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In 2001, Nasutitermes corniger (Motschulsky), common name conehead termite, were discovered near a marina in Dania Beach, FL, where the invasive species was probably transported from its native range in Central and South America or the Caribbean. In January 2016, an infestation was found in Pompano Beach, Florida, approximately 21 km north of the Dania Beach population. This study compares variants in seven microsatellite loci across specimens from 11 nests in Dania Beach and 8 nests in Pompano Beach. Results are consistent with all N. corniger in both locations being descendants of a single introduced colony, spreading within Broward County, FL through human transport of infested materials. No more than four alleles were found at any of the seven microsatellite loci analyzed, inferring that a single Queen and King, or multiple sibling reproductives descended from a monogamous pair, headed the colony that arrived in Florida. The potential economic and environmental impacts of this invasive termite are enormous due to its broad diet, including agricultural crops and orchards, native and ornamental plants, natural landscapes, and structures. Conspicuous tunnels and aboveground nests are the key aspects of N. corniger biology that render colonies vulnerable to discovery and control. The now proven ability of N. corniger to establish breeding populations in the United States, to cause extensive property and landscape destruction, and to spread by human transport underscores the need for continued aggressive efforts toward eradication of known infestations as well as quick operational actions the next time invasive N. corniger are discovered.

Territory size in social insects depends on the rules by which border conflicts are resolved. We present three mechanistic mathematical models of conflict, inspired by the behavior of the pavement ant Tetramorium immigrans, to predict the advantage of larger colonies in pairwise contests and the resulting scaling of territory size with worker force. The models track the number of ants in the nest traveling to and from the boundary or engaged at the boundary. Ants at the boundary base their recruitment response on the relative numbers of ants from the two colonies. With two colonies, our central result is that the larger colony gains a territory disproportionately larger than the ratio of worker forces would indicate. This disproportionate territory control determines the scaling relation of territory size with worker force in a population. In two dimensions, if territory size were proportional to worker force, the slope of the scaling relation between log territory size and log worker force would be 1.0. With disproportionate territories, this slope is larger and can be explicitly approximated in terms of model parameters, and it is steepest when colonies are packed close to each other, when ants run quickly, or when colonies are small. A steeper slope exaggerates the advantage of larger colonies, creating a positive feedback that could amplify the inequality of the worker force distribution.

The Eurasian ant Myrmica rubra (L.) (Hymenoptera: Formicidae) was first discovered in North America in the early 1900s in Massachusetts. Populations have since appeared in at least seven states within the United States and in seven Canadian provinces. We conducted a systematic search for the ant across southern New England-the states of Connecticut, Massachusetts, and Rhode Island-where M. rubra is spreading from multiple loci. The species occurs in two large regions in Massachusetts, each spanning approximately 75 km, and in several smaller populations in Massachusetts and Rhode Island. No populations were discovered anywhere in Connecticut or across large expanses of central Massachusetts and northern Rhode Island, despite the presence of apparently favorable habitat. This pattern of distribution suggests a combination of long-distance dispersal by human transport coupled with slow local spread. Resurveys of sites previously known to support M. rubra showed that populations persist for decades. Within invaded areas, M. rubra was strongly associated with particular habitats. Colonies were most prevalent in freshwater wetlands and in moist forests near wetlands and water; they were uncommon in drier forests and were rare in open habitats outside of wetlands. The slow rate of spread over the last 110 yr suggests that the ants do not easily disperse between patches of suitable habitat.

1. Patterns of aggression between ants from different nests influence colony and population structure. Several species of invasive ants lack colony boundaries over large expanses, forming ‘supercolonies’ with many nests among which workers can move without encountering aggression. 2. Bioassays of aggression were used to determine the colony structure of the invasive ant Myrmica rubra (L.) at eight sites in Massachusetts, the state where the species was first discovered in North America. To improve the ability to distinguish systematic patterns from background variability in aggressiveness, a repeated‐measures design was used and replicate assays for each pair of nests were conducted. 3. Aggressive responses showed that populations at all sites consisted of multiple distinct colonies. Patterns of aggression were repeatable and transitive, with few exceptions. Colonies were identified as clusters of nests whose workers showed little to no aggression towards one another but were aggressive towards conspecifics from more distant nests. 4. The degree of aggression varied considerably among different colony pairs but did not depend in any consistent way on the distance of separation or on whether colonies were neighbours. 5. Territories of neighbouring colonies abutted, indicating that they were restricted by intraspecific competition. Mapped territories ranged in size from 0.03 to 1.2 ha, but colonies at the study sites have not undergone the enormous expansions seen in introduced populations of some other species of invasive ants, and neighbouring colonies compete locally.

