Interaction between a threatened endemic plant (<Emphasis Type="Italic">Anchusa crispa</Emphasis>) and the invasive Argentine ant (<Emphasis Type="Italic">Linepithema humile</Emphasis>)

Seed dispersal mutualisms are essential to ensure the survival of diverse plant species and communities worldwide. Here, we investigated whether the invasive Argentine ant can replace native ants by fulfilling their functional role in the seed dispersal of the rare and threatened endemic myrmecochorous plant, Anchusa crispa, in Corsica (France). Our study addressed the potential of Linepithema humile to disperse elaiosome-bearing seeds of A. crispa, examining L. humile’s effects on (1) the composition of communities of ants removing seeds, (2) the number of seed removals, (3) seed preference, (4) the distance of seed dispersion, and (5) seed germination. We caught seven native species at the control site, but only the Argentine ant at invaded sites. L humile removed A. crispa seeds in greater numbers than did native ants, respectively 66 and 23%, probably due to their higher worker density. The invader was similar to native ants with respect to distance of seed transport. Finally, rates of seed germination were not significantly different between seeds previously in contact with either Argentine ants or not. Taken all together, these results suggest that the Argentine ant is unlikely to pose a threat to A. crispa population. These results have important implications for the management of this rare and threatened endemic plant and provide an example of non-negative interactions between invasive and native species.     

Modification of Diet and Foraging Range by Harvester Ants in Response to Altered Seed Availability

Food collection is a critical component of an individual’s life, and for eusocial insects, the colony that individual foragers support and maintain. Changes to the distribution and composition of food types in the environment are expected influence diet selection if the economics of foraging are altered. For seed-harvesting ants, the abundance and composition of seed types available on the ground typically shows a high degree of spatial and temporal variability, and not all types of seed are equally valued by foragers. We evaluated the response of Owyhee harvester ants (Pogonomyrmex salinus) to reductions in the availability of Sandberg bluegrass (Poa secunda) seeds, a preferred food type, while leaving the availability of cheatgrass (Bromus tectorum) seeds, a less favored food type, unmanipulated. At control colonies (N?=?8), cheatgrass seeds comprised 3.9?±?1.6% of total seed intake, while Sandberg bluegrass seeds accounted for the remainder of the diet. At colonies where bluegrass was trimmed to prevent new seeds from dropping within 12 m of the nest (N?=?8), cheatgrass seed intake increased significantly to 8.2?±?1.4% of the diet. Despite the uptick in collection of cheatgrass seeds, bluegrass seed collection remained high and very similar between treatment and control colonies. Treatment colonies were significantly more likely than control colonies to have at least one trunk trail that extended beyond the 12 m foraging range of the colony, and ants returning along these trails carried bluegrass seeds but not cheatgrass seeds. These results suggest that when preferred seeds dropped in abundance near nests, the economics of foraging by harvester ants favored a small increase in acceptance of less preferred seeds as well as more distant forays to locate and collect preferred seeds.     

Ant interactions with native and exotic seeds in the Patagonian steppe: Influence of seed traits,disturbance levels and ant assemblage

Invasive plants may establish strong interactions with species in their new range which could limit or enhance their establishment and spread. These interactions depend upon traits of the invader and the recipient community, and may alter interactions among native species. In the Patagonian steppe we studied interactions of native ant assemblages with seeds of native and exotic plants, and asked whether ant–seed interactions differ with seed types and disturbance levels and whether the amount and type of ant–seed interactions can be predicted if both ant and seed traits are known. To characterize and quantify ant–seed interactions, we offered baits with large seeds of Pappostipa speciosa (native) and medium-sized elaiosome-bearing seeds of Carduus thoermeri (exotic), near and far from a road (high vs. low disturbed areas), and compared ant abundance and composition between areas. Interaction frequency was the highest for C. thoermeri seeds far from the road. Composition of ants interacting with C. thoermeri in these areas differed from that near the road and from that interacting with native seeds. Ant composition and abundance were similar between areas, but some species interacted more with exotic seeds in low disturbed areas. Ant foraging type predicted ant–seed interactions since the abundance of seed harvesters was positively correlated to interactions with P. speciosa, and that of generalists and predators, with interactions with C. thoermeri. The high interaction of ants with exotic seeds in low invaded areas suggests that ant activity could influence plant invasion, either by predating or dispersing seeds of invasive plants.     

