Publications

preference of food particle size among several urban ant species.	appropriate particle size may be a critical characteristic for effective granular ant baits. we examined the particle size preference of six species of pest ants to an anchovy-based bait. we also examined head capsule widths of argentine ants, linepithema humile (mayr) (mean = 0.54 mm), california harvester ants, pogonomyrmex californicus (buckley) (mean = 1.63 mm), red imported fire ants, solenopsis invicta buren (mean = 0.9 mm), and southern fire ants, solenopsis xyloni mccook (mean = 0.76 mm) ...	2002	12539835
protein that makes sense in the argentine ant.	with a protein-based approach, we have identified and cloned the cdna encoding a chemosensory protein (lhumcsp) in the argentine ant, linepithema humile. the open reading frame of the cloned cdna encoded a signal peptide (20 residues), and a mature protein (pi 4.62) of 106 amino acid residues. the calculated molecular mass (12,453 da) was in agreement with the molecular mass measured by on-line chromatography-electrospray ionization mass spectrometry (12,448 da), given the formation of two disul ...	2002	12451452
plasticity in queen number and social structure in the invasive argentine ant (linepithema humile).	in many polygynous social insect societies, ecological factors such as habitat saturation promote high queen numbers by increasing the cost of solitary breeding. if polygyny is associated with constrained environments, queen number in colonies of invasive social insects should increase as saturation of their new habitat increases. here i describe the variation in queen number, nestmate relatedness, and nest size along a gradient of time since colonization in an invading population of argentine a ...	2002	12449488
evolution of supercolonies: the argentine ants of southern europe.	some ants have an extraordinary social organization, called unicoloniality, whereby individuals mix freely among physically separated nests. this type of social organization is not only a key attribute responsible for the ecological domination of these ants, but also an evolutionary paradox and a potential problem for kin selection theory because relatedness between nest mates is effectively zero. the introduction of the argentine ant in europe was apparently accompanied by a dramatic loss of in ...	2002	11959924
effects of aromatic cedar mulch on the argentine ant and the odorous house ant (hymenoptera: formicidae).	in laboratory studies, the argentine ant, linepithema humile (mayr), and the odorous house ant, tapinoma sessile (say), avoided aromatic cedar mulch as a nesting substrate. both ant species were killed when confined with fresh aromatic cedar mulch in sealed containers. however, when confined with cedar mulch that had been aged outdoors for up to 140 d, mortality of l. humile was complete regardless of mulch age, whereas t. sessile mortality declined significantly over the mulch-aging period. arg ...	2001	11777059
model of droplet dynamics in the argentine ant linepithema humile (mayr).	the formation of droplets of ants linepithema humile (mayr) is observed under certain experimental conditions: a fluctuating aggregate forms at the end of a rod and a droplet containing up to 40 ants eventually falls down. when the flux of incoming ants is sufficient, this process can continue for several hours, leading to the formation and fall of tens of droplets. previous work indicates that the time series of drop-to-drop intervals may result from a nonlinear low-dimensional dynamics, and th ...	2001	11732177
an oral bioassay for the toxicity of hydramethylnon to individual workers and queens of argentine ants, linepithema humile.	we have developed an oral bioassay to determine the toxicity of hydramethylnon to individual workers and queens of the argentine ant, linepithema humile. we fed seven concentrations of hydramethylnon in suspension to individual workers or queens, determined the amount of hydramethylnon ingested and evaluated the individual ants for mortality 14 days later. at concentrations > or = 0.37 g liter-1, the amount of liquid the queens ingested decreased dramatically, indicating that argentine ant queen ...	2001	11721517
consequences of a biological invasion reveal the importance of mutualism for plant communities.	seed-dispersal mutualisms have a fundamental role in regenerating natural communities. interest in the importance of seed dispersal to plant communities has been heightened by worldwide declines in animal dispersers. one view, the 'keystone mutualist hypothesis', predicts that these human-caused losses will trigger a cascade of linked extinctions throughout the community. implicitly, this view holds that mutualisms, such as seed dispersal, are crucial ecological interactions that maintain the st ...	2001	11675787
relationships among native and introduced populations of the argentine ant (linepithema humile) and the source of introduced populations.	the argentine ant (linepithema humile) is a damaging invasive species that has become established in many mediterranean-type ecosystems worldwide. to identify likely sources of introduced populations we examined the relationships among native linepithema populations from argentina and brazil and introduced populations of l. humile using mitochondrial cytochrome b sequence data and nuclear microsatellite allele frequencies. the mitochondrial phylogeny revealed that the populations in brazil were ...	2001	11555258
hydrocarbon-released nestmate aggression in the argentine ant, linepithema humile, following encounters with insect prey.	argentine ants, linepithema humile, were attacked by their nestmates following contact with a particular prey item, the brown-banded cockroach, supella longipalpa. contact with prey, as brief as 2 min, provoked nestmate aggression. argentine ants contaminated with hydrocarbons extracted from s. longipalpa also released nestmate aggression behavior similar to that released by the whole prey item, confirming the involvement of hydrocarbons. in contrast to s. longipalpa, little or no nestmate aggre ...	2001	11435142