Kin selection theory predicts that workers in social insect colonies should preferentially aid close relatives over less related or unrelated individuals if such behaviors increase inclusive fitness. For example, a worker in a polygynous (multiple-queen) colony is predicted to tend its own mother rather than an unrelated queen if this nepotistic behavior increases its mother’s reproductive success in excess of costs. Despite predictions, experimental tests conducted in the social Hymenoptera have found no clear evidence of nepotism. No tests for nepotism have been carried out in the Isoptera (termites), another major insect taxon showing highly developed sociality. We tested for nepotistic behavior in the termite Nasutitermes corniger by determining if workers preferentially fed and groomed their mothers in a laboratory assay. We collected workers from nine naturally occurring multiple-queen colonies as they tended queens and determined their parentage using highly variable microsatellite markers. Our results provide no evidence that workers tend their mothers in preference to co-occurring queens. The absence of evidence for nepotism is consistent with previous results reported from numerous studies of eusocial hymenopterans.

Loss of aggression between social groups can have far-reaching effects on the structure of societies and populations. We tested whether variation in the genetic structure of colonies of the termite Nasutitermes corniger affects the probability of aggression toward non-nestmates and the ability of unrelated colonies to fuse. We determined the genotypes of workers and soldiers from 120 colonies at seven polymorphic microsatellite loci. Twenty-seven colonies contained offspring of multiple founding queens or kings, yielding an average within-colony relatedness of 0.33. Genotypes in the remaining 93 colonies were consistent with reproduction by a single queen and king or their progeny, with an average within-colony relatedness of 0.51. In standardized assays, the probability of aggression between workers and soldiers from different colonies was an increasing function of within-colony relatedness. The probability of aggression was not affected significantly by the degree of relatedness between colonies, which was near zero in all cases, or by whether the colonies were neighbors. To test whether these assays of aggression predict the potential for colony fusion in the field, we transplanted selected nests to new locations. Workers and soldiers from colonies that were mutually tolerant in laboratory assays joined their nests without fighting, but workers and soldiers that were mutually aggressive in the assays initiated massive battles. These results suggest that the presence of multiple unrelated queens or kings promotes recognition errors, which can lead to the formation of more complex colony structures.

Lanchester's models of attrition during warfare have served as the basis for several predictions about conflicts between groups of animals. These models and their extensions describe rates of mortality during battles as functions of the number and fighting abilities of individuals in each group, allowing analysis of the determinants of group strength and of the cumulative numbers of casualties. We propose modifications to Lanchester's models to improve their applicability to social animals. In particular, we suggest that the per-capita mortality rate of a group is a decreasing function of the fighting abilities of its members, that the mortality rate is an increasing function of the number of individuals in both groups, and that there will often be diminishing returns for increasing numerical advantage. Models incorporating these assumptions predict that the ability of social animals to win fights depends less on group size and more on individual prowess than under Lanchester's original models. We discuss how data on casualties can be used to distinguish among alternative attrition models. Copyright 2003.

Alternative models of territoriality are based on contrasting assumptions about the behavioral processes determining territory size. In a series of controlled field experiments on the fire ant Solenopsis invicta, I tested whether territory size is affected by the availability of food, as predicted by most economic models, and whether territory size is affected by fighting ability, as predicted by models of competition among neighbors. Abundant food was offered for 30--35 days to selected colonies either immediately next to the nest (experiment 1) or at peripheral sites near the territory boundary (experiment 2). These food supplements had no detectable effect on territory size. Furthermore, food placed near the periphery of the territory did not significantly alter local boundary positions. During both experiments, large colonies lost more territory than did small colonies, reflecting temporary declines in worker number due to the seasonal production of reproductives. Such losses by large colonies during the summer months create opportunities for newly founded colonies to expand territories. In a third experiment, colonies from which workers were removed lost significantly more territory than did unmanipulated controls. These results show that territory areas in S. invicta are strongly affected by the relative fighting ability of neighboring colonies but provide no evidence that colonies adjust territory area in response to short-term changes in the availability of food. Copyright 2003.

