Predator-prey interactions between the digger wasp Clypeadon laticinctus and the harvester ant Pogonomyrmex occidentalis

Females of the digger wasp Clypeadon laticinctus prey exclusively on workers of the western harvester ant Pogonomyrmex occidentalis. There is considerable variability in the size of ant workers both within and between ant mounds, and wasps tend to select larger workers as prey. Worker ants were most likely to be outside the nest at surface temperatures of 25–35°C. Wasps were seen at ant mounds most frequently when surface temperatures were between 40 and 50°C. Wasps captured ants outside and inside ant nests. Predation attempts were equally likely to result in a successful capture in either location, but entering the ant nests was more time consuming. Approximately 63% of visits by wasps to ant mounds resulted in a successful prey capture. In general, ant mounds that were visually conspicuous or close to wasp nest aggregations were more likely to be visited by wasps. However, frequency of visitation and rates of predation at a given mound varied considerably from week to week. Agonistic interactions between female wasps involving chases and occasional fights were likely to occur whenever two wasps were simultaneously present at an ant mound, especially when the only access to prey was by entering the mound.     

Natural history of a saline mound ecosystem

Along the margins of playas in northwestern Nevada, a salt-tolerant plant community occupies mounds that dot a largely unvegetated landscape. In this environment we studied soil development and plant-soil relationships. The mounds, averaging 0.3 m in height, are occupied by the shrubs Allenrolfea occidentalis (iodine bush), Sacrobatus vermiculatus (black greasewood), and Atriplex lentiformis spp. torreyi (Torrey saltbush). Distichlis spicata (desert saltgrass) is the only herbaceous plant occupying this community. Soil salinity decreases with depth in this environment, and content of aqueous-extractable solutes is significantly influenced by site-specific vegetation. Content of silt, clay, and salt in mound surface horizons suggests a chronosequence of mound formation, with the youngest at the barren playa interface and the oldest at the upland vegetation border. Plant demography and mound soil stratigraphy suggest that a pulse of plant recruitment and mound building occurred during a time of neoglacial cooling. As a substrate for plant recruitment, mounds have a limited lifespan because deposition of eolian-transported salts and geochemical cycling by plants quickly render them too saline for seed germination. The apparent productivity of mound formation precludes definitive conclusions regarding those mound characteristics favorable for plant recruitment and survivorship.     

Plant age/size distributions in black sagebrush ( Artemisia nova ): effects on community structure

The demography of black sagebrush ( Artemisia nova Nelson) was investigated in the Buckskin Mountains of western Nevada to determine patterns of stand renewal in sagebrush communities currently free from wildfires. Biomass sampling was conducted to develop growth classes that reflected apparent age of the shrubs. The density of black sagebrush plants was twice that of basin big sagebrush ( A. tridentata ssp. tridentata Nutt.) in adjacent communities on contrasting soils (2.2 versus 1.1 plants per m 2 ). Black sagebrush accumulated only 75% as much woody biomass as big sagebrush. Regression equations were developed and tested for predicting total woody biomass, current annual growth (CAG), and leaf weight of black sagebrush plants. Apparent age classes were developed both for the black sagebrush plants and the sub-canopy mounds on which they grew. Discriminant analysis was used to test this classification system. Plant succession, apparently controlled by nitrate content of the surface soil, appeared to eliminate the successful establishment of black sagebrush seedlings on the mounds. After the shrubs die, the mounds eventually deflate. We propose that mounds reform around shrub seedlings, but because seedling establishment is so rare in these communities, this could not be verified.     

Small-stone content of Mima mounds of the Columbia Plateau and Rocky Mountain regions: implications for mound origin

Mima moundfields were investigated at the Lawrence Memorial Grassland Preserve, located on the Columbia Plateau in southern Wasco County, Oregon, and at three locations in the San Luis Valley and Sangre de Cristo Mountains, southern Colorado, to test the alternative hypotheses of mound origins by erosion, frost action, and soil translocation by geomyid pocket gophers. The concentrations of two size classes of small stones, gravel (8-15 mm diameter) and pebbles (15-50 mm diameter), were sampled along mound-to-intermound transects and at different depths within the mounds. Numbers and masses of small stones per unit soil volume increased from intermounds to mounds tops at the Colorado sites and from mound edge to mound top at the Oregon site, where thin intermound soils lay directly on the weathering surface of basalt bedrock. Numbers and masses of small stones in the surface soil of mound tops were greater than or similar to concentrations in deeper layers. Mean masses of individual pebbles were greater in the intermound zone than in mound soils at the Oregon site, but did not differ along mound-intermound gradient at the Oregon site and at one Colorado site, being highest at mound edges or in intermounds. These observations support the hypothesis that mounds are formed by centripetal translocation of soil by geomyid pocket gophers, and are contrary to predictions based on theories assuming erosion or frost action to be the mechanism of mound formation.     