Composition of harvested seeds and seed selection by the invasive tropical fire ant, <Emphasis Type="Italic">Solenopsis geminata</Emphasis> (Hymenoptera: Formicidae) in Taiwan

Solenopsis geminata (F.) is an invasive ant that is widely distributed in weedy areas and agricultural fields in Taiwan. Previous studies have found that S. geminata harvests the seeds of numerous plants. In the present study, we further investigated the composition of harvested seeds in ant nests and seed selection by workers. The seed caches in S. geminata nests sampled in eight areas in Taiwan suggest that the seeds harvested by workers were diverse and belonged to 52 plant species in 17 plant families. Twenty-three species (44%) belong to the family Gramineae, and most of the seeds weighed from 0.02 to 2.29 mg, which might suggest that these are the main seeds harvested by S. geminata from their habitat. Ten common species with similar seed weights were used to compare the seed preferences of workers from two experimental sites. The results suggest that the seed preference was different between the two experimental sites. The seeds of Casuarina equisetifolia showed the most obvious difference in seed removal speed, which might suggest that S. geminata potentially prefers the encountered seed species in the habitat. The various plant species in the ant nests and seed preference suggest that fire ants easily accept newly encountered plant species. As more than half of the plant species (52%) and the total seed number (63%) belonged to exotic species, the role of S. geminata might be negative because it tends to harvest exotic seeds and has a high opportunity to improve the establishment of exotic seedlings.     

Ants Associated with <Emphasis Type="Italic">Turnera subulata</Emphasis> (Turneraceae): Elaiosome Attraction,Seed Dispersion and Germination

Symbiosis between plants and ants include examples in which the plant provides shelter and/or food for ants that, in turn, act in the defense or in the dispersion of seeds from the host plant. Although traditionally referred as mutualistic, the results of these interactions may vary with the ecological context in which patterns are involved. A range of species have facultative association with Turnera subulata (Turneraceae). Here, using behavioral bioassays, we investigated the effects of the most frequent ant species associated with T. subulata (Brachymyrmex sp.1, Camponotus blandus (Smith), Dorymyrmex sp.1, Crematogaster obscurata Emery, and Solenopsis invicta Buren) in the dispersion of plant host seeds and in the number of seedlings around the associated ant nests. We also evaluated the effects of these ant species in the germination of T. subulata seeds, in the consumption of elaiosome, and in the attractiveness to elaiosome odor. Our results showed that the ant species associated with T. subulata presented variation in the attraction by the odor and in the rate of consumption of the elaiosomes. However, none of the ant species studied contributed significantly to the increase of seed germination and seedling growth. Our results suggest that the consumption of the elaiosome by ant species is not a determinant factor to the success of germination of T. subulata. However, such species could contribute indirectly to seed germination by carrying seeds to sites more fertile to germination. In general, our results help to elucidate the results of ecological interactions involving ants and plants.     

Diminishing importance of elaiosomes for acacia seed removal in non-native ranges

Myrmecochorous plants produce seeds with lipid-rich appendages (elaiosomes) which act as a reward for seed-dispersing ants. Seed dispersal is important for exotic species, which often need to establish new mutualistic interactions in order to colonize new non-native habitats. However, little is known about the importance of elaiosomes for seed removal in many of their non-native ranges. We studied ant–seed interactions of elaiosome-bearing and elaiosome-removed seeds of the Australian trees Acacia dealbata and Acacia longifolia in order to assess the relative importance of elaiosomes for seed removal between their native (Australia) and non-native (Portugal) ranges. In Portugal, we also studied the co-occurring native plant species with myrmecochorous seeds, Pterospartum tridentatum and Ulex europaeus, across three contiguous levels of acacia invasion: control (i.e. no acacia), low, and high acacia tree density. Acacia seeds were successfully removed by ants in their non-native region by a diversified assemblage of ant species, even in sites where native plants interacted with only one specialized ant species. In the invaded range, diminishing relative importance of elaiosomes was associated with changes in the ant community due to acacia invasion, and for A. dealbata, ant species richness decreased with increasing acacia tree density. Although seed removal was high for both acacia species, the importance of elaiosomes was proportionally lower for A. dealbata in the non-native region. Native plant species experienced significant reductions in seed removal in areas highly invaded by acacia, identifying another mechanism of displacement of native plants by acacias.     