Summary 1 We tested for density-dependent regulation of biomass in a population of the fire ant Solenopsis invicta and examined the mechanisms of population recovery following replicated colony removals. 2 All colonies were killed within the core area (1018 m2) of six plots, while six additional plots served as undisturbed controls. Over the next 5 years, colonies were mapped several times per year and the biomass of each colony was estimated from the volume of the nest-mound. 3 The average biomass and density of colonies within the removal areas gradually converged on those of control plots and were no longer detectably different after two years. Thereafter, ant biomass on experimental and control plots showed nearly identical seasonal and yearly fluctuations. 4 Territories of colonies surrounding the removal areas rapidly expanded following the deaths of neighbours, while average territory size on control plots showed little short-term change. 5 Significantly more new colonies were established within core areas of experimental plots than within core areas of control plots during the first year following removals. 6 The per-colony probability of movement and the net influx of colony biomass were significantly higher in central regions of the experimental plots than in control plots during the first year. The directions of colony movements were clustered towards the centres of experimental plots in the first 2 years, but did not show significant directional trends on control plots. 7 In all 5 years of the study, annual mortality rates were lower for larger colonies, but the size-specific risk of mortality was not significantly affected by the experimental removal of competitors. 8 The growth rates of colonies, adjusted for initial size, were significantly higher in central regions of experimental plots than in control plots during the first two years of the study. In all years, colony growth rates declined with increasing colony size. 9 These results indicate that populations of S. invicta are regulated by competition among neighbouring colonies. Due to large intraspecific variation in colony size, the dynamics of ant populations are described more accurately by measures of total ant biomass than by colony density alone.

The genetic organization of colonies of the subterranean termite Reticulitermes flavipes in two subpopulations in Massachusetts was explored using five polymorphic allozymes and double-strand conformation polymorphism (DSCP) analysis of the mitochondrial control region. Empirically obtained estimates of worker relatedness and F-statistics were compared with values generated by computer simulations of breeding schemes to make inferences about colony organization. In one study site (G), worker genotypes indicated the presence of a mixture of colonies headed by monogamous outbred primary reproductives and colonies headed by inbreeding neotenic reproductives, both colony types having limited spatial ranges. A second site (S) was dominated by several large colonies with low relatedness among nestmates. Mixed DSCP haplotypes in three colonies indicated that nestmates had descended from two or three unrelated female reproductives. Computer simulations of breeding schemes suggested that positive colony inbreeding coefficients at site S resulted from either commingling of workers from different nests or different colonies. Such an exchange of workers between nests corresponds to the multiple-site nesting lifetype of many subterranean termites and resembles colony structure in polycalic Formica ants. Our study demonstrates considerable variation in R. flavipes colony structure over a small spatial scale, including colonies headed by monogamous outbred primary reproductives, colonies containing multiple inbred neotenic reproductives and large polydomous colonies containing the progeny of two or more unrelated queens, and suggests that the number of reproductives and nestmate relatedness change with colony age and size.

Although colonies of the fire ant Solenopsis invicta are often founded by small groups of queens, all but one of the queens are soon eliminated due to worker attacks and queen fighting. The elimination of supernumerary queens provides an important context for tests of discrimination by the workers, since the outcome of these interactions strongly affects the workers' inclusive fitness. To test whether workers in newly founded colonies discriminate among nestmate queens, paired cofoundresses were narrowly separated by metal screens that prevented direct fighting, but through which the workers could easily pass. Soon after the first workers completed development, they often attacked one of the queens; these attacks were strongly associated with queen mortality. When one queen's brood was discarded, so that the adult workers were all the daughters of just one queen, the workers were significantly less likely to bite their mother than the unrelated queen; however, this tendency was comparatively weak. Queens kept temporarily at a higher temperature to increase their rate of investment in brood-rearing lost weight more rapidly than paired queens and were subsequently more likely to be attacked and killed by workers. Workers were more likely to bite queens that had been temporarily isolated than queens that remained close to brood and workers. When queens were not separated by screens, the presence of workers stimulated queen fights. These results show that workers discriminate strongly among equally familiar queens and that discrimination is based more on the queens' condition and recent social environment than on kinship.

