Small Ant Species Research Articles

Conditions affecting ant nesting in stumps in a temperate coniferous planted forest

Dead trees are an important component of forest ecosystems as they play various roles in these ecosystems and their biodiversity. The use of dead trees as a habitat and foraging resource by various organisms affects the decomposition of the trees. Ants use dead trees as nests and slow their decomposition by weakening the function of decomposers, such as fungi and termites, through interspecific interactions. However, our understanding of the characteristics of dead trees in which ants nest and the environmental conditions under which they exist is limited. In planted forests, stumps left after harvesting account for the largest biomass of deadwood. In the present study, the characteristics of such stumps, their location, and the relationship between these factors were determined in relation to ant nesting in a warm temperate conifer planted forest (a university forest with clear past history located in central Japan). In total, 85 stands consisting of Cryptomeria japonica or Chamaecyparis obtusa were surveyed, and various environmental conditions as well as the presence or absence of ant nests in stumps logged by forestry operations were recorded. In total, 1551 stumps were surveyed, of which 113 stumps contained ant nests with 16 different ant species. Modeling and Akaike information criterion evaluation results revealed that both large and small ant species tended to nest in old stumps located in areas with an open canopy, large species tended to nest in stumps with moss or lichen cover, and small species tended to nest in stumps with bark cover. Older stumps are typically softer owing to more decomposition, and solar heat can facilitate temperature control inside the nest, which may explain why ants tended to nest under the observed conditions. Based on these findings, long-term continuous thinning rather than clearcutting, which results in excessively large canopy openings and uniformly sized stumps, is the preferred management practice for promoting ant nesting in stumps in planted forests.

Native European ants can discourage host colonization and reduce reproductive success of the invasive ambrosia beetle Xylosandrus compactus

Due to their ubiquity and their nature as generalist predators, ants have long been used as biological control agents in forest and agricultural systems. Several exotic ambrosia beetles (Coleoptera: Curculionidae: Scolytinae, Platypodinae) are considered emerging widespread pests of various trees and shrubs growing in forests, nurseries, orchards, and urban areas. Among them, the Scolytinae Xylosandrus compactus (Eichhoff) is an invasive fungus-farming species native to Asia and able to cause serious damage to a broad range of natural and cultivated plants worldwide, exerting significant ecological and economic costs. Its biology makes conventional control strategies often ineffective, while little is known about natural enemies. We explored the potential of native European predators as natural enemy of this pest, conducting laboratory tests with four widespread ant species using chestnut and laurel as beetle hosts. In particular, we evaluated the interactions between X. compactus and four species of native Euro-Mediterranean ants that usually forage on plants: Crematogaster scutellaris (Olivier), Tapinoma magnum Mayr, Temnothorax affinis (Mayr), and Temnothorax mediterraneus Ward, Brady, Fisher & Schultz. Results indicate that ants may significantly limit the reproductive success of X. compactus, increasing the mortality of the beetle foundresses and reducing their offspring. Smaller ant species may also invade X. compactus nests, killing larvae, pupae and adults, while female beetles avoid nesting in twigs previously visited by ants. These results encourage to explore possible applications of ants in the biological control of X. compactus and the ecological implications of these interactions in the field.

Negative correlation between dispersal investment and canopy openness among populations of the ant-dispersed sedge, Carex lanceolata

Flowering plants exhibit a wide variation in the resources they invest in dispersal structures (dispersal investment), but the environmental correlates still remain unclear in many cases. Canopy openness is predicted to be negatively correlated with dispersal investment, because selective pressures on increased dispersal investment, including host-specific natural enemies and the paucity and/or ephemerality of safe sites, will be more prevalent in shady sites. Here, we tested this prediction by firstly examining the correlation between dispersal investment and canopy openness as well as abundance of the representative natural enemy (rusts, Puccinia spp.) through seven populations of an ant-dispersed sedge, Carex lanceolata (Cyperaceae). Secondly we conducted a cafeteria experiment to verify the effect of intraspecific variation in dispersal investment on diaspore preferences of seed dispersing ants. Lastly, a seedling transplant experiment was performed to clarify whether seed dispersal distances by ants are sufficient to reduce infection by the rusts. We found a negative correlation between dispersal investment and canopy openness, thus supporting the prediction. Moreover, there were more signs of rust infection caused by Puccinia spp. on adult plant leaves in more shady sites. The cafeteria experiment showed that a large ant species (Formica japonica) with relatively long seed dispersal distances tended to prefer diaspores with greater dispersal investments, while smaller ant species with shorter dispersal distances preferred diaspores with lower dispersal investments. The seedling transplant experiment revealed that rust severity in sedge offspring was considerably reduced by the typical seed dispersal distance (ca. 4 m) afforded by the large ant species, F. japonica. The increased rust severity at shady sites, combined with the narrow dispersal ranges of rusts, can partially explain the negative correlation of dispersal investment with canopy openness. These results support the importance of canopy openness as a factor underlying the variations in dispersal investment seen among flowering plants.