Ant–aphid relations in the south of Western Siberia (Hymenoptera: Formicidae; Hemiptera: Aphididae)

Aphids, the main suppliers of energy-rich honeydew, play an important role in the life of ants. However, the data on the trophobiotic ant–aphid associations in the majority of regions are still limited. We present the first data on the ant–aphid relations in the south of Western Siberia. Investigations were carried out in the most typical biotopes of forest-steppe and steppe zones in the territory of Novosibirsk and Kurgan regions (Russia) during 1993–2014. There were revealed 35 species of ants and 198 species of aphids. Detected 456 ant–aphid associations involved 28 ant species and 134 myrmecophilous aphids. Seven ant species were found to consume honeydew of 9 non-myrmecophilous aphids, scraping it from the plant. This behaviour is typical of subdominant and subordinate ants which do not protect their foraging areas. Ants associate with various numbers of aphid species. About 36% of ants attended aphid colonies of less than 5 species. The largest number of myrmecophilous aphids is associated with L. niger (Linnaeus, 1758) (103 species), Formica pratensis Retzius, 1783 (50), Formica rufa group (25–33), F. (Serviformica) fusca Linnaeus, 1758 (26) and F. (S.) cunicularia Latreille, 1798 (27). Different ants play unequal roles in the formation of trophobiotic interactions with aphids. Due to complex territorial and foraging behaviour, including high functional specialization among honeydew collectors, dominant ants of Formica s. str. are one of the leaders in this process. The role of L. niger and Formica ants of the subgenus Serviformica requires further detailed investigation.     

Ambush Predation of Stingless Bees (<Emphasis Type="Italic">Tetragonisca angustula</Emphasis>) by the Solitary-Foraging Ant <Emphasis Type="Italic">Ectatomma tuberculatum</Emphasis>

Social insect colonies are high-value foraging targets for insectivores, prompting the evolution of complex colony defensive adaptations as well as specialized foraging tactics in social insect predators. Predatory ants that forage on other social insects employ a diverse range of behaviors targeted at specific prey species. Here, we describe a solitary foraging strategy of the ant Ectatomma tuberculatum, on nest guards of the stingless bee Tetragonisca angustula. We observed multiple instances of E. tuberculatum ambushing and successfully capturing the hovering and standing guards of T. angustula near nest entrances. The unique hovering behavior of the guard caste of this bee species, an adaptation to frequent cleptoparasitism by other stingless bees, may make these guards particularly vulnerable to ground-based, ambush attacks by E. tuberculatum. Likewise, the behavior of the foraging ants appears to adaptively exploit the defensive formations and activity patterns of these bees. These observations suggest an adaptive and targeted predatory strategy aimed at gathering external guard bees as prey from these heavily fortified nests.     

Thermal constraints on foraging of tropical canopy ants

Small cursorial ectotherms risk overheating when foraging in the tropical forest canopy, where the surfaces of unshaded tree branches commonly exceed 50 °C. We quantified the heating and subsequent cooling rates of 11 common canopy ant species from Panama and tested the hypothesis that ant workers stop foraging at temperatures consistent with the prevention of overheating. We created hot experimental “sunflecks” on existing foraging trails of four ant species from different clades and spanning a broad range of body size, heating rate, and critical thermal maxima (CT_max). Different ant species exhibited very different heating rates in the lab, and these differences did not follow trends predicted by body size alone. Experiments with ant models showed that heating rates are strongly affected by color in addition to body size. Foraging workers of all species showed strong responses to heating and consistently abandoned focal sites between 36 and 44 °C. Atta colombica and Azteca trigona workers resumed foraging shortly after heat was removed, but Cephalotes atratus and Dolichoderus bispinosus workers continued to avoid the heated patch even after >5 min of cooling. Large foraging ants (C. atratus) responded slowly to developing thermal extremes, whereas small ants (A. trigona) evacuated sunflecks relatively quickly, and at lower estimated body temperatures than when revisiting previously heated patches. The results of this study provide the first field-based insight into how foraging ants respond behaviorally to the heterogeneous thermal landscape of the tropical forest canopy.     