(1) In subterranean termites of the genus Reticulitermes, colonies are difficult to delineate because physical nest structures are concealed or amorphous, and colony boundaries are difficult to define. The ambiguity of colony architecture and the cryptic nesting and feeding habits of these ecologically and economically important termites hinder our understanding of their population biology. We review and synthesize current information on Reticulitermes life history, reproduction, and genetics to develop an understanding of colony and population structure, and possible modes of reproductive organization. (2) To infer colony structure, we simulate several breeding systems that might be found in Reticulitermes and determine the F statistics and relatedness coefficients expected for groups of workers drawn from the simulated populations. Available field data on the distribution of worker genotypes within and among colonies are then used to distinguish between alternate hypotheses regarding population and bree...

Many aggressive animals form territory mosaics marked by distinct boundaries. This paper describes an approach to modeling territory size and shape within mosaics based on boundary disputes among neighboring animals. The model assumes that each resident applies pressure against its neighbors, as a result of aggression and display, and that boundaries form curves along which the pressure exerted by adjacent residents is equal. To illustrate, I predicted territory boundaries for populations of the fire ant Solenopsis invicta using several alternative mathematical descriptions of territorial fighting. According to the most successful formula, the aggressive pressure applied at any point on the territory perimeter increases linearly with the biomass of the defending colony but decreases with territory area and with the square of the distance to the colony’s nest. An iterative algorithm predicts the size and location of boundary segments given the positions and sizes of colonies. By all measured criteria, this...

We developed eight highly variable microsatellite markers for the termite Nasutitermes corniger. Allele number per locus ranged from nine to 34, and expected heterozygosity from 0.45 to 0.94, in samples from seven sites in the former canal zone of Panama. The utility of these markers was assessed for five congeners varying in phylogenetic distance to N. corniger. The markers will be useful for fine-scale examination of population and colony genetic structure in N. corniger and other closely related species.

Genetic markers were obtained for the termite Nasutitermes corniger by DSCP (double-strand conformation polymorphism) analysis of PCR-amplified mitochondrial control region DNA. This procedure revealed twenty-one haplotypes in forty-four colonies, whereas a restriction fragment length polymorphism analysis detected only nine haplotypes. Sequence analysis of DSCP fragments of contrasting mobilities suggests that the electrophoretic haplotypes are caused by DNA curvature in this highly AT-rich region. DSCP markers showed that some termite colonies contained maternally unrelated queens, each of which produced worker offspring. This pattern is consistent with nest founding by unrelated queens. Due to the availability of conserved primers for the mtDNA control region, DSCP analysis may readily reveal comparatively high levels of variation in a wide variety of organisms.

Brood raiding, or reciprocal stealing of brood, is common among incipient colonies of the Ere ant SoUnopsis invicta. Paradoxically, workers from a colony that loses its brood during a raid often abandon their nest and join the winning colony. Queens abandoned by their workers may then migrate from their original nest site and attempt to forcefully usurp another incipient colony by displacing that colony's queen or queens. This study examined factors that influence the success of usurpation attempts. Queens attempting to usurp a nearby colony after laboratory brood raids were successful in less than 30% of trials. Usurpation attempts were more successful if workers familiar to the migrating queen were present in the nest, as would happen if a queen were to find the colony to which her workers had moved. Cross-fostering experiments showed that this effect was due to familiarity rather than relatedness. Usurpation attempts were less successful if they were delayed by 16 h. The probability of usurpation success was not reduced by doubling the number of defending workers in the invaded colony. However, colonies founded by three queens were almost always able to resist usurpation attempts. These results support the hypothesis that workers abandon their natal colony after losing a brood raid to increase the likelihood that their queen can usurp the colony to which they migrate. These results also provide the first evidence that colonies of ants founded by several queens are better able to resist usurpation attempts than colonies founded by a single queen.