XXX.—A new Cicada from Arabia

Summary

Carebara nests occur in between 2% and 10% of Macrotermes mounds, but can also occur well away from mounds. A brood of alate ants is regularly produced ready to fly in the short rains (November) but flights can also take place in the long rains (April). Male and female alates are usually produced in separate nests. After the flight, male alates seek out the females, and several males appear to mate with one female.

Dealate female ants exposed to Macrotermes workers remained passive and elicited no aggression. Fecundated female ants reared broods of about 1000 workers after 39 days in the laboratory. These workers were able to overpower, kill and eat the much larger workers of Macrotermes.     

Microtopography of microbiotic crusts on the Colorado Plateau, and distribution of component organisms

We analyzed the microtopography of microbiotic soil crusts at 3 sites on the Colorado Plateau of southern Utah and investigated distributions of cyanobacteria and several lichens in distinctive microhabitats created by this topography. At all 3 sites the long axes of linear soil mounds were oriented nonrandomly in a NNW—SSE direction. The conspicuous and consistent orientation of soil mounds may result from a combination of physical and biotic processes. Subtle differences across sites in mound orientation and organismal distribution suggest that these variables may be useful in comparing disturbance histories of crusts retrospectively. Differences in colonization frequencies, abundances, and distributions of microorganisms comprising the crusts, as a function of mound aspect or exposure, suggest that these organisms are associated with particular aspects due to distinctive and favorable microhabitats on these exposures. Polysaccharide sheath material, deposited by cyanobacteria, and associated filaments occurred in greater quantities on ENE than WSW mound exposures, and cover by Collema spp. lichens exhibited the same pattern. Colonization of mounds by common lichen species occurred significantly more frequently on ENE than WSW mound aspects at 2 of 3 sites. In contrast, the 3 most common lichen species, aside from Collema spp., did not exhibit a tendency for greater cover on ENE than WSW mound aspects. Physiological differences between gelatinous cyanolichens and green-algal lichens may explain the different distributional patterns of Collema spp. and the 3 other lichens.     

The termites of the Mayombe Forest Reserve,Congo (Brazzaville): transect sampling reveals an extremely high diversity of ground-nesting soil feeders

Sampling using a replicated standard transect method in an extensive undisturbed primary hill rain forest in Congo (Brazzaville) revealed a very high species richness of termites, especially soil-feeding soldierless termites (Apicotermitinae). The assemblage, as estimated by the transects, resembled that previously characterized in comparable forest in southern Cameroon, but with some species turnover reflecting the gamma diversity of the Guinean-Congolese block as a whole. Species richness was three or four times that shown by a previous study addressed to mound populations alone, emphasizing the importance of sampling soil-feeding termites neither building nor living in mounds.     

Thermal ecology and activity patterns of the short-horned lizard ( Phrynosoma douglassi ) and the sagebrush lizard ( Sceloporus graciosus ) in southeastern Idaho

A mark - recapture study of the short - horned lizard ( Phrynosoma douglassi ) and the sagebrush lizard ( Sceloporus graciosus ) was performed from 1976 to 1977 in southeastern Idaho. Both species had mean cloacal temperatures of approximately 33 C. However, P. douglassi had more variable cloacal temperatures, particularly during morning and evening periods. This was caused by differences in sleeping sites chosen by the two species. Adults of both species were active from mid - April through late August, with peak activity in June. Juvenile P. douglassi displayed a seasonal activity pattern similar to that of adults. Juvenile S. graciosus were most active later in the year (August), when adults were disappearing. In both species, young - of - the - year appeared in early to mid - August. Adult and juvenile P. douglassi were active during all daylight hours and displayed no activity peaks, whereas young - of - the - year displayed a bimodal activity pattern. Adult and juvenile S. graciosus were active over all daylight hours but had peak activity between 1200 and 1500 h. Ants ( Pogonomyrmex ) were the lizard's principle prey. However, only young - of - the - year P. douglassi had activity patterns that paralleled that of ants on their mounds.         