The Behavior of <Emphasis Type="Italic">Acromyrmex crassispinus</Emphasis> (Hymenoptera: Formicidae) on Trail Bifurcations and the Influence of Ant Flow on Error Rates of Nestbound Laden Workers

Ants are ordinarily faced with a succession of bifurcations along their foraging networks. Given that there is no directionality in pheromone trails, each bifurcation is potentially an opportunity for error in the trajectory of laden workers to the nest, which could entail considerable inefficiencies in the transportation of food to the colony. Leaf-cutting ants (Atta and Acromyrmex) commonly show intense traffic and complex foraging trail systems, which make them ideal organisms to study worker behavior in trail bifurcations. The behavior of leaf-cutting ants of the genus Acromyrmex in trail bifurcations is still largely unexplored. Thus, this study aimed to assess the behavior of Acromyrmex crassispinus workers on trail bifurcations and to investigate whether differences in ant flow on foraging trails influence the error rate of nestbound laden workers at trail bifurcation. There was a negative relationship between ant flow and error rate of nestbound laden workers. Most workers walked in the central part of the foraging trails but occupied a broader area of the foraging trail when the ant flow was high. The results of this study provide valuable insight into the organization of traffic flow in A. crassispinus and its impacts on the foraging strategy of the species.     

Soil disturbance effects on the composition of seed-dispersing ants in roadside environments

Myrmecochory (the dispersal of seeds by ants) is a significant ecological process in sclerophyll woodlands, but habitat disturbance is known to alter the extent and success of this mutualism. We investigated the influence of soil disturbance on the composition of the seed-dispersing ant community. Surveys were conducted in roadside verges where soils are regularly disturbed by road maintenance activities. Using a ‘cafeteria’ bait station approach, we selected 24 roads of different widths to investigate ant composition and abundance in relation to soil disturbance. We found ant species richness was greater in non-disturbed than disturbed zones, where road verge width significantly influenced results. The composition and abundance of individual seed-dispersing ant species varied between disturbed and non-disturbed zones. Rhytidoponera metallica were more abundant in non-disturbed sites, whereas Melophorus bruneus and Monomorium rothseini were more frequently recorded in disturbed areas. Commonly found Iridomyrmex purpureus was significantly more abundant in disturbed zones in narrow roadsides and vice versa in wide roadsides, and strongly influenced total community composition. Variation in the abundance of commonly recorded Iridomyrmex and Monomorium genera were related more to site conditions (roadside width and habitat) than soil disturbance. The rich composition of seed dispersing ants in roadside environments, and the effects of soil disturbances on these ant communities that we describe, provide a key insight to important seed dispersal vectors occurring in fragmented rural landscapes.     

Seed harvesting by a generalist consumer is context‐dependent: Interactive effects across multiple spatial scales

Granivore foraging decisions affect consumer success and determine the quantity and spatial pattern of seed survival. These decisions are influenced by environmental variation at spatial scales ranging from landscapes to local foraging patches. In a field experiment, the effects of seed patch variation across three spatial scales on seed removal by western harvester ants Pogonomyrmex occidentalis were evaluated. At the largest scale we assessed harvesting in different plant communities, at the intermediate scale we assessed harvesting at different distances from ant mounds, and at the smallest scale we assessed the effects of interactions among seed species in local seed neighborhoods on seed harvesting (i.e. resource–consumer interface). Selected seed species were presented alone (monospecific treatment) and in mixture with Bromus tectorum (cheatgrass; mixture treatment) at four distances from P. occidentalis mounds in adjacent intact sagebrush and non‐native cheatgrass‐dominated communities in the Great Basin, Utah, USA. Seed species differed in harvest, with B. tectorum being least preferred. Large and intermediate scale variation influenced harvest. More seeds were harvested in sagebrush than in cheatgrass‐dominated communities (largest scale), and the quantity of seed harvested varied with distance from mounds (intermediate‐scale), although the form of the distance effect differed between plant communities. At the smallest scale, seed neighborhood affected harvest, but the patterns differed among seed species considered. Ants harvested fewer seeds from mixed‐seed neighborhoods than from monospecific neighborhoods, suggesting context dependence and potential associational resistance. Further, the effects of plant community and distance from mound on seed harvest in mixtures differed from their effects in monospecific treatments. Beyond the local seed neighborhood, selection of seed resources is better understood by simultaneously evaluating removal at multiple scales. Associational effects provide a useful theoretical basis for better understanding harvester ant foraging decisions. These results demonstrate the importance of ecological context for seed removal, which has implications for seed pools, plant populations and communities.     