The ant cricket Myrmecophilus orientalis on the Dodecanese Islands, Greece (Orthoptera: Myrmecophilidae)

This study reports the occurrence of the ant cricket Myrmecophilus orientalis Stalling, 2010 on the Dodecanese Islands Kos and Tilos, Greece. This is the first evidence of M. orientalis from Greece and Europe. The species lives in ant nests under stones and in dead wood in open scrubland and pine forests. The adults were found in the nests of large Camponotus species, while the juveniles were found in the nests of small ant species of the genera Crematogaster and Lepisiota. We assumed that the species changes the host ant species during its life cycle.

A preliminary survey of the taxonomic composition of contents of Nepenthes smilesii Hemsl. pitchers in Bi Doup ' Nui Ba National Park (South Vietnam)

We present a taxonomic analysis of contents of Nepenthes smilesii Hemsley, 1895 (Nepenthaceae) pitchers collected in Bi Doup – Nui Ba National Park (South Vietnam). 230 specimens of insects, belonging to 7 orders and 17 families, as well as 7 specimens of arachnids (2 orders), 2 specimens of chilopods, 2 specimens of isopods and 1 specimen of oligochaetes were identified. Animal composition from N. smilesii pitchers is dominated by flightless and poorly flying invertebrate forms. Small ant species Technomyrmex yamanei Bolton, 2007 is a predominant prey. Besides ants, Heteroptera and Blattodea are groups dominating in ration, that distinguishes N. smilesii from other Nepenthes species, studied before in this context.

Urban habitat complexity affects species richness but not environmental filtering of morphologically-diverse ants.

Habitat complexity is a major determinant of structure and diversity of ant assemblages. Following the size-grain hypothesis, smaller ant species are likely to be advantaged in more complex habitats compared to larger species. Habitat complexity can act as an environmental filter based on species size and morphological traits, therefore affecting the overall structure and diversity of ant assemblages. In natural and semi-natural ecosystems, habitat complexity is principally regulated by ecological successions or disturbance such as fire and grazing. Urban ecosystems provide an opportunity to test relationships between habitat, ant assemblage structure and ant traits using novel combinations of habitat complexity generated and sustained by human management. We sampled ant assemblages in low-complexity and high-complexity parks, and high-complexity woodland remnants, hypothesizing that (i) ant abundance and species richness would be higher in high-complexity urban habitats, (ii) ant assemblages would differ between low- and high-complexity habitats and (iii) ants living in high-complexity habitats would be smaller than those living in low-complexity habitats. Contrary to our hypothesis, ant species richness was higher in low-complexity habitats compared to high-complexity habitats. Overall, ant assemblages were significantly different among the habitat complexity types investigated, although ant size and morphology remained the same. Habitat complexity appears to affect the structure of ant assemblages in urban ecosystems as previously observed in natural and semi-natural ecosystems. However, the habitat complexity filter does not seem to be linked to ant morphological traits related to body size.

Genetic differentiation in Horus Chamberlin (Arachnida: Pseudoscorpiones: Olpiidae) as indicated by mitochondrial DNA analysis

Horus is an olpiid pseudoscorpion of which nine species have been described from southern Africa; a tenth, debatable species was described from the Ivory Coast. The two most widely distributed species are H. granulatus and H. obscurus, the former occurring especially in the west and the other in the east, but their distributions overlap; in two instances they have been recorded from the same site. All species have a preference for rock outcrops, which are largely disjunct, and their regular prey comprises small ant species. Fieldwork over a period of 15 years indicated a very low dispersal rate; therefore one would expect localized ‘island’ populations rather than widely dispersed species. This means that the current species delimitations which lump geographically widespread populations may be incorrect. Mitochondrial DNA of specimens from each of 20 different localities across South Africa were analysed to test the hypothesis. Five of these localities did not yield results, but 14 yielded DNA from specimens which proved to belong to Horus and a fifteenth turned out to be a misidentified pseudoscorpion unrelated to Horus. The results were unequivocal: populations from each locality or group of closely-spaced localities were genetically distinct from any other one tested, and the greater the distance between localities, the greater the genetic differences (i.e. significant isolation by distance). This means that the current species delimitations for Horus are incorrect. It will require detailed micro-anatomical study to identify new characteristics on which species delimitations can be based in future.