Breeding biology of Mountain Plovers ( Charadrius montanus ) in the Uinta Basin

The known Mountain Plover population breeding on the Myton Bench, Duchesne County, Utah, is small, composed roughly of 30 adults and young after each breeding season. Currently, its location is peripheral to the species main range. This shrub-steppe breeding habitat differs from the shortgrass prairie habitat with which this bird is historically associated. Between 1996 and 1998 we made observations at nesting sites located consistently in 2 concentrated areas surrounded by large tracts of similar habitat. Activity may be focused in these specific areas because of breeding-site fidelity; this behavior is common among most shorebirds and has been documented for the Mountain Plover in Colorado. Also, Mountain Plovers are social and tend to choose nest sites near others. Most nests in Utah were located within close proximity of mounds of white-tailed prairie dogs ( Cynomys leucurus ), and all were situated near roadways or oil well pads. Mountain Plovers were often observed with broods on these bare areas at night. We conclude that Mountain Plovers on the Myton Bench are distributed in clumped breeding colonies within large areas of apparently favorable habitat.     

Nest site selection by Mountain Plovers ( Charadrius montanus ) in a shrub-steppe habitat

The known Mountain Plover population breeding on the Myton Bench, Duchesne County, Utah, is small, composed roughly of 30 adults and young after each breeding season. Currently, its location is peripheral to the species main range. This shrub-steppe breeding habitat differs from the shortgrass prairie habitat with which this bird is historically associated. Between 1996 and 1998 we made observations at nesting sites located consistently in 2 concentrated areas surrounded by large tracts of similar habitat. Activity may be focused in these specific areas because of breeding-site fidelity; this behavior is common among most shorebirds and has been documented for the Mountain Plover in Colorado. Also, Mountain Plovers are social and tend to choose nest sites near others. Most nests in Utah were located within close proximity of mounds of white-tailed prairie dogs ( Cynomys leucurus ), and all were situated near roadways or oil well pads. Mountain Plovers were often observed with broods on these bare areas at night. We conclude that Mountain Plovers on the Myton Bench are distributed in clumped breeding colonies within large areas of apparently favorable habitat.     

Preliminary assessment of velvet ant (Hymenoptera: Mutillidae) diversity in the deserts of southern California

The deserts of southern California house a diverse and unique insect fauna. Velvet ants (Hymenoptera: Mutillidae) are common in these deserts. Velvet ants are important to ecosystem health, particularly in desert environments, because they are parasitic on the bees and wasps that help maintain overall ecosystem function. The goal of this study was to measure velvet ant diversity across the deserts of southern California. We made preliminary collections from 10 sites in a variety of areas in the western Sonoran Desert (Colorado Desert), the Mojave Desert, and the Great Basin Desert. We measured β-diversity using Sørensen’s similarity index to compare velvet ant richness and relative abundance between different sites. To determine how accurate our similarity estimates were, and to gain an understanding of actual velvet ant diversity, we also compared velvet ant richness of 2 sites (Algodones Sand Dunes and Deep Canyon) using data obtained from the examination of museum specimens borrowed from over 12 museums across the West. Comparisons of velvet ant faunas between sites revealed low similarities (0.167–0.75 species richness only; 0.022–0.67 both abundance and richness). Low similarity values indicate that a rich velvet ant fauna exists in the deserts of southern California.     

A field study of the nesting ecology of the thatching ant, Fomica obscuripes Forel, at high altitude in Colorado

A field study of the thatching ant, Formica obscuripes Forel, at 2560 m elevation in Colorado provided information on mound density, composition, dimensions, and temperatures; worker longevity; and mite parasitization. Density was 115 mounds/ha. Mounds had 1-52 entrances and Peromyscus fecal pellets in the thatch. Mounds conserved heat and exhibited thermal stratification. Excavations of 4 nests revealed depths of 0.3 m to almost 1 m, novel myrmecophiles, and 0-198 wingless queens per nest. Marking experiments demonstrated that some workers overwinter and live more than a year.     

Pocket gophers ( Thomomys talpoides ) in successional stages of spruce-fir forest in Idaho

This study examined (1) the relative abundance of the pocket gopher ( Thomomys talpoides ) in four successive stages (1–10, 11–39, 40–79, and 80+ years following disturbance) of spruce-fir forest; (2) the relationship between number of gopher sign (mounds and earth plugs) with gopher density; and (3) a method of sampling pocket gopher populations using a 500 by 4 m strip transect. The number of gopher mounds was significantly correlated with the number of earth plugs. Data were pooled and a categorical log linear analysis used to test for significant differences in pocket gopher sign between the four successive stages. The 1–10 and the 80+ -year-old sites had significantly more gopher sign than the 11–39 and the 40–79 year-old sites. No significant differences were found between the 11–39 and the 40–79-year-old sites, or between the 1–10 and the 80+ -year-old sites. The difference in population densities may be due to understory vegetation differences between the successional stages. There was a significant correlation between amount of gopher sign and gophers caught in each of the study sites. This indicates that counts of pocket gopher sign may be used to estimate pocket gopher density. The strip transect is recommended as the most appropriate method when sampling heterogeneous habitats or when there is cause to suspect gopher populations may be aggregated within the area rather than spaced randomly or regularly.     

