne cue that appears long after mating, preventing attacks on gynes without the workers necessary for colony founding.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Worker oviposition and policing behaviour in the myrmicine ant Aphaenogaster smythiesi japonica Forel

In eusocial Hymenoptera, worker reproduction is affected by various factors, especially the genetic structure of the colony. Kinship theory predicts that hymenopteran workers prefer to produce sons rather than brothers when a single, once-mated queen is in a colony, while such worker reproduction is expected to be mutually inhibited by other workers under multiple mating of the queen. To test these predictions we observed the behaviour of the myrmicine ant Aphaenogaster smythiesi japonica. Observation of the social structure of 60 queenright colonies indicated monogyny and microsatellite DNA analysis of 14 colonies showed monandry. Under laboratory conditions, workers with functional ovaries laid only trophic eggs in the presence of the queen and produced viable eggs in her absence. In an experiment in which colonies split and reunited, workers that had well-developed ovarioles with viable oocytes were frequently attacked by other workers from the queenright groups. The number of oocytes in a worker's ovarioles was positively correlated with the frequency of being attacked. The results show that a worker's production of males in this species is potentially inhibited by worker policing, contrary to the prediction that worker policing is not predominant in monogynous and monandrous societies. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.