In several species of ants, queens often form temporary cooperative associations during colony foundation. These associations end soon after the eclosion of the first workers with the death or expulsion of all but one of the queens. This study examined competition between foundress queens of the fire ant Solenopsis invicta. Although attacks by the workers contributed to queen mortality, queens gained no advantage by producing more workers than their co-foundresses. Restriction fragment length polymorphism analysis of mitochondrial DNA showed that the queen producing more workers during colony founding was no more likely to survive than the less productive queen. In experimentally manipulated colonies in which all the workers were daughters of only one of the queens, the mother of the workers was no more likely to survive than the unrelated queen. Queens producing diploid males reared fewer offspring but were as likely to survive as queens producing only workers. These results suggest that workers do not discriminate between related and unrelated queens within colonies. Aggressive encounters between queens were common. Queens were more likely to die or be expelled if paired with heavier queens or if they lost more weight than their co-foundress during the claustral period. Finally, when queens were separated by screens through which workers could pass, the workers usually attacked and killed the queen farther from the brood. These results suggest that queen survival is promoted by a high fighting ability relative to co-foundresses, rather than by increased worker production, and that workers respond to queen differences that are independent of kinship.

Workers from incipient colonies of the fire ant,Solenopsis invicta, are less aggressive towards conspecific non-nestmates than are workers from reproductively mature colonies. This often leads to brood raiding between incipient colonies, where workers take brood from other incipient colonies without opposition. The development of aggressive reactions by incipient colony workers and queens towards non-nestmate workers and queens was examined. Both workers and queens show nestmate discrimination from the earliest stages of colony activity. Workers from the colony’s first cohort vigorously attacked workers from mature colonies. These same workers rarely attacked non-nestmate workers from incipient colonies, although they were more aggressive towards them than towards nestmates. Workers and queens often vigorously attacked non-nestmate queens, and were more aggressive towards unfamiliar than familiar queens. Queens bitten by workers were likely to be expelled or killed within 3 days of introduction. The highly aggressive response of incipient colony workers towards unfamiliar queens suggests that brood-raiding colonies do not consolidate for mutual benefit. Rather, they struggle for possession of brood while attempting to prevent the entry of additional reproductive females into the colony. In addition, heritable cues were neither necessary nor sufficient for worker acceptance of queens. Finally, although incipient colony workers from colonies with four foundresses were slightly less aggressive towards non-nestmates than workers in colonies with single foundresses, they still discriminated against non-nestmate queens. This result suggests that cooperative nest founding alone cannot explain the development of non-territorial, polygyneS. invictacolonies.

In several ant species, colonies are founded by small groups of queens (pleometrosis), which coexist until the first workers eclose, after which all but one queen is killed. It has been hypothesized that, by producing a larger cohort of workers, cooperating queens may increase colony success during brood raids, a form of competition in which brood and workers from losing nests are absorbed into winning colonies. To test whether this benefit is sufficient to favor pleometrosis, newly mated queens of the fire ant Solenopsis invicta were assembled in groups of one, two, three, or four, reared in the laboratory until the first workers eclosed, then planted in the field in replicated assemblages. The proportion of colonies engaging in brood raids increased with average foundress number per nest and with colony density but was unaffected by variance in foundress number among interacting colonies. Within mixed assemblages of single-queen and multiple-queen colonies, queen number had no effect on the likelihood of engaging in raids or the probability of nest survival through the brood raiding period. However, following nearly 30% of raids, queens moved to new nests and displaced the resident queens. When queen relocation and subsequent mortality were accounted for, it was found that the survival of queens from four-queen groups was substantially higher than that of solitary queens. By contrast, the survival of queens from two-queen colonies was no greater than that of solitary queens. These results show that the competitive advantages of multiple-queen colonies are sufficient to counterbalance the increased mortality of queens within groups only when the number of foundresses is greater than two and when colonies are founded at high density. When colonies lose brood raids, the workers appear to abandon their mothers to join surviving colonies. However, in laboratory experiments, queens attempting to enter foreign nests were significantly more likely to displace the resident queen if their own daughters were present within the invaded nest. Thus, workers may be able to bias the probability that their mother rejoins them and displaces competing queens.