Mass Occurrence and Dominant Behavior of the European Ant Species <Emphasis Type="Italic">Formica fuscocinerea</Emphasis> (Forel)

Recently, masses of the ant Formica (Serviformica) fuscocinerea (Forel) have been occurring at numerous sites in Southern Germany. Although F. fuscocinerea is native to Southern Germany, these mass occurrences resemble ant invasions in density and dominance. This study aimed to investigate the underlying mechanisms that promote sudden mass occurrence of a previously inconspicuous ant species within its native range. To estimate the competitive dominance of F. fuscocinerea, species occurrence and abundance considering biotic and abiotic parameters were studied in a natural habitat where F. fuscocinerea co-occurred with two other common ant species, Myrmica ruginodis (Nylander) and Lasius niger (Linnaeus). To understand the species’ distribution in the field, laboratory experiments on interspecific competition were conducted. Finally, the colony structure of F. fuscocinerea was investigated with intraspecific aggression tests. Formica fuscocinerea dominated an area that, as indicated by strongly frequented foraging trails on the trees, provided important food sources, e.g. trophobionts, to the ants. Other ant species coexisted only at the periphery of the F. fuscocinerea range. Laboratory experiments revealed F. fuscocinerea as highly dominant species. Additionally, F. fuscocinerea showed a complete lack of intraspecific aggression between ants originating from distances up to 58 km, indicating weak or nonexistent behavioral boundaries among ants of physically separated nests. Since extraordinarily high worker densities, strong interspecific dominance and a lack of colony boundaries within supercolonies are considered to be important traits of several invasive ant species we conclude that the same traits also promote the dominance of F. fuscocinerea.     

Patterns of floral resource use by two dominant ant species in a biodiversity hotspot

Ecological dominance in ants is often fuelled by carbohydrate intake. Most studies have focused on the importance of invasive ant mutualistic associations with trophobionts whereas few studies have investigated the importance of floral nectar on invasion success. In this study, utilisation of temporarily available floral nectar by the invasive Argentine ant, Linepithema humile, was compared to that of the dominant native ant, Anoplolepis custodiens, within the Cape Floristic Region (CFR), a biodiversity hotspot. The effect of these two focal ant species on species composition and abundance of ground foraging ants as well as floral arthropod visitors in inflorescences of Proteacea species was assessed. Foraging activity, and trophic ecology inferred from the abundance of natural stable isotopes of Carbon (δ¹³C) and Nitrogen (δ¹⁵N), and the ratio of Carbon to Nitrogen (C:N) were compared between the two ant species during three flowering periods. Linepithema humile significantly reduced the abundance and species diversity of both above-ground and floral arthropod species abundance and composition. Linepithema humile increased its foraging activity with increasing nectar availability, switching its diet to a more herbivorous one. Anoplolepis custodiens did not respond as effectively to increasing floral nectar or negatively impact floral arthropod visitors. This study showed that the availability of floral nectar and ability of L. humile to more effectively utilise this temporarily available resource than native ants, can contribute significantly to the further spread and persistence of L. humile in natural environments in the CFR.     