Genetic Differentiation inHorusChamberlin (Arachnida: Pseudoscorpiones: Olpiidae) as Indicated by Mitochondrial DNA Analysis

Horus is an olpiid pseudoscorpion of which nine species have been described from southern Africa; a tenth, debatable species was described from the Ivory Coast. The two most widely distributed species are H. granulatus and H. obscurus, the former occurring especially in the west and the other in the east, but their distributions overlap; in two instances they have been recorded from the same site. All species have a preference for rock outcrops, which are largely disjunct, and their regular prey comprises small ant species. Fieldwork over a period of 15 years indicated a very low dispersal rate; therefore one would expect localized ‘island’ populations rather than widely dispersed species. This means that the current species delimitations which lump geographically widespread populations may be incorrect. Mitochondrial DNA of specimens from each of 20 different localities across South Africa were analysed to test the hypothesis. Five of these localities did not yield results, but 14 yielded DNA from specimens which proved to belong to Horus and a fifteenth turned out to be a misidentified pseudoscorpion unrelated to Horus. The results were unequivocal: populations from each locality or group of closely-spaced localities were genetically distinct from any other one tested, and the greater the distance between localities, the greater the genetic differences (i.e. significant isolation by distance). This means that the current species delimitations for Horus are incorrect. It will require detailed micro-anatomical study to identify new characteristics on which species delimitations can be based in future.

An update of the world survey of myrmecochorous dispersal distances

We update the global assessment of seed dispersal by ants and test the hypothesis that the body size of seed‐dispersing ant species varies with latitude in the same way as dispersal distance. We compiled all published data about seed dispersal distance by myrmecochory through March, 2011. We then broke the data down by vegetation type, geography and taxonomy. We also compiled data on body size (body length) of the seed‐dispersing ant species from the studies consulted. Based on 7889 observations, the mean dispersal distance was 1.99 m, although the curve has a long tail extending to 180 m. Considering the mean dispersal distance by ant species and study as independent data, the mean dispersal distance was 2.24 ± 7.19 m (n = 183). Shorter distances are associated with smaller ant species, while the tail of the dispersal curve is due to larger ant species. The mean dispersal distance of myrmecochorous seeds dispersed by ants decreased with increasing latitude, but there was no significant relationship between the body size of dispersing ant species and latitude (i.e. myrmecochorous seed‐dispersing ant species do not follow Bergmann's rule). In 1998 we made three predictions: 1) the dispersal distances of the Southern Hemisphere will decrease with as more data from mesophyllous vegetation are obtained; 2) assuming that ant nest density is higher at lower latitudes, the differences in distances between hemispheres would probably decrease with more data; and 3) numerical differences between dispersal distances in mesophyllous and sclerophyllous vegetation zones would increase with more data. The results obtained since 1998 support the only the third prediction. The dispersal distances in mesophyllous vegetation zones are shorter than in the sclerophyllous vegetation zones, and the difference between 1998 have increased. The differences in dispersal distances between hemispheres are consistent with the avoidance of parent–offspring competition (escape hypothesis).

Non-random dispersal by ants: Long-term field data versus model predictions of population spread of a forest herb

Abstract Myrmecochory, i.e. dispersal of seeds by ants towards and around their nests, plays an important role in temperate forests. Yet hardly any study has examined plant population spread over several years and the underlying joint contribution of a hierarchy of dispersal modes and plant demography. We used a seed-sowing approach with three replicates to examine colonization patterns of Melampyrum pratense , an annual myrmecochorous herb, in a mixed Scots pine forest in north-eastern Germany. Using a spatially explicit individual-based (SEIB) model population patterns over 4 years were explained by short-distance transport of seeds by small ant species with high nest densities, resulting in random spread. However, plant distributions in the field after another 4 years were clearly deviating from model predictions. Mean annual spread rate increased from 0.9 to 5.1 m per year, with a clear inhomogeneous component. Obviously, after a lag-phase of several years, non-random seed dispersal by large red wood ants ( Formica rufa ) was determining the species’ spread, thus resulting in stratified dispersal due to interactions with different-sized ant species. Hypotheses on stratified dispersal, on dispersal lag, and on non-random dispersal were verified using an extended SEIB model, by comparison of model outputs with field patterns (individual numbers, population areas, and maximum distances). Dispersal towards red wood ant nests together with seed loss during transport and redistribution around nests were essential features of the model extension. The observed lag-phase in the initiation of non-random, medium-distance transport was probably due to a change of ant behaviour towards a new food source of increasing importance, being a meaningful example for a lag-phase in local plant species invasion. The results demonstrate that field studies should check model predictions wherever possible. Future research will show whether or not the M. pratense –ant system is representative for migration patterns of similar animal dispersal systems after having crossed range edges by long-distance dispersal events.