population genetics and colony structure of the argentine ant (linepithema humile) in its native and introduced ranges.	introduced species often possess low levels of genetic diversity relative to source populations as a consequence of the small population sizes associated with founder events. additionally, native and introduced populations of the same species can possess divergent genetic structuring at both large and small geographic scales. thus, genetic systems that have evolved in the context of high diversity may function quite differently in genetically homogeneous introduced populations. here we conduct a ...	2001	11430657
acceptance and intake of gel and liquid sucrose compositions by the argentine ant (hymenoptera: formicidae).	liquids and gels are common delivery forms used in commercial ant baits, but the relative effectiveness of each is unknown. we compared the feeding responses of the argentine ant, linepithema humile (mayr), to liquid and gel compositions of sucrose. in choice assays, more workers were counted on gel than liquid; however, substantially more liquid was consumed. because workers could stand on the gel, more workers could feed simultaneously on the gel. the feeding bouts of individual workers, howev ...	2001	11332847
colony disassociation following diet partitioning in a unicolonial ant.	discriminating nestmates from alien conspecifics via chemical cues is recognized as a critical element in maintaining the integrity of insect societies. we determined, in laboratory experiments, that nestmate recognition in an introduced population of the argentine ant, linepithema humile, is modified by hydrocarbons acquired from insect prey, and that workers from spatially isolated colony fragments, each provided with prey that possessed distinct cuticular hydrocarbons, displayed aggressive be ...	2001	11320891
patterns of spread in biological invasions dominated by long-distance jump dispersal: insights from argentine ants.	invading organisms may spread through local movements (giving rise to a diffusion-like process) and by long-distance jumps, which are often human-mediated. the local spread of invading organisms has been fit with varying success to models that couple local population growth with diffusive spread, but to date no quantitative estimates exist for the relative importance of local dispersal relative to human-mediated long-distance jumps. using a combination of literature review, museum records, and p ...	2001	11158600
"you are what you eat": diet modifies cuticular hydrocarbons and nestmate recognition in the argentine ant, linepithema humile.	nestmate recognition plays a key role in the behavior and evolution of social insects. we demonstrated that hydrocarbons are the chemical cues used in argentine ant, linepithema humile, nestmate recognition, and that these hydrocarbons can be acquired from insect prey. consequently, argentine ant cuticular hydrocarbon patterns reveal the same hydrocarbons present in their diet. diet alters both the recognition cues present on the cuticular surface and the response of nestmates to this new colony ...	2000	11091966
toxicity and repellency of borate-sucrose water baits to argentine ants (hymenoptera: formicidae).	the oral toxicity of boron compounds to the argentine ant, linepithema humile (mayr), was evaluated in laboratory tests. the ants were provided 25% sucrose water containing 0.5 and 1% boric acid, disodium octaborate tetrahydrate, and borax. lethal times of these solutions were a function of the concentration of boron. in field tests, the ants showed no discrimination between disodium octaborate tetrahydrate and boric acid. there was a significant reduction in consumption of sucrose water with > ...	2000	10985039
oral toxicity of abamectin, boric acid, fipronil, and hydramethylnon to laboratory colonies of argentine ants (hymenoptera: formicidae).	comprehensive laboratory baiting studies with the 4 insecticides abamectin, boric acid, fipronil, and hydramethylnon were conducted against argentine ant, linepithema humile (mayr). serial dilutions of each insecticide prepared in a 25% sucrose solution were provided for 24 h or 14 d to groups of workers and queens. sucrose-water baits containing 1 x 10(-5)% fipronil and 0.1% hydramethylnon provided complete mortality of l. humile workers baited for 24 h. baits containing 1 x 10(-4) and 1 x 10(- ...	2000	10902342
reduced genetic variation and the success of an invasive species.	despite the severe ecological and economic damage caused by introduced species, factors that allow invaders to become successful often remain elusive. of invasive taxa, ants are among the most widespread and harmful. highly invasive ants are often unicolonial, forming supercolonies in which workers and queens mix freely among physically separate nests. by reducing costs associated with territoriality, unicolonial species can attain high worker densities, allowing them to achieve interspecific do ...	2000	10811892
mechanisms of dispersed central-place foraging in polydomous colonies of the argentine ant.	many species of ants occupy multiple nests, a condition known as polydomy. because of their decentralized structure, polydomous colonies may be removed from some of the constraints associated with classic central-place foraging. we used laboratory and field experiments to assess the mechanisms involved in dispersed central-place foraging in polydomous colonies of the argentine ant linepithema humile, a widespread invasive species. both in the laboratory and in the field, argentine ants establish ...	2000	10675266
patch sampling behaviour and future foraging expectations in argentine ants, linepithema humile	nests of argentine ants, l. humile, were exposed to pairs of foraging patches of varying quality. these patches varied from never having food to having food for 4 h every day. after 15 days, colonies were allowed an added access to a new patch. the new patch, however, never contained food. the sampling behaviour of nests towards the initial patches and the new patch suggested that the nests were using a sampling rule based on maximizing net benefits of finding food minus the cost of sampling. th ...	1998	9514665