Individual foraging components of harvester ants: movement patterns and seed patch fidelity

Summary We investigated individual foraging components of the western harvester ant,Pogonomyrmex occidentalis, in the native seed background of a shrub-steppe environment. Our study identified factors affecting foraging movements and seed selection by individual ants. Some assumptions and predictions of central-place foraging theory and a correlated random walk were evaluated for individual foragers. Results showed that ant size was only weakly correlated with the seed sizes harvested; seed size was a more important constraint than a predictor of seed selection. Individual ants spent more time in localized search behavior than traveling between search areas and nests.P. occidentalis foragers encountered seeds randomly with respect to time, and handled a mean of 1.7 seeds/trip. A correlation of increased search effort with greater travel distances was consistent with central-place foraging theory but, contrary to it, search and travel effort were not associated with energetic reward.Individual ants exhibited fidelity in both search site and native seed species. Spatial analyses of foraging movements showed a highly oriented travel path while running, and an area-restricted path while searching. Searching ants moved in a manner consistent with a correlated random walk. The deterministic component of patch fidelity and the stochastic component of search may override energetic foraging decisions in individualP. occidentalis ants.     

Influence of temporal fluctuations in seed abundance on the foraging behaviour of harvester ants (Pogonomyrmex spp.) in the central Monte desert,Argentina

The simultaneous study of the temporal dynamics of foraging behaviour, diet and seed abundance is essential to assess the way in which resources affect the behaviour and ecology of harvester ants. Here, we evaluate how fluctuations in grass seed abundance during three consecutive growing seasons influenced the foraging behaviour and diet of the harvester ants Pogonomyrmex rastratus, P. mendozanus and P. inermis in the central Monte desert, Argentina. Seed abundance of the most consumed grasses varied greatly through ant activity season, and ants altered their foraging behaviour in response to those changes. Foragers spent more time travelling and searching for food, and their foraging trips took longer during the low seed availability season. Foraging distance was very similar among species and, contrary to our expectations, did not vary between seasons. Foraging success of P. rastratus and P. inermis increased during the high availability season. This matched the seasonal pattern of foraging activity, suggesting that colonies may detect seed abundance and regulate their foraging effort with the rate of forager success. Although grass seeds were the main item in the diet of the three species, P. mendozanus, and to a lesser extent P. rastratus, turned more generalist when grass seeds were scarce. In contrast, P. inermis showed a very narrow diet breadth, only harvesting grass seeds in both seasons. Our results indicate the relevance of seed availability on foraging behaviour of harvester ants, which should be taken into account when predicting and evaluating the effect of ants on seed resources as well as numerical responses of harvester ant populations to the temporal and spatial variations in grass seed abundance.     

Reduced ant defenses in <Emphasis Type="Italic">Macaranga</Emphasis> myrmecophytes (Euphorbiaceae) infested with a winged phasmid <Emphasis Type="Italic">Orthomeria cuprinus</Emphasis>

Macaranga is a tree genus that includes many species of myrmecophytes, which are plants that harbor ant colonies within hollow structures known as domatia. The symbiotic ants (plant–ants) protect their host plants against herbivores; this defense mechanism is called ‘ant defense’. A Bornean phasmid species Orthomeria cuprinus feeds on two myrmecophytic Macaranga species, Macaranga beccariana and Macaranga hypoleuca, which are obligately associated with Crematogaster ant species. The phasmids elude the ant defense using specialized behavior. However, the mechanisms used by the phasmid to overcome ant defenses have been insufficiently elucidated. We hypothesized that O. cuprinus only feeds on individual plants with weakened ant defenses. To test the hypothesis, we compared the ant defense intensity in phasmid-infested and non-infested M. beccariana trees. The number of plant–ants on the plant surface, the ratio of plant–ant biomass to tree biomass, and the aggressiveness of plant–ants towards experimentally introduced herbivores were significantly lower on the phasmid-infested trees than on the non-infested trees. The phasmid nymphs experimentally introduced into non-infested trees, compared with those experimentally introduced into phasmid-infested trees, were more active on the plant surface, avoiding the plant–ants. These results support the hypothesis and suggest that ant defenses on non-infested trees effectively prevent the phasmids from remaining on the plants. Thus, we suggest that O. cuprinus feeds only on the individual M. beccariana trees having decreased ant defenses, although the factors that reduce the intensity of the ant defenses remain unclear.     