Several analyses of intraspecific animal communication have suggested that threat displays must convey reliable information about the abilities of the signaller in order to be evolutionarily stable. In this paper, a game-theoretic model shows that bluffing by animals of low fighting ability can persist as a profitable tactic in a stable communication system. It is assumed that use of the threat display depends upon variation in fighting ability that is not visible to the opponent and that there is a fitness cost, or “handicap”, paid by animals that threaten and subsequently lose. Analysis of the model shows that a handicap is necessary for stable communication and that the effectiveness of the threat increases with the magnitude of the handicap. However, the handicap does not ensure fully reliable communication and bluffing always forms part of the evolutionarily stable strategy (ESS). At the ESS, the very strongest and the very weakest members of the population threaten, while animals of intermediate strength do not. This is possible because, although weaker animals are liable to greater handicaps when they signal, they also gain greater benefits than strong animals using the same display. If all animals that threaten pay the handicap regardless of the outcome of the fight, then there is no ESS. These results provide a possible explanation for bluffing by the stomatopod crustacean,Gonodactylus bredini,a species in which animals weakened by molting successfully repulse stronger opponents by use of threat displays.

Neighbouring colonies of the arboreal ant Azteca trigona establish distinct territory boundaries that unequally partition foraging space. This paper presents a series of field experiments designed to reveal how boundaries are established and how space is divided during contests between colonies that differ in worker population. In battles staged at territory edges, ants from the colony with the greater local density of workers were more likely to recruit nestmates and were more likely to retain control of the contested area. The decision to attack or to withdraw depended upon the relative number of nestmates and intruders. Experimental manipulation of bridges leading to baited platforms showed that prior owners were more likely to win contests, due to strong recruitment by the first ants to discover new regions. On a larger scale, when colony strength was lowered by removal of nests and by application of pesticides, weakened colonies lost more territory to their neighbours than did size-matched controls. These results show that the outcome of boundary disputes depends upon asymmetries in strength between adjacent residents.

Lanchester's models of attrition describe casualty rates during battles between groups as functions of the numbers of individuals and their fighting abilities. Originally developed to describe human warfare, Lanchester's square law has been hypothesized to apply broadly to social animals as well, with important consequences for their aggressive behaviour and social structure. According to the square law, the fighting ability of a group is proportional to the square of the number of individuals, but rises only linearly with fighting ability of individuals within the group. By analyzing mortality rates of fire ants ( Solenopsis invicta ) fighting in different numerical ratios, we provide the first quantitative test of Lanchester's model for a non-human animal. Casualty rates of fire ants were not consistent with the square law; instead, group fighting ability was an approximately linear function of group size. This implies that the relative numbers of casualties incurred by two fighting groups are not strongly affected by relative group sizes and that battles do not disproportionately favour group size over individual prowess.

Colonies of the termite Nasutitermes corniger often contain multiple reproductive queens and kings. We used double–strand conformation polymorphism (DSCP) analysis of mitochondrial DNA (mtDNA) to determine the probable origins of co–occurring reproductives. Colonies differed in queen and king number, in the number of nests containing reproductives, and in the genetic relationships among reproductives. Most of the 44 colonies contained a single pair of maternally unrelated reproductives. In the two single–nest colonies with a pair of queens, the two queens differed in mtDNA haplotype, suggesting nest–founding by unrelated queens. In the seven single–nest colonies with larger numbers of reproductives (11–49), all reproductives shared the same haplotype, a pattern consistent with replacement of a single pair by several offspring. As predicted by theory, the number of coexisting queens was greater for replacement reproductives than for co–foundresses. Several complex colonies contained multiple queens of two or more haplotypes distributed among several interconnected nests. This indicates that several matrilines can persist within a colony through one or more generations of budding and replacement, a hypothesis confirmed by orphaning experiments. The various modes of termite colony formation rival the diversity seen in ant species and demonstrate the remarkable convergence of behaviours between the two groups.