Ant behaviour and seed morphology: a missing link of myrmecochory

Seed dispersal by ants (myrmecochory) is mediated by the presence of a lipid-rich appendage (elaiosome) on the seed that induces a variety of ants to collect the diaspores. When seeds mature or fall onto the ground, these ant species transport them to their nest. After eating the elaiosome, the seed is discarded in nest galleries or outside, in the midden or farther away, where seeds can potentially germinate. The final location of seeds with their elaiosomes removed was evaluated to assess the importance of possible handles (structures that ants can grasp to carry) in transporting ants during re-dispersal experiments of seeds from nests of six species of ants. The results indicate that seeds remained within the nest because the ants were not able to transport them out of the nest. As a consequence of the elaiosome being removed, small ant species could not take Euphorbia characias seeds out of their nests. Only large ant species could remove E. characias seeds from their nests. Attaching an artificial handle to E. characias seeds allowed small ant species to redistribute the seeds from their nests. On the other hand, Rhamnus alaternus seeds that have a natural handle after the elaiosome removal were removed from the nests by both groups of ant species. If a seed has an element that acts as a handle, it will eventually get taken out of the nest. The ants' size and their mandible gap can determine the outcome of the interaction (i.e. the pattern of the final seed shadow) and as a consequence, could influence the events that take place after the dispersal process.

Behavior of Usurping Queens in Colonies of the Ant species Leptothorax nylanderi (Hymenoptera: Formicidae)

Animals can reduce their costs of parental care by exploiting the behavior of unrelated conspecifics. Such 'intraspecific parasitism' has been observed in the small ant species, Leptothorax nylanderi. This study aims to identify how parasite queens of Leptothorax nylanderi are integrated into established colonies. Both in natural multi-queen colonies and in manipulated laboratory colonies, workers were temporarily aggressive towards the usurper queen, which herself remained initially passive and inconspicuous but later attacked the resident queen, the workers and the brood. Queen-queen aggression led to the elimination of one of the two queens and the restoration of monogyny. Usurpation is not associated with size polymorphism in L nylanderi.

Efect of nectar-foraging ants and wasps on the reproductive fitness of Turnera ulmifolia (Turneraceae) in a coastal sand dune in Mexico

Evaluamos durante dos años el efecto de diferentes especies de hormigas sobre el éxito reproductivo (estimado como número total de frutos por temporada) de Turnera ulmifolia. El estudio se llevó a cabo en el matorral de duna costera en la costa central del estado de Veracruz, México. Los resultados muestran que (i) plantas asociadas con la especie de hormiga más grande (Camponotus abdominalis) produjeron más frutos que plantas asociadas con las especies de hormiga más pequeñas, y (ii) plantas asociadas con las hormigas sufrieron niveles de herbivoría menores, que plantas sin hormigas. Consequentemente, la presencia de hormigas no es sinónimo de protección para una planta, y el nivel de protección por hormigas dependerá del tamaño de las hormigas obreras en un gremio de hormigas visitantes. Más aún, cuando se excluyeron a las hormigas, aumentaron las visitas de avispas y abejas, las que efectuaron un nivel de protección mayor que aquel ofrecido por las especies pequeñas de hormigas. Sin embargo, el efecto diferencial de las avispas requiere atención futura.

Unpredictability in the facultative association between larvae of Euphilotes enoptes (Lepidoptera: Lycaenidae) and ants

Larvae of the lycaenid butterflyEuphilotes enoptesare facultatively associated with ants. To determine whether variation in this association is predictable, I documented the proportion of larvae tended by ants and the identity of those ants over a three-year period in two study areas in central Washington state. Each study area contained numerous patches ofEriogonum compositum, the sole host plant ofE. enoptesin this region. Using complete censuses and random subsampling, I estimated the dispersion and densities ofE. enopteslarvae occupying each patch. The results of these observations indicated significant spatial and temporal variation in the identities of ants tending larvae and the frequency of ant attendance. In addition, early instar larvae were tended less frequently and by smaller ant species, than fourth instar larvae. Although larvae were aggregated at two spatial scales: individual plants within a patch and individual inflorescences on a plant, attendance rates did not vary consistently with aggregation size at either scale. Similarly, attendance rates were independent of the patch-wide density of larvae. I discuss the potential sources of such unpredictable variation and its implications for the evolution of further specialization in this facultative association.