Variation in ant populations with elevation, tree cover, and fire in a pinyon-juniper–dominated watershed

Climate change and fire suppression have facilitated expansion of pinyon-juniper woodlands into sagebrush-steppe ecosystems of the Great Basin, USA, resulting in a loss of biological diversity. To assess the effects of using prescribed fire in restoration efforts, ant abundance, species richness, and composition were examined pre- and post-burn along the elevation and tree cover gradients encompassed by a pinyon-juniper woodland in a central Nevada watershed. Ants were sampled using pitfall traps in 6 sites for the elevation study and in 2 sites for the tree cover study, representing paired burn and control sites in a randomized block design. Vegetation and ground cover variables were also sampled to determine how variation in ant populations was correlated with differences in vegetation and ground cover. Ant species richness remained unchanged for all treatments. Tree cover had no significant effect on ant populations. Significantly more ants were trapped after the burn treatment on burn plots. Variation in ant populations was not directly correlated with any of the vegetation or ground cover variables. According to ANOVA and multivariate analyses, elevation had the greatest effect on changes in ant communities, likely due to increased moisture availability. Our results suggest that management for conservation of sagebrush-steppe ecosystems in this and similar watersheds should include a range of elevations to ensure maximum ant species diversity.     

Food habits of clouded salamanders ( Aneides ferreus ) in Curry County, Oregon (Amphibia: Caudata: Plethodontidae)

Stomach contents of 650 clouded salamanders ( Aneides ferreus ), collected monthly throughout the year from Curry County, Oregon, were examined. Samples from three age classes were involved: (1) 489 adults, (2) 131 juveniles, and (3) 30 hatchlings. Foods did not vary by sex, but did vary by age and by season. Hatchlings ate small items, particularly mites, springtails, flies, and small beetles. Juveniles fed mainly on flies, isopods (sowbugs), beetles, mites, and centipedes in winter; beetles, ants, and isopods in spring; ants and beetles in summer; and isopods, beetles, and ants in fall. Adults ate isopods and beetles as their major foods in winter, spring, and fall and isopods, ants, beetles, and earwigs in summer. Four species were exceedingly important as foods for these salamanders: an unidentified isopod, the snout beetle ( Trachyphloeus bifoveatus ), the European earwig ( Forficula auricularia ), and an ant ( Lasius alienus ).       

Effects of Douglas-fir beetle (Coleoptera: Scolytidae) infestations on forest overstory and understory conditions in western Wyoming

Douglas-fir beetle ( Dendroctonus pseudotsugae Hopk.) infestations frequently result from disturbance events that create large volumes of weakened Douglas-fir trees, Pseudotsuga menziesii (Mirb.) Franco. Previous research has focused on determining susceptibility of forest stands to Douglas-fir beetle and predicting the amount of tree mortality from Douglas-fir beetle infestations following disturbance events. Little work has been done on consequent changes in the forest overstory and understory. In the early 1990s, populations of Douglas-fir beetle increased in fire-scorched trees, subsequently infesting undamaged neighboring stands in the Rocky Mountains of western Wyoming, USA. In 1999 transect sampling and 25 pairs of previously infested and uninfested plots were used to quantify changes in forest stand conditions and ensuing responses in the understory caused by Douglas-fir beetle infestations. Significant effects of the Douglas-fir beetle infestation comprised 3 general categories: (1) overstory effects: basal area was reduced by 40%-70%, average tree diameter decreased by 8%-40%, and the Douglas-fir component of the overstory decreased by more than 12%; (2) regeneration effects: conifer seedling regeneration increased nearly fourfold in infested plots and 90% of the regeneration was Douglas-fir; (3) understory effects: understory vegetation (forbs, grass, and shrubs) had a threefold increase in infested compared with uninfested plots. In addition, basal area of Douglas-fir killed by the Douglas-fir beetle was significantly correlated with initial Douglas-fir basal area and percentage of Douglas-fir, but not with stand density index, tree diameter, or trees per hectare. Significant inverse relationships also were found between post-infestation basal area and abundance of forbs, grass, and shrubs, and understory height. Thus, we found that Douglas-fir beetle infestations cause significant short-term effects in both the overstory and understory and contribute to an altered mosaic in forest structure.     