Mosaics of exclusive foraging territories, produced by intra-and interspecific competition, are commonly reported from arboreal ant communities throughout the tropics and appear to represent a recurring feature of community organization. This paper documents an ant mosaic within mangrove forests of Panama and examines the behavioral mechanisms by which one of the common species, Azteca trigona, maintains its territories. Most of the mangrove canopy is occupied by mutually exclusive territories of the ants A. trigona, A. velox, A. instabilis, and Crematogaster brevispinosa. When foraging workers of A. trigona detect workers of these territorial species, they organize an alarm recruitment response using pheromonal and tactile displays. Nestmates are attracted over short distances by an alarm pheromone originating in the pygidial gland and over longer distances by a trail pheromone produced by the Pavan's gland. Recruits are simultaneously alerted by a tactile display. No evidence was found for chemical marking of the territory. Major workers are proportionally more abundant at territory borders than on foraging trails in the interior of the colony. The mechanisms of territory defense in A. trigona are remarkably similar to those of ecologically analogous ants in the Old World tropics.

Workers of the Neotropical termite Microcerotermes arboreus distinguish nest mates from other conspecifics by odor. A controlled breeding experiment demonstrated a genetic component to variation in colony odors. Workers were less aggressive toward unfamiliar relatives than toward nonrelatives and distinguished degree of relatedness among unfamiliar workers. Unfamiliar relatives were attacked more often than nest mates, despite similar levels of genetic relatedness; thus, nest-mate recognition is not based solely upon heritable characteristics of individual workers. No difference was detected between the effects of cues inherited through the mother and cues inherited through the father.

1. The allometry of colony mass to territory area governs the total biomass of ants that a given habitat supports. This relationship serves as an important link between the performance of individual colonies and the behaviour of populations experiencing density-dependent competition for space. 2. Territory area, colony mass, and the numbers of ants of each caste and developmental stage, were measured for colonies of the fire ant Solenopsis invicta across a wide range of sizes. 3. Most of the variation in territory area was explained by colony size, measured either by worker number, worker biomass or colony biomass. 4. The nature of this relationship was linear in May, when colonies were near their annual minimum size, but non-linear in November, when they were near their annual maximum. Territories of a given size were occupied by larger colonies in November than May, probably because in this saturated population the simultaneous increase in worker number in all colonies occurred without room for territorial expansion. 5. Mound volume, which can be quickly measured without disturbing the colony, provided a reasonable estimate of colony or worker biomass and explained most of the variance in territory size.

In mangrove forests on the Atlantic coast of Panama, the arboreal ant Zacryptocerus maculatus was positively associated with territorial ants in the genus Azteca. Systematic sampling showed that this association was not caused by shared preference for the same size or species of tree. Furthermore, Z. maculatus was not forced to live within territories of Azteca by being excluded from the territories of other abundant ants. Instead, the association appeared to be caused by direct interactions between colonies of Azteca and Z. maculatus. When in the presence of A. trigona, colonies of Z. maculatus engaged in an unusual form of social parasitism. Workers followed pheromone trails deposited by scouts of A. trigona in order to locate newly discovered food sources. In effect, Z. maculatus parasitizes the foraging efforts of A. trigona by reading information contained within its recruitment signals. Z. maculatus workers were able to gain access to these resources because of their stealthy approach and unusual body armor. Observations on related ants suggest that this parasitic habit is shared by other species of Zacryptocerus within the subgenus Harnedia.

The importance of active mate choice as a component of sexual selection remains controversial, despite recent studies identifying traits that correlate with male mating success. We analyzed the sampling sequences of individual female Guianan cock-of-the-rock, providing quantitative documentation of active female choice in this lekbreeding species. We compared observed sampling patterns with null models of random female movement and of movement weighted by the observed distribution of male success. The courts actually visited by individual females were significantly more clumped and centrally located than predicted by computer simulations of either random or weighted movement. Contrary to simplified hypotheses of female choice, hen cock-of-the-rock were not limited either to sequential comparisons or to threshold decision rules when selecting mates. Instead, they repeatedly sampled a subset of potential mates, using the “pool-comparison” tactic. Within this pool, females preferentially mated with the males ranked highest in terms of total courtship visits received, and rejected low-ranking males. Our results suggest complex interactions between patterns of female sampling and male dispersion in lek mating systems, and also provide insights into the constraints on female sampling in lek species.

Workers of Monomorium minimum forage above-ground for dead arthropods. Small particles (