Unpredictability in the facultative association between larvae ofEuphilotes enoptes(Lepidoptera: Lycaenidae) and ants

Larvae of the lycaenid butterflyEuphilotes enoptesare facultatively associated with ants. To determine whether variation in this association is predictable, I documented the proportion of larvae tended by ants and the identity of those ants over a three-year period in two study areas in central Washington state. Each study area contained numerous patches ofEriogonum compositum, the sole host plant ofE. enoptesin this region. Using complete censuses and random subsampling, I estimated the dispersion and densities ofE. enopteslarvae occupying each patch. The results of these observations indicated significant spatial and temporal variation in the identities of ants tending larvae and the frequency of ant attendance. In addition, early instar larvae were tended less frequently and by smaller ant species, than fourth instar larvae. Although larvae were aggregated at two spatial scales: individual plants within a patch and individual inflorescences on a plant, attendance rates did not vary consistently with aggregation size at either scale. Similarly, attendance rates were independent of the patch-wide density of larvae. I discuss the potential sources of such unpredictable variation and its implications for the evolution of further specialization in this facultative association.

Body size and microclimate use in Neotropical granivorous ants.

The stability of tropical microclimates has left microclimate use by tropical species little unexplored. At La Selva Costa Rica, I related foraging activity at seed baits to humidity in two forests types. I recorded 38 and 35 ant species at seed baits in closed and open canopy forest. The microclimate 5 cm above the forest floor in the younger, Open Forest was warmer, drier, more variable, and more sensitive to current weather than in the older Closed Forest. Ant species within both forests foraged at different Vapor Pressure Deficits (kPa), a measure of the drying power of the air. VPD use was not confounded with diel activity patterns. Body size explained 46% of the variance in mean VPD use among ant species. Small ant species tended to forage in moist microclimates; large species tended to be microclimate generalists. Larger species were also more active in the drier Open Forest. Foraging activity by these assemblages varies 4-fold, and peaks close to the mean VPD for each habitat. The behavior of these assemblages suggest that 1) small ant species at La Selva potentially compete with the entire range of ant body sizes, whereas large ants forage when and where small ants are inactive; and 2) seeds dispersed to the forest floor at dawn will be consumed or further dispersed by a larger suite of ants species than those falling in the heat of the tropical afternoon.

Influence of Crystal Size and Size of Insect on the Toxicity to Ants of Insecticidal Residual Deposits123

In laboratory experiments, 60 and 400 μm crystal length DDT deposits were compared for toxicity to ant species of different size. After 60 h of exposure of the larger species, Lasius fuliginosus Latreille, the LD90 was 1.54 μg/cm2 on the smaller crystals, not significantly different to 1.67 μg/cm2 on the larger crystals. After 60 h of exposure of the smaller species, L. flavus F., the LD90 was 0.74 μg/cm2 on the smaller crystals, significantly different to 3.11 μg/cm2 on the larger crystals. Selective toxicity was recorded. On 1.091 μg/cm2 deposits of 60 μm length crystals, LD90 of 22.21 h for the smaller species L. flavus was not significantly different to LD50 of 26.76 h for the larger species L. fuliginosus . However on 1.091 μg/cm2 deposits of 400 μm length crystals, LD90 of 54.62 h for the larger ant species was significantly less than 76.7 h LD50 for the smaller ant species.

Some Notes on the Life-history and Habits of Theraptus sp. (Coreidae)

The life-history and bionomics of the Coreid bug, Theraptus sp., which causes premature nutfull of coconuts in Zanzibar, were studied in the laboratory and in the field.From the various experiments carried out it is concluded that:—The development of the insect from the egg to the adult took from 26–39½ days depending on temperature and the food available.The average length of life of the female is 45 days during which time she may produce over 100 fertile eggs.The primary host-plant of Theraptus is the coconut palm, but the bug readily infests mango, guava, cinnamon and cacao trees when they are fruiting.The pest will attack and develop successfully on nuts from the newly emerged to the mature ones.Agents which exert a measure of biological control include the tree-nesting ant, Oecophylla longinoda (Latr.), an internal Strepsipteran parasite, an unidentified Reduviid, two unidentified Hymenopterous egg-parasites and possibly some small ant species which prey on the eggs. Of these, only the ant, O. longinoda, is capable of giving complete protection to the palm which it occupies.