Effects of different ant species on the attendance of neighbouring hemipteran colonies and the outcomes for the host plant

Ants commonly participate simultaneously in mutualisms with honeydew-producing hemipterans and extrafloral nectar-bearing host plants. These interactions are based on the exchange of resources (honeydew and extrafloral nectar) for ant protection against natural enemies. The benefits may vary according to the species of ant interacting, and the outcomes for the host plant and hemipteran will depend on the results of the ant-plant-hemipteran relationship as a whole. We studied a plant-mealybug association with Camponotus crassus Mayr (Formicinae) and Ectatomma tuberculatum Olivier (Ectatomminae) in a Brazilian tropical savanna. We aimed to elucidate whether the frequency of visitation by different species of ants can be affected by neighbouring colonies of mealybugs, and whether these ant species influence the number of hemipterans in a different way. Furthermore, we intended to find out whether the interaction between ant and hemipteran has any effect on the proportion of fruit production or on the abundance of trophobiont and non-trophobiont herbivores, also influenced by the ant species. Our results show that neighbouring aggregations of mealybugs influenced the frequency of ant visitation and the ants affected the number of nymphs over time, with both positive results only for C. crassus. We also detected an indirect negative effect on proportion of fruit production and an increase in abundance of trophobiont and non-trophobiont herbivores in the presence of C. crassus-mealybug interaction. Thus, we provide further evidence that colonies of hemipterans interacting with ants can be beneficial for these herbivorous insects, but they are quite harmful to the host plant. Nevertheless, the outcomes can be highly conditional in relation to ant species.     

Ecological studies on Aechmea bracteata (Swartz) (Bromeliaceae)

In the Yucatan peninsula, Mexico, Aechmea bracteata is more frequent in the low inundated forest than in hummocks or the semi-evergreen forest. Due to its flat smooth, ovoid seeds disseminated by birds, this epiphyte generally develops on rough-barked trees at the point where a large branch forks out. The presence of a rhizome permits the formation of groups of ramets comprising different levels of development from young shoots to blossoms and the differential rotting of dead dry ramets. In green mature ramets, an amphora-shaped leaf develops around the inflorescence, delimiting a central watertight cavity. Around this central cavity, inter-leaf spaces correspond to peripheral cavities where rainwater may accumulate. This structure permits the plant to be both a phytotelm and a myrmecophytic epiphyte, with green ramets sheltering a large diversity of both aquatic (mostly Diptera larvae) and terrestrial animals (mostly ants, cockroaches, mites, and springtails). Concerning ants, peripheral cavities sheltered small Myrmicinae (31·3% of the ramets), central cavities Pachycondyla villosa (Ponerinae) or Dolichoderus bispinosus (Dolichoderinae) (91·9%; N = 248). Rotting dry ramets sheltered only terrestrial animals, mostly detritivores which are classically present in the leaf litter and ants such as Cyphomyrmex minutus, a primitive Attini and numerous Ponerinae, predators of the detritivores. Both green and dry ramets constituted good shelters for incipient colonies.     

Prey choice and raiding behaviour of the Ponerine ant Pachycondyla analis (Hymenoptera: Formicidae)

Termite raiding behaviour of the African poneromorph ant Pachycondyla analis was studied at Mpala, Kenya. In all, 330 raids were observed with the raiding activity showing peaks in the morning and evening. Time spent at the termite source was positively correlated with the numbers of termites taken. The sizes of foraging parties, number of termites taken, distance travelled and time spent at termite sources also showed a positive correlation. Pachycondyla analis preyed significantly more on Microtermes spp. than they did on Odontotermes spp. but no significant differences were found in terms of predator efficiency even though many ants were injured in raids on Odontotermes spp. compared with those on Microtermes spp. Our results indicate that P. analis seems to forage optimally, balancing the costs of energy with prey reward and prey choices were not only influenced by prey abundance, but also by the costs of foraging, as influenced by prey defences, size and foraging behaviour.     

The influence of ants on the mating strategy of a myrmecophilic jumping spider (Araneae,Salticidae)

Phintella piatensis is an unusual jumping spider because, despite being neither myrmecophagic nor myrmecomorphic, it associates with ants, including dangerous weaver ants. Although salticids typically spin cocoon‐like nests for use as shelters, the nests of Phintella are unusually dense. These play an important role in how Phintella adapts to living with ants. In experiments, intraspecific interaction and mating increased the risk of being killed by ants when there was no accessible nest, while access to a nest eliminated this risk. Additionally, while outside nests, seeing ants made Phintella reluctant to mate, this being an unusual example of a small animal with exceptional eyesight compensating for predation risk when making vision‐based mating decisions. On the whole, the behaviour of Phintella during intraspecific interaction had broad similarity to the pattern that is common in salticids, but with some of the details of courtship suggesting further adaptation to interacting in the presence of dangerous ants.