Spatial and Temporal Variation of Plant Fragment Removal by Two Species of <Emphasis Type="Italic">Atta</Emphasis> Leaf-Cutting Ants

Leaf-cutting ants are responsible for much of living plant fragment removal in Neotropical regions, causing major damage in both in natural and agricultural systems. To understand the variation in plant fragment removal by leaf-cutting ants and the influence that temporal and spatial factors have on such variation, we evaluated plant fragments collected by two ant species, Atta laevigata and A. sexdens rubropilosa in different seasons (rainy and dry) and in different forest systems (natural area of cerrado sensu stricto and monoculture of Eucalyptus sp.) in 2014 in Goianésia, Goiás, Brazil. Heavier plant fragments were removed during the dry season and in monoculture areas; A. laevigata removed heavier fragments than A. sexdens rubropilosa. Furthermore, we observed a positive association between the weight of collected fragments and the weight of worker ants and higher weights in A. laevigata. The study shows that the weight of plant fragments removed by leaf-cutting ants is conditioned temporally and spatially, and by the ant species involved. More detailed studies of each of these factors are need to better understand the dynamics of these foraging ants and how abiotic and biotic factors affect this process.     

Microhabitat selection by ovipositing females and pre-diapause larvae of a Welsh population of <Emphasis Type="Italic">Euphydryas aurinia</Emphasis> (Lepidoptera: Nymphalidae)

Habitat requirements of the marsh fritillary Euphydryas aurinia have been studied intensively in recent years in order to inform conservation action on this rapidly declining species. Autecological studies have been undertaken on various spatial scales to account for differences in mobility between life stages. It has become clear that resource utilisation by the species varies between different geographic areas and also on a local scale. We studied the microhabitat surrounding Succisa pratensis plants chosen for oviposition and around resulting larval webs in a key Welsh population, UK. Microhabitat preferences were shown to differ between ovipositing females and pre-diapause larval groups. For oviposition, females showed a preference for host plants within clusters of S. pratensis surrounded by a relatively low sward. In contrast, larval webs were found in relatively high vegetation with relatively low S. pratensis cover in the immediate vicinity. The marked difference between oviposition and larval web microhabitat was achieved through very long distance dispersals undertaken by the pre-diapause larval groups. This gives rise to questioning the common assumption that pre-diapause larval web location can be used as a proxy for oviposition location. It also underpins the importance of managing E. aurinia habitats for maximum structural variability on a small scale.     

Larvae of the exotic predatory ladybird <Emphasis Type="Italic">Platynaspidius maculosus</Emphasis> (Coleoptera: Coccinellidae) on citrus trees: prey aphid species and behavioral interactions with aphid-attending ants in Japan

An aphidophagous ladybird, Platynaspidius maculosus (Weise) (Coleoptera: Coccinellidae), is originally distributed in China, Taiwan, and Vietnam. The ladybird has recently intruded into the southern and central parts of Japan. The present study found that the larvae of this ladybird preyed on three aphid species, Aphis spiraecola, Aphis gossypii, and Toxoptera citricidus (all Hemiptera: Aphididae), feeding on young shoots of various Citrus species in August to early October in Shizuoka Prefecture, central Japan. Laboratory rearing of the sampled larvae confirmed that the larvae completed their development (adult emergence) by consuming each of the three aphid species. The ladybird larvae were observed foraging in aphid colonies attended by one of the four ants, Lasius japonicus, Pristomyrmex punctatus, Formica japonica, and Camponotus japonicus (all Hymenoptera: Formicidae). Field observations revealed that the foraging/feeding larvae were almost completely ignored by honeydew-collecting ants even when they physically contacted each other. Thus, in Japan, the larvae of the exotic ladybird exploit colonies of the three aphid species attended by one of the four ant species on many Citrus species. On the basis of the results, I discuss the possibility of the ladybird’s reproduction on citrus trees in Japan, probable adaptations of the ladybird larvae to aphid-attending ants, and potential impacts of the ladybird on native insect enemies attacking ant-attended aphids